Đồ Án Tổng Quan Về Chuẩn Nén MPEG-4 H

DA TN. Téng quan vé chuén néii MPEG-4 H. 264/A VC va kha

Trang I

NH A} N XET CUA GIAO VIEN HLDG DAN

Tén de tai : “Tong quan vé chuan nén MPEG-4 H.264/AVC v:i kha nang

ig dung

GVHD SVTH MSSV UP

: TS. TRAN DUNG TRINH: NGUYEN QUANG HOANG SON: 103101088: 03DDT2

Tp.HCM ngiiy th:ing niim 2008GVHD

TS. Tran Dung Trinh

GVHD. TS. TIN D VG TRINH

SVTH . NGUYEN QUANG HOANG NON

DA TN. Tong quan vé chu n nen MPEG-4 H. 264/A VC va kha ning urig dung trong th¿c tien

Trang 2

NQ IT CUA GIAO VIEN PHAN BIENTe‘n de‘ tiii : “Tong quan ve chufin ne’n MPEG-4 H.264/AVC va kha nang ring

dpng trong thpc tie‘n”GVHD GVPB SVTH MSSV UP

: TS. TO DOING TRINH: KS. TRAN DUY CU©NG: NGUYEN QUANG HOANG SON: 103101088: 03DDT2

Tp.HCM ngd y

théng niim 2008GVPB

KS. Tran Duy Cué'ng

SVTH .- NGUYEN QUANG HOANG SON

DA TN. Téng quan vé chuan nén MPEG-4 H. 264/A VC va kha ning ung dung trong thiic tien

Trang 3

SU CAN THIET CUA NEN

QUA TRINH SO HOA TIN HIEU ................ .............................................. 121.2

I.2.1I.2.2I.2.3

LAYMAU .12LUONG TU HOA. ........................................................................... 12MA HOA.......................................................................................... 13

1.3 TOC DO BIT VA THONG LU‘ONG SNH TRUYEN TIN HIEU SO ....... 14

I.3. 1I.3.2

TOC DO BIT.................................................................................... 14THONG LUONG KENH TRUYEN................................................. 14

1.4

1.5

1.6

QUA TRINH BIEN DOI TIN HIEU MAU ................................................. 14

CAC TIEU CHUAN LAY MAU TIN HIEU VIDEO SO ......................... ... 16

MO’ HINH NEN TIN HIEU VIDEO.............. .............................................. I.6.1I.6.2

NEN TIN HIEU VIDEO................................................................... 17LUONG TIN TRUNG BINH (ENTROPY) ...................................... 18

CHU‘ONG II. CAC KY THUAT NEN VIDEO .................................. 21II. 1

11.2

PHAN LOAI CAC KY THUAT NEN......................................................... 21

QUA TRINH BIEN DOI ...... ................... ...... .................. ......................... ... 2 1

II.2. I II.2.2

II.2.2. 1

DIEU XUNG MA VI SAI DPCM ...... ................... ........................ ... 22MA HOA BIEN DOI. ...... ................... ...... ................... .................... . 22

Bién doi cosin rci i rac DCT............. ...... ............. ...... ................... .....22Bién doi Hadamard ................. ....... .................. ......................... II.

3QUA TRINH LU ONG TU ... .................. ....... .................. ......................... ... 24

II.3.1II.3.2

LUONG TU HOA VO HU©NG ...................................................... 24LUONG TU HOA VECTOR ........................................................... 2511.4 QUA TRINH MA HOA .............................................................................. 25

II.4. 1II.4. 1.1II.4.

1.2 II.4.2II. 5 TIEU

MA HOA DO DAI THAY DOI.......... ...... ................... .................... . 25Ma hé*a Huffman ... ...... ................... ...... ................... ........................26Ma hoa muc doc chiéu dai RLC ..... ...... ................... ........................26

MA HOA SO HOC .... ................... ...... ................... ......................... ..


5 VTH . NGUYEN QUANG HOANG SON


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CHU‘ONG III. CAC CHUB NEN THUOC HO MPEG TRU’€JC MPEG-4 H.264/AV

III. 1 GI 1 THIEU VE LICH SU PHAT TRIEN CUA KY THUAT MPEG ........ 31

III.2 CAC TIEU CHUAN NEN TRU©C MPEG-4 H. 264/AVC.......................... III.2. 1III.2. 1 . 1111.2. 1.2

III.2.2III.2.2. 1 III.2.2.2

TIEU CHUAN MPEG-1 ................................................................ ... 31Cac dac diém ciia tie’u chuan MPEG-1 .............. ..............................32Cau truc dong bit cua MPEG-1......................... ................... ...... ......33

TIEU CHUAN MPEG-2.. ................... ......................... .................. .. . 34Cac dac diém ciia tiéu chuan MPEG-2 .............. ...... ................... ..... 34Su khac nhau chinh giira MPEG-1 va MPEG-2 ....... .................. CHUONG IV. CHUAN NEN MPEG-4 H.264/AVC

..........................38

IV. 1 . 1IV. 1 .2

IV. 1.2.1IV. 1.2.2

LICH SU PHAT TRIEN CUA MPEG-4 H.264/AVC .............. ......... 38CAC PROFLIES VA LEVELS TRONG H. 264/AVC.............. ......... 39

CAC PROFILES ... .................................................................... ......39CAC LEVELS ...... ................... ................................................ . ......40IV.2

IV.3

NHUNG DAC TINH NO BAT CUA CHUAN NEN H.264/AVC .... ...... ... 41

KY THUAT NEN VIDEO H.264/AVC ....................................................... 44




Trang 5

IV.3.4.2IV.3.4.3

1V.3.5IV.3.5. 1 IV.3.5.2

IV.3.6IV.3.6. 1 IV.3.6.2 IV.3.6.3 IV.3.6.4

Ma héia do dai bién d éi thich nghi

dung CAVLC ................. ......84Ma hoa so hoc nhi phan thich nghi riot dung CABAC ......... ............

87BO LOC TACH KHOI TRONG VONG................ .................. ......... 89

‘Nguyén tac ciia loc tach khoi.......... ......................... .................. ......90Qu:i trlnh loc aoi . .................................................................... ......91

CAU TRUC VA CU PHAP CHUAN H.264/AVC. .................. ......... 94Lop triru tuong mang NAL....... ......................... .................. ............95Lop ma hoa video VCL (Video Coding Layer). ................... ...... ......96Ky thuat FMO va Data Partitioned Slices ................ .................. CHU‘ONG V. MOT SO USG DUNG CHUAN H.264/AVC .............. 99

V. 1

V.2

V.3

TRUYEN HINH INTERNET IPTV ....... ......................... ................... ...... ... 99TRUYEN HINH VE TINH DVB-52.........................................................

TRUYEN HINH DI DONG ......................................................................

100

100

CHU‘ONG VI. MO PHONG QUA TRINH NEN-GIAI NEN CUAH.264/AVC BANG MATL 03

103

103

104

06

VI. 1

VI.2

VI. 3

LUU DO GIAI THUAT ............................................................................

CHUONG TRINH MO PHONG: ..............................................................

IT QUA MO PHONG............................................................................

TAI LIEU THA



DA TN. Téng quan vé chuan nén MPEG-4 H. 264/A VC va kha ning ung dung trong thuc tien

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LV GI€fI THIEU

ién nay, chung ta dang song trong mot ky nguyén moi “Kj ng

riyén trnyén thing da phiroiig tic:ii” cac thiét bi mmi, cac ky thuat moi

lan luot

ra doi nham muc dich dap ring nhu cau giai tri cho con ngucii ngay mot tot hon. Cac

ung dung da phuong tién thoi gian thuc truyén trén mang di dong, mang lntemet,

mang truyén hinh. . .ngay cang phat trién r:tin ro, cac nha san xuat thiét bi chu trong ap

dpng c:ic cfing ngh( ne'n tién tién viio th iét bi cua minh nham thfia man nhu cau

“chat luong trung thuc vé fim thanh, hinh anh” ciia con ngu‹ii cling nhu kha nang

drip ung yéu cau thuc té cua cong nghé. Thé nhung khong phai nhu cau nao cua

chung ta déu co the’ dupc d:ip kg mot c:ich thu an l pi, vi sir gan lien giira do phuc

tap, ton kém chi phi dau tu cc so ha tang, thiét bi dau cuoi. . ., lufin di kém voi cfing

nghé cao. Bén canh do van dé truyén thong nfii dung da phuong tién hién nay dang

gap mot so kho khan. héng théng diréng truyen, nh ten kénh, giéri hqn ciia pin cho céc

irng dung... . Trong khi bang thong kénh truyén ph:ii cho dci mot cfing nghé moi cfia

tuong lai moi co thé cai thién, con viéc cai thién gioi han cua pin duéng nhu khfi ng

dap ring duoc su phat trién cua cac dich vu trong tuong lai, thi phuong phap giam kich

thuoc dir liéu bang cac ky thuat nén 1:i mot c:ich gi:ii quyét hi(u qu:i c:ic kho khan

trén.

Cho dén nay co rat nhiéu ky thuat nén dir lieu da phuong tién nhu: chuan JPEG, chuan

JPEG2000 va chuan MPEG. .. tuy nhién hiéu qua nén cua cac tiéu chuan nay cung

chua dupc cao, va van chua dap ting tot yéu cau ciia truyén hinh HDTV. . . cung

nhu vi(c luu trfr dung tuong cfin rat 1én. Gan day nhat lit sq thiinh cfing cua tiéu

chuan ma hoa MPEG-2 duoc danh dau riot bat tu nhting lan phong thuong mai dau

tién cac hé thong vé tinh DTH vao gi ira nhfmg nam 1990 va thanh cong ciia chuan

nén MPEG-4 Part 2 trong ung dung truyén hinh so, ciic ring dung do hoa. . . Nhung

voi yéu cau bo ma hoa co thé tuong thich véri cac ung dqng toc do bit thap, thi no

khong dap irng hiéu qua. Tir viéc nghién ciiu khac phuc nhuoc diém cua MPEG-2,

phat trién bfi sung cho MPEG-4 Part 2 dé cho ra doi nhfiiig chuan nén tién tién hon,

ma noi bat la MPEG-4



DA TN. Téng quan vé chuan nén MPEG-4 H. 264/A VC va kha ning ung dung trong thuc tien

Trang 7

mot vi du minh hoa trong truye’n hlnh so, neu sir dung ky thuat nén MPEG-2 cung cap

dinh dang SDTV v‹ i do phan giai 640x480 pixel thi can bang thong 4.3Mbps trén mot

kénh truyén con doi voi HDTV thi can l9Mbps, nhung néu su dqng chuan nén H.264thi bang thong cho truyén hinh SDTV chi co 1.5 2 Mbps hoac 6-9 Mbps doi voi

HDTV. Chinh vi nhirng uii diem dfi ma MPEG-4 H.264/AVC da dan dan chirng to vi

thé so 1 cua minh, nh irng iru vi(t ma chuan nén nay mang lai chac chan

ti¼ii” tain dé tai tot nghiép cua minh. Sau hon 3 thang ' luc hét minh, ve cc ban Do

an cung da cho ta cai nhin tong quat vé chuan nén MPEG-4 H. 264/AVC, dong thoi

voi su minh hoa bang chuong trinh Matlab 7.01, ciing giup cho ta hiéu ro hon nhfrng

uu diém cua chuan nén nay, tuy nhién do co su han ché vé kinh nghiém, th‹ii gran,. .

.nén se khfing tranh khoi sai sot, kinh mong Quy Thay Co, ban bé, dong nghiép tham

khao d é rig géip y kie'n.

Em xin chan thanh cam on TS. Tran Dfing Trinh da bo ra chut thoi gran guy biiu,

huérng dan tan tinh va cung cap tai liéu bfi ich trong qua trinh tain Do an. Dong thcii

cung xin cam on Quy Thay Co Truong Dar Hpc Ky Thuat Cfing Ngh( Thanh Pho Ho

Chi Minh, da tan tinh day do, truyén thu kién thuc va kinh nghiém cho em trong suot

hon bon nam qua, cam on cac ban be da quan tain, chia xe’ , d éing gép y kie'n.



DA TN. Téng quan vé chuan nén MPEG-4 H. 264/A VC va kha ning ung dung trong thuc tienTrang R

CAC THUAT NG U’ TIENG ANH

BAC CA CC CIF

‘ hoc nhi phan tBinary Arithmetic Coding) Ma hoa thich nghi theo nfii dung (Context A‹1aptivc) Ma xoa tClear code)Dinh dang ma hfia hinh anh co kich thuoc 352 x 288 (CommonIntermediate Format)Phii t quang b:i am thanh so (Digital AuJio Bi oaJc as ting) Bién dfii Cosine rot rac tDis crete Cosine Transform) Bién dfii Fourier rcii rac (Discrete Fourier Transform1Diéu xung ma vi sai tDifferential Puts e Code Modulation )Thuat toan tim kiéu hinh thoi (Diamond Search)

DAB DCT DFT DPCM DS DTH DWT EOIESExp-Golomb FLCFMO GOP GMC HDS HDTV HEXBS ICTIDR

Bién dfii Wavelet roi rac i'Di.fcrc/e Wavel I Transform)Ma két thuc tEnd Of ln]’ormation) Dong cc ban (Elcmenatary Stream) Mtr Exponential GolombMa h‹ia co chiéu dai co dinh tFixed-Length Codel Thir tu MB mem de’o tFlcxihle Macrohlock Order) Nhé*m iinh (Group Of Pictures)Bit chuyén dong toan phan (Globa I Mo tion Compens ation)Thuat toan tim hinh thoi nam ngang (Horizontal Diamond search 1Truyén hinh ph:in giai cao (High Defin ition Television)Thuat to:in tim kiéu hinh liic gi:ic tHexagon-Based Search)Bién dfii nguyén Cosine r‹ i rac (Integer Discrete Cosine Transform) th lam tiroi tuc thoi bo giai ma (ID.f t ntaneou.f Decoder fic/i .A/i Pictu re)Bién dfii ngiroc Cosine roi rac (Invcrsc Disc i etc Cos inc Transfor in1Giao thirc Internet ( Internet Protocol)Mang tich hop dich vu so (Integrated Service Digital Network )Chuan nén anh cua try ban JPEG quf›c té tJoint Photograph ie ExpertsGroup)Chufin nén anh JPEG2000Ky thuat nén anh khong ton hao (khfing mat dir liéu)Ky thuat nén anh co ton hao (cé› mat dir li(u)Da khoi (Macroblock)Mtr hfia khiing in:inh th ich ngh i tMacroblock-Adaptive Frame-FieldcodinglBit chuyén dong tMotion Compensation)U‘oc lirong chuyén dfing(Mo/ion Es timate)Dich vu tin nhan da phuong tién (MultimcJia Mess agingSai so hinh phuong trung binh (Mean Square Error)Nhé*m chuyen gia nén anh dong (Moving Pictures Experts Group 1

IDCT IP ISDN JPEG

JPEG2000 LOSSLESS LOSSYMBMBAFF

MC ME MMS MSE MPEG



DA TN. Téng quan vé chuan nén MPEG-4 H. 264/A VC va kha ning ung dung trong thuc tienTrang 9

NALNNs PCM PF MF PSNR QCIF

H8 ' co dan (Parameter FactoryHé sfi nhan /Mu//iyy Factor)Ty so tin hi(u dinh trén nh iéu tPeak Signal to No ise Ratio)Dinh dang hinh iinh céi kich thu‹ c 1 76 x 144 tQuarter Common IntermeJ iatc For mat)Thong so tuong tu tQuantization Parameter ) (Raw Byte Sequence Payload)Ba in:iu cc ban mau d ci /Xanh/Lam (ReJ/Green/B Inc)Ma hoa dpc chiéu dai (Rtn Length CodinglGiao thirc danh riéng tai nguyén mang tRL.f tirce /? .UkuthiProtocol)Giao,th iuc truyén tai thoi gian thuc (Real Time Transpo i I Pt otoe of)Truyén hinh tiéu chuan I Standard Televison 1Ngf›n ngii tich hop Multimedia df›ng bo USynch ronized MultimediaIntegration LanguagelDiéu khién toc dfi bit bién doi duac ( Sc alah Ie Rate Centre I )Thufit toan tim ba buéic (Three-Step s

carch) tUniversal Mohilc T lccommica/t h.f 5 .JUL Lop ma hé›a Video tVidco Coding Layer )Mtr co chiéii diii thay dot tVariahle Length Code)DC i tirpng Video (Video ObjectlDfii tirong mat phang Video tVi‹leo Object Plane )Do chfii, in:iu lam, mau dfi tLuminancc, Blte chrom mance, Red chi omin‹in‹ e)Tfi ch iuc quoc té vé tiéu chuan chat tuong (Intcrnationa I Organization for StanJarclization)Uy ban ky thuat dién qufic té (International Electro-technicalCommission)Uy ban ky th uiit 1 (Joint Technical Corumittee I )Uy ban phu 29 tsuh-committee 2 9)Nhé›m 1:tin vi(c 1 1 ( Work Group 11)

qP RBSP RGB RLC RSVP

RTP SDTV SMIL

SRC TSS UMTS VCL VLC VO VOPYCbCr

ISO

IEC

JTC1 SC29 WG1 1



DA TN. Téng quan vé chuan nén MPEG-4 H. 264/A VC va kha ning ung dung trong thuc tienTrang I II

L€JI M€J DAUDe co thé di sau vao nghién cliu chuan nén MPEG-4 H.264/AVC, thi chung ta can

nam dupc cac thuat ngfr, cac ky thuat can thiét cho vi(c nén tin hi(u, ciing nhu 1:i cac

uu nhupc diem cua cac chuan nén tru‹ c déi da mang lai.Vi day la mot de’ tar 1y

thuye't, nén buérc quan trong nhat ciia qua trinh lam Do an tot nghiép la tim kiém tai

liéu va tong hop no thanh mot chuoi cac kién thiuc lién tuc tranh lang man va yéu to

thuyét phuc ngi roi tham khao cling rat quan trong, do do bén canh trinh bay chi tiét

ve c:ich

phan uu diem ciia chuan nén nay nham gop

phfin sinh dong cho dé Hi.

TO CHIC DO AN

Do :in dupc trinh bay th:inh 6 chuong va 1 php luc.

Chvong I.• Trinh bay cc so ve nén tin hi(u video, c:ic thong so dac trung cua tin hi(u

so va qua trinh bién dfii tin hiéu mau, phan loai cac nguyén ly nén.

Chvong IT.• Trlnh bay c:ic ky thuat dupc su dpng trong nén Video, cac phép bién d éi

v:i c:ic ky thuat ma héia, c:ic tiéii chuan d:ing gia chat tuong :inh nén MSE, PSNR,

MAE,SAE

Chrrang III.• Trinh bay cac chuan nén thufic ho MPEG, cau truc dong bit, cac uu diem

da dat duoc.

Chrrorig IV.• Cling la chuong quan trpng nhat, trinh bay chuan nén tién tién nhat hién

nay: MPEG-4 H.264/AVC, c:ic dac tinh nfii bat vii c:ic ky the at m‹ i trong chuan

ne'n nay.

Chvong V.- Cac irng dung cfi a MPEG-4 H.264/AVC trong thpc te’ v:i tuong lai.

Chvong VI.• Mo phong mot ph:in qua trinh nén v:i gi:ii nén ciia MPEG-4

H.264/AVC, mo phcing kiéu ma héia tién tién nhu bit chuyén d cing voi kich thuoc

4x4, su dung bang luong ti r vfi huong 52 giii tri.

Tiiy nhie’n, do kinh ngh i(m con han ché, dong thoi MPEG-4 H.264/AVC Ta mot ky

thuat con trong giai doan nghién ciiu va phat trién, nén chac chan Do an se khong

tr:inh khci i sai sot, kinh mong Quy Thay Co, va ban bé d cing nghiép d éing gop y

kién



DA TN. Téng quan vé chuan nén MPEG-4 H. 264/A VC va kha ning ung dung trong thuc tienTrang I I

CHU©NG I. C© S© VE NEN TIN HIEU VIDEO

khan trong vi(c luu trfr va truyén di trong mot bang thong kénh truyén han che’. Voi sir

phat trién ciia khoa hpc ky thuat, ngay nay da san xuat duoc bo cam bién mau co do

phan giai lén dén 16 triéu pixel tuong duong voi mot buc anh co do phan giai

4096x4096 pixels, nhung thuc té Eng ding can do ph:in giai cao nhat hién nay ciing

ch i dung lat ci 1920x1080 pixel, do do de’ céi thé tiét kiém khong gran liru trir vii

bang thong kénh truyén thi ct nén tin hiéu.

Qua trinh nén anh thuc hién dupc la do thong tin trong birc anh co tfi chirc, céi trat to,

vi vfiy néu xem xét ky tinh trat tu, cfiu truc anh se phat hién va loai bo dviac c:ic tuong

thong tin du th ira, chi gifra lai cac thong tin quan trpng nham gram so luong bit khi

fun trfr cung nhu khi truyén ma van dam bao tinh tham my ciia buc anh. Tai dau thu,

bo giai ma se to chuc, sap xép lai duac biuc :inh xfip xi gfin chinh xac so voi anh

goc nhung van dam b:to thong tin cfin thiét. Tin hi(u video thuéing chira d g in I

lupng

= Céi sir du th ira thong tin ve khong gran: gifia c:ic diém anh fan can trong

pham vi mot buc anh hay mot khung video, con got la thua tinh bén trong timg

frame. Cé* su du thua thong tin vé thoi gran: gi ira cac diém anh ciia cac

khung video trong chuoi anh video, con goi la thua dong gifra cac frame

Céi sir du thua thong tin ve’ phfi: gifia c:ic man cua c:ic dfi 1i(u thu dirpc ID c:ic

bfi c:tin bién trong camera, miiy quay. .

Cé* su du thua do thong ké: do ban than cua cac ky hiéu xuat hién trong dong

bit voi c:ic x:ic suat xuat hién khfi ng dong déu.

Céi su du thua tain thi gi:ic: thong tin khong phu hop voi hé thong thi giac con

nguoi, nhirng tan s6 qua cao so voi cam nhén ciia mat ngu‹ii.

=

=

=

=

Uu diém cua vi(c nén tin hieu:

= Tiét kiém bring thong kénh truyén ( trong thoi gian thuc hoac nhanh hon).



DA TN. Téng quan vé chuan nén MPEG-4 H. 264/A VC va kha ning ung dung trong thuc tien Trang 12

= Kéo dai their gian su dung ciia thiét bi luu trfr, giam chi phi dau tir cho thiét bi

= Gram dung lirong thong tin in:i khong lam mat tinh trung thuc ciia hinh anh.

Co nhiéu phuong ph:ip nén tin hieu, phuong ph:ip nén bang cach so hfia tin hi(u van

ter ra him hi(u trong moi thoi dai, mot mat no co thé 1:tin gi:tin tuong thong tin khfing

quan trong mot cach dang ké, mat kh:ic no con giup cho tin hiéu duoc bao mat hon.

I.2 QUA TRINH SO HOA TIN H UQtr:i trinh so ho:i tin hi(u tirong

, bao gfim qua trinh lpc tru‹ c i prefiltering), lay mau,

luong tu va ma hoa minh hoa nhu hinh I. I . Qu:i trinh loc truoc nhém loai bfi cac tan so

khf›ng c:in thiét ér tin hiéu cling nhu nhiéu, bo lpc nay con goi la bo loc chong nhiéu

xuye’n kénh Aliasing.I.2.1 LAY MAUThuc chfit day la mot phép toan roi rac hay la mot phép diéu bién xung PAM va duoc

thuc hién bang cac mach Op-amp co cuc khién strobe. No tao ra gia tri tin hiéu tuong

tu tai mot so hint han c:ic gi:i tri co b ién rcri rac gpi lii c:ic man. C:ic mau dirpc lay c:ich Tan mau phai thoa man dinh ly Nyquist-

1.2.2 LUQNG TO HOA.

Qtr:i trinh lupng ID lit qua trinh chuyén mot xung lay mau thanh mot xung céi bie’n do

bang muc luong ti r gan nhfit hay noi ciich kh:ic la tuong tu chuyén dfii cac muc bién

dfi ciia tin hiéu da lay mau sang mot trong cac gia tri him han cac muc nhi phan.

Luong tu ho:i b ten doi tin hiéii lie’n tijc theo thoi gran thanh tin hiéu co bién do rem

rac, nham tain gram anh huong ciia tap am trong he thong, han ché cac muc cho phép

cua tin hiéu lay mau va chuan bi truyén tin hiéu goc tu tuong tp sang so. Gia tri thap

phan ciia cac mau sau khi lupng tir ho:i sé dirpc bie’u die’n duoi dang so nhi phan n bit

(N= 2“), voi n la do




Do 1:tin trfi n cac mtrc ne’n tin hieu bi méo dang do sai so luong tit goi la méo luong tir,

ty so tin hi(u trén méo luong tir (S/N) dirpc x:ic dinh boi:— = 6,02» 1,76(dB)

Hinh I. I.- So dé quci trinh tao tin liié u .sc›.

Lirong tir hoa co hat loai:

= Luong tir tuyén tinh: phép nén tin hi(u theo guy luat duong cong dong déu,

buoc luong tir bang nhau.

Luong tu phi tuyén: phép nén tin hiéu theo guy luat duéng cong khf›ng dong

déu, tap trung n hieu mirc lupng tir c› nhiing viing tin hi(u nho. Trong ky thu

iit nén anh, nén video thi loai luong tu phi tuye’n dupc diing nhiéu hon vi né›

gi:tin

=

1.2.3 MA HOA

La qu:i trinh thay thé

goi la tin ma. Tat ca cac ti r ma déu chua so xung nhi phan co dinh va duoc truyén trong




khoang thoi gian gifra 2 thoi diém lay mau canh nhau. Bo ma dupc su dung de’ Hi tao

cac xung nhi phan hoac c:ic tir ma tir cac gi:i tri da lirong tu xuat hi(n o dau ra cua bo

luong tu hoa.

I.3

I.3.1

TOC DO BIT VA THONG LUQNG KENH TRUYEN TIN HIEU SO

TOC DO BIT

' luon bit duoc truyén di hay fun trfr trong mot don vi thoi gian.

I.3.2 THONG LU’1)NG KENH TRUYENLa toc do so liéii circ dat co the’ truyén dupc trén kénh tniyén co do rong bang tan B.

Trong déi

= C lit toc do b it (bps)

y la ty so tin hieu trén nhiéu trang.

B la bang thong kénh truyén (Hz).

Toc do bit cang lori thi tin hi(u tuong t ir khfii phuc lai c:ing trung thirc tuy nhie’n no

se’ la cho dung luong luu trii v:i bang thong kénh truyén c:ing léin. Trong thuc té de’

tin hieu co toc do bit la C tbps) thi can bang thong kénh truyén la: B (Hz)

Vi du: véri n = 4, fs = 44, lKhz thi:

Toc do truyén thong tin la : C = n x fs = 4 x 44, I = 176,3. 103 bits/s

? — C -— x 176,4.10’ = 132,3 Kliz

I.4 QUA TRINH BIEN DOI TIN HIEU MAU

RG , B

IG HOANG SON


Mot bfic tinh dupc chuyén tir RGB sang YUV nham gi:tin dung luong hut trit ciing

nhu truyén di, trong qua trinh giai ma, trirérc khi hién thi anh thi n‹i

nguoc lai th:inh RGB. Cf›ng thirc minh hpa qua trinh bién doi nhu sau:

Y —— k,R = (I — k — /:, )G + /:, B

duoc bién dfii

B — Y)

R

0.5(/? — I') 0.5 R — 0.419G — 0.08 I B1 —

0.299Nén ta cé* ma tran bién dfii tu RGB sang YUV nhu sau:

F

Ch

Cr

0.299

—11.169

h.3

0.587

—11.331

—11.419

0.114

II.5

—0.tl 8l

4

G

B

Thuc hién tirong ti r ta suy ra duoc ma tran bién doi tu YUV sang RGB nhu sau:

fi

G

B

1

= 1

1

0

— 0.344

1.772

I .402

— 0. 7 14

0

Y

Cb

Cr



DA TN. Téng quan vé chuén néii MPEG-4 H. 264/A VC va kha

Trong 16

I.5 CAC TIEU CHUAN LAY MAU TIN HIEU VIDEO SOKiéu lay mau cho :inh video cung la mot van dé kha quan trong ctia ky thuat nén :inh.


SVTH . NGUYEN QUANG HOANG NON

DA TN. Téng quan vé chuan nén MPEG-4 H. 264/A VC va kha ning ung dung trong thuc tien Trang 1 7

Trong kie’u 4:4:4, tong so mau can thiét la 12 mau, do dfi tong ' bbiitt la 12 × 8 =

96 bits, vii trung binh lit 96/4 24 bits/p ixel

Trong kiéu 4:2 :0, tin hiéu duoc quét xen ke, do dé* chi can thiét 6 mau, 4 mau cho

thanh phan Y, 1 mau cho thanh phan Cb, 1 mau cho thanh phan Cr, do do tong so bits

can thiét lit 6 × 8

48 bits, v:i trung binh 1:i 4874 12 bits/pixel.

Ta thay kiéu lay mau 4:2:0 giam mot so luong bits so voi 4:4:4, dé cfing chinh la ly

do ma kiéu lay mau nay duoc su dung pho bién.

I.6 MO HINH NEN TIN H@ U VIDEO

ngé ra ma héa

Luu tru anh

Hinh I. 4. Sa dé kh i nén tin h iéu Video cc hén

C:ic khoi chinh lit:

- Khoi nén dir thua th‹ i gran.

= Du doan chuyén dong

= Bit chuyén dong

- Khoi nén du thua theo khong gran.

=

=

=

Bién dfi i DCT,

DWT Luong tu héia

Xap xép lai trat tu va ma hfia Entropy

I.6.1 NEN TIN HIEU VIDEO

Tin hieu video co d:ii phfi nam trong kho:ing 0 -> 6Mhz, do th:inh phfin tan so cao chi

xuat hie’n o c:ic diréng vie’n ciia hinh anh nén nang liron g phfi rat it tap trung o in ten

tan



Bo ma hé›a ENTROPY'

Nén khong gran

DA TN. Téng quan vé chuan nén MPEG-4 H. 264/A VC va kha ning ung dung trong thuc tienTrang I R

Trong cac h( thong nén, ti so chinh la tham so quan trong danh gi:i kha nang nén

cua h( thong, ta gpi n1, n2 la

cfing thuc nhu sau:

' lupn b it cua tin hie tnroc v:i sau khi ne'n nén ta co

Nett n I n2 thi ta co C =J , va R 0 nghia lit khong co sir du th ira dtr liéii.

Néu n2<<n1 thi C ---› ×, R -—› 1, ta riot rang co su du thua dir lieu l6n.

Vi dp : n I I 00Mb/s, n2 20Mb/s thi C 5 : 1 , R 80%. Tirc la anh co sq du thua

lén, hieu qua nén dat 80%.

I.6.2 LU’QNG TIN TRUNG BINH (ENTROPY)Truoc khi nghién ciiu cac phuong ph:ip ne’n, ta can danh gia luong thong chu yéu

dupc ch ira dimg trong hinh anh, tir do xac dinh dung lirong tot thiéu can sir dung de

in iéu ta, triiye’n t:ii thong tin ve hinh anh.

Thong tin duoc

thiuc sau:

hiéu la a, va cé* xac suat p(a,) thi luong tin duoc xac dinh theo cong

Theo cfing thirc trén ta thay luong tin chira dung trong mot hinh anh se ti lé nghich

voi kh;i nang xuat hie’n ciia anh d‹i , nghia I:i su kién it xay ra sé chira dung nhie’u

thong tin hon va b:ing tong so luong thong tin ciia tirng ph:in tir anh.

Got lirong tin trung binh cua hinh anh la H(I) v:i duac tinh bang cong thiic sau:

X:ic suat ph:in bo cang nhiéu thi luong tin trung binh entropy cang nhfi. Entropy dat

gia tri cuc dai doi véri phan bo déu, do dé* néu mf›t

Entropy nho.

hiéu cé* xac suat lén se co so




Gia su ta cé* kich thuérc 4x8 pixels nhu sau:

21

21

21

21

21

21

21

21

2 1

21

21

2

95

95

95

95

169

169

169

169

243

243

243

243

243

243

243

243

243

243

243

243

Ta se xét cac do du thiia cua cac pixel trong anh, hoac gifra cac anh lien tiép nhu sau.

= Gia su cac m irc xém ciia tin hiéu hinh den trang doc lap thong ké voi nhau, dua

vao so 1i(u thong ké cp the la.

M irc

xam 21

95

169

243

So luong pixel

12

4

4

12

Xac suat.

3/8

1/8

I /8

3/8

Entropy cua phan

anh tinh nay la:

6

= —0,75 x 1,58 + 3 = 1,815 6//i I pixel

Tuy nhién, trong thirc té c:ic muc x:tin cua c:ic pixel khfi ng doc lap thong ké

voi nhau, nén ta co thé biéu dién theo tung cap pixel lien tiép nhu sau:

Giii tri cap muc

xam (2 1, 2 I )

(2 1, 95)

(95, 169)

So luong cap

8

4

4

X:ic suat

1 /4

1/8

1/8



DA TN. Téng quan vé chuan nén MPEG-4 H. 264/A VC va kha ning ung dung trong thuc tien Trang 2t1

4(169, 243)

(243, 243)

(243, 2 1) 4

H(x) -—— Io 4

4

/ ca p pixels

Ngoiii ra cfi n céi the b iéu dren theo phan chénh 1(ch mdc x:tin ciia 2 pixel

1i’en tiép nhu sau.

21

21

21

21

0

0

0

0

0

0

0

0

74

74

74

74

74

74

74

74

74

74

74

74

0

0

0

0

0

0

0

0

X:ic suat.

1/8

1 /2

3/8

Giii tri miuc

x:tin 2

0

74

So luong

4

16

12

H(x)

= —0,75 .i 1,58 = 3 = 1,4 I hits I pixel

Nhu vfiy, so luong tin trung binh Hi thiéu can thiét dé truye’n mot phan tu anh se khac

nhau, nghia la do du thua trong anh va gitra cac bfic :inh se’ phu thuoc vao c:ich ma

hé*a Entropy. Do déi can phai xem xét ky dé chon ra loai ma héia hiéu qua nhat.




CHUONG II.

CAC KY THUAT NEN VIDEO

II.I PHAN LOAI CAC KY THUAT NENNén video duoc chia thanh hat ho léin: Nén khfing ton hao va nén ton hao.

= Nén khong ton hao la guy trinh biéu dién cac ky hiéu trong dong bit ngufin

thanh dong cac ti r ma sao cho anh duoc khfii phuc hoan tot giong :inh goc,

ciic thuat toan chi phu thuoc vao cach thong ké noi dung dir lieu v:i thuong dna

trén viéc thay thé mot nhom cac ky tu triing lap boi mot nhom cac ky tu dac

biét kh:ic ngan hon ma khong quan tain de'n y nghia cua dong bit dir 1i(u,

nén dfii hci i phai céi thiét bi luu trit va duéing truye’n lén hon.

= Nén co ton hao, tuc la anh duoc khoi phqc khong hoan toan giong anh goc,

dang nén nay thich hop cho viéc luu tru va truyén anh tinh, anh video qua mot

mang co bang thong han ché. C:ic dang ne'n n:iy thuéng co h( so ne'n cao hon

(tir 2: 1 dén 100:1) va gay nén ton hao dir liéu va su suy gram anh sau khi giai

nén do viéc xoa va lam tron du liéu trong mot khung hay giua c:ic khung. No

lién quan de’n vi(c diing c:ic phe’p bién dfii tin hieu to mién nay sang mién

kh:ic.

thuat nén ton hao thuong su dung nhu: ma hoa vi sai, bién doi

luong ti r vfi huong, quét zig-zag, ma hoa Entropy.

cosin rot rac DCT,

II.2 QUA TRINH BIEN DOI

Tin liiéii Vide o vao

Gidi nep

Hinh 111. Mo hinh hi théng né n tin hao.


5 VTH . NGUYEN QUANG HOANG

SON

Gia i in:iD

Gifi i lir0ng tiI

hfia R

Bién doi ngir0c T '

Lir0ng tit hfiaBién doi T


II.2.1 DIEU XUNG MA VI SAI DPCM

C:ic phuong phap nén dung DPCM d¿a trén nguye’n tac phat h ten su giong nhau vii

kh:ic nhau gifra cac die’m anh gan nhau dé loai bfi cac thong tin du thira. Trong

DPCM chi co phan kh:ic nhau gifra mau — mau dupc truyén di, su kh:ic nhau n:iy

dupc cong

vrdeo van

Hinh II. 2. Bet

m‹i hoa va bé gia i mii DPCM

Vi du

Mau tin hiéu v:to

Sir kh:ic nhau

Dong bit dupc ne’n nhu sau:

115 117

2

2

116

-1

-1

117

1

1

118

I

1

117

-I

-1

115

-2

-2

116

1

1115

II.2.2 MA HOA BIEN DOINham bién dfii cac h( so trong mién thoi gran (video so), khfi ng gran 2D (bfic anh

tinh) thanh c:ic hé so trong mién tan so. Cac hé so nay it tuong quan hon co pho nang

luong

phan chi a th iinh c:ic MB bie’ii d ten c:ic mdc x:tin ciia diem anh. Vi(c phan kho i n:iy

sé lam giam duoc mot phan thcii gran tinh to an cac hé so chung, mat khac bién dfii

cosin d i véi cac khoi nho sC lam tiing dé chinh xac khi tinh to:in voi dau phay tinh,

gi:tin

ma trfin vuong cua mau sai

DCT dirpc in inh hpa nhu

sari: Y = AXA"

két qua cho ta mot ma tran Y la nhfrng h( so

Trong dfi A la ma tr:in h( so bie’n dfi i, c:ic thanh ph:in ciia A nhu sau:



M:i hfia entropy


A = C cos "’ "" Voi ' Néu i > 0

Phép bién dfi i DCT nguyén 4x4 cua chuoi ngfi vao X duoc cho boi cfing thuc

— cos 02

— cos0 2

— cos0 2

1 5«

8

1 7«

8— cos 2

— cos 22 8 2 8

2 8 2 8 2 8 2 8

— cos

Tuong duong voi:

cfing va tru trén c:ic ma

theo cong th irc sau:

H ' —— H ,' trong déi

H„ tuong irng voi c:ic

trén 2‘ x 2‘ truc giao, doi ximg, tuyén tinh. . . duoc dinh nghia

la ma tran NxN voi N - 2‘, in thuéng la cac gia tri 1, 2

,3 2x 2, 4x4, va 8x8, H, dupc tao ra ID phép to:in Kronecker

nhu© H, ....

sau: H, = j-j g

Vi du H H, ® H,

Véi H,=




II.3 QUA TRINH LUQNG TO

Sau khi thuc hién bién doi DCT, cac he so se duoc luong tu hoa dua trén mot bang

luong tu Q(u, v) vé i iU , v_< n-1, n la kich thuoc khoi. Bang n:iy dupc d|nh nghia

boi t lmg ung dung cu thé, cac phén tir trong bang luong tir co gi:i tri tu 1 dén 25 5

duoc goi la cac buoc nhay cho cac hé so DCT. Qua trinh luong tu duoc cor nhu la viéc

chia cac h( so DCT cho biroc nhay luong It.r tuong ring, két qii:i nay sau do sé dirpc

trim tron xuong so nguyén gfin nhat. Cac hé so nang luong thap nay, tuong trung

cho cac su

tinh xa c:ic tin hiéu ngfi vao dé chon duoc c:ic tu ma tuong rong mot cach tot nhfit cho

tap hop cac hé so duoc tao ra. Co 2 loai lupng tu hoa chit yéu:

II.3.1 LU’QNG TU’ HOA VO HU’©NGLuong tu tung gia tr] mot c:ich doc lap hay noi c:ich khac la :inh xa mot mau cua tin

hiéu ngo vao tao thanh mot hé so luong tu o ngfi ra. Dfiy la mot qua trinh ton hao vi

khi giai luong tu, khong thé xac dinh chinh xac gia tri goc tu so nguyén da duoc tain

trfin. Luong tu hoa thuan theo cfing th irc FQ = round(X/QP)

Luong tir hfia ngi roc theo cfing thuc Y = FQ*QP. Voi QP la buoc nhay luong tu. Vi du

qua trinh giai luong tu cho mot tin hiéu ngfi vao nhu sau:


5 VTH . NGUYEN

QUANG HOANG SON

X QP= 1 QP=2 QP= 3 QP= 5

-4 -4 -4 -] -5

-3

0

0 0

0 0 0

0 0

0

4 4 4

4 6


II.3.2 LUQNG TO HOA VECTOR

La mot qua trinh bie’u dién mot tap vector (moi vector gom nhiéu gi:i tri ) bang mot tap

" céi c:ic

goc. Vector luong tu sC duoc luu ci ca bfi ma hoa va bo giai ma, qu:i trinh nén mot buc

anh su dpng luong tu vector bao gom cac buoc sau.=

=

=

=

Phan chia buc anh goc thanh cac phan vung MxN

pixel Chon vector thich ung nhat tu bang ma

Truyén chi so ciia vector thich irng dén bo giai ma.

Tai bo giai ma, anh cau tmc lat sé xap xi voi phan viing da 1¿a chpn

vector luong tir.

Va so dfi khoi ciia lupng tu vector nhu sau:

Hinh II. 3. Quci trinh lirong tit vector

II.4 QUA TRINH HOABo ma hoa co chuc nang loai bo dfi du thua trong ciic ky tu o - ra luong tu hfia va

tinh xa cac ky tir nay th:inh cac tir ma tao thanh dong bit ci ngii ra bang cac loai ma héia

nhu: ma hoa du doan, ma hé*a VLC, ma hoa so hoc nhi phan, ma h‹i a theo hinh dang.

luong bit nguyén. Cac ky hieu co xac suat cao ’ dupc gan

cac ky hieu céi x:ic sufit thfip se duoc gan tin




thiéu chiéu dai trung cfi a t ir ma. Tai phia giai ne’n co cac chi d]nh ma giong nhau

dupc dung de’ khfii phuc lai cac gi:i tri dii liéu goc. C:ic loai ma héia VLC cc b:in nhu:

ma hoa Huffman, ma hoa RLC, ma hoa Exp-Golomb. .

TT.4.1.1 I Ié héa HeffmanMa hoa Hiiffman I:i ma hfia thfia man Hi uu tinh prefix v:i phirong ph:ip ma hé*a

thuéng dua vao mo hinh thong ké. Dua v:to dir liéu goc, nguoi ta tinh xac suat xuat

hi(n cua c:ic ky ty. Vi(c tinh to:in x:ic suat dupc thuc hién bang c:ich duyét tiiiin ½ t(p

goc to dfiu dén cuoi va cac ky tu nao cé› xac suiit cang cao thi tir ma cang ngan nen

gram chiéu d:ii trung binh cua tu ma mot c:ich rfi rét, ma hoa Huffman thuéng duoc

biéu dién duéri dang cfiy in:i nhir sau:

Hinh II. 4. Céy ma Hoffman

Cac buéic thirc hién ma her a Hu ffinan.

Bu‹ c I : C:ic ngufi n tin dupc I iét ké trong cot theo thir tir x:ic suat xiiiit hi(n gram dim.Bu‹ c 2: Hat tin

suat nhc› nhat dirpc hop thiinh tin phu moi co x:ic suat bang

II.4.1.2 Mii hoé mdc dpc chién déi RLCThong thuéng du liéu hay co su trung lap, chang han néu mot buc anh cé* cung mot

mau, do choi thi nhiing vii ng bén canh tinh d é ciing giong nhu vfiy. Do do cé› thé ma

hoa bang mot tir ma dac bi(t nhiim ch i b:to sq bat dau vii két thiic ciia gi:i tri lap lai,




': so trong bit 0 dirng tru‹ c do vii mirc cua no sau kh i luong tir, dé tao ra tir ma I:i

mf›t doi (level va run), trong do Level biéu thi gia tri cua bit v:i Run biéu thi so lan lap

lai ciia bit. Khi dir liéu truyén cci sir triing lap thi truyén tir ma nay thay cho no. Hinh

II.5. in inh hpa ma hoa RLC nhu sau

Run of5

Escape Code/ R eser v ed C ode)Hinh II. 5. Minh lioa md hé a

RLC

MA HHOOAA SO HI)CDiém bat loi cc ban cfia ma hfia dpc chiéu dai 1:i vi(c tao ra bang tra chira toan bo so

luong bit trén moi mau nén khfing that su Hi uu, vi so luong bit Hi uu nhat cho mot

tu tiiy thuoc viio nfii dung thong tin, in:i thuéng lit nhiing so rat nho. Do i voi nhiing

tu cé* xac xuat l6n hon 0.5 thi hiéu suat nén khfing cao, né* chi hiéu qua khi ma hé*a

nhfrng ky hieu nay bang mot tu ma bit don. Con ma héia so hoc thi dna vao xiic suat

cua not dung thong tin nén cfi n céi ten got la ma hoa so h pc thich nghi theo not

dung, ma hfi a so' hh ppcc ssiirr dduunng cc:aicc ddaacc ttiinnhh vvéé kkhhoonng

giiaann vv:ai tthhc‹rii giiaann ddee i‹rroocc lturoonng kkhhooaanng xac sufit. Néi bién

doi lufing dir liéu vao thanh mot phan so don lé, va su dung phan so Hi uu nhat dé ma

hfia dir lieu, do dfi hieu qua ne’n ciia no co thé dat mirc Hi da ina gi:tin chi phi dau

tu cho luu tnr.

Gia su ta co 5 gia tri vector chuyén dong (—2, —1, 0, 1, 2) va xac suat cua no nhu

bang duoi day. Moi vector se duoc gan mot nguong trong khoang tu 0.0 dén 1.0 tuy

thuoc vao x:ic suat xuat hién cua chung. Vi dii gi:i tri “-2” céi x:ic suat la 0. 1 sé nam

trong



DA TN. Téng quan vé chuan nén MPEG-4 H. 264/A VC va kha ning ung dung trong thuc tienTrang 2R

0.2 ’ trong kho:ing tu 0. 1->0.3 tirc la bang 20% . . . Nhu vay viec

chia vii ng

riéng cho tirng gi:i tri x:ic suat sé thuan ti(n cho vi(c ma héia.

C:ic vector sé dupc chia nho thanh cac khoang nho theo x:ic suat nhu sau:

()(()

cho chuoi cto ( , — , , nh sau:


5 VTH .

NGUYEN QUANG HOANG SON

Pham vi(L H)

Ky hiéu(LV H)

Khoangchia nho Chu thich

Cai pham vi bat dau 0-›L0Tim kho:ing con nrongring cho hiéu dau tien (0) 0J -›07

Cai lai khoang mcii cliokhoang con.

03-›07

Tim kho:ing con tuongring cho hi(:u tiép theo

(-1) 0. 1 ---› 0.3

Cai lai khoang bat daumcii nam trong khoang trucic dfi

0.34 --› 0.420.34 = 10%0.42 30%

Tim khoang tiép theo (0) 0J -›07

0. 364---›0. 3960.364 = 30%0.396 = 70%

Tim kho:ing tiép theo 0.9-L0Cai lai khoang bat d:inmcii nam trong kho:ing

0.3928 0.3960.3928 = 90%0.396 100%

Vector Xiic suat Luong tin trung binh = log (1/P) Kho:ing chia nho-2 0. I 3.32 0 ---› 0.-1 0.2 2.32 0. I ---› 0.30 0.4 1.32 0.3 --› 0.7

I 0.2 2.32 0.7 --÷ 0.9

2 0.1 3.32 0.9 --+ 1.0


1og2(1/P ) + log2(1/P.,) log2(1 /P ) + log2(1/P ) = 8.28bits

Totin bo chuoi dir li(u co the dirpc truyén di bci i bat ky mot gi:i tri phan so niio nam

trong khoang 0. 3928 -0. 396, gia su gia tri 0. 394 co thé duoc ma hoa nhu la mot phan

so co dau chain tinh bang tu ma 9 bit, do dé* chuoi vector (0, -1, 0, 2) se duoc nén big

tu ma 9bits.

Hinh II. 6. Minh hpa sv sap xép trong khoéng [0- I thénh nhiing vung nhé

hum f t Hi hiéti dirac ma hc›a.

Hieu qua cua in:i hé›a Entropy co duoc nhir mong muon hay khong la my thufic vao dfi

chinh xac trong xac suat cfia

Qii:i trinh giai init so hpc.

hi(u.



Qua trinli giai ma Pham vi Khoang chia nho Ky liie giai ma

Cai pham vi bat dau 0 ---› 1Tim kho:ing con tuong ring choliiéu dfiu tién 03-›07

Cai lai khoang mcri cho khoang con 0.3 0.7

Tim kho:ing con tuong ring cho liiéu tiép theo

034 042

Cai lai khoang bat dau mcri “‘trong khoang trué'c dfi0.34 ---› 0.42

Tim kho:ing tiep theo


II.5 TIEU CHUAN DANH GA CHAT LUQNG ANH NEND:inh gia ch:it lirong video thong qua cac gi:i tri cung cap béii hé thong xir ly, v:i viéc

suy gi:tin chat luong tin hi(u céi thé nhin th;iy dupc ( thong thu‹5n g chiing dupc so

s:inh voi tin hi(u goc. Qua hé thong ta co the’ thay dupc nhfrng thay dfi i ’ hinh

dang,

dinh chufin chat luong video la rat quan trong. De danh giii chfit luong cua b iuc anh

(hay khung anh video) ci dau ra ciia bo ma hoa, ngucii ta thuong su dqng cac tham so

truyén thong sau dé danh gia:+ Sai so binh phuong trung binh — MSE tmean .squarc error) dinh nghia cho

cuong do sai khac gifra :inh goc v:i anh du doan

Mean Squared Error . MSE ——

+ Ti so tin hie trén nh iéu dinh — PSNR tpeak /o signal /o noise rp/io).

(2’ I)' (dB)PSNR —— 10lo

' MSE

Trong dé NxN kich thuoc bfi chuyen dong

hé R, , tuong dug voi mau hién tai va vitng mau tham khao.

b so luong bit/ mau.

Thong thu6ng, néu PSNR _> 40‹IB thi he thong mat ngucii gan nhu khong ph

duoc giira anh ‘c va anh khfii phuc, tuc la anh nén co chat luong xuat sac.

biét

+ 30 dB < PSNR < 33 dB thl chat luong anh ne’n binh thuéing, mat nguoi

céi sir phan biét dirpc.

+ PSNR 30 dB thi chat luong anh nén kém.

+ Sai so tuyét doi trung binh - MAE (Mean Ahs ohi tc Ei ror)

Mean A hsolute Error . MAE

Tong cua cac sai so tuyét doi- SAE (Sum of Abs elute Err ore )

Sum o[ A hsolute Errors . SAE



Cai la i khoang bat dfiu mcri nam 0.364 0.396trong khoang truoc dfi

Tim kho:ing tiép theo 0.3928v 0.396 2


CHU©NG III. CAC CHUAN NEN THUOC HO MPEG TRU©CMPEG-4 H.264/AVC

III.I GI©I TH U VE L

!

CH SP PHAT TRIEN CUA KY THU A) T MPEG

1993 1995 1997 1999 2000 2001 2003 2005

Hinh III. 1. Qué trinh phét trien cua thu t nén MPEG qua céc giai doqn

Thuat ngfr MPEG viét tat ciia cum tu Moving Picture Experts Group la 1 nhom chuyén

nghién cim ph:it trién c:ic tiéu chuan vé hinh anh so v:i nén am thanh theo chuan

ISO/IEC tu nam 1988. Cho den nay nhé*m lam viéc MPEG da phat trién va phat hanh

nhiéu tiéu chub nén cho cac loai dug dung kh:ic nhau, nhung noi bat la ciic chuan

MPEG-1, MPEG-2, MPEG-4, va H.264/AVC. MPEG chi la mot te’n riéng, ten

chinh

III.2 CAC TIEU CHUAN NEN TR ©C MPEG-4 H.264/AVCVi thoi gran co han nén trong Do an tot nghiep nay, chung ta luért qua mot so nét riot

bat nhat cua 2 chuan MPEG-1 va MPEG-2, cfin chuan nén MPEG-4 part 2 la ne’n

tang ph:it trie’n cua chuan ne'n H.264/AVC ne’n co rat nhie’u diém giong nhau se

dupc trlnh

III.2.1 TIEU CHUAN MPEG-1Chufin MPEG-1 xufit hién vao 1 1/1992 la chuan khcri dau cho viec nén cac anh d

jug va day cung la nén tang ph:it trién cho c:ic chuan nén kh:ic trong ho MPEG, no

dirpc ménh danh la chuan “khéi d(i ng thiét b[ sit“. MPEG-1 dinh nghia mot tiéu

chuan



MPEG-4 v3(2001 )

MPEG-1 (11/1992)

MPEG-4 v2 f 1999/00)

MPEG-4 v1( 1998/99)

MPEG-2 (H.262)

(1994/95)

MPEG-4 H.264 (2003)


vao khoang 1 ,5Mbit/s, d phan gi:ii anh la 352 x 240 (30 frame/s) hay 352x288

(25 frame/s). Chuan MPEG-1 dirpc irng dung trong c:ic phan mém huan luye’n bang

may tinh, cac game hanh dong, video chat luong VHS, Karaoke..

Tin hiéu video so MPEG-1 bao gom mot tin hiéu ché*i Y va 2 tin hieu mau Cr, Cb voi

ty so lay mau la 2: I . Truoc khi ma hfia c:ic anh co the’ dupc sap xe'p lai theo trat tu

gi:ii ma moi vi bo gi:ii ma chi co thé giai ma dupc anh B sau khi da giai ma anh P va I.

Sau qua trinh giai ma, cac anh duoc se duoc sap xép lai nhu cdi.

Sau khi chon kiéu anh, bfi ma hoa se danh gia chuyén d cing cho moi khoi MB va tao

ra mot vector chuye’n dong cho mot anh P va 2 vector chuyén d jn g cho anh B.

Tity thufic kiéu anh ma tin hieu sai so duoc phat hién bang cach tim ra sai so gifra du

doan bu chuyén dong va dir liéu hién tai trong moi MB. Tin hiéu sai so du doan duoc

chuyén de’n khoi DCT 8x8 v:i bo luong tir dé tao hé so luong tit. Mot bo diéu khién

toc dé bit céi nhiém vu diéu chinh din liéu ngfi ra thong qua diéu chinh buoc luong tir.

Ciic he so nay duoc quét theo ma tran Zig-Zag va ma ho:i bang ma Entropy 'i méri

dua ra

=

=

Chi co kha nang quét lie’n tiép.

Biéu dren mau bang tu ma 8 bits, do chinh xac cua qu:i trlnh luong tu va bién

dfii DCT la 9 bits.

Su dung phuong phiip DPCM dé luong tu hoa cho hé so DC. Bu chuyén dong

cho cac MB 16x16 trong cung mot khung hinh hoac gifra cac khung véri nhau.

Do chinh xac dir do:in chuyén dong la 1 pixel.

Chufin MPEG-1 co 4 kiéu :inh dé la Intra, Predicted, Bidirectional va énh D

(DC coded p icture). No gan giong anh I nhirng ch i co thanh phan mot chie’u

o dau ra DCT duoc thé hién. No cho phép do nhanh nhung cho chat luong

anh thap.

=

=

=




III.2.1.2 Chi trtic dimg bit ciia MPEG-1Chuan MPEG-I dinh nghia mot kie’ii phan cap can tnic trong dtr lie Video va day

cung 1:i cau trtic dir li(u chung cho ca chuan MPEG ve sau. Cau trilc dir li(u nhu sau:

Khoi (Block) gom 8x8 pixels tin hieu choi va mau duac dinh nghia dung cho nén

DCT.

* To hop khoi (Macrob lock) gfim cac khoi Y, Cb va Cr tuong ring voi noi dung thong

tin cua mot khoi 16x16 pixel cua thanh phan chfii hoac khoi 8x8 ciia 2 thanh phan mau

trong hinh anh goc. Mot MB bao gfim 6 khoi trong do co 4 khoi Y, 1 khoi Cb va 1 Cr

nhu hinh ve’, cac khoi se dwac danh so thu tir bat dau bang 1 .

* Mang (Slice) gom nhie’u MB. Kich thuoc slice lori nhat la 1 anh, nhfi nhat la 1 MB

Th ir tp cac MB bén trong slice duoc xac dinh tu trat qua phai, trén xuong duoi. Phan

header cua slice china thong tin vé vi tri cua mang trong toan bfi anh va hé so cua bfi

luong tu. Slice rat quan trong trong vi(c d|nh ne’u

ma co thé bfi qua va tiép tiic o slice ké tiép. Nhiéu slice trén dong dir lieu cho phép

che giau 1o i tot hon vii dupc dung dé c:ii thi(n chat lirong hinh :inh.

* Anh (Picture): gfim nhiéu slice cho phép bo giai ma x:ic d|nh loai ma hoa khung.

Thong tin header dé chi thir tu truyén khung dé bo giai ma sap xép lai c:ic anh dung

th ir tu, ngo iii ra thong tin header cfi n chua c:ic thong tin ve dong bo, dfi phan gi:ii,

pham vi cua vector chuyén dong .

Nhéim :inh (GOP): gom nhiéu anh bat dau ti r anh 1. Chi biro diém bat d au cho

viéc bién tap va vi(c tim kiém. Phan header chua ma diéu khién v:i ma thoi gran 25 bit

cho thong tin dinh thoi.Cau truc cua mot GOP duoc mo ta bang 2 tham so:

- N: la cac anh trong GOP

- M: la kho:ing c:ich giira cac anh P-pictures.

Vi dp: Ta co 1 GOP nhu sau :

B I B2 13 B4 B5 B7 B8 P9 B 1 0 B 1 1 PI 2.

Tirc N = 12 va M = 3.




= Chuoi anh (Sequence): bat dau 1:i mot Sequence Header, 1 hay nhiéu GOP va 1 ma

ke't thuc chiioi End-of-Sequence. Thong tin header chira kich thiroc moi chie’u cua

buc anh, kich thuoc diem anh, toc do bit ciia dong video so, tan so anh, bo dem toi

thiéu can co. Chuoi anh va thong tin header con duoc goi chung la dong cc ban ES.

viu÷o s÷9uen«e

Hinh III. 2. C u trhc chti ii video MPEG

Tiéu chu fin ne’n MPEG-1 cho phép truy cap cac khung hinh ngau nhién video,

tlm kiém thuan nghich trén donh tin hiéu nén bién tfip va ph:it lai trén dong tin hieu

nén. Cac cfing cu cua no déu cé* trong cac tiéu chuan MPEG-2, nén MPEG-2 van co

the giai

III.2.2 TIEU CHUAN MPEG-2

“truyén hinh st”. MPEG-2 co thé tao hinh anh lori gap 4 lén MPEG-1 voi do nét cao

hon va ro hon (720 x 480 va 1280 x 720) cho phép ma hoa o nhiéu muc do phan giai

kh:ic nhau dap irng cho nhiéu Eng diing nhir ung dung 2-5Mbps trong SDTV v:i 6-

8Mbps trong DVD, 20Mbps trong HDTV, dac biet dupc ting dung trong truye’n hinh

‘i thiét




= Co kha nang quét xen ke va lién tuc, cho phép xap xi bu chuyén dong, xay

dung cc so du bao trén cc so manh.

Kha niing tach loi va gram dfi nhay tin hiéu nén doi voi cac Hi truyén, néu ty so

nén cao bi anh huong.

Do chinh xac mau vao la 10 bit. Dung lupng tu DPCM chinh xac cho cac hé so

DC.

Céi tinh tuong hop va co dan cao theo khfing gian, thoi gran.

Do phan giai uoc luong chuyén d cing la I pixel, 1 pixel.

=

=

=

=

MPEG-2 dinh nghia cac profile va cac level kh:ic nhau cho phu hop voi nhiéu loai irng

dpng. Co 5 dinh nghia profile va 4 level nhu sau.



MPEG-1 MPEG-2

Bang thong cr mirc trung binh (tfii da I .5

Mbits/sec)

Bang thong lori (Hi da 40 Mbits/sec)

I .25 Mbits/sec video 352 x 240 x 30 Hz

2 kénh am thanh 250 Kbits/sec Lén dén 5 kénh ann thanh (nhir surroundsound)

Khfi ng quét xen ke. Co thé quét xen kC.

Thich hop cho luu trfr CD.Co thé dung trong truyén hinh phan giai cao

HDTV

Simple Main SNR Spatially

4: 2: 0, 352 x 288

4Mbps

4: 2:0, 352 x 288

4Mbps, I, P ,B

Main4:2 : 0 720 576

15 Mbps, I, P

4:2:0 720 × 576

15 Mbps, I, P, B

4:2:0 720 × 576

15 Mbps, I, P, B

4:2:0 720 x 576

20Mbps, I, P, B

High

1440

4:2: 0 1440 x 1 152

60 Mbps, I, P, B

4:2:0 1440 x 1152,

60 Mbps, I, P, B

4:2:0, 4: 2:2

1440 x 1 152

80 Mbps, I, P, B

4:2:0 1192 x 1 152

80 Mbps, I, P, B

4:2: 0, 4:2:2

1 192 x 1 152

100 Mbps I P, B


III.2.3 TIEU CHUAN MPEG-4

Phién ban dau tién cua MPEG-4 xuat h ién viio 2/1999. Cuoi 1999 MPEG-4 v2 ra doi

va tro thanh tie’u chuan quoc te’ vao dfiu nam 2000. So voi MPEG-1, MPEG-2

thi MPEG-4 co nhiéu nfi i bat hon nhu hieu suat nén cao, van hanh trén cc sci nfii

dung. . .va ro rang co nhie’u irng dpng hon. MPEG-4 dinh nghia mot tie’u chuan cho

cac ting dung truyén thong da phuong ti(n, cac hinh anh, am thanh va dir li(u dfi

hoa va viéc tai hop chung trén thiét bi thu, hay riot cach khac no la su hfii ngo grin a

truyén hinh va Web. Dac diem chinh ciia MPEG-4 la ma hoa video va audio o toc do

bit rat

=

=

=

Duoi 64kbps|

Tu 64 dén 3 84 kbps|

Tu 384 de'n 4Mbps|Hon nfra mot dac diém quan trong cua MPEG-4 la cho phép khfi i phuc loi tai phia thu

nén rat thich hop cho c:ic kg dung truyén qiia moi truén g se xay ra Hi nhu moblie,

wireless. . . Chuan MPEG-4 I:i chuan quoc Ie dari tién dinh nghia cac VOP in:i trong

do cac phan cua mot canh co thé duoc thao tac riéng re trong khi nhirng phan khac

van khong doi. Nhfiiig profile va level khac nhau trong MPEG-4 cho phép su dung

toc dfi bit lén dén 3 8.4Mbps va vi(c xu ly chat luong studio lén dén 1 .2Gbps.

MPEG-4 dat yéu cau ting dqng cho cac dich vp noi dung video co tinh tuong tac

va cac dich vu tniyén thong video trirc tiép hay luu trfr.

Cac doi tuong khac nhau trong anh goc dwac ma héia va truyén di mot c:ich riéng bi(t,

nhir ta da bie't khong co mot phuong ph:ip ma hé*a n:to lit to i uu ho iin to:in. DCT

va phép lupng tu ch i toi uu v‹ i cac irng dpng co bang thong han che', cac anh céi do

choi it thay dfii, nhung voi anh nhiéu chi tie't, co kich thuoc nhfi thi khfing Hi uu.

Lay vi du néu mot canh co chua cac dong text, néu ma hoa bang MPEG-1, MPEG-2

thi se khong hi(u qu:i vi no ch i xem dé* nhu la chi tie't anh thong thuong.

Trat lai, MPEG-4 cho phép giai ma luong text két hop voi video va cac thong tin trong

lufing bit co thé hién thi nhiéu dang khac nhau tuy thufic vao lua chon cua nguoi su

dpng vi du nhu tuy chon ngon ngfr... ne’n mang lai hi(u suat cao hon.




Tuy nhién MPEG-4 cung co mot so nhuoc die’m la bo

ma ph:ii co kha nang giai

ma he't tat c:i cac lufi ng b it in:i no ho trp va co kha nang két hop. Do dfi phan cling

bo giai ma MPEG-4 phuc tap hon MPEG-2 rat nhiéu. Cung chinh vi vay ma cac

nha

III.2.4 SO SANH DAC DIEM NOI BAT CUA CAC CHUAN NEN

Trong tie'n trinh ph:it trién cua chuan ne'n MPEG, cac chuan nén sari ra doi 1:i sir ké

thira va phat trién ciia chuan triroc, chinh vi vay cac chuan nén tién tién hon phai co su

phfin cap, mém deo dé céi thé dap uiig c:ic ung dung cua chuan nén cfu. B:ing sau so

siinh su kh:ic biét va su Hi uu giua cac chuan nén thufic ho MPEG.

Hinh IV. 7. So sénh sit toi iru giiia céc chuan nén



Standard MPEG-1 MPEG-2 MPEG-4 H.264MB size 16 x 16 16 x 16 16 x 16 16 x 16

Block size 8 x 8 8 x 8 16 x 16, 8 x 8l6x16, 16x8, 8xl68x8,8x4,4x8,4x4

Transform DCT DCT DCT, DWT 4x4 Int transform

Entropy coding VLC VLC VLCVLC, CAVLC,

CABACME, MC Yes Yes Yes 41 MVs/MB

Pixel accuracy ? pixel ? pixel ? pixel ?‹ pixel

Referenceframes frame I frame 1 frame 5 frame

Picture type I, P, B I, P, B I, P, B I, P, BTransmission

rateI .5 Mbps 2- l5Mbps 64kbps-2Mbps 64kbps-150Mbps


CHUONG IV. CHUAN NEN MPEG-4 H.264/AVC

IV.1 TONG QUAN VE CHUAN NEN MPEG-4 H .264/AVC

IV.1.1 LJCH SP PHAT TRIEN CUA MPEG•4 H.264/AVC

Tir c:ic bo ma ho:i don gran, hoat dong tot nhung dfii khi co mot so hinh anh ma né*

khfing the nén duoc, diéu nay da thuc day cac nha thiét ké phat trién cac cfing cu nén

moi dna trén nén ciia ciic chub truoc, trong déi hiéu qu:i ma héia la van dé duoc quan

tain nhat, vi the' MPEG-4 ra d‹ i la die’u t:it yéu trong tie'n trinh ph:it trién. Sir ph:it

trie’n cua MPEG-4 H. 264/AVC trai qua nhiéu giai doan nhu: MPEG-4 part 2 duoc

ISO cong bo vao 1999, no la tiéu chuan cho nhirng ung dung truyén thong da

phuong tién voi toc do bit thap va cho Eng dung truyén hinh quang b:i trong tuong

lai. Tuy nhiéu chfit lupng cua no van chira dat dupc nhu mong muon, chinh vi vay

ma ISO/IEC (MPEG) va ITU da cung nhau hop tiic va thanh lfip nhom Joint Video

Team (JVT), de nghién c liu phat trién chuan ma hoa tién tién la Advanced Video

Coding (AVC). Va dén 2003 da cho ra doi chuan MPEG-4 part 10, te’n theo tie’u

chuan ISO/IEC 14496-10 va H.246 AVC trong ITU hay con gpi Ta MPEG-4

H.264/AVC, got tat la H.264/AVC.

Phién ban thu 2 duoc to chuc JVT phat trién mo rong va phfi bién véri tén got Fidelity

Range Extensions (FRExt) co do phan giai video mang tinh trung thuc cao dupc cong



Coding Tools High High 10 High 4:2:2 High 4:4:4

Main Profile Tools X X X X

4:2:0 Chroma Format X X X X

8 Bit Sample Bit Depth X X X X

8x8 vs. 4x4 Transform Adaptivity X X X X

Quantization Scaling Matrices X X X X

Separate Cb and Cr QP control X X X X

Monochrome video format X X X X

9 and 10 Bit Sample Bit Depth X X X

4:2:2 Cliroma Format X X

11 and 12 Bit Sample Bit Depth X


Bdng IV. 1. Nhitng trong H. 264/A VC FRExt.

Su mo rong nay cho phép ma ho:i chat luong hinh :inh cao hon bang vi(c tang do

ch inh x:ic chiéu sau bit lay mau va thong tin do phan gi:ii mau, bao gfim c:ic cau truc

lay mau nhir YUV 4:2:2 va YUV 4:4:4. Ngoai ra con bfi xung mot so d*ac tinh

nhu chuyén mach thich nghi gi ira phép bién doi nguyén 4x4 v:i 8x8, bo ma hoa theo

giac quan dna trén ma tran luong tu, ky thuat ma hoa ton hao trong khoi va ky thuat

loc

IV.1.2 CAC PROFLIES VA LEVELS TRONG H.264/AVC

De tao diéu kién cho nguoi su dung lua chon cfing cq H.264/AVC, cac thiét bi duoc

chia thanh cac nhom cf›ng cu iprofile). Moi profile lai c‹i cac mirc levels khac nhau thé

hi(n mirc dfi phirc tap xir ly tinh to:in dtr 1i(u cua “n cii do (thong qiia viéc x:ic dinh

toc do bit, con so Hi da cfia cac doi tupng trong frame, do ph irc tap cua qu:i trinh

giai

IV. 1.2. 1 CAC PROFILES

H. 264/AVC dinh nghia 4 profiles nhu sau



H.264/AVC Profiles

BASELINEEXTENDED[Streaming)

MAIN

(Bro‹rdcnst)

HIGH

I Slices I Slices I Slices I Strees

P Slices P Slices P Slices P Slices

CAVLC CAVFC CAVLC CAVLC

4x4 Transtorm 4x4 Transti›rm 4x4 Trans torm 4x4 Transtorm

Weighted Prediction Weighted Weighted

B Slices B Slices B Slices

CABAC CABAC

Quantization

8x8 Transform

4:4:4 Chroma Format

Residual Color Transform

Pred ictive Lossless Coding


Bang ID. 2. H. 264/A VC Profiles

IV.1.2. 2 CAC LE VELS

Trong H.264/AVC dinh nghia 16 level xac dinh cac gioi han trén cho kich thuoc anh,

toc dfi xir ly, kich thuérc viing nho dém, toc dfi bit video.


5 VTH . NGUYEN

QUANG HOANG SON

tvlax video bit rate (\/CL) t‹›r High 4:2:2 and

I+igh 4:4.4 Pre‹1i ctive

£:samples for high resolution @

6ame rate

1 1485 99 64 kbit/s 80 1‹bit /s 192 kbit/s 256 1‹bit/s 128 96½«30. 9 (8)176x144 4 15.0 (4)

. (7 44 . (4)

1.1 3000 396 192 Mbit/s 240 Mbit/s 576 Mbit/s 768 Abide

1.2 6000 396 384 kbit/s 480 kbit/s 1152 kbit/s 1536 t‹bit/s 320×240 ×200(7)352×288#4l 5 2(6)

1.3 11380 396 768 kbit/s 960 kbt t/s 2304 kbit/s 3072 k btt /s

2 11880 396 2 MbiCs 2. 5 Mbit/s 6 tvlbi Es 8 MbiVs 320×240×360(7)352×288Q©3006)

2.1 19300 792 4 Mbi t/s i Mbit/s 1 2 M bit/s 16 M bit/s 352×?76×2? 0(6)

352 480[§6L4(I2)3J2 J76;§J. (0)720×4B0Q«300()720×576#425 0(5)4 . 0 (

6 66.7 ( )0 0 0.0 (

I 2R0x720#&600(5)7?80 1 0?4@42. 2(4)

ASO A

FMO M

Redundant Slices Redundant Slices

Data Partitioning

SP Slices, SI Slices


H. 264/AVC tro thanh mot tiéu chuan xu ly tot voi toc d bit thfip hon so voi cac chuan

cfu ma khfing qua phuc tap trong khi thiét ké. Mat khac néi cling co tinh mém déo cho

phép hoat dong trén nhiéu he thong va mang khac nhau ma van co toc do bit, do phan

giai,...nhu nhau. H.264/AVC dupc irng ding rong rai trong nén anh ky thuat truyén

hinh so, cac uiig dung ve dfi hoa va Video tuong tiic 2 chiéu nhu Games, Video

Conferencing, World Wide Web hoac cac ring dung nham phan phat dir lieu Video

nhu truyén hinh cap, Internet TV. . . H.264/AVC tro thanh tiéu chuan cfing nghé

trong qu:i trinh san xufit, phan phoi va truy nhap vao hé thong Video.

Ma ho:i H.264/AVC ngoai viec quan tain dén hieu qu:i ma hoa giong nhu cac tiéu

chuan ma hoa tru‹ c day, cfin bfi sung them mot so cong cp cho c:ic chuc nang kh:ic

nhu: Ma hoii ciic doi ti rong co hinh dang bat ky, nén hiéu qua c:ic tin hieu video lién

tic v:i hinh anh tre’n mot pham vi rong cua ty lé bit, phfin cap ’ khfi ng gian, thoi granv:i ch iit luong, khii nang truyén dan tot trong

nghiet.

IV.2

=

NHUNG DAC TINH NOI BAT CUA CHUAN NEN H .264/AVC

Du doan khfing gian dinh huéing trong kiéu ma hfia Intra: hfi tro Hi 17 kieu dp

do:in, tain cho vi(c du do:in mau dupc chinh x:ic hon, dat hiéu qua ne'n cao hon.

Bit chuyén dong voi kich thuoc nhc› co the’ thay doi. Tiéii chuan nay mang lai

sir mém déo cho su lua chon kich thuérc va hinh dang, kich thuoc bu chuyén

dong

=



4 245760 8192 20 MbiEs 25 Mbit/s 60 tvlbi Es 80 Mbit/s1280 720½68. 3 (9)

2048x1024 «30.0 (4)

4.1 245760 8192 50 tvlbi Es 62.5 Mbit/s 150 MbiCs 200 tvIbit/s1280 720½68. 3 (9)

(4)2048 1024 «30.0 (4)

4.2 522240 8704 50 MbiCs 62. 5 Mbit/s 150 Mbi t/s 200 Mbi t /s 1 920×1088Qd640(4)204B×10B8/«600(4)

9 Skills 6 .7 Skills Skills 4 Skills

. (4 .0 (

88@67. (60 9 0 0. ( )6 l 6 6. ( )


chuye’n dong ¼ lam giam tinh phirc tap cfia xu ly riot suy so voi c:ic tiéu

chuan truoc do.

Bit chuyén dong v‹ i nhie’ii hinh tham kh:to. Do camera thay dfii géic quay

hay chuye’n qua lai gifra cac canh, vi(c doan triroc cac chuyén d rig la rat

phuc tap ta can phat co nhiéu frame tham khao dé nang cao hiéu suat va

chat lupng.

H. 264/AVC cho phép su dung Hi da 32 frame tham khao trong khi MPEG-2

chi sir dung 2 frame tham khao mang tinh chat chu ky. Bit chuye’n dong

voi nhiéu hinh tham khao se la chain qua trinh ma hé*a va giai ma nhung se

tang chat luong anh véri cung ti so nén.

Tach riéng hinh tham khao va hinh hién thi: o cac tiéu chuan truoc cé* su phu

thuoc gifra hinh tham khao va hinh hién th|, con trong H.264/AVC bo ma héia

co thé chon hinh :inh dé tham khao gan nhat voi hinh :inh duac ma hfia cho muc

dich tham khao du doan nén co thé hién thi v6i tinh tinh hoat cao, do do khoang

th‹ii gian tré sC duoc loai bo.

Gi:tin du th ira vé khong gian tot hon: sir diing phe'p bién doi nguyén thay vi

sir dung phép bién d éi DCT nhu MPEG-2, lam giam anh hucrng do sai so lam

tron. Luong tu hé*a thich nghi: trong qua trinh ma hoa voi toc dfi bit bién thién,

khi su dung luong ti r hoa thich nghi, moi frame co thé duoc nén voi nhirng

bfi luong tu khac nhau phu thufic vao ban chat hinh anh cua chung thong qua

viéc diéu khién toc do bit. Vi du nhirng phan chuyén dong hay nh ilng phan

hinh anh sam

1éin hon (do nén cao

hon, dung luong nho hon), nhfrng phan hay duoc hé thong mat nguoi chu y

nhiéu hon se dupc xu ly voi hé so luong tu thap hon (dc› nén nho hon, dung

luong 16n hon). H.264/AVC cho phép sir dpng tot 52 muc lirpn g ii trong khi

MPEG-2 chi co 31 m iuc.

Su dung bo loc tach khoi: Trai nguoc voi bfi tién xu 1y hay bfi hau xu ly, bo lpc

t:ich khoi duoc :ip dung trong suot quit trinh ma hoa trén moi frame don le, tién moi n:iy dupc hi(n tuong két khoi lam :inh huong de’n chfit




luong hinh anh, dac biét la voi toc do bit thap. Nhung toc d ma héia, gi:ii ma se

bi gram sut.

Kiéu du doiin trong so. H.264/AVC céi the ho tro qua trinh mo dan hay Hi dan

khung hinh trong nh irng doan film co hiéu ting mo dan (nhfrng frame dén sau

rat giong so voi nhtrng frame ngay tru‹ c no, chi co sac do la khac mot chut),

Ma hfia Entropy th ich nghi: trong H.264/AVC st dung 2 phuong phap ma hé*a

phuc tap hon déi la CAVLC va CABAC thay vi bién dfii VCL tinh trong

MPEG-2, nén hieu qua ma héia clung cao hon ro rét.

dac tinh tain tang cuong kha nang chong sai so va mat dir 1i(u nhu

Thong so cai dat cau truc: tfip hop c:ic thong so nham tang cuéing cho thong tin

dau mdc cfi a qua trinh truyén dupc hieu qu:i hon. €i nhfrng tiéu chuan truoc,

néu mat mot s6 thon tin quuaann trong nhu thong tin dau muc cua chuoi :inh

sC anh huong rat lérn dén qua trinh giai ma. Con trong H.264/AVC thi cac

thong tin nay dupc I:ich riéng tao tinh linh hoat va chuyén dpng hon.

Cfiu truc cu ph:ip cua NAL: Moi cau truc cu phap trong H.264/AVC duoc dat

trong go i dtr liéii vat 1y gpi la NAL.

Ho tro ky thuat sap xe’p thir tu mém déo FMO va sap xe’p th ir tu slice bat

ky ASO

Hfi' tro 22 anh chuyén mach dong bo SI/SP va ky thuat phan vii ng dir 1i(u

(Data Partitioning).

nang ciia H. 264/AVC co thé tong hop trong nhirng ch irc nang chinh nhu sau:

Hiéu suat nén: hiéu suat nén la mqc tiéu chinh trong MPEG-1, MPEG-2. Do do

o H.264/AVC, vi(c c:ii tién h i(u suat ma hoa c:ic lufing dir lie sé mo rong kh:i

nang Eng dung cfia no trong thuc tien. Tiéu chuan H. 264/AVC tiét kiém lén

dén 50% toc do bit so v‹ i MPEG-1, MPEG-2, MPEG-4 part 2 khi ma hfia cung

mot cap do.

Kha nang tuong t:ic: cho phép ngucii sir diing céi the tuong I:ic trijc tie'p c:ic nfii

dung chuong trinh dang xem.




= Kiéu truy nhap phfi bién: tang cuong kha nang chong Hi trong moi truéng khac

nghiét, cung cap ciic ‘n cu can thiét dé giai quyét viéc mfit mat goi dir liéu

trong kh i truyén trong mang gfii v:i Hi bit trong moi trircr ng khfi ng day.

Ké tfi déi de’n nay H.264/AVC lién tpc dwac car tién va su thanh cfing ciia

H.264/AVC thé hién ro trong viéc giam toc dci bit cho ciic rong dung khac nhau nhu

sau:

= Doi vert dich vu hfii thoai hoat d cing tot o toc dfi < lMbps voi dfi tré thap.

= Do i voi dich vu giai tri hoat dong tot c› toc do I - 8Mbps v‹ i do tré trong kho:ing

0.5 -2s.

> Tniyén hinh qii:ing b:i qua cap, v( tinh, mat dat, DSL.

DVD cho truyén hinh phfin giai cao.

> Truyén hinh theo yéu cau qua cac kénh khac nhau.

IV.3 KY THUAT NEN VIDEO H .264/AVC

IV.3.1 GIAI THICH NGUYEN LY HOAT DONG CD BAN

Anh his“n tai

17 kiéu du doan Intra

Intra

Bindoi nyvoo

Hinh IV. 1 Pa do kh i ma hoa H. 264 'AVC

Mot bfic anh ngfi viio gom co 3 thiinh phan mau cc ban R, G, B, sé dupc bién dfii

thanh Y, U, V sau do anh sé duoc tach thanh cac khoi MB co kich thuérc la nxn voi

n=2, 4, 8, va 16 tii y thuoc vao dfi phiuc tap cua buc :inh. Kich thuoc nho 2x2 se gi:tin



Bién doi


toc do duong truyén nhung thoi gian ma hoa se’ lau hon. Anh dau tién hoac diém truy

nhap ngau nhién thi dupc ma hoa Intra, c:ic anh cfi n lat ciia day dung du doan bu

chuyén dong tu cac anh da ma hoa truoc dé ma hoa Inter. Dir liéu tu cac MB can duoc

ma hoa se duoc dna dén ca bo trir va bo du doan chuyén dong. Bo du doan chuyén

dong sé so sanh c:ic MB mcii dirpc dna v:to voi cac MB tham kh:to da dirpc dira

vao truoc dé , ré i tim ra cac MB trong frame tham kh:to gén giong nhat voi MB can

dw ac ma hoa nay. Bo du doan chuyén dong se tinh toan vector chuyén dong, vector

nay se dac truiig cho su dich chuyén theo ca 2 chiéu ngang va thang d i rng cua MB

moi can dwac ma hfia so voi frame tham khao. Bo dp do an chuyén dong cung d ci ng

thoi giri cac MB tham khao toi bo tru voi MB méri can duoc ma hoa, de tao ra cac sai

so tién doan dac trung cho su sai khac gifra MB du doan va MB can ma hoa. Tin hiéu

sai khac nay se dupc bién doi nguyén de’ tao ra tap hé so bién dé i sau dé dupc dna

qua bo luong tu de lam giam so luong bits can truyén. Dén day, ciic he so luong ti r

duoc chia tain 2 huérng, mot hu6ng sap xép lai va dna vao ma hoa Entropy, tai day

so bits dac trirng cho cac hé

giai luong tu va bién d fii nguoc de tao ra khoi sai so. Sau d éi dna vao bfi cfing voi

tin hiéu du doan va duoc loc tach khoi trong vong nham lam giam hiéu ung khoi tao

thanh

:inh cau truc lai, dupc luu trfr nham m pc dich uoc luong v:i dir doan chuyén dong. Dir

liéu tai dau ra bo ma hé›a Entropy se két hop voi vector chuyén dong va cac thong tin

kh:ic nhu thong tin vé anh I, anh P, va anh B rfii truyén ra ngoai kénh truyén duoi dang

dong bit nén ciia cac don vi NAL, gmt Hi bo giai ma. Trong H.264/AVC, co ho trp 5

Ann

NAL

Bit chuyén dong


Dau tién bo giai ma Entropy nhan dupc cac dong bit nén tir NAL, mot mat se’ giai ma

Entropy de I:ich thong tin dari muc va vector dir doan chuye’n dong dna vao bit chuyén

dong, mat khac cac hé so DCT duoc giai luong tu va bién dfii nguoc IDCT dé bién tin

hiéu t ir mién tan so thanh tin hiéu o mién khfi ng gian, cac hé so bién doi nguoc thu

dupc sé con v‹ i tin hiéii dir do:in. Sau dé* mot phhaann dirpc dna quuaa bo l pc t:ich

khoi de loai bfi hién tuong nhieu truoc khi dna vao luu trii, ph:in cfi n lai dupc su dung

cho muc

IV.3.2 KHOI NEN THBI GIAN

De truyén mot birc anh dong lén man hinh, thuc chat may ph:it hinh sé truyén mot

chuoi c:ic anh tinh co t pa do chénh l(ch lien tiép v‹ i toc dfi kh:i cao 30 anh/s doi v‹ i

h( NTSC va 25 anh/s doi voi hé PAL. Do cam nhan ciia mat nguoi va hién tuong luu

anh trén ’n macnen ta xem nhu néi dang chuyén ding lien tuc trén man hinh, do do

mot frame tai th‹ i diem nhat dinh vii c:ic frame dirng truoc hay sau do cc ban la

giong nhau, chi co khac nhau vé tpa dfi cua phan tu chuyén dong, an ddeenn su du

thua vé mat thoi gian. Nén theo thcri gian co nghia la bo qua phan thong tin giong

nhau giira ciic

IV. 3.2.1 of doén in I chléu (mii hoa érih Predlctlon).

Khi mot doi tirpng chuyén dong chain thi khoang thay dfii toa dfi ciia 2 frame lién tiép

la nho, khong vuot ra ngoai vung tim kiém va hé thong se su dqng phuong phap du

doan thuan hay cfin got la du do tin mot chiéu de tao :inh P. Anh P chua din liéu

anh, vecto chuye’n dong ciia anh hién tai va anh trtroc dfi hoac c:i hai, anh P co thé sir

dung cac anh I hoac P ngay sat phia truoc no dé bit chuyén dong va tién doan cac

anh tiép theo nén ta co cfiu truc anh IPPPPIP. . . Moi khoi anh trong anh P céi the duoc

ma theo kie’u tién doan hoac ma mot cach doc lap, do no su dung ne’n theo khfing

gian va thoi gian nén hi(u qua ne'n cao hon so v‹ i anh I.

Ngoai cac kiéu bu chuyén dong trén, MB P cé* the duoc ma hoa trong kiéu SKIP. Doi

véri kiéu ma hoa nay, ca tin hiéu loi du doan luong tir hoa fan vector chuyén dong hoac

tham so de’u khong dupc tniyén di va kiéii ma héia nity rat co lpi trong viéc ma hoa mot

buc anh ton ma khong cé* su thay dfii chuyén dong, chi ton mot vai bit de ma hoa.




tao énh ¼colachodU doannAp

IV. 3.2.2 of doen hat chién( mii hoci Huh Bidiriectiona I Prediction)

Khi doi tuong chuyén dong nhanh thi khoang thay doi toa dfi cua 2 frame lién tiép la

lén, vuot ra ngoai vitng tim kiém, khong thé thuc hién du doan bit chuyén dong tu cac

khung hinh truoc dwac, khoi diém anh bie’u dren d i tuang chuyen d jug st dupc ma

hoa dang anh I va su dung ky thuat bu chuyén dong theo 2 hu6ng th‹ii gian con got la

nfii suy bit chuyén dong. Trong ky thuat bu chuyén dong theo 2 huéng, anh hién tai se

dwac dir do an dna trén cc so thong tin ve hinh anh truoc dfi va sau dfi dé tao thanh

anh B, do dé hiéu qua nén se cao nhfit. Phuong phap du doan 2 chiéu nay co uu diem

nfii bat la cé* thé du doan ngoai viing tim kiém nhci cac khung hinh tiép theo ma

phuong ph:ip dir do:in mot ch iéu khong thuc hi(n dupc, ngo:ii ra phuong ph:ip nity

con cho ty so nén cao hon, giam nhiéu trong khung hinh hién tai bang muc nhié'uu

trun binh cua frame truoc va frame sau. Trong chu fin MPEG-2 anh B khfing bao

gio dupc ding dé tham khao khi du do:in anh kh:ic. Kh i dfi, ma héia co chat lirong

thap co the’ dung nhie’u anh B boi ciic chi tiét mat in:it khfing anh huong dén anh du

dotin ké dfi, con trong



Dit doén chuvé n dci ng

Da nh giachuvén donv


Hinh IV. 4. So do nzuvcn lv nén anh B

IV. 3.2.2.b Bh chuyén dc›ng trong cac slice B

Trong Slice B, co 4 dang dir doan lnter khac nhau duoc ho tro: dir doan list 0, list 1,

hai huéing va dir doan truc tiép.

Du doan List 0: chi co anh tham kh:to tru‹ c do dirpc dung dé d¿ do:in, anh hi(n tai

duoc danh chi ' n, tiép theo la nhting buc anh ci vi tri n-1, n-2,. . ., tiép theo la b irc

anh o vi tri n+1, n+2,.. v:i chi mot vector chuye’n dong duy nhfit dupc truyén di.

Trong du doan list 0, tin hiéu du do:in duoc tao ra nho bit chuyén dcing :inh khao dau

tién da luu trong bo nho dém, con anh tham khao thu 2 duoc su dqng cho viéc xay

dung tin hiéu du do:in néu su dung du doan list 1.

Du dotin List 1 : chi céi anh tham kh:to sau dé duoc su dung dé du doan, anh hién

tai duoc danh chi ' n, tiép theo la nhfrng anh o vi tri n*1, n+2,. . . va tiép theo la nh

irng



Pha n vii ng Mo ta kié u du’ doa n16 x 16 True tiép, list 0, list 1, 2 hu’éng

16 x 8 ho:i c 8 x 16 List II, list 1, 2 hu’fi ng

Tru’c tiep, list 0, I ist 1 , 2 hufing


Vi dp: Bo giai ma H.264/AVC chua 6 buc anh tham khao voi cac thu tu 123, 125, 126,

128, 1 29, 130. Buc anh hién tai 1:i 1 27, tat ca 6 birc :inh tham kh:to dupc d:inh dau

nhu trong list 0 va list 1. Thu tp ciia cac buc anh nhu sau:

Du do:in hat huong: ca 2 anh tham kh:to tru‹ c v:i sau déu dupc sir dpng de d¿ doan

va 2 vector chuyén dong duoc truyén di, két qua du doan duoc nfii suy tii ca 2 gia tri

tham khao bang tri trung binh trong so cua tin hieu du doan bu chuyén ding list 0 va

list 1 . So luong anh tham kh:to dupc st diing tiiy thuoc v:to do phuc tap cua :inh hi(n

tai, qua trinh du doan hat hu6ng duoc minh hoa nhu sau:

Hlnh IV. 5. Céc min elm doén trong énh B

Du doan tri rc tiép: C:i 2 :inh tham khao triroc va sau déu duoc su dung dé du

dotin. Trong slice B hoac phan vung dupc ma hfia o ché d trw.c tiép thl khong can

truyén vector chuyén dong cua cac anh truoc va sau, thay vi bfi giai ma phai

tinh toan vector du doan list 0 va list I dua vao nhirng vector duoc ma hoa truoc

do thi chi



Chi so List 0 List 10 1 26 1 281 1 25 1 292 123 1303 1 28 1 264 129 125


lieu du thira. Loai MB SKIP trong slice B ciing dupc cau triic

tie'p.

Ng uyéii IQ cc sé ctia Mode trvc tiép

de“ du do an tri c

Vi tri cua MB hen tai

PO BI P2 P3

Hinh IV. 6. Nguyén Ij bu chuyén d‹›ng tire tiép. Vector chuyén dong trade

.f t MVJ,“ MVh fetch ra tir MV trong VOP tham ch ié’u ngiracDoi tuong video hién tai trén hinh 1V.6 la loai anh B 1. Bo gi:ii ma da biét tri roc

vé VOP tham chiéu nguoc P3 va to chuc cac vector chuyén dong cua né* truoc khi

VOP hién tai dwac giai ma. Trong mode trirc tiép, nhfrng hiéu bie’t ve’ c:ic vector

chuye’n d cing nay duoc svi dung de lai cac vector chuyén dong truoc va sau cho viéc

du doan MB hién tai. Hon nfra, co su dqng vector chuyén dong cua MB xap xép thu tp

(MB cé ciing chi st ch iéu die vé ch iéu ngang nhir MB trong h inh ve) trong VOP

P3 tham chiéu nguoc. Dé lay duoc cac vector chuyén dong cua MB hién tai thi

vector chuyén dong phai dupc phan cap, tuy thuoc vao thoi diém cua :inh B giira 2

VOP tham chiéu. C:ic h( so phan cap dupc tinh to:in t ir thoi gian khac nhau gitra 2

VOP tham chiéu v:i

=

=

TRb - thoi gian hién thi (VOP hién tai) - thcii gian hién thi (tham chiéu truoc)

TRd - thoi gian hién thi (tham chiéu nguoc) - thoi gian hién thi (tham chiéu

truoc)

luc do, vector chuyén dong Delta (MVD) duoc cong thém vao. Tiép theo quitCung

trinh nay, cac vector chuyén dong B-VOP dupc xac dinh nhu sau:

= MVF = TRb/TRd. MV + MVD

= MVB = (TRb — TRd).MV + MVD

Vay doi v‹ i vi dp trén thi ta céi




= MVF - 1/3 MV MVD

= MVB = -2/3 MV MVD.

Doi vcri bu chuyén dcing trong c:ic B-VOP chi co thé su dung mode lMV, co nghia la:

chi mot vector chuye’n dong duy nhat co thé dupc truyén di cho mot MB cho moi mot

huong du doan. Nhung trong mode trirc tiép neu MB tuan tu trong VOP tham chiéu

nguoc duoc ma hoa voi ché dfi 4MV, voi MB hién tai trong mode truc tiép thi 4 vector

chuyén dong duoc su dqng cho 4 khoi 8x8 tuong ting ciia MB hién tai trong B-VOP.

Néu MB hi(n tai dupc ma hoa trong ché dfi SKIP thi no cung la bit chuyén dong sir

dpng mode truc tiép voi vector chuyén dong Delta zero nhung bo qua ma ho:i sai

so

IV.3.2.3 of doén liéri énh (Inter-Frame)Nén lién anh chinh la viéc loai b‹i nhirng thf›ng tin giong nhau giira cac anh lien

tiép, chi ma hoa phfin thong tin kh:ic nhau giiua chung, dfiy ciing la nfii dung chinh

cua khoi nén theo thoi gian. Dna vao nguyén tac dfi, ciic bfi ma hoa sC quét lan luot ti

rng MB va ph:it hi(n xem co su thay doi tu frame nay sang frame khac hay khfing.

Mat khac, cac bfi ma hoa con tién do:in su xuat hién cua cac MB khi biét vi tri va

hu6ng chuyén d ci ng cua no. Do dci, chi nhfiiig su thay dfii gifra ciic khoi moi duoc

truyén dén phia thu. Bo giai ma da luu trfr st nhfrng thong tin khfing thay dfi i vao

bo nho d ¼m v:i khi khfii phiic lai anh goc thi ch i vi(c die’n mot c:ich déu dan vao

cac vi tri cfin trong. Vi dp hat frame lién tiép trong chuoi anh duoc minh hoa nhu hinh

IV.7. Trong do frame 2 duoc du do:in tir frame 1, céi sir giong nhau ve’ anh nen,

quyén sach, cay d:in,. .. phfin sai khac grin a 2 buc anh la phén mau xém noi rdi duoc

minh hoa nhu hinh IV. 8, chi co phan sai khac nay moi duoc bién doi va truyén di.

Tuy nhién nang luong van con tap trung o phfin sai so du dotin cu thé la nhfiiig

viing sang Hi, nén cfin phai bit chuyén dong dé

Frame 1 Frame 2


Hinh IV. 8. Phén dir giiia frame I vé frame 2

Su sai khac gifra cac btrc :inh trong chuoi video thuong do sq chuyén d n g cua VOP,

su kh:ic nhau n:iy chinh la su khac nhau vé guy dao vi tri cua c:ic pixel trong anh, viéc

du do:in sé tao ra mf›t luong thi gi:ic hay noi cach kh:ic sé tao ra mot manh huong

chuyén dong cfia c:ic vector dupc minh hoa nhu hinh IV.9.

Hinh IV. 9. Vector chuyén ding

H. 264/AVC cho phép du doan bit chuyén dong voi 5 anh tham khao va ngoai vector

chuyén dong ra cac chi so anh tham khao cfing dupc truyén di nhu hinh IV. 10 ne’n vi(ckhoi phuc lat anh tham kh:to céi the thuc h ten

trung thuc hon

de dang va chat lupng anh nén cling

Four prior-decoded picturesas reference

Currentpicture

GVHD. TS. TK.. . _... . _ HOANG SONHinh IV. 1 II. Minh hoa dir doan lién khc› i cua H. 264

'AVC. Sir dung 5 Frame cho h’u chuyén déng


Ca bo ma hfia v:i bo gi:ii ma phai liru trit cac anh tham kh:to dw ac sw ding cho dir

doan Inter trong bo nho d(m da anh. Bo giai ma sé sao lai bfi nho dém da :inh ciia

bo ma hoa, theo dang nho dém anh tham khao va cac hoat dong diéu khién quan ly

bo nhér

cho mot anh, chi so bén trong bfi nho d(m da anh phai dupc hi(u.

IV. 3.2.4 Mii hoa anh SP (switching P) vé SI (switching I).Hat dang anh SI, SP Ta mot kie’ii ma hfia dac bi(t ciia H.264/AVC cho phép chuyén

mach hieu qua gifra c:ic dong bit dupc ma hfia o cac toc do bit khac nhau. Cac frame

SP duoc luong tu hoa trong mién bién doi va dna vao dat bién do thfi hon, cho phép

ma héia o toc dé bit thap. Frame SP tain cho du doan bit chuyén d cing co thé khai thiic

Hi da du thira thoi gian trong chuoi :inh tuong tu nhu anh P. Nhung frame SP co iru

diém hon anh P la né* cho phép cac frame dong nhat cé* thé cau truc lai ngay ca khi

chung dupc du do:in tir cac :inh tham kh:to kh:ic nhau. Vi the frame SP co the’ sir diing

thay thé cho cac anh I trong cac ung dung chuye’n lufing, truy cap ngau nhie’n, tién, liii,

hay phuc lat. C:ic frame SI thuéng ke't not cung voi frame

SP nén rat co l pi trong truéng hop d¿ do:in Inter bi Hi truyén dan.

Vi du: véri citng mot video duoc ma hoa o nhiéu toc do bit khac nhau dé truyén qua

duong Internet, bo gi:ii ma nhan duoc luong co toc dé bit cao co the yéu cau chuyén

mach tu dong xiiong toc do bit thap hon néu dir 1i(u bi Hi. Nhu hinh IV. 1 1 . bo giai ma

dang giai ma luong A va muon chuyén sang giai ma luong B. Dé don gran, gia su moi

frame duoc ma hfia tuiig slice don tu mot frame tham khao truoc déi. Sau khi gi:ii ma P

slice A0, Al bo giai ma muon chuyén sang giai ma silce B2, B3 trong lufi ng B. Ne’u

tfit ca slice trong lufing B dupc ma hfia o dang P-slice, bo gi:ii ma sé khong thé giai

ma dung anh tham kh:to can th iét de cau tmc lat slice B2 (vi B2 dupc dir do:in tir BI ).

Giai ph:ip dna ra la, slice B2 se’ dupc ma héia dang I (vi dang I khfi ng can anh tham

khao) do dfi co thé thuc hien chuye’n mach giira 2 lufing A va B. Viec chuyén mach

can dwac die’u tiét bang c:ich che’n the’m slice ma hé*a dang I theo mot chia ky déu

dan de tao ra diém chuyén mach hiéu qua. Tuy nhién, anh I se chua nhiéu dir lieu ma

hoa hon anh P




Hinh IV. 11. Chuyé n ma ch luéng sit du ng slice 1IV.3.3 KHOI NEN KHONG GIANNén theo khfing gian hay con goi la nén tao anh Intra, chi sir dpng thong tin trong birc

:inh hién tar in:i khfi ng céi su tham khao anh kh:ic, tirc I:i ma ho:i doc trip in:i khfi ng can

thong tin phu cho giai ma khf›ng can tham khao c:ic anh khac, do do hiéu qua nén chiphp thuoc vao su loai bo thong tin du thira ve khfing gian nen hi(u qu:i

lam. Nhung anh I cho phép nguoi xem chuyén doi cac kénh, cung cap diem truy cap

ngau nhién vao dong bit nén va ngan chan sai so truyén. Ngoai ra anh I con duoc dung

lién tuc dé tao thanh c:ic diém tua cho dong dir lieu trong quit trinh giai ma, clung nhu

dviac sir dung lam diém chuyén mach tronv qu:i trinh phan cap. Anh I chi ditn v 2 bit/

pixel duoc ma hoa.

Ser dci khéi mii hoa énh I




TV.3.3.1 Chia éiih thimh cac MacroBJock:Mfit trong nhfmg iru diem cua chuan H.264/AVC 1:i no co the phan chia th:inh c:ic

kich thuoc nhci dé mo ta chuyén d rig. Phan viing cua th:inh ph:in luma co c:ic kich

thuoc mau nhu 16 x 16, 16 x 8, 8 x 16 va 8 x 8 phii hop cho c:ic chuyén dfing éi

nhirng khu vpc giong nhau trong :inh. Khi sir dung khoi 8x8, con cé› thé ph:in chia

thanh 4 co nho hon 1:i 8x8, 8x4, 4x8 hoac 4x4 r:it thich hop khi xir ly' chuye’n d rig tai

cho co nhiéu chi

I 6x8 8x l616x16

Hinh IV. 13. Phé n chia MB — Sub MB cho bti chuyéri da ng.

Cau trtic dp do:in thoi gian dupc mo ta nhu hinh IV. 14 sau:

10

(rop _co ded = 0)

Hinh IV. 14. Ctrl ra ihii tit séa xé i› ciia ccic VOP

Gi:ii thich: anh I khfing su dung anh tham khao va duoc ma hfia kiéu Intra duoc ky

hieu la Ix. Cac anh P va anh B co sir dung tham khao, dupc ky hieu la Px. Cac miii tén

miéu ta hu6n g du doan.

Khi sir dpng anh B tain :inh tham kh:to cho anh I va anh P, thi anh B sé dirpc hién thi

sau do voi thoi gian hién thi rie’ng, c:ic anh tham kh:to dupc truyén di truoc cac anh B




tuong ting. Theo hinh IV. 14 thi thu tu truye’n la 10 P 1 P3 B2 P5 B4 P7 B6. Boi vi

khong co thong tin dupc truyén cho c:ic :inh B2 va P5 nén cac :inh B6 va P7 se’ la anh

tham khao cho VOP P3 ma khfi ng anh huong cau truc tham khao.

TV.J.3. 2 Dv doén trong énh (Tntra-frame)

Dir doan Intra la kie’u dir doan sir diing cac MB ke' bén dii dirpc ma hfi a trong cung

mot frame dé tham khao, nham khai thac su tirong quan vé khfi ng gian. Kiéu du doan

Intra thi khfi ng dupc st dung cho dir do:in c:ic duéng bie’n cua slice dé gifr tinh

doc lap giira cac slice. Doi voi c:ic chuan truoc day vi(c 6v doan se thuc hién trong

mién bién dfii, con o H. 264/AVC thi du doan duoc thuc hién trong mién khfing gian

bang viéc tham kh:to Hi cac mau bén canh cua cac khoi da duoc ma hoa. Trong

H.264/AVC ho tro ciic kie’u dp doan INTRA 4 x 4, INTRA 8 x 8, INTRA 16 x 16

va kiéu d p doan INTRA-

IV. 3.3.2.a INTRA LUMA 4 x 4Moi MB dupc chia th:inh 16 khfii con 4x4,

cac khoi be’n canh. De céi the’ dir do:in gia tri mau

dupc du doén khong gian tu

cua khoi 4x4 luma can st dpng 13

mau ké can bao gom 4 mau cua khoi ké can bén trat, 4 mau cua khoi ké can bén trén, 4

mau cfia khoi ké can dinh ph:ii, va 1 mau ciia khoi ké c(an dinh trai. Moi khoi 4x4 cua

thanh phan luma co the’ dung I trong 9 kie’u du do:in. Ngo:ii kiéu dir do:in DC, con ho

tro 8 kiéu du doan dinh huéing sau:

1. Kiéii dv doén DCMau dupc not suy t ir gia tri triing binh cua c:ic mau be’n canhLT T0 T1 T2 T3

D | EL0

L 1 L2 L3

a a a a

a a a a

a a a a

a a a a

Trong do:

Néu bfi du do:in ci din trén va phia bén triii thfia man thi:

a - (T0

T1 T2 + T3 L0 + LI + L2 L3) / 8

Nett ch i co bo dir doan o dinh tre’n thfia man thi:

a = (T0 TI T2 + T3 2) / 4




Néu chi co bo dir doan cr be’n tr:ii thiia man thi:

a

hoac

(L0 = L I

L2 + L3 2) / 4

a - 128

2. Kiéu dy doén dpc (Vertical)

Cac mau o bén duoi sao chép lai c:ic mau bén trén theo chiéu dpc.

LT T0 T1 T2 T3 D| E | F

L0 L 1 L2 L3

T0 T0 T0 T0

TI TI TI T1

T2 T2 T2 T2

T3 T3 T3 T3

LT T0 TI T2 T3

L0 L I L2

L0 LI L2 L3

L0 LI L2 L3

L0 LI L2 L3

L0 LI L2 L3

4. Kiéii dy doén chéo x néng/tréi (Diagonal Down7Teft)C:ic man dupc no i suy theo goc 45’ gifra gi:i tri. be’n trat o trén v:i bén phai o duoi theo duong chéo.LT T0 TI T2 T3 T4 TS T6 T7

L0 L 1 L2 L3

a b c d

b c d e

c d e I

d e Ig

Trong do:a = (T0 + 2 *TI

T2 2) / 42) / 42) / 42) / 42) / 42) / 42) / 4

b = (TI 2*T2 + T3c - (T2 + 2*T3

T4d = (T3 2*T4 +

TSe (T4 + 2*T5 T6 T7f - (T5 2 *T6

g = (T6 3 *T7



L VTN. Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tien Trang 58

5. Kiéii dy doan chéo x ncing/ph é i (Diagonal Dow 7Right)Cac mau duoc ngoai suy theo géic 45’ tir trén xuong, tu triii qua phai.LT T0 TI T2 T3

L0 L I L2 L3

d c b a

e d c b

Ie d c

g f e d

Trong do:a = (L3 + 2 *L2

LI 2) / 42) / 4b = (L2 2*L 1 +

L0c = LI + 2*L0 LT + 2) / 4d e

(L0 2*LT T0 2) / 4(LT + 2 *T0

TI + 2) / 4T2 2) / 4f = (T0 2 *T

1g - (T1

2*T2 + T3 2) / 4

6. Kiéii dy doén dpc/phéi (Vertical7Right)Cac mau dupc ngoai suy theo géic xap xi 26.6’ t ir phai sang trai theo chiéu dpcLT T0 TI T2 T3

M A B C D E F G H

L0 LI L2 L3

a e i

bIa

c g b f

d h c g

J

Lj eTrong do:a = (LT + T0 + 1) / 2b = (T0 TI 1) /

2c = (TI + T2 + 1) / 2d = (T2 T3 1) /

2L0 + 2*LT T0 + 2) / 4e =f - (LT + 2*T0

T1 2) / 42) / 42) / 42) / 42) / 4

g = (T0 2*T1 + T22*T2 + T3h (TI

= (LT + 2 *L0 LIj = (L0 2

*LIL2

7. Kién dy doan d‹›c/ trat (Vertical7Left)Cac mau dupc ngoai suy theo géic xap xi 26.6’ t ir trai sang phai theo chiéu dpcLT T0 T1 T2 T3 T4 T5 T6 T7

L0 a b c d M A B C D E F G H

LGVHD. TS. TIN D VG TRINH

CN QUANG HOANG SON


L 1 |L2 |L3 |

Ibg

gc d eh i j

Trong dé*: a = (T0

TI + 1) / 2T2 + 1 ) / 2T3 + 1 ) / 2T4 + 1) / 2TS + 1) / 2

b c

(TJ(T2

d = (T3 e - (T4f - (T0 g = (TI h = (T2 i = (T3

2) / 42*T2 + T3 + 2) / 42*T3 + T4 + 2) / 4

2 *T42 *TS

TS T6

2) / 42) / 4

8. Kién dy doan ngang/xricing (Horizoiitat’Down)Cac mau duoc ngoai suy theo goc xap xi 26.6’ tu trén xufing theo chiéu ngangLT T0 T1 T2 T3

E | F

L0 |L 1 |L2 |L3 |

a e g i

b Ih

c a eg

d b Ihj

Trong déi : a - (LT L0 + 1) /

2b (L0 2*LT2 *T0

T0 2) / 4c = (LT d = (T0 e = (L0 f - (LT

TI 2) / 42*T1 + T2 + 2) / 4 LI + 1) / 22*L0 + L1 L2 + 1 ) / 2

2) / 4g h

(LJ(L0 2*L I + L2 + 2) /

4 L3 + 1) / 2g = (L2j = (LLII + 2 *L2 L3 2) / 4

Cac mau dupc i ssuuy theo goc xfip xi 26.6’ tir duoi lén theo chiéu ngangLT T0 T1 T2 T3

L0 |LI |L2 |

a c e

b d I

c e g

d Ig



L VTN. Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tien Trang 6t1

L3 | g 8 8 8Trong déi :a = (L0 b - (L0 c = (LI

LI + 1) / 22*L1 + L2 + 2) / 4 L2 + 1) / 22*L2 + L3 + 2) / 4 L3 + 1 ) / 22 *L3 + L3 2) / 4

d e

(LJ(L2

I= (L2 g - L3

IV. 3.3.2.6 INTRA L Ul IA lb x 16

Chi 1 kiéu du doan dupc ap ding cho toén bo MB thich hop cho nhfmg mién :inh tron

tru, phang déu. Bon kiéu du doan duoc ho tro la: chiéu ngang, chiéu thang dung, du

doan DC va du doan mat phang. Trong kiéu du doan mat phang su dung phuong trinh

ducrng cong 3 thong so dé dir do:in do luma, do doc theo chie’u ngang, chiéu

thang dving cho phit hop voi cac diem :inh bén canh, va kiéu du doan nay co hiéu qua

rat cao trong Eng co thanh phan luma it thay dfii.

De cé* thé du doan gia tri mau ciia khoi luma 16x16 can su dqng 33 mau ké can bao

gfim 16 mau ciia khoi ké cfin bén tr:ii, 16

khoi ké can dinh trai.

?. Kiéii dy doen DC

'u cua khoi ké cén bén trén va 1 mau cua

Su dung 16 bo du do:in (T0..T15) va 16 bo du doan bén trai (L0..L15), cai tat ca 256

gia tr] vé gia tri trung binh, theo cong thfic sau:

Néu bo du do:in bén trai vii dinh trén thfia man thi:

mean - (sum(T0..T15) sum(L0 ..L15) 16) / 32

Néu bo du do an dinh tre’n thfi a man thi:

mean (sum(T0..T15) 8) / 1 6

Néu bo du doan bén trai thfia man thi:

mean - (sum(L0. . L15)

Hoac

mean - 128

8) / 16

2. Kiéii dy doén niim d‹›c (Vertical)

Ngoai suy tu ciic mau bén theo chiéu doc



L VTN. Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tienTrang 6 I

LT | T0 T T2 T3 T4 .. T15

L0 | T0 L1 | T0 L2 |

T1 T1 TI

T2 T2 T2

T3 T3 T3

T4 T4 T4

..

..

..

T15 T15 T15

L15 T0 TI T2 T3 T4 .. T153. Kiéii dy doén nhin ngang (Horizontal)

Ngoai suy tfi cac mau

chiéu ngang

LT | T0 T

T2 T3 T4 .TI5

L0 |LI |L2 |

L0Ll L2

L0 LI L2

L0 LI L2

L0 LI L2

L0Ll L2

.. L0 LI L2..

US L15 L15 L15 US L15 .. L15

4.Kién dy doén mat phiing Plane

Cho 16 bo du do:in dinh trén (T0..T15), 16 bo dp do:in bén trai (L0..L15) va 1 bo dir

doan o goc dinh trai (LT) sap xép nhu sau:

LT | T0 TJ T2 T15

L 15 c[ 0, 15] c[ 1, 15] c[ 2, 15] .. c[15,15]

IV. 3.3.2.« INTRA CHROMA 8x8

Du doan cho thénh phan chroma dupc thuc hién mot lan cho toan bo MB, 64 gia tri

mau chroma su dung cac kiéu du doan giong nhu du doan Intra 16x16 cho thanh phan

Luna: Du dotin theo chiéu ngang, du dotin theo chiéu dung, du doan DC, du doan mat

phang.

ID. 3.3.2.d IN TRA-PCMLa mot MB 16x16, chua mot mat phang ciic th h phfin luma va chroma chua nén.

L:tin cho bo ma hfia xir ly don gian hon bang c:ich xu ly' ma hfia v:i bie’n dfii thay

vi phai gfri t c tiép mau c:ic gi:i tri init héia. Va kiéu dir do:in I-PCM con co mot so

lot




=

=

Cho phép ma hoa chinh xac tp dat dién cua gia tri mau.

Cung cap gia tr| ding cho nhfing buc :inh co noi dung bat thuong ma khfing can

mo rong dir liéu quan trong.

Cho phép dat gioi han so luong bit diéu khién MB ma khfing anh hucrng dén

hiéu suat nén.

=

IV.3.3.3 of doén trpng sit.•La mot phuong phap diéu chinh mau cho bit chuyén dong dir lieu trong MB P ho:ic

MB B rat thich hop cho ma hfia mat nguoi hoac ma hoa chuyén dong. Céi 3 loai dp

do:in trong so nhu sau:

1. P slice macroblock, du doan trpng so “hién thi” (explicit)

2. B slice macroblock, du doan trong so “hién thi” (explicit).

3. B slice macroblock, du doan trong so “an” (implicit).

Moi mau dir do:in pred0(i, j) hoac pred1(i, j) dwoc co dan boi trpng so thong ké W0

hoac WI trong du do:in bit chuyén dcing tri roc do. O loai “hién” thi trong ‘ thon ké

dviac :xa c dinh bcii bfi ma hoa va truyén di o Slice header. Néu sir dung loai “an” thi

trong so thong ké W0, WI dupc tinh to:in dna v:to moi quan hé vi tri thoi gian cua list

0 v:i list I trong anh tham kh:to. Gi tri trong so thong ké lérn néu anh tham kh:to gan

giong voi anh hién tai va gia tri trong so thong ké nho néu anh tham khao khac voi anh

hién tai.

Mfi t so ung dung cho phép ca 2 ham an va hién diéu khién su lién quan cua :inh tham

khao doi voi qua trinh bu chuyén dong, du doan trong ’ co hiéu qua dac biét trong ma

hoa cac hiéu ring m‹i dan nhu minh hoa ci hinh lV. 15.




cac birc anh, nham thay thé g:in diing c:ic anh thénh ph:in trong day video. Ngoai ra

bii chuyén dong con I:inn giam su du thira vé mat khong gian giira cac birc anh, han

ché cac thong so chuyén dong béri viéc diing vector chuyén dong dé mo ta su dich

chuyén.

kh:ic nhau va dirpc tinh to:in trong MB. Gia tri du do:in la gi:i tri triing

binh ciia cac uérc luong nay. Du doan chuyén dong ciia MPEG-2 co nhuoc diém la anh

tham khao thich ring nhat voi MB hién tai phai kich thuoc 16x16 va vitng thich irng

ph:ii nam ngay trong :inh tham khao do dan den hiéu qu:i nén chua cao. Nguyén tac

bu chuyén dong trong H . 264/AVC cling giong nhu cac chuan triroc la tim kiém trong

anh tham khao khoi thich hop nhat sao cho nang lupng cua phan sai so du doan la

nho nhat, tuy nhién uu diém cua chuan H.264/AVC co thé bu chuyén dong voi kich

thuoc nhfi 8x8, 4x4 hoac bit chuyén dong trén cc so cac diém anh con, dac die’m

n:iy da

IV. 3.3.4.a Bh chnyén dc›ng thich nghi khéi

Bu chuyén dong voi kich thu‹ c kho i thay doi se’ dan den vi(c phirc tap trong tinh

to:in, vi thao I:ic tim kiém se nhiéu hon vii so bit can thiét cho vi(c ma hé*a cung sé

nhie’u hon, do do H.264/AVC bo sung phuong phap bu chuyén d jug thich nghi

khoi, nghia




ngupc Hinh IV. 16.

hoa su khac nhau giira sai so cé› bii chuyén dong va khfing

1 6x 1 6.bit chiiye’n dong ciia khoi

Frame 1 Frame 2

Khong h’u chuyén déng Cc› h’u chuyén dérig

IV. 3.3.4.6 Bh chuyén dcing m tphén tir

Trong cac thuat toan bu chuyén dong truoc thi su dung loai 1 pixel nén cac thanh phan

ciia vector chuyén dong bi gioi han boi mot con so nguyén, ma chuyén dong thuc gifra

2 hinh anh lién tiép thuéing khong bang so nguyén buoc cua pixel dan dén su han ché

ve“ ddoé phhffiinn gii::iiii, sai so trong du doan bfi chuyéénn dong va lam tang sai so'

dduu ddoo::iinn..

O MPEG-1 , MPEG-2 va H.263 sir diing bu chuyén dong voi dfi phan giai I pixel, do

d é c:ic th h phan ciia cac vector chuyén dong céi the lay gi:i tri ?› hoac ca mot pixel.




mot thii tiic chuyén hfia nhfrng mau tai v] tri ph:in so bang cach sit dpng mau tai vi tri

nguyén va dupc minh hpa nhu hinh IV. 1 7:

A

a

BO ++

+ Vi tri nguyén Ian p ixel

O Vi tri mot n±a pi×el

b

c d

C.D.

Hinh IV. 17. Mit not .suy cho cac MV ’/’z pixel

Theo hinh IV. 17. tai vi tri a, ca 2 thanh phan vector chuyén dong déu la mot pixel, do

dé khfi ng can c:ic mau not suy, tai v] tri b va c, mot trong cac thanh phfin ciia vector

chuyén dong bang ?› pixel, do do mau noi suy co gi:i tri bang ghép nfii suy 2 chiéu

tuc

b (A B)/2

c = (A C)/2 (tat ca gia tri nay la gia tri chroma va luma).

Tai vi tri d, ca 2 déu la I pixel nén gia tri mau duoc tinh toan nfii suy 2 chiéu tir tat ca

bon mau lién ké: d (A+ B + C *D)/ 4.

Chuan H.264/AVC su dung thuat to tin bu chuyén d cing voi dfi phan gi:ii ¼ pixel

thay vi ? hoac 1 pixel nhu c:ic chuan truoc day nham tang kha nang du do:in, giam

thiéu sai so dir do:in mot c:ich dang ké va toc do bit cung dupc tang ten. Kiéu not

suy cho

IV. 3.3.4.6.1Qtr:i trinh bu chuyén dong /‹ dupc chia thanh 2 buoc sau:

Bvcrc thii nhtit, '7i pixel dupc tinh toan bang cach ghe’p noi suy c:ii tién. O day khfi

ng chi 2 hoac 4 mau lién ké dupc su dung cho nfii suy ma cfin co thé la 8 mau

theo 2




r

Hinh IV. 18. Minh hpa phé p ’/z pixel theo hirérng nhin ngang cho tha nh phé n luma.Cac mau o vi tri ?› pixel nam canh 2 mau nguyen duoc

bang cach su dung bo lpc FIR 8-nhanh (Finite Impulse

(8/256, -40/256, 40/256, 40/256, -40/256, 8/256) tirong

suy nhfrng mau nguyén

Response) voi cac trong so

duong voi (1 /32,-5/32,

5/8,-5/32, 1/32). Vi du, vi tri mau ?› pixel “b” dwac tinh toan tu 6 mau nguye’n nam

ngang E, F, G, H, I va J nhu sau:

/' = round( E - SF 2tlG = 2tl H - 51

32

Qua trinh riot suy “h” theo hu6ng thang dting cung dupc thuc hi(n tuong tp tir cac

mau A, C, G, M, R va T. Trong tri réing hop ca 2 thanh phan vector chuyén dong déu

la

? pixel thl viec lpc dwoc thuc hién theo huong nam ngang truoc rfi i moi dén huong

thang drug.

gia tri mau / pixel tir buoc thir nhat u hinh sau:

Hinh IV. 19. N‹› i s uy min ‹he thanh phan luma tai vi tri ’/.

Cac mau ér vi tri ¼ cé* ten la a, c, d, n, I, i, k, va q dupc suy ra b:ing c:ich lay tri trung

binh 2 mau o vi trI nguyén va vi tri ?› pixel gan nhat, vi du nhu:



L VTN. Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tien Trang 6 7

2

C:ic man o vi tri ¼ co ten lit e, g, p va r dirpc suy ra bang cach lay tri tning bi nh 2 man

o vi tri / mau theo duéng chéo gan nhat, vi dq nhu:

c = round(h = h) 12

Doi voi mode d¿ do:in I pixel, binh thirérn g thi mot khoi (8 + J ) x (8 1) = 81 pixel

duoc doc tu VOP tham khao, va khoi tham khao bao gici cling nhiéu hon khoi 8x8 mot

hang va mot cfi t duoc du dotin dé cho phép riot suy mau hai chiéu pixel con tai bién

cua khoi. Doi voi mode dir do:in ¼ pixel phai dung the’m 3 pixel ngoai khoi tham

khao cho vi(c not suy (vi sir dung bo loc FIR 8 nhanh) ne’n khoi tham khao la phan

mcr rong d i ximg tai bién cua khoi va thuéng duoc goi la guong duéng bién khoi

minh hoa

Hinh IV. 20. Girong diréng bién kh i.

Theo lap luan trén thi 3 gia tri cong the’m vao ngoai khoi tham khao

(8*6*1) x (8*6+1) = 225 mau bat buoc phai doc tu bfi nho cau truc VOP, cfin néu su

dqng guong thi so mau sé la (8+1) x (8+1) - 81, vay guong duéng bién khoi se tain

giam 64% dfi rong bang tan yéu cau trong qua trinh du doan bit chuyén dong.

IV. 3.3.4.6.2Nhirng die’m anh chroma co gi:i tri

chroma.

¼ pixel dupc noi suy bang c:ich 1:iy trong so trung

binh ciia khoang c:ich ID diém tinh moi Hi bon duong vién ciia diém tinh goc nhu hinh

ve IV.2 1.



L VTN. Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tien Trang 6R

ahé n chroma.

p ppJ [(8 - dx ). (8 - dy)A dx.(8 - dy)B = (8 - dx ). dyC = dx . dyD]

64

10B+ I 8C 6D)

64

ID. 3.3.4. c Bii chuyén d(i ng cho céc TOP hinh chit nhat vé bét kjDo i tupng chuyén dong trong mot buc anh thuong it tap trung o diréng bién kho i,

ne’n o do thuéng céi hinh dang bat ky nhu minh hoa o hinh IV.22. Trong dfi hinh oval

la d i tuong chuyén dong, va hinh chin nhat la doi tuong d iung yen. Qua trinh bu

chuyén dong cho cac VOP céi hinh dang bat ky se 1:tin tang h i(u qii:i hién thi cua

buc anh. Nhung viéc tim duoc khoi thich ring nhat trong anh tham khao cho cac khoi

viia chua anh dong va anh tinh ciing khfing don gian, hon nua gap kho khan trong

viéc nhan dinh ch inh x:ic diréng bie’n kho i, sir phan doan, tin h i(u b:to hi(u ducr ng b

ten khoi cho

Reference frame Gii rrent frame

IV. 22. Bii chuyén

d ng cho rnpt VOP ct h inh dqng

hatGVHD. TS. """’


dong toan phan VOP va co the’ dupc su dung luan phién cho cac vector chuyén dong

cua MB de bit chuyén dong nham tranh gay sai sot vi ciic thong so chuyén dong toan

phan khfi ng ph:ii o dau cung nhu nhau. No kha quan trong trong c:ic chuoi chuyén

dong to tin phan nhu anh chup tu Camera hay chuyén dong khong tinh tién nhir Zoom

hay quay Camera. Cac thong so chuyén dong toan phan duoc truyén di ci trong phan

header ciia VOP, voi '‘ii MB bfi ma hfia quyét dinh su dung cac thong so GMC hay

c:ic vector chiiye’n dong uoc lupng cua MB.

Cac thong so chuyén dong toan phan la tap hop ciia 4 vector chuyén dong cho mot

VOP, voi lvector chuyén dong ti rong uiig xiic dinh mot vi tri tham khao cua VOP

hién tai. Vi dii nhu hinh IV.23. c:ic vector chuyén dong GMC dupc dat tai 4 goc cua

IV. 3.3.4. e Bii chuyén d rig cho céc MB dir g biénTrong triréng hop cac VO co hinh dang bat ky, VOP tham khao dung cho du doan bit

chuyén dong clung se co hinh dang bat ky, dan dén trirong hop du dotin khfi ng hiéu

qua o cac pixel trong suot. Dé ngan ngua tinh trang n:iy, cac pixel trong suot cr VOP

tham khao duoc xu ly dém tu VOP da duoc giai ma truoc do. Tirc la, toan bo cac pixel

trong suot ciia VOP tham kh:to dupc guy ve gi:i tri két cau lay tir c:ic pixel khfi ng

trong suot trong ciing VOP. Cfin doi voi cac MB dw© g bién, MB trong suot th l su

dpng thuat



MB hién tai


Truoc tién c:ic pixel trong suot hi(u boi chfr x, ’ dupc lap

duong bién sao che'p lat theo chiéu ngang vii thang dig nhu hinh vé. C:ic VOP duongbién duoc

danh dau.

hiéu boi A va B, con cac pixel ngoai VOP la trong suot nén khong duoc

Ivl B duong bié n

(E -r J) / 2 (E + J) / 2

Hinh IV. 24. Qué trlnh ‹finn ‹he ‹ é‹ Macrohlock ‹firing hien

Quit trinh dém duoc thuc hién nhu sau: Cac pixel trong suot duoc lap day boi gia tri

duong bién tuong ring o bén trai hoac bén phai. Néu cé* mot gia tri duéng bién VOP tai

2 bén pixel thi 1:iy gia tri tning binh, sari dfi thirc hi(n tuong tij cho chiéu dirng. C:ic

pixel da duoc lap day thi theo hu6ng nam ngang no duoc cor nhu la da co san tai VOP,

nghia 1:i se dupc sao luu mot cach tirong ting neu nam tai bién cua VOP. Tuy

nhie’n, trong khi thuc hién buoc nay, cac pixel o tai dinh hay d:iy thi két qii:i se’ lay

gi:i tri trung binh. Cuoi cung thi toan bfi c:ic pixel trong khoi duéng bién duoc dim

va sC khfing cfi n cac pixel trong suot cr phia bén trai nfra.

C:ic MB nam bén ngo:ii VOP dupc dém nhir sau: cac MB trong suot n:iy sé dupc tain

day boi cac mau sao chép lai tai duong bién cua cac MB lién ké. Néu chi co mot MB

duong bién lién ké tién nhu hinh sau:

t h é cho cac MB 6ua r 9 bié n

" "GVHD. TS. TIN D lANG HOANG SON


Néu céi nhiéu hon mot MB duéing bién lién ké thi MB trong suot duoc dém bang cach

sao lai cac mau trén, duoi, trai hay phai tir du'ong bién ngang hay thang dtrng cua MB

duong bién bc›i con so' mi tién lléérnn nnhhiaitt.. C:ic MB trong suot khong co MB

lien ke’ dirpc lap dfiy boi gia tri 2bits/ pixel. Doi voi tin hiéu luma va chroma 8 bit,

duac lap day bcii

IV. 3.3.5 Phép blén dc›l rigsyén ICT (Integer Discrete Cosin Transform)

= Day la mot phép bién doi nguyén xap xi véri phép bién doi DCT, tat ca cac buoc

dupc thuc hi(n voi so nguye’n, qii:i trinh giai ma se’ khfi ng mat dir 1i(u.

C:ic biroc tinh to:in dupc tich hop trong bo luong tu hoa nham tain gi:tin so

lupng buoc tinh toan.

Tat ca cac bién dfii va luong tu chi dung cac thuat toan cong hoac thuat toan

dich bit trén cac giii tri nguyén 16 bit va chi thuc hién nhan trén tiing hé so chu

khfing can thuc hi(n phép chia ne’n dam bao khfing mat di d chinh x:ic.

=

=

1.3

1

0.54

0.54

— 1

— 1.3

— 0.54 — 1.3 2

1

1

1

— 1

— 2

— 1

— 1

— 2

— 2

1

— 1

DCT —— ICT ——— 1 1

— 1,3 — 0.54

Gié tr] thyc Gici tri nguyé n


5 VTH .

NGUYEN QUANG HOANG SON


H. 264/AVC cung cap 3 kiéu bién dfii tii y thuoc v:to

sai mot 1:i bién d fii

16x16, 2 I:i bién dfiiHadamard cho in:ing 4x4 h( so DC luma trong kiéu d¿ do:in Intra

Hadamard mang 2x2 hé so DC chroma va tat ca cac block 4x4 o trong du liéu du thiia

duoc bién doi ICT.

Phép b ten dfi i ICT cho c:ic khoi 4x4 theo cfi ng thuc sari:

a a

c

— a

— b

a

— c

— ‹z

a

— b

n

a

a

a

a

h

c

—c

—b

a

—a

—‹z

a

c

—b

/›

—c

b

‹z

c

XY = AXA =

b — c

Thuc hi(n co dan ma trfin Y voi ma tran E nhu sau:

a phép bién doi 2 ch iéu

’ I lé

X la ma tran 4x4 cua tin hi(u video, hinh anh ngfi v:to.

Phép to an O co nghia la

hé so ty Ie o cung vi tri trong ma tr:in E (nhén vfi hu6ng).

CXCTTrong do

d - —- 0.414

De don gi:in, o chufin H.264/AVC thuc hién xap

xi a = 0.5, b —— , d5

Hang thu 2 va thru 4 cua ma tran C, cot thu 2 va thu 4 ciia ma trfin CN duoc co dan boi

he so 2. Ma tran ti rong duong se co két qua la:

2 I — I — 2 1 1 I — 1 — 2 ab / 2 " / 4 ab / 2 6' / 4©

1 — 2 2 — 1

Phép bie'n dfi i n:iy x:ip xi vcii DCT 4x4, vi

— 2 1 — I ab / 2 -" / 4 ab / 2 6' / 4

sir thay dfii cua phan ID b vii d, tain cho ngfi

ra cua phép bién doi moi khfing dong nhfit voi DCT 4x4.




Ta céi X 1:i ma tran ngfi v:to:

Két qii:i bién doi ICT cho tin hi(u trén dupc mo phong bang doan ma

nhu sau:

trong Matlab

A = [ 0.5 0.5 0.5 0.5,0.653 0.271 0.271 —0.653; 0.5 —0.5

—0.5 0.5;0.271

A GA MA TRAN HE SO DAN

6 15 7];

BIEN DOI DCT

—2 2

X -

Y1

-

[

A*X*A'

[

l/2;b-

8 X LA MA VAO

% GIA TRI PHEP

1; 2 —1 —2;

;d

—1 —1

l/2;

1; LA MA HE SO

35.0 10.218

— 6.241 I

5. 193.

— l .5

— 3.887

2.0

— 14.756

— 5.0241

— 0.253

3.75

5.5Y 1 —— AXA'—

— 8.288 0.8951 — 2.42 10 5.4030

35.0

—3.004

5.5

—4.2691

—0.1581

—3.900

2.6879

— 3.200

—1.5

1.1068

2.0

9.3287

1.1068

—9.200

4.9015

— 2. 100

Phan chénh léch gifra 2 phe'p bie'n dfii la

0

— 6. 7542

0

4.0189

— 10.376

— 2. 34 1 1

— 2.5051

— 4.095 I

0

4.9938

0

15.8628

— 4. 1759

5. 1545— 1 I .7497 — 7.5030

Thuc hién bién dfii tuong tu ta co cong thuc bién doi nguoc nhu sau:



j=0 j=1 j=2 j=3i=0 5 11 8 10i=l 9 8 4 12i=2 1 10 1 1 4i=3 19 6 15 7


IV. 3.3.5.a Bién déi Hadamard cho céc h sci DC lame cds I‹h‹›i 4x4Néu MB dupc ma hfia trong ché do Intra 16x16, dau tién c:ic khoi du 4x4 se dupc bién

dfii Hadamard mot fan nfra theo cfing thirc:

Y — / 2

C:ic h( so DC dirpc lupng tir theo cong thirc sau:

2"“’ / 3 Intra

Trong *D‹ , 1:i két qu:i cua phép bie’n doi Hadamard. Truoc khi luong f. *D(›, ,

se chia cho 2 va lam tron.

>> 1:i phép dich phai bit nh i phan

Tai bo giai ma, phe’p bién dfii Hadamard ngupc dwac thuc hién nho phépgiai luong tu.

dfi²

1 l 1 1 1 1 1 1

Qu:i trinh co dan tai bo giai in:i nhir sau:




Hé so DC ciia 'i khoi 4x4 ciia thanh phén chroma dupc nhom th:inh khoi 2x2

dupc bie'n doi va lupng tu héia:

va

Ngfi ra cfia luong tu héia khoi 2x2 dupc thpc hién nhu sau:

Trong qua trlnh giai ma, phép bién d éi ngupc dupc thuc hién truoc khi co dan.

Hé so DC co dan lai W'D duoc thay thé vao cac khoi 4x4 cua hé so chroma tuong ting.

Cling giong he so DC luma, phép bién doi mo rong se la giai tuong quan cho hé so DC

chroma 2 x2 va car thién hi(u qua nén.

ffi J.J. 6 Qtié mints firing iiiH. 264/AVC su dqng bo luong tu vo hu6ng nén sé khong xuat hién “viing chét

diém zero” nhu trong bo luong tu vector. Truoc tién, sau khi X bién dfi i nguyén dir

liéu ngfi vao tao thanh cac hé so DCT, cac hé so DCT W, , se dupc luong tir hfia va

co d theo

PFZ ; = tuong duong véri Z ; = round(W ;

" Qstep' Qstep

Trong do + Y„ lit h( so da b ién dfi i ICT.

+ Qstep -2"”“' "' la cap do luong tu hoa

+ Z„ la hé so luong tu héia

Voi gi:i tri ciia PF nhir sari:




«'= 0.25 (/, )) = (0, 0),(0, 2),(2, 0),(2, 2)

PF , —— b’ / 4 = 0. 1 (/, j) = (1,1),(1, 3), (3, 1),(3, 3)

Moi MB chpn mot trong so 52 buoc luong tir Qstep nhu bang boi tham

QP, néu kich thuoc buoc ton, pham vi gia tri luong tir sC nhci do dfi hieu qua nén sC

cao, nhung bit lai gia tri giai luong tu se xap xi tho voi gi:i tr] tin hieu goc. Néu kich

nhirng pham vi gi:i tri lupn g tfr sé lérn do do gi:tin h i(u qii:i nén. Theo két qua

nghie’n ciru thpc nghi(m gia tr| Qstep dupc sap xep sao cho khi tang QP lén mob

dv vi thi tang khoang 1 1 %->12% kich thuoc bir‹ c lupng ID, krc lit gi:i tri Qstep sé

tang gap dfii néu tang QP ten 6 don vi, nham ma hfia chinh x:ic va d iéii khién su can

bang gitra toc dfi truyén bit va chat luong, diéu do co nghia la da ID gram di 12% toc

do bit.

De don gi:in hoa phép tinh trong phan mém tham khao bo sung he so nhfin MF va

phép dich ph:ii ' nhi phan, nham tr:inh thuc hi(n phe' p tinh chia nén cong th irc

tuong duong

Voi qbits = 15+floor(QP/6). (Gia tri nguyén co gia tri tin -2 '’ cho dén 2' ’-1). Voi

floor la ham lam tron ve gia tri nho hon.

MF la h( so nhan, tuy thuoc vao gi:i tri QP va h( so vi tri (i, j) nhu sau.

‹z ’ * 2""' I Qstep

= /› / 4 * 2"'” Q.step

(/, j) = (0,11),(0, 2),(2,11), (2, 2)

(/, j) = (1, 1),(1, 3),(3, 1), (3, 3)

vi tri kh:ic‹z/› / 2 * 2”

/ Q.step

Theo cong thuc trén ta co bang torn tat 6 giii tri dau tién cua MF nhu sau,



Vi tri (0,0),(2,0),(2,2),(0,2)

Vi tri (1,1),(1,3),(3,1),(3,3)

V] tri khac

13107 5243 8066

QP 0 1 2 3 4 5 6 7 8 9 10 11 12Qstep 0.625 0.6875 0.8125 0.875 1 1 .

1251.25 1.375 I . 625 1.75 2 2.25 2.5

QP 18 24 30 36 42 48 51Qstep 5 10 20 40 80 160 224


TV.3.3. 7 Qiia zriirJr gi‹ii firjziig tir:' co dan truérc trong bo giai luong tu ( tii ma tran E, chua cac gia tri a', ab va b'

‘ vi tri) duoc tich hop trong phép tinh nay, cung voi hang ’ co dan

Gi:i tri ngfi ra bo bién doi ngupc dupc chia cho 64 de’ loai be› thua ' co dan ho*ac

trong cach bo sung thi ditng phép dich bit nhi phan. Trong chuan H. 264/AVC thi

khong ghi

Vi du :

QP= 3, nen Qstep = 0.875

(i,j) = (1, 2) nén PF = ab = 0.3162 va 2'“' "' "' = 1

V- (Qstep.PF.64) - 0.875 x 0.3162 x 64 -

18. W = Z,, x 18 x1.’ co dan V nhu sau :

Vr d ir .-m“ir‘ir“enh 4 :4 dirpc mii“ hoe I‹’t“ee I nfer. QP—— 10



QP Vi tri (0,0),(2,0),(2,2),(0,2) Vi tri (1, 1),(1,3),(3,1),(3,3) Vi tri khac.0 10 16 131 11 18 142 13 20 163 14 23 184 16 25 205 18 29 23

1 0.6875 1 1916 4660 74902 0.8125 10082 4 194 65543 0.875 9362 3647 58254 1 8192 3355 52435 1.125 7282 2893 45 59


Bie’n doi Y=CXC T

Ngfi v:to X

MF = 8192, 3355 hoac 5243 tuy thufic vao vi tri he so va qbits = 16 va I=Luong tu Z„ = round(F„ * PM / Qs/ep) : Giai wigg N W' - Z. Qs tep.PF.64 la

:

V- 16, 25 hay 20 tuy thufic vao vi tri va 2'“' "’ "" 2'- 2. Ngfi ra bo bién doi nguoc chinh X”= round(C'W' C / 64)

Qtr a trinh thirc hi(n vi du trén dirpc

’ phong trong Matlab nhir sau:

A - [ 0.5 0.653a = 0. 5;b= PF

[a’2a*b/2 b’2/4

—0.5 —0.50.271 ];% A LA MA TRAN

HE 8O CO DANsqrt(2/5} ;a*b/2 a’2 a*b/2; a*b/2a’b/2 b’2/4]

b’2'4 a*b'2 b’2/4; a’2 a*b/2 a’2 a*b/2;

X = BY1z

CO

[5 8[ 1 1 1B*X*B'

10,91; 2

81

10-1 -2; 1 -1

4; 19 6 15 7], X LA MA NGO VAO-1 I; 1 -2 2 -I] ; %B LA MA TRAN HE SOGIA TRI PHEP BIEN DOI DCT

[1 1 1 l; l l/2 -l/2 -1; l -1 -l l; l/2 -l l -1/2];% A LA MA TRAN HEDAN

IV. 3.3.8 Q f t Zig-zagQuét Zig-Zag nham chuyén ma tran hé so DCT 2 chiéu sau khi luong tir thanh mot

gian tang dan theo mot thru tir



j=0 j=1 j=2 j=3i=0 4 13 8 1 0i = l 8 8 4 1 2i=2 10 10 3i=3 1 8 5 14 7

j=0 j=1 j=2 j= 3i=0 544 0 -32 0i = l -40 -100 0 -250i=2 96 40 32 80i-3 -80 -50 -200 -50

j=0 j= I j=2 y3i-0 17 0 -1 0i-l -1 -2 0 -5i=2 3 1 1 2i-3 -2 -1 -5 -1

i=0 5 1 1 8 1 0i = l 9 8 4 1 2i=2 1 10 11 4i=3 19 6 15 7

i=0 140 -1 -6 7i = l -19 -39 7 -92i=2 22 17 8 31i=3 -27 -32 -59 -2 1


nhat dinh hay néii c:ich kh:ic no nhfi m nhfing so khac 0 va so 0 thanh mot mang

tuyén tinh. Gi:i tri lupng tir se’ dupc sap xe'p de tao ra mang tuyén tinh bang c:ich dat

gi:i tri theo thu tir (0,0), (0,1), (1,0), (2,0), (1,1), (1,2), (0,3). . . Hau hét nhirng gia

tri tan so

C:ic MB dupc ma hoa trong ché do 1 6x 16, thi h(

' DC

(dinh tr:ii) cua khoi luma 4x4

dwac que’t truoc, sau déi Hi 15 h( so AC. Tuong tu, moi hé so DC 2x2 cfia th:inh phanmau duoc quét triroc sau do toi 15 hé so AC trong trinh quét nay sé sap

xép nhfmg hé so co su khac nhau nhiéu nhat o vi tri dau tién, rfii Hi hé ‘ co nhiéu

0 lie’n tiép.

Néu MB duoc nén su dung kiéu bién doi 4x4 trong ché do frame, thi cac hé so luong

tu duoc sap xép nhu sau:

Htnh IV. 26. Quét Zig-Zag cho kiéu mii héa Jrame

Néu MB dwac nén su dung kiéu bién dcii 4x4 trong ché dci manh, thi ciic hé so luong

tir hoa dupc sap xe’p nhu sau:

Hinh IV. 2 7. Qtr ét Zig-Zag cho kiéu ma héa [icld

Kiéu quét n:iy hiéu qua hon, phan anh qua trinh tain gram df› tuong quan dir liéu goc

theo chiéu thang dirng




TV.3.3.9 llii héa men k:é.De loa' tflf hlefl tirong chép s:ing H.264/AVC ' trp

mahoa v:i giai ma cho kiéu quét

lién tic hoac que’t xen ke dupc cach ly ve’ mat thoi gian boi mot chu ky slice (mot nua

chu ky frame), dinh dang lay 'u mac dinh la kiéu quét 4: 2 :0 lién tuc. Hai phuong

ph:ip giong nhau o cho dong di(n tir ciing quét tir trén xufing duoi, t ir trai sang phai,

cac dong quét ngupc cfing dupc xoa. Diém khac cc ban 1:i cr day nguoi ta chia 1

anh thanh 2 manh va thuc hién quét theo nguyén li nhu sau: Moi :inh duoc truyén

lam 2 luot, luot dau truyén tat ca nh iing dong lé goi la manh lé; luot 2 truyén tat ca

nhfmg

Z/2 dong. Mfii

in:inh 1 nfia :inh mang 1 nira lupng tin tirc cua anh. Bo ma hé*a cho

phép chon ché do quét khung hoac in:inh. Viéc chon kiéu quét field sé tiét kiém duoc

bo nho hoac gi:tin thoi gian truyén tir bo ma hoa cho dén bo gi:ii ma, minh hoa nhu

sau:

= Ma hoa frame : 2 slice (field) cua mot Name dupc ma hfia ciing nhau

= Ma h‹ia slice : 2 slice (field) cua mf›t frame duoc ma hoa riéng biét

‹ov ›•" a‹•= " °'"

• ºº'" o »='•"

Hinh ID. 28. Minh hoa ci ué trinh ma héa xcn kc

IV. 3.3.10 Siip xép thé ty Slice.Ky thuat nén H.264/AVC cho phép bo ma héia céi thé chon tan so v:i vi tri cua anh I,

diéu nay rat co ich cho nhfrng irng dung yeu cau diém truy cap ngau nhie’n, o d é :inh

I dupc sir diing voi chu ky 2 tan/gray. Bo ma hfia cling cho phép chon so lupng anh

B grin a 2 cap anh tham kh:to bat ky (I hoac P) dna vao dung luong bfi nho trong bo

ma



L VTN. Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tienTrang 8 I

thanh 2 anh tham khao lie’n tiép, kiéu sap xép cfia anh I, anh P va anh B theo trat tu

////ih /? 29. Trét tir hién /hi cn‹z cfc béc anh.

Trat tu cua cac buc anh ma hoa va giai ma co su khac nhau do du doan bu chuyén

d cing 2 chiéu ciia anh B. Bo ma hoa MPEG sap xép lai trat tu anh trong lufing video

nhu sDisplay Order

V i oe o Strearri Order

Hlnh IV. 30. Thit tit luong Vicleo khéc vé‘i trét If h ién thi.

Thin tu ngufi n thong tin va thu tu ngfi vao bfi ma hoa nhu sau

I(1) B(2) B(3) P(4) B(5) B(6) P(7) B(8) B(9) P(10) B(1 1) B(12) I(13)

Thu tp ma hfia va thir tu trong dong bit nén nhu sau

1(1) P(4) B(2) B(3) P(7) B(5) B(6) P(10) B(8) B(9) I(13) B(11) B(12)

Th ir tu ngfi ra bo giai ma (hie’n th| giong nhu tin hieu ngfi vao ma hfia) nhu

sau I(I ) B(2) B(3) P(4) B(5) B(6) P(7) B(8) B(9) P(10) B(1 1 ) B(12) I(I 3)

IV.3.4 MA HOA ENTROPYMa hoa Entropy 1:i mf›t ky thuat ma h‹i a khfing ton hao co cac ky hiéu ngii vao I:i

nhirng hé so luong tu, vector chuyén dong, thong tin header. . .No gfim nhiéu loai ma

hfia nhu ma hoa du doan, ma hfia Huffman, ma hfia céi chiéu dai bie’n d fii VLC va ma

hoa so hoc nhi phan BAC. Trong H.264/AVC su dqng kiéu ma hoa thich nghi theo nfii

dung CA nhu CAVLC va CABAC nghia la chi co mot anh xa cho mot bang tu ma don

dwac thuc hién theo thong ké dir 1i(u, cfin cac tie’u chuan truoc thi su dung mot bang

VCL cho moi phan tu kh:ic nhau. C:ic thanh phan cii ph:ip o 16p be’n trén sé dupc ma

hoa VLC hoac FLC, con thanh phan cu phap o lop bén duoi se duoc ma hoa VLC




hoac CABAC thy thuoc v:to kiéu ma héia Entropy. Khi co chi ché do ma hfia Entropy

dupc c:ii ve “0” thi c:ic khoi dfi 1i(u du thua sé dupc ma hoa CAVLC hoac ma hé*a

VLC nao dé* nhu ma hé*a Ex-Golomb. Cac thong so can ma hé*a nhu bang sau:

TV.3.4.1 I Ié héa Entropy Exp-Golomb.

Ma Exp-Golomb (Exponential Golomb codes) la ma co chiéu dai thay doi dupc v‹ i

cau triic déu dan vi du nhu sau.

Car tmc bang ma Exp-Golomb [M zeros][1 ][INFO]

Trong do INFO la triréng M-bit mang thong tin. Tit ma dau tién khong cé* so 0 bat dau

va truong INFO két thuc. Tu ma th ti 1 va 2 céi triréng INFO don bit, tir ma thu 3-6

co truéng INFO 2 bit, va cu tiép tuc nhu vay. Chiéu dai ciia mot tu ma la (2M*1) bits

va moi tu ma duoc bo ma hfia cau trtic lai dna vao chi code num:

M = floor(log [code num*1])



Dang chuoi bit Pham vi gi:i tri codeNum

0 1x0

00 1x1x0 3 -6

0001 x2x1 x0 7-1 4

00001 x3x2 x 1 x0 15-30

000001 x4x 3x2x I x0 31 -62

Thong so Mo t:i

Thanh phfin cu ph:ip cuaSequence, picture va slice-layer

Thong tin mao dfiu va cac thong so

Macroblock type mb type Phuong ph:ip du doan cho moi MB ma hoa

Coded block pattern Chi dinh in:iu khfii trong MB dupc ma hfia

Quantiser parameter ‘ QP cua

Reference frame index

Motion vector

Residual data Hé so dir liéu dir thua tir cac khfii 4x4, 2x2


INFO = code num + 1 - 2“

Mfit tir ma dupc gi:ii ma theo thu tir nhir sau:

=

=

=

Dpc trong M

Doc truéng M-bit INFO.

Code num - 2M* INFO -

1Doi voi tu ma so'00 t(h6l1IFNNFFOO va MThong so k

sau:

se’ dupc ma hé*a va dupc

:inh xa vao Code

num theo mot trong c:ic c:ich



Mau héia (Inter prediction) Code num0 (no nonzero b1oc1:s) 0

1 6 (chroma DC block nonzero) II (top-left 8 × 8 luma block nonzero)

2 (top-right 8 × 8 luma block nonzero)4 (lower-letl 8 × 8 luma block nonzero)8 (lower-right 8 × 8 luma block nonzero)32 (chroma DC and AC blocks nonzero) 6

3 (top-left and top-right × 8 luma blocks nonzero) 7

k Code num

22-2

Loai :inh xa Mo t:iAnh xa truc tiép khong dan, code num = k.

L:i phien ban cua bang ma Exp-Golomb, trong dfi tu ma ngan bi cat bfi.

se

Anh xa co dau, su dung vector chuyen dong sai khac, delta QP vanhung vector khac, gia tri k se dircrc anh xa vao gia tri code num nhrr

big IV. Voi cac gia tri code num nhu sau.Code num 2 | k | (k < 0) Code num = 2 k —1 (km 0)

meKy tu anh xa, thong so K se dupc anh xa vao code num. B:ing IV 1i(tke mot phén cac ma’uukhoicho du doan Inter, chi ra nhfrng khoi

8x8 trong MB chira cac hé so khac 0


'i loai :inh xa (ue, te, se va me) se tao ra mot tu ma ngan cho gia tr] x:iy ra nhie’u, va

ID ma dai cho gi:i tri xay ra it. Vi du trong MB Inter loai P LL00 1 6x1 6 (co nghia doan khoi luma 16x16 t ir buc anh truoc) se duoc danh dau Code num ra

thuéng xuyén, MB loai P 8x8 (du doan khoi luma 8x8 tu birc anh truoc) duoc danh

code num 3 vi no it x:iy ra.

IV. 3.4.2 Mii hoa dc› dél hién dc›i thich right rift dang CAVLCBo ma hfia CAVLC sir dung nhie’u bang tra VLC cho c:ic thanh phan can truc, sir

thich nghi cfia no the’ hién cr cho: no lua chon mot b:ing tra cho thanh ph:in cii ph:ip

hién tai dua v:to bang tra da dupc truyén di, do dé* hiéu qua ma h‹i a Entropy sé tang lén.

Sau khi du dotin, bién dfii va luong tir, dac trirng cua khoi hau hét déu la

CAVLC su dung ma héia Run-Level de’ ma hoa chuoi zeros. Nhfrng h( so khac 0 tan

so cao, sau khi quét Zig-Zag thuong két thuc big nhiéu so ±1 thi CAVLC se bao hiéu

so lupng chuoi so két thuc la I ( ’Trailing Oves ’). Trong chuoi sap xép lat bién do cua

h( so khac 0 céi khuynh hu6ng lén dan o vi tri dau tie’n (gan hé so DC) va nhci dfin vé

phia tan so cao. Nam bat d iém nay, bo ma hoa CAVLC su dpng vi(c chon bang

do tim VLC thich nghi cho thong so muc tuy thuoc v:to mdc bién do ma hfia gan nhat.

Qua trinh ma hoa mot ma tran cac hé so da bién doi duoc thuc hién qua 5 buérc sau:

1) Ma hfia so luong hé so khiic 0 (TotalCoeffs) va he so két thuc bang 1

(coeff token)

2)

3)

4)

5)

Ma hoa hiéu cho tung Trailingone

Ma hoa ciic cap dfi cua ciic hé so khac 0 con

lai. Ma hoa tong so gi:i tr| 0 truoc h( so cuoi

cung.

Qtr:i trinh thirc hi(n nhu sau:

Mii hoa 'Irrpng h“‹r st khéc 0 (TotalCoeffs) vé hc: st k ét thtic bérig 1 (coeff token)

Gi:i tri cua TotalCoeffs c {0, I, 2, 3, ... 16} va Trailingones c {0, I, 2, 3} . SC co 4 b:ing dfitim cho ciic hé so coeff token bao gom 3 b:ing VLC va 1 bang ‘ co chiéu

dinh FLC. Viéc chon bang do tim tuy thuoc vao so luong hé so khac 0 bén tay trai va

bén trén cua bang ma triroc do tuong ting voi nA va nB.




Vi du: ne’u c:i 2 khoi nA, nB de’u nam cr bén tay trai phia tre’n

thi nC round((nA n B)/2).

Néu chi nam bén trén thi nC - n B hoac chi nam bén trai nC - nA, con khfing thfia

man thi nC - 0.

Trong dfi thong so nC sé lira chon b:ing do tim nhu sau, vi vay vi(c chon bang ma

VLC se phu thuoc vao gia tri cfia c:ic khoi bén canh (thé hi(n sir thich nghi theo noi

dung CA).

Mii héa ky hi‹:n cho tirng TrailingOne

Moi mot Trailingone dupc ma hfia bang tfi bits dv, néu 1:i 0 thi ma héia thanh “ +”

néu la 1 thi ma hoa thanh “-” theo trat tu ngiroc lai, bat dau voi he so Trailingone co

tan so cao nhat

Mii hoa céc cép d ciia céc hc: st khéc 0 céri liL

Cap do bao gom ky hiéu va gia tri bién dfi cua cac hé so khac 0 duoc ma hoa theo trat

’ ccaaoo nhat

level dupc tao ra tir mot tién to level v:i mot h:iu to level. Tién to level co thé cé› 0->6

bits tuy thuoc v:to bién do ma hoa lie’n mc theo bang sau:



Chiéu d:ii tién tfi hién tai Mirc nguiing de t:ing chiéu dai tién to

0 0

6

4 24

N Bang cho coeff token

J Bang 1 : so lirong lié la néu TotalCoeffs co gia tri nlio se diroc m5 lifiab5ng tir ma ngan va ngunc lai3 Bang 2 so luong hé so trung bl nh, tuc la néu gia tri cua TotalCoeffs trong

khoang

4, 5, 6, 7

Bang “ co’ ddiinnhh 6bits cho c5p gia tri TotalCoeff va Trailingones


Mii hoa dc›c chf ld I

So luong h( so “0” truoc déi (run before) dupc ma hfia theo thu tu ngupc lai. Néu

khong con so “0” nao nira thi giii tri run before = total zeros, khfing can ma hoa gia

tri run before.

Néu con lai 2 so “0” chua ma héia, thi gia tri run before se nhan c:ic gia tri {0, 1, 2 }

va vi the' ma VLC khong can st dung tir ma 1éin hon 2bits

Vi du cho mot khoi 4x4 nhu sau:

Qii;i trinh quét Zig-zag sé sap xép theo trat tu moi.

0, 3, 0, 1, —1, —1, 0, 1, 0.

So luong hé so khac 0 : TotalCoeffs = 5

So lupng h( so bang 0 : Total zeros 3

So luong hé so két thuc bang 1 : Trailingones - 3 (thuc té co 4 gia tri trailingones

nhung chi co 3 gia tri duoc ma hfia nhu truéng hop dac biét).

Quit trinh ma hoa.


5 VTH . NGUYEN

QUANG HOANG SON

Thanh phfin Gia tri

coeff token TotalCoeffs 5, 0000100Trailingone sign

(4)Trailingones= 3 (use

Tabte I )0

Trailingone sign

Trailingone sign(2)

Level (1) 1 (prefix)

Level (0) *1 (use suffixLength = 0) 001 (prefix) 0 (suffix)

Total zeros +3 (use suffixLength = I)

run before(4) ZerosLeft = 3 ; run before i o

run before(3) ZerosLeft 2; run before

0 3 -1 00 -1 1 01 0 0 00 0 0 0

48

6 N/A (chiéu d:ii cao nh:it)


Chuoi bit phat la 0000 10001 110010 1 1 101101.Qua trinh giai ma

Bo giai ma da chén thém 2 so 0, Totalzeros =3, va vi thé 1 so 0 dw ac chén vao truoc héso thap nhat, mang ngo ra nhu sau:

0, 3, 0, 1, —1, —1, 0, 1

IV. 3.4.3 l Ii héa thtch nghi ncii dang CABAC

trong pham vi [0 1] thay vi phai thiét ké mot bang ma, ma hoa ' hoc nhi phan thich

nghi CABAC cho phép an dinh so bit khfi ng nguyén/symbol, thich nghi cac thong kédupc d¿ doan theo

symbol dong trong pham vi [0 1 n:iy. X:ic suat cho '’i th:i nh phan

not dung de diéu khién bo ma hfia so h pc. So s:inh vcii CAVLC, thi CABAC thuong

cho giém toc dfi bit khoang 10-15% khi ma hoa citng mo I tin hiéu truyén hinh.

’in ’ 3 buoc chinh: kiéu noi dung, nh| phfin héia va ma héia so

nhi phan dupc in inh hpa nhu hinh vé



1 Thanh phan Gia trj Mang ngfi ra

oooo i oo °oeft token TotalCoeffs 5, Trailingones 3 Empty

0 Trailingone sign * 1

Trailingone sign - 1, I

1 Trailingone sign - 1, -1, 1

+1 (suffixLength = 0; ting chiéudat tién t‹› sau Llii giai ma

00 1 0 Level *3 (suflixkength = 1) 3, 1, — I, —1, 0, 1

111 total zeros 3 3, 1 , —1, —1, 1

i o ×n before 1 3, 1, — I, —1, 0, 1

run b f 0 3 .I , —1, 0, 1

1 rim before 0 3, , i , —1, 0, 1

o i ×n before 1 3, 0, 1, —1, —1, 0, 1

=0run before(2) ZerosLeft = 2 ; run before

=0

run before(I)ZerosLeft 2; run before

run before(0)ZerosLeft = l ; run before

=1

H(: so cufii cung, klifing can ma

hfia.

Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tienTrang 8R

Qné trinh mii héa.-

Gia su ta co mot khoi duoc ma hoa ché dfi Inter va cé* vector chuyén dong Mvd cua

mot huéng bat ky n:to déi. Dau tién, se’ tién hanh nhi phan hfia gia tri Mvd, Mvd se

dviac tinh xa vao b:ing ma nhu sau:



|Mvdx| Nhi phan


Bit dau tién cua bang tir ma nhi phan got la bin 1, bit thu 2 got la bin 2. . . Chon kiéu nfiidung cho tung bin. Doi voi bin 1 se cé* 3 kiéu noi dung nhu bang, dua vao gia tri Mvd

ciia 2 khoi da ma hoa truoc dfi la gia tri e,.

' b in cfi n lai se chpn mot trong 4 kiéu no i dung sau:

IV.3.5 BI) L1)C TACH KHOI TRONG VONG

Ma hfia dpa trén cc so bién doi DCT cho khoi 4x4 co thé nhin thfiy cau trtic khoi

nhirng mot d*ac trung cc ban cua ma hfia dua trén c:ic khoi lit se’ tao ra mot cau truc

tho. Ngoiii ra, qii:i

trinh du doan bu chuyén dong cung gay nén nhié'uu khoi duoc minh hoa nhu hinh

IV.32. Ta thay rang, c:ic canh khoi cau triic lai thi co do chinh x:ic kém hon c:ic diem

:inh bén trong vi khong ph;ii tiit c:i c:ic pixel tham kh iio niio cling hoan hao, co thé no

cling chira mot so diém anh khfing lién tiép.



Bin Kiéu not dung

2 Kie’u 3

3 Kie’u4

4 Kiéu 5

Kiéu 6

e Kie’u nnfoiii dduunng

Kiéu 0

Kiéu 1

Kiéu 2

11 10s

4 1 1 110s

1 11 110s

6 I 1 1 1 1 1 0s

7


Trong tie’u chuan H.264/AVC, su dpng bo lpc I:ich khoi trong vfing, nghia 1:i ca

trong qu:i trinh ma hoa vii giai init, :inh cau triic lai sé dupc l pc t:ich kho i truoc khi

luu trfi cho bit chuyén dong tiép theo, cucrng do loc duoc diéu khién béri gia tri cua

nhiéu phan

’ ssaauu khi dir do:in. Bo l pc I:ich khoi dirpc sir dung th ich ngh i nhie’u mirc

gi iim nhci sai

= O mirc mau. Ph:in quyét dinh I:i su khac nhau gifra ma'uuf›c vvaa mau dupc luong

tu hfia tu cac he so bién dfii.

TV.J. 5. 1 Nguyén téc ciia lcic téch k:heirNguyén tac cc ban 1:i néu do diroc su sai khac giira cac mau gan nhau o mép khoi nhir

minh hoa ér hinh IV.33, thi can phai han ché, sai khac na/ dé tranh hién tuong két khoi

dun

0


Hinh IV. 33. Nguyen Iy loc tdch khc›i


Trong do:

= Giii tri offset cua ‹z v:i 9 dac trung cho cu6ng do lpc, gia tri am cho cuéing do

yéu va gi:i tri duong cho cuéng dfi manh, va gia tri cua ‹z va /I nhu sau:

o = I(QP + n offset)

§ = I(QP = § offset)

o offset = [—6, — 5, — 4, — 3, — 2, — 1, 0, + I, = 2, + 3, + 4, + 5, = 6]

§ offset = [—6, — 5, — 4, — 3, — 2, — I, 0,= 1,= 2,= 3,= 4, + 5, + 6]

= Gi:i tri cua ‹z va ,/I phu thuf›c v:to tham

bén c h.

QP trung binh cua 2 khoi

IV. 3.5.2 QUA tti h lpc khc›iMoi MB va moi th h phan se duoc tach riéng de loc, cac mép theo chiéu thang dung

se dupc loc truoc, bat dau tai mép nam bén tay trai cua MB cho dén c:ic mép cuoi

ciing nam bén tay phai ciia MB, sau do loc theo chiéu ngang, bat dau voi mép nam

phia trén MB cho téri mép nam phia duoi cung ciia MB. Trinh tij cac buoc lpc duoc

minh hpa nhu hinh sau.

= Buoc 1 : Chia b iuc anh thanh c:ic MB va tim khoi bi nhiéu176

Khoi can dunc loc

Birc anh duoc chia th:inh c:ic MB




= Buoc 2 : Lpc canh thanh phan Luma theo chiéu doc

= Buoc 4 : Lpc canh thanh phan Chroma

Loc theo chiéu dpc ngang

Loc theo chiéu

bS lii cuéng do duéng bién quyét dinh kiéu ma hfia cling nhu tham so lupng ii cua c:ic

' bS phai tufin

theo guy d|nh sau:




Qua trinh lpc P0 va Q0 x:iy ra khi theta man cac diéu kién sau:

Trong dci 9 <a. No se tang cung voi gia tr| birc luong tir trung binh QP cua 2 khoi P

va Q. Qua trinh lpc P 1 va QI xay ra khi thfia man cac diéu ki(n sau:

Triréng hpp fit e {1, 2, 3}

Mot bo lpc dap ting xung hfru han FIR-4 tap dupc diing dé loc cac gia tri p1, p0, q1, q0

tao thanh cac giii tri p’0 va q ’0. Néu do la thanh phan luma va co |p2-p0|< /7 thi sC su

dpng mot FIR-4 tap kh:ic dé lpc cac gi:i tri p2, p I , p0 v:i q0 de tao ra p’ 1 . Con néu |q2-q0| /I thi sC su dung mot FIR-4 tap khiic dé loc cac gia tri q2, q 1, q0 va p0 de tao ra

Triririig hpp 65 —— 4

Néu do la thanh phan luma va co |p2 - p0| /I , |p0 - q0 round( n / 4 ) thi

+

+

+

Sir diing mot FIR-5 tap kh:ic de’ lpc c:ic gia tri p2, p I , p0, q0 va q1 tao ra

p’0 Su dung mot FIR-4 tap khac dé loc cac gia tri p2, p1, p0 v:i q0 tao ra p’

1

Su dung mot FIR-5 tap khac dé loc cac gia tri p3, p2, p1, p0, va q0 tao ra p’2

- q0

round(ci / 4 )

+

+

Sir diing mot FIR-5 tap kh:ic de’ lpc c:ic gia tri q2, q I , q0, p0 va p1 tao ra q’0

Su dung mot FIR-4 tap khac dé loc cac gia tri q2, q1, q0 v:i p0 tao ra q’ 1



Néu ca p va q déu ma hfia Intra va co duirng bién khoi giua chiingbS = 4 (Loc

manh nhfit)

Neu c:i p va q déu ma lifia Intra va khong co dircrng bién khfii giira chung

bS 3

Hoac p liay q m5 hfia Intra, p va q chua hé so ma lifia. bS 2

Hoac p hay q m5 hfia Intra, hoac p hay q chira hé so ma hfia, p va q su dung

:inh tham khao khac nhau hoac khac nhau vé so luong anh tham k1i:to. . . .

bS 0 (khong

loc)


+

+

Su dung mot FIR-5 tap khac dé loc cac gia tri q3, q2, q1, q0, va p0 tao ra q’2

Su dung mot FIR-3 tap khac dé loc cac gia tri q 1, q0, va p 1 tao ra q’0

IV.3.6 CAU TRUC VA CU PHAP CHUAN H.264/AVC.

De co thé truyén trong c:ic moi truéng khac nhau dupc hie qua, sq tich hop c:ic giao

thirc va cau truc mang la rat quan trong. H.264/AVC co su phfin bi(t gifra dac tinh ma

hoa va truyén tai cua 2 l6p VCL va NAL nhu hinh IV.35. mang lai hiéu qua cao trong

mo‘ii tri réiing mang khac nghhiiéétt..

Video Coding Layer

Coded Macroblock

Data Partitioning

Hinh IV. 35. C u trim dc›ng h it H. 264

Ngoai ra trong H. 264/AVC con ho tro anh IDR, anh nay duoc tao ra tu :inh I hoac

anh SP nham xéia noi dung vung nho dém anh tham khao hay néii cach khac la lam

tuoi bo nho. Khi nhan dirpc anh IDR thi bo giai ma sé d:inh dau tat ca c:ic bfic :inh

trong bo



Network Abstraction Layer(H.320, MP4FF,H. 323/IP, MPEG2. . .)


di ct thé giai ma ma khfi ng can bat ky mot :inh tham khao n:to truoc anh IDR. Cau tril c

cua mot dong bit H.264/AVC in inh hpa nhu hinh sau

Hinh IV. 36. Cau tnic dong b it.

IV.3. 6.1 Lép trim tircrng mprig NALTfit ca dir liéu duoc chiia trong cac khoi NAL, moi khoi chira mfi t so nguyén byte xac

dinh dinh d g chung cho ca hé thong dinh huéin g goi (packet - oriented) va hé thong

dinh huéng dong bit tbitstream), ngoai trir 'i khoi NAL trong 16p truyén tai dinh

huong dong bit co thé co mot tién to ma hoa ci truoc, va céi thé la mot trong 2 dinh

dang sau: dinh dang theo ti:rug dv vi NAL hoac theo ting byte.

= Dinh dang theo tirng don vi NAL la mot kiéu dinh dang cc ban, bao gom cac

chuoi cau tmc cu ph:ip NAL dupc sap xép dé giai ma.

= Dinh dang theo tung byte co thé duoc xay dung lai tu cfiu truc cua NAL bang

cach xap xe’p c:ic don v j NAL trong qua trinh giai ma v:i thém v:to mot tién

to ma bat dau cho moi NAL.

Mfit chuoi video H. 264 bao gfim mot chuoi cac don vi NAL,

cac th:inh phan RBSP nhu bang 1, RBSP la mot tap hop dir li(u tuong ting voi dir lieu

video dirpc ma héia hay thong tin dari muc, vi dp mot chuoi c:ic don vi RBSP nhu hinh

IV. 3 7, trong do cac don vi duoc truyén di duoi dang cac don vi NAL riéng biet. Byte

dau tién ciia NAL hay cfin goi la header co chiéu dai 1 byte chi ra loai RBSP dupc sir

dung, cfin nhfrng byte con lai thi chua dir lieu cho viéc truyén tai hoac fun trfr.

Hinh IV. 3 7. Minh hpa mot chuéi thénh phén RBSP.

Bang ciic thanh phan RBSP duoc miéu t:i nhu sau:



Mo titThong so ve kf cli tliuérc, dinh dang video, vi tri anh xa

MB, so luong anh tham khao, thong so luong tu.

Thong tin mo rc›ng ma dung thfr tu chuoi video

Sequenceparameter set

Picture Picture

.NALheader

RBSPNALheader

RBSP NALheader RBSP


Bang 1 : Cac thanh phfin RBSP

IV. 3.6.2 Lop mii héa video VCL (Video Coding Lciyer)

Ngfi ra cua qua trinh ma hoa 1:i c:ic dir 1i(u VCL bao gom mot chuoi c:ic bits dac

tnrng cho dir lieu video ma hfia dupc anh xa vao NAL dé truyén di hoac luu trfr. No 1:i

su ke’t hop du doan theo thoi gian va khfi ng gian va voi ma chuyén v|. Thuat toan

ma hfia ngiion cc b:in van d¿a trén ky thuat nén tién anh de’ khai th:ic, thong ké su

phu thuoc du thua ve thoi gian va du doan ma hoa bién dfii dé khai thac su du thira vé

mat khong gian nham muc dich cuoi cung la nang cao hiéu sufit nén. Hon nfra, lop

VCL bao gom nhiéu d*ac tinh nhu 1 7 kiéu dir do:in Intra, the at toan b ten dfii, l pc

t:ich khoi, ma hoa Entropy hay ma hfia thich nghi khung v:i manh. . .cung cap mot

moi truong mang than thién va tang cuéng kh:i nang chong loi phu hop cho cac dich

vu thoi gian thuc nhu

IV. 3.6.3 KQ theat FMO vii Data Partitioned SlicesKy thuat FMO mo ta cach phan chia buc :inh thénh c:ic slice va MB bang cach su

dung kh:ii ni(m nhom slice. Nham che giau cac kénh co khuynh huéng b| loi voi

cac Eng dpng co dfi tre’ thap. Dir 1i(u ma hoa tir cac Slice dirpc chi thanh 3 loai phan

vung nhu A, B, C chua tap hop con cua slice duoc ma hoa. Phan vitng A ch ira slice

header va du 1i(u header cho moi MB. Ph n vung B chua phan dir lieu sai khac dupc

ma hfia cho slice Intra v:i SI va phan viing C chira phan dir 1i(u sai kh:ic dupc ma hoa

cho MB ma hoa Inter. Moi phan viing co thé duoc dat riéng biét va truyén tach biét

trong tirng NAL. Néu dir lieu phan viing A bi mat, thi rat kho khan cho viéc cau truc

lai Slice, vi



Dircrng bién giira cac anh, néu khfing co tlii bfi giai maframe trong moi tién to slice dé phan doan

Slice ma hfia Chira tien to va dir liéu ma hfia

Phan viing dir liéu A, B, c Ba d g ph:in vitng nham tang cuong kha nang chfing

Chi dinh buc anh ké tiép trong thir tir giai ma la anh

IDR. tKli Eng edu thiét)Khfing con anh tiép theo n:to ca.Chua dii Iie‘u “gia” nham tang so luong byte trong

chufii.(Khonp can thiét)


ho*ac ch i A va B.

IV. 3.6.4 Kj thua I Arbitrary Slice Ordering

Ky thuat sap xép trat thu tu slice bat ky ASO cho phe'p bo giai ma céi the’ xir 1y slice

dung theo thu tu dé co the bat dau xu ly chung. Diéu nay lam giam do tré

gi iii init, két qu;i la do tré tiém an trong c:ic irng dpng truyén video thoi gian thirc sé

nhfi di.

TV.3.b.5 Chi trtic dimg bit I-I.264/A VCCau trtic dong bit H.264/AVC dwac minh hoa nhu hinh IV.38.

Trong do:

••• Seq : thong tin ve chuoi anh (Squence)

-

-

-

Video Params : thong so chiéu cao, rong, ty lé khufi n hinh cac phan tu

anh. Bistream Params : toc dfi bit va cac thong so khac.

QTs : co 2 loai QTs

+ Ne'n trong anh

+ Nén lién anh

•:• GOP : thong tin ve nhé*m anh

Time code : SMPTE time code : Gio, phut, giay, anh.

GOP Params: Mie’u ta cau trilc va cac thong so cua

GOP.

PICT : thong tin ve’ anh (Picture information.)

- Type ::inh loai I, P hay B.

+ Buffer Params : thong tin vé bo dém.

+ Encode Params : thong tin ve vector chuyén dong.

Slice : thong tin ve Slice anh.

- Vert Pos : Slice bat dau tu dong nao.

- Qscale : thong tin vé bang luong tu.

•••

•••

•••




- Addr Incr : So luong MB duoc bo qua.

Type : loai vector chuyén dong diing cho MB.

Code Block Pattern (CBP) : chi ro loai khoi dirpc ma ho:i.

GOPSeq QC Video Bitstream Par

QTs Misc

GOP

PSC Type Buffer Params

Encode Params

Slice Slice

Hinh I V.38. C u tribe dong hit MPEG-4 H. 264/A FC



Addr Iner

Type Motion vector

Qscale CBP b0 b5

SSC Vert Qscale MB MB

GOP SC TimeCode

GOPParams

Pict

Seq Seq


CHU©NG V. MOT SO VG DUNG CHUAN H.264/AVC

.264/AVC danh dau mot buoc ngoat trong linh vijc nén video, nho ap dqng

dam lai chat luong anh cao hon va dfi tré thap. Voi ciic ky thuat nay, H. 264/AVC co

thé giam toc do bit xuong hon 50% so voi chuan MPEG-2. Tuy nhie’n, H.264/AVC

doi hot mot cap do phirc tap cao hon trong c:i qua trinh ma hfia tan giai ma. Mac du

vay, thu thach nay hoan toan co thé chinh phqc duoc nho co nhirng tién bo moi tién

tiép trong kha nang xu ly phan me’m cfing nhu phan cling. Diéu nay céi

nghia la

H. 264/AVC la mot ung ct vie’n tie’m nang co kh:i nang thay the MPEG-2 trong nh

irng nam sap Hi ci cac linh virc nhu truyén luong Internet toc dfi bit thap toi cac ung

dung qu:ing ba HDTV va Cinema ', truyén thong video qua mang Internet, truyén

hinh di d cing theo chuan DVB-H, truyén hinh so mat dat, truyén hinh theo yéu cau,

tin nhan da phuong tién MMS. . . qua cac mang ISDN, DSL, Wireless, LAN va ve tinh.

.

Cong nghé truyén hinh so ta da khac phuc dirpc nh iéu khuyét diém cua truye’n hinh

tuong tir nhung hon ca la mci ra cho ta mot tiém nang phat trién vo citng rong lori. Co

thé thay su ho tro mang tinh ban chat cho cac hoat dong tuong tac la su khac nhau chu

yéu, thé hi(n tinh nang uu viét cua cfing nghe’ H.264/AVC so voi MPEG-2, lit chuan

hién dang duoc ap dung rong rai trong cac hé thong truyén hinh. Trén thuc té cac hang

cung cap dich vu truyén thong theo dong da phuong tién déu da ho tro chuan

H. 264/AVC trong cau truc ha tang va san pham dang trién khai cua minh, nham khac

phuc nhuoc diém cua cac mo hinh truyén dan phat song phat thanh va truyén hinhV.1 TRUYEN HINH INTERNET IPTVIPTV 1:i mang truyén hinh két hop chat che voi mang vien thong. Nfii rong hon IPTV

la dich vu gi:i tri gia tang sir dung mang bang rong lP phuc vu cho nhiéu nguoi ditng.

Cac user co thé thong qua may vi tinh PC hoac may thu hinh phfi thong ‘n voi STB

d é st ding d|ch vu IPTV. Dac diém nfii bat cua IPTV la dna trén nén ’n n é IP

co kh:i niing tuong I:ic. IPTV st dung chuan nén H.264/AVC tain gi:tin di mot nira

bang thong can thiét dé phan phoi video so chat luong DVB day man hinh dén kh:ich



L VTN. Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tien Trang I t1t1

h:ing, va giam yéu cau bang thong truye’n 'n tru én hinh so chat luong chufin SDTV

xuong 700 kb/s - ca hat nam trong gioi han cua vfi ng DSL 1 .5 Mb/s. H.264 mci ra

c:ic cc hoi moi va cung giam gia thanh ap dung va gia thanh diéu hanh khi so sanh

voi MPEG-2. H. 264 nén video hiéu qua hon, giam gia thanh truyén dan qua cac két

riot vé tinh va m*at dat.

fi nuoc ta mot so Website ciing da cung cap thir nghi(m cac chuong trinh truye’n

hinh truc tuyén nhu VietNamNet, Cong ty VTC, Dai truyén hinh HTV da ghi nhan so

luong truy cap rat lori, cho thay suc http dan ciia dich vu nay doi voi cfing chung. Voi

mang bang hep truyén thong, chi mot so dich vu don gian cfi a IPTV 1:i co thé thpc

hi(n dupc. Con dé co thé trién khai thanh cfing dich vu IPTV thi mang bang rong dong

vai tro tién quyét, boi vi chi voi mang bang rong méri co the bao dam cung cap day du

bang thong

V.2 TRUYEN HINH VE TINH DVB-52DVB-S2 da chon H.264/AVC cho ma hoa ngufin audio va video ci toc do 8Mb/s rat

phii hop voi mot DVD thong thuong. Vo h i(u suat sir dung bang thong tang tir 30%

den 13 1%, so chuong trinh ma H.264/AVC mang lai co the tang gap ba so voi viéc

dung MPEG-2, vi du nhu co thé phat 21-26 chuong trinh SDTV hoac 5 -6 chuong

trinh HDTV tre’n mot transponder 36Mhz. Cong ngh( nay thuc su la bo

cho c:ic dich vu tuong tiic qua ve tinh. Truyén hinh tuong tac la mot phuong thuc

qu:ing cao truyén hinh moi két hop diém manh giira tiép thi truc tiép va truyén hinh,

qua dfi ngiroi xem co the chon mii a, xem thong tin ch i tiét... ch i don gian qua mot

thao tac click, hoac trong khi xem chuong trinh truyén hinh, nguoi xem co thé tham

gia vao cac trfi choi qua cac hinh thuc gut tin nhan SMS . . . Truyén hinh HDTV da

tro thanh mot mot san pham thiét yéu trong c:ic gia dinh. Co khoang hon 1 0 triéii

hfi gia dinh trén to:in cau hién su dung HDTV, con so nay dir kién se tang lén 52

tri(u v:to nam 2009. Dfiy thuc su la mot tién ich hap dan voi kh:in gi:i truyén hinh. SC

:inh huéng tich

V.3 TRUYEN HINH DI DONGTruyén hinh so Hi cac thie’t b| di dong voi man hinh nho co mot su tuong tu nhat dinh

véri truyén hinh co dinh. Dé cac kénh truyén hinh co thé hién thi ro nét véri chat luong



L VTN. Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tienTrang I Ill

cao tre’n cac thie’t bi xem truyén

di dong va di kém voi né› la cac ti(n ich tuong tac

d*ac thu, c:ic luong tin hiei chira nfi i dung ph:ii dupc dong got, truyén t;ii v:i gi iii

ma trong mot guy trinh khép kin, dong bf›... Dau tién, riot dung phai duoc tao ra phii

hop véri thiét bi di dong cé* man hinh nho, va diéu n:iy yéu c:iu phai cé* ky thuat thu

hinh tinh té néii muon hinh tinh dupc thé hie’n tot trén m;in hinh nay (vi du céi the

dung 2 camera dé 1:iy ciing mot canh, mot cho man hinh TV lén, mot cho man hinh

di dong

khac nhau). Thu hai, cc cau phan phoi riot dung cung co

thé kh:ic lien quan Hi van de su dung pho tan so. Thu ba, co nhiéu giao thiuc phan

phoi noi dung. Va cuoi cfing, kha nang phan phoi kénh tuong tac ciing phong phu

hon. Voi toc dfi bit thap ciia H. 264/AVC cho phép Hi riot dung da phuong tién trén

cac dqng cu nhu dién thoai, PDA, laptop,.. qua cac cfing nghé Wireless, DAB,

CDMA2000, UMTS va DBV-T. Ma hi(u suat nén tiing gap dfii so voi cac chuan truoc.

Hién nay truyén hinh di 6ong da tro nén pho bién ci nuoc ta voi hai cong nghé 3G -

CDMA 2000 lx EV-DO ciia S-Fone va cfing nghé DVB-H - Nokia va VTC. Viét Nam

la nuoc dfiu tie’n tai chau A va 1:i nuoc thir 2 trén thé gioi (sau Phan Lan) dupc

Nokia trién khai dich vu truyén hinh di dong. Co thé hiéu nom na la THDD hién co 2

chiéu huérng, mot la xem truyén hinh nhu ban van xem trén tivi o nha (cfing nghé

DVB-H va DMB) v:i viio mang Internet xem tivi trén may tinh (Media- Flo v:i 3G).

DVB-H cung sir dung ciic bfi ma hoa am thanh hinh anh tién tién nhu H.264, cho

phép dén 50 kénh truyén hinh hoac dfi lieu co thé dupc truyén qua DVB-H

multiplex. Theo Nokia, uu die’m ciia thie't bi nay la tie't ki(m pin v:i co tinh nang

manh ngay ca trong moi truong tiép nhfin khfi khan; giup tiét kiém chi phi mot cach

hiéu qua trén cac mang truyén hinh; céi dung luong bang tan rong cho nfii dung

hinh anh, am thanh phong phu; sir dpng dat tan UHF, dupc to tin cau su dpng cho

truyén hinh. O 3 G vi(c truyén dir 1i(u phu thufic vao toc dfi du6ng truyén cua

mang di dong, chinh vi vay 2G hay 2,5G khong du manh dé dap ung doi hoi duéng

truyén ciia dich vu nay, do tin hiéu video yéu cau bang thong kénh truyén tuong doi

lori (khoang vai tram kbps). Voi ky thuat nay, mo'‘ii thué bao duoc cap mot kénh

trao doi thong tin trong tai nguyén cua mang dién thoai dé trao dfii thong tin truyén



L VTN. Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tien Trang I t12

thuéng). Truye’n hinh theo cach nay ciing khong cén ph:ii co tan so riéng. Kénh

thong tin trén cong ngh( tniyén hinh 3G co tinh chat 2 chiéu (tiron g tir nhu 1

kénh dam thoai), nhung la kénh truyén dir liéu duoc tram thu phat goc (BTS) cap

cho thué bao. Nhu vay, moi thué bao se chiém mot phan tai nguyén thong tin cua

tram BTS khi ho sir dpng dich , vi vay se han ché so ngiroi dung cung luc. Khi

lirong nguoi dung ton, d é co the’ phpc vu. tot cho nguoi su ding d|ch vu, bat buoc

nha khai thac mang phai




CHU©NG VI. MO PHONG QUA TINH NEN-GIAI NEN CUAH.264/AVC BANG MATLAB

VI.I LTU DO GUI THUATSau day la qua trinh ma hoa va giai ma mot frame bang cac ky thuat cua H . 246:

END

VI.2 CHUONG TRINH MO PHONG:So voi MPEG-2 thi H. 264/AVC cé* rat nhiéu uu diém noi bat nhung vi con nhiéu han

ché, nén em chi céi thé mo phong mot phan cach ma hoa tién tién cua H.264/AVC nhu

sir dung 52 buoc luong tfi, su dpng bién doi ICT cho khoi 4x4...De’ co thé hoan thanh

dupc chuong trinh

ngoat sir co gang cua ban than, sir dinh huéng diing

dan cua TS. Tran Dfung Trinh, em cfi n tham kh:to mot so module Matlab co san tre’n



Tai tao lai MB tu cac block 4x4

Luu th:inh file“la,stmov ”

Bién doi frame In YUV sang RGB

Ma hfia Entropy

DCT

Bién dfii ICT cac block 4x4 du th a

Tim vector chuyén d(ong trong file " /‹ix/inov ’

Phan chia thanh cac block 4x4

Can ture lai etc blocL 4x4 dé tham ldrao

Du doiin chuye’n dcing

Phan chia thanh cac macroblock

Phan chia thanh cac frame

Chuyén file YUV sang Matlab movie

Nap tileYUV


Web, mot so ham ho tro tir Matlab...va dac biet dupc sp giup do cfia c:ic anh chi trong

cfi ng ty Stone da giiip em ho iin th:inh tot Do an nay. Tiiy nhién, vi vi(c ma hfia

mot buc anh co qua nhiéu cfing doan phuc tap, va viéc ma hoa cling ton kha nhiéu

thcii gian, yéu cau bo xu ly toc dfi cao nén khong thé tach riéng timg qua trinh

dé mo phc› ng.

Cac module mo phcing nhu sau:

+ H:tin main

+ H:tin playmov

Ham

: chuong trlnh chinh, se’ gpi c:ic h:tin con dé ma hfia, giai ma.

: h:tin play file movie da dupc nén.

: ham vC vector chuyén dong trong anh P va anh BHam progressbar : ham ho tro tu Matlab, dung de minh hoa tién trinh xu ly cua

Matlab, ham duoc tham khao tu trang web mathexchange.com.

Ham yuv2mov

: ham ho tro tir Matlab, dung dé chuyén file YUV sang file movie

trong Matlab, ham dwac tham khao tir trang web mathexchange. com.

Ham sec2timestr : ham ho tro tir Matlab, dung dé chuyén mot chuoi s6 sang dang

thoi gian thuc, ham dupc tham khao tu trang web mathexchange. com.

VI.3 KET QUA MO PHONG

Voi citng gia tri QP - 31, Frame thu 1 cua buc anh foreman. yuv duoc nén bang ky

thuat H. 264/AVC co dung luong

va ty so PSNR - dB nhu sau



L VTN. Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tienTrang I HS

Cfin nén bang ky thuat MPEG-2 co dung luong va ty ‘ PSNR =— dB nhu sau




function main()clear all;

fprintf('\riLUAN VAN TOT NGHIEP\n')fprintf(’\nTONG QUAN VE CHUAN NEN MPECi-4 H.264/AVC VA KHA NANG UNG DUNG TRONG THUC TIEN\n')fprintt('\nGVHD : TS. TRAN DUNG TRINH\n') fprintf(’\nSVTH : NGUYEN QUANG HOANCi SON\n’) fprintf('\nMSSV : 103 10 Iclionf = input('\riNHAP 5 O kUONG FRAMES SE MA HOA = ’);chong input('\nNHAP GIA TRf BUOC LUONG TU TRONG KHOANGrig = chong; nf = clionf,it (rig 0 rig 51 | nt 300)

‹<«:('NHAP SAI GIA TRI LUONG TU HOAC SO FRAMES! !!!')endsave rig;fprintf(’\nSE MA HOA %«d FRAMES VOI BUOC LUONCi TU QP=%d\n',nf, nq);mov napmov(nt);

QP=');

avc = ma1ioa(mov);fprintf('THOI CiIAN MA HOA : %s\n',sec2timestr(toe));

mov2 giaima(avc);fprintf(’THOI GIAN CiIAI MA : %«s\ri’,sec2timestr(toc)); save lastmov mov2 avc mov;

%%%% HAM MO FILE YUV ROI LUU THANH MATLAB MOVIE %%%%function movdata = napmov(nf)mov = yuv2mov('earphone. yuv’, 176, 144,'420');%mov yuv2mov('foreman. yuv',352,288,'420'); save mov;load mov; it nf 0

nt length(mov);end% MOV( 1) : MA TRAN CHOI, MOV (2), MOV(3) MA TRAN MAUmovdata = repmat(uint8(0),size(mov(I ).cdata), nf);%« tai tao lai MANG MOV RONGfor i = 1 : nf

% MA HOA TU FRAME 1 DEN FRAME THU nfmovdata(:,:,:, i) = mov(i).cdata;% kUU DU kIEU CUA CAC

FRAMEend%%%%%% HAM MA HOA FILE MATLAB MOVIE %%%%%%%fpat 'IBBPBBPBBPBBPBB I', % LOAI MAU FRAME (CHO TOAN BO

MOVIE)k = 0;pt []; progressbar

% FRAME DAU TIEN% MA TRAN MAU FRAME LA RONG

for i I : size(mov,4) % VONG LAP FRAME, TRA VE GIA TRI COT% THU 4 TRONG MOV% BfEN DOI FRAME SANG GIA TRI

I I

double(mov(:,:,:, i)); rgb2yuv(I);




if k ° length(fpat)endfiype = fpat(k);

% DAT TEN kOAI FRAME THU k[avc i },pt] mhframe(I, ttype,pt);% GOI HAM MA HOA CHO FRAME

THU iprogressbar(i/(size(mov ,4))) % HIEN THI % QUA TRINH MA HOA,

end%%%%% HAM MA HOA TUNG FRAME

ANH%%%%%%

function [avc,df| mhframe(f,ttype, pf)[M,N,i] size(I), mbsize [M, N] / 16;

% M 1 76, N= 1 44, i 3 TRONG I% PHAN CHIA THANH CAC MACROB LOCKavc struct('type',[],'mvx', [],'mvy',[],'scale',[],'coet',[]),

avc(mbsize(I ), mbsize(2)).type = [];

dt zeros(size(I));for in

: mbsize(I ) % VONG LAP THEO CHIEU CAO% VONG kAP THEO CHIEU RONCi

for n = 1 :mbsize(2)× = 16*(<-1)*1 : 16*(<-1)+16;% LAP TU 1-CAO

I 6*(«- 1)= 1 : I 6*(«- 1 )³ I 6;% LAP TU I -RONG

[avc(in, n),df(x, y,:)] = mhmb1ock(I( x, y,:),ftype, pf, pfy,x, y);

end %%%%%%%%%% HAM MA HOA MAROB LOCK %%%%%%%%function [avc,dmb] = m1imb1ocL(mb, fiype,pf, pfy, x, y)persistent q I q2;it‘ i sempty(q

I ) q 1 = 9intra; q2 = 9inter;

endload rig; scale nq;avc.type 'I';avc. mvx 0;avc.mvy = 0;

%Neu mang q I la rong.

%THONG SO BUOC LUONG TU% CAU TRUC AVC

% TIM VECTOR CHUYEN DONG CHO ANH Pif ftype =='P'

avc. type = [avc,emb] mb = emb; q

q2;

getmotionvec(avc, mb,pf,pfy,x,y);%« kAY PHAN SAI SO GIUA CAC FRAME P DE MA HOA

% NEU GA ANH P THI DU DOAN INTER%NPU LAANH I

q

% TIM VECTOR CHUYEN DONG CHO ANH Bit‘ ftype 'B'

avc. type ='B';[avc,emb] getmotionvec(avc, mb,pf,pfy,x,y);ml› em1›; % LAY PHAN SAI SO GIUA CAC FRAME B DE

MHOA




end

% CHON KHOI VA TIEN HANH BIEN DOI DCT VA LUONG TUb = getb1ocks(mb);

avc. scale(i) = scale; % DAT VECTOR kUONG TU CHO KHOI icoet dct2(b(:,:,i)); % BIEN DOI DCT HAf CHfEU CHO KHOI THU iavc. coet(:,:,i) round( 8 * coet ./ (scale *

q)); end% CAU TRUC LAI KHOf DE THAM KHAOdmb gmmb1ock(avc,pt,x,y);%%%%% PHAN CHIA MACROBLOCK THANH 18 KHOI

4×4%%%%%

function b = getb1ocks(mb)b zeros([4, 4,b(:,:, 1) ml›( 1 .4,b(:,:,2) mb( 1 :4,b(:,:,3) = mb( 1

% TAO l8 MA TRAN 4x4 ZEROS 1.4, 1),5: 8, 1);9: 12, 1);13: 16, 1);1 :4, 1)i5: 8, 1);9: 12, I );13: 16, );

b( ³ . ³,5)

h( 5 : 8,b(:,:,6) = mb( 5

:8,b(:,:,7) = mb( 5 : 8,b(:,:,8)b(:,:,9)b(:,:, 10)

mb( 5 :8,mb( 9: 12, 1:4, I);mb( 9: 1 2, 5 : 8, 1

);b(:,:, 11) = mb( 9: 12, 9: 12, 1);b(:,:, 12) mb( 9: 1 2, 1 3 : 16, 1);b(:,:, 13) = mb( 13: 1 6, 1 .4, I ),b(:,:, 14) = mb( 13:16, 5: 8, 1);b(:,:, 15) = mb( 13:16, 9: 12, 1);b(:,:, 16) = mb( 13: 16, 13: 16, I );% HAI KHOI CHROM (GIA TRI TRUNG BINH CUA 4 KHOI BEN CANH)b(:,:, 17) 0.25 * ( mb( 1 .4. 15, I . 4. 15, 2) ml›(1 . 4. I 5,2.4. 16, 2)

.= mb(2:4: 16,1 : 4: IS, 2) mb(2:4: I 6,2:4: 16, 2));

0.25 * ( mb( 1 .4. 15, I . 4. 15, 3) ml›(1 . 4. I 5,2.4. 16, 3) .

b(:,:, 18)

%%%% HAM TINH TOAN VECTOR CHUYEN DONG

%%%%%%%function [avc,emb] = getmotionvec(avc, mb, pf,pfy,x, y) mby mb(:,:, 1); % CHI TIM TRONG THANH PHAN Y[M,N] = size(ply) ;% TIM KIEU MOI KHI A CANH% ma›:step = 10; % Largest aJJowab Ie motion vect or in x and y% mvxv -maxstep: maxstep;% mvyv = —maxstep: maxstep;% tor i I . leneº(•×××

%%%%

if (tx(1) < 1) (M < tx(end)) continue

endtor =— I1 ::l1eength(mvyv)




'%%%%%%

if (ty(1) 1) (N ty(end)) continue

endsad = sum(sum(abs(mby-ply(tx, ty))));it sad minsad

minsad = sad; mvx mvxv(i);

%%

end end

% end

% TIM KIEU Logarithmicstep = 8;dx =

% KICH THUOC BUOC TIM KIEM Initial step size for logarithmic search

0 -1 -1 -1 0 1]; % VECTOR CHI HUONG TIM KIEMdy [0 0 1 1 1 0 - 1 - I - 1]; % [origin, right, right-up, up, lett-up,% left, left-down, down, right-down]

mvx = 0;mvy = 0;whi Ie step >= I

minsad = inf;for i = I :1ength(dx)

tx x + mvx + dx(i)*step;if(tx( 1) < 1) (M tx(end)) % NEU GIA TRI tx( I ) ² I HOACcontinue % M GIA TRI tx CUOI

CUNGendty 7 “ °Y + dy(i)*stcp; it (ty( 1) 1) (N ty(end))

continueendsad = sum(sum(abs(mby-ply(tx,ty)))); if sad minsad

minsadend

endmvx = mvx mvy = mvy

sad;

dx(ii)*step; dy(ii)*step;

step = step / 2; endavc.mvx = mvx; %» kUU VECTOR CHUYEN DONCi avc.mvy mvy;emb = mb - pf(x*mvx, y*mvy,:); % MAC ROBLOC K SAI SO

HAM CiIAI

function mov giaima(avc)movsize = size(avc });mov repmat(uint8(0),[ 16*movsize( I :2), 3, length(avc)]);

for i I

I :1ength(avc) gmt1ame(avc {i },pt);

% GIAI MA TOAN BO KHOI TRONG AVC

% GIAI MA FRAME


5 VTH . NGUYEN

QUANG HOANG SON

MA

L VTN. Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tien Trang I I II

pt I)I= yuv2rgb(I);

% LUU FRAME TRUOC DO% BIEN DOI FRAME SANCi RGBI min( max(f,0), 255); % GIOI HAN MOVIE TRONG KHOANG 8

BITS mov(:,:,:, i) uint8(I); % LUU FRAMEprogressbar(i/(length(avc)));

end%%%%%%%%%%% HAM GIAI MA

FRAME%%%%%%%%%%%%%

function fr gmframe(avc,pt)midsize size(avc); M = 16 * mbsize( 1); N 16 * mbsize(2); fr

zeros(M, N,3), for in : mbsize(I )

tor n I . midsize(2)

% KICH THUOC MB CHINH LA KICH THUOC FILE

%LAPTOANBO VB

× = 16*(<-1)*1 . 16*(<-1)+16,% TAO LAI FRAME y I 6*(n-1)³ 1 . I 6*(n-1 )³ 16,fr(x, y,.) gmmb1ock(avc(in, n), pt,x, y), % GOI HAM GIAI MA MB CHO

KHOI end % macroblock loopend%mse = floor((mov(i).cc1ata)-(avc(i).cdata)),%psnr 10*1og1 0(25 5º2/mse),%save psnr,%%%%«%%«%%%%«%% HAM DAT KHOIfunction mb putb1ocks(b) mb zeros([ 16, 16, 3]),ml›( 1 .4, 1.4, 1) b(. ,., I ),mb( 1.4, 5. 8, 1) = b(.,.,2),ml›( 1 .4, 9. 12, I ) 1›(.,.,3),ml›( 1 .4, 13. 1 6, 1) = b(. ,.,4),mb( 5.8, 1.4, 1) = b(. ,.,5),mb( 5.8, 5. 8, 1) = b(. ,.,6),mb( 5.8, 9. 12, I) = b(.,.,7),

%%«%%«%%%%%%%%%%«%

mb( 5. 8, 13. 16, 1)ml›( 9. 12, I .4, I )mb( 9. l 2, 5.8, I )ml›( 9. 12, 9. 1 2, 1

b(.,. ,8),1›(.,.,9),b(.,., 10),

b(.,., 1 1 ),mb( 9. 12, 13. 16, I) = b(.,.,12),

mb( 13. 16, I .4, 1) = b(.,., 13),mb( 13. 16, 5.8, 1) = b(.,., 14),mb( 13. 16, 9. 12, I) = b(.,., 15),mb( 13. 16, 13. 16, 1) b(.,. , 16),z = [1 1 1 1, 1 1 1 1, 1 1 1 1, 1 1 1 I ],ml›(.,.,2) kron(b(.,., 1 7), z),mb(. ,. ,3) = 1cron(b(. , .,l 8),z),

% HAI KHOI MAU CHROMA

GIAI MA

function mb gmmb1ock(avc,pt,x, y)persistent q 1 q2it isempty(q1)

q I qintra;% MA TRAN HE SO LUONG TU

end



MBHAM

L VTN. Tong quan ve chuén nén MPEG-4 H. 264/A VC vé kha ning ung ding trcng thuc tienTrang I I I

mb zeros(I 6,1 6,3);% DU DOAN VOI VECTOR CHUYEN DONG CUA ANH Pif avc.type ’P'

mb pt(x=avc. mvx, y+avc. mvy,:);

else

end% DU DOAN VOI VECTOR CHUYEN DONG CUA ANH Bif avc.type =='B'

mb pt(x*avc. mvx,y+avc.mvy,:);else

end% GfAI MA KHOI

coet avc.coet(:,:, i) . * (avc.scale(i) * q) / 8 ; % GIAI LUONG TUb(:,:, i) = idct2(coet); % BIEN DOI DCT NGUOC CHO HE SO MA HOA

end% CAU TRUC Bmb = mb putb1ocks(b);%%%% %%%%% HAM BIEN DOI TU RGB SANG

YUV%%%%%%%%% %%function yuv rgb2yuv(rgb) % BfEN DOI TRUOC KHI MA

HOA< [ 0.299

0.587 0. 144;

%Y 0.299R * 0.5 87R + 0. I 44B% MA TRAN BIEN DOI

-0. 168736 -0.331264 0. 5;0.5 -0.4 18688 -0.081312];

% MAY DU LIEU MOVIE[nr,nc, c] = size(rgb);rgb = reshape(rgb, nr*nc,3); % TAI TAO CHO MA TRAN NHAN% MA HOA MAU BIEN DOIyuv yuv yuv

in * rgb',yuv + repmat([0; 0.5; 0.5], I , nr*nc);reshape(yuv’,nr, nc,3); % TAI TAO LAI ANH

GOC%%%%%«%«%%%%%«%%%%«function rgb = yuv2rgb(yuv)

HAM BIEN DOI TU YUV SANC RGB %%«%%«%%%%%%% BIEN DOI SAU KHI GIAI MA

in = [ 0.299

0.587 0. 144,-0. 168736 -0.331264

0.5,0.5in = mº-1,

-0.4 18688 -0.0813 l 2],% kAY NCiHICH DAO MA TRAN in[nr,nc,c] size(yuv), % LAY DU LIEU MOVIE

% TAI TAO LAI CHO MA TRAN YUV

yuv = reshape(yuv, rir*nc, 3),rgb yuv - repmat([0, 0.5, 0.5], nr*nc, I ),% MA HOA BIEN DOI MAUrgb = in * rgb',rgb = reshape(rgb',nr,nc,3),

% rgb' hoan vi ciia rgb% TAI TAO LAI ANH GOC

%%%%%%%%%%%% BANG kUONCi TU CHO ANH INTER 4x4 P VA Bfunction q qinter q [ 17, 1 7, 16, 1

6;I 7,16, 15, 15;

%%%%%




1 6, 15, 1 5, 15];%%%%%%%%%%% BANG LUONG TU CHO ANH INTRA 4×4function q qintra q [ 9, 13, 18,21 ;

13,18,2 1,24;I 8,2 I ,24,27;2 1,24,27,30];

%%%%%%%

Hém plotvector. infunction plotvectorload lastmov,[M,N] size(avc 1});tor I 1.l ens'º(avc)

if avc {I}(I ,I ). typecontinue

end

'I'%« neu la anh I tlii bo qua

for i I : Mfor j = I : N

mvx(i,j) = avc {I}(i,j).mvy;mvy(i,j) avc I)(i,j). mvx,

endfigure quiver(f1ipud(mvx),f1ipud(mvy))set(gca,'XLim',[- 1, N=2],'VLim',[-1 , M=2])% CAI DAT TOA DO CUA HINHtit1e(sprintf('Vector chuyen dong clio anti thu %i', I))

end

function p1aymov(n) load lastmovtor i I . size(mov,4)

in(i). cdata uint8([mov(:,:,:,i) mov2(:,:,:,i )]);% mov anh goc, mov2 anh giai nen in(i). co1ormap [] ,

endfigure('Position',[30, 100,750,400,]);axs=axes('Position',[0.05 0. 15 0.8 0.5 5]);

' Ann ¿ ......................................................>>>>>> QJ NEN');gJabe j(movie(m,n,5); % Play mang in n lan, nhung lan sau play voi toe do 5fps




TAI LIEU THAM KHAO[ 1] TS. Nguyen Thanh Binh, Ths. Vo Nguyen Quoc B:to, “Xu 1y' fim thanh, hlnh anh”,

Hoc vién cong nghé Burt chinh vi½n th‹›ng, Ha Néi.

[2] KS. Truong Thi Thuy, “Tiéu chuan ma hoa tién tién H.264-MPEG-4 AVC”, Tapch i khoa hoc

thuét truyén h lnh 1 '2004.

[3] KS. Cao Van Liét, “Bit chuyén dong trong ky thuat ma héia riot dung ngufin video

tu nhie’n su dung tiéu chuan nén MPEG-4”, Tap chi khoa hoc theft truyén h inh

[4]Th. S. Nguyén Minh Hong, “Chuan nén H.264/AVC va kha nang ung dung trong

truyén hinh”, Tap ch i khoa hoc thtidt truyen hinh 2/2005.

[5] Gs. TS. Nguyén Kim Sach, “Truyén hinh ’ cé* nén va Multimedia ”, Nhé xuat bén

khoa hoc thuét, 7/‹i /Vfii

[6] TS. Tran Dii ng Trinh, “Truyén hinh trén Internet IPTV’, Tap chi khoa hoc thtiat

truyén hinh 3/2005

[7] Iain E.G. Richardson, “H.264 And MPEG-4 Video Compression”, The Robert

Gordon University, Aberdeen, UK

[8] John Arnold, Michael Frater, Mark Pickering, “Digital Television Technology and

Standards”, The University of New South Wales, A DFA Canberra, A CT, Australia

[9] JVT “Draft ITU-T recommendation and final draft international standard ofjoint

video specification (ITU-T rec. H.26W ISO/IEC 14496-10 AVC),”

[ 10] THOMAS SIKORA, “MPEG- I and MPEG-2 Digital Video Coding Standards”,

McGraw Hill Publis h ing Conipany.

[1 1 ] T. Wiegand, G.J. Sullivan, G. Bjontegaard, A. Luthra, ”Overview of the

H. 264/AVC Video Coding Standard,”

[ 12] Siwei Ma, Xiaopeng Fan, Wen Gao, “Low Complexity Integer Transform and

High Definition Coding”

[13] Cac trang web http://voovle.com, http://mathexchanve. com

http //forum doom9 o rg, University of Illinois at Chicago (U ICJ, http //www uic edu/




http://www.chiariqlione. org/mpe g /,

http: //www.mathworks.com/,

http://en.wikipedia.org

http://media.x iph.oru/video/derf/

http //www stanford edu/class/ee398b/samples html



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