Bao Cao 4-10-2010 (Repaired)_quang

ti: Video Watermarking implemented on TMS320C5515 eZ dsp USB Stick Thy HD: PGS.TS L Tin Thng

TRNG I HC QUC GIA TP.HCM I HC BCH KHOA

BO CO LUN VN ti: VIDEO WATERMARKING IMPLEMENTED ON TMS320C5515 EZ DSP USB STICK

Phn 2: NHNG THNG TIN VO NH V VIDEO S DNG GII THUT DCT

Thy hng dn : PGS-TS L Tin Thng SV thc hin : Trn Quc Vit Dng Tn V

Phn 2 : Gii thut thit k video watermarking V

1

SVTH:Trn Quc Vit - Dng Tn

ti :Video Watermarking implemented on TMS320C5515 eZ dsp USB Stick

Thy HD: PGS.TS L Tin Thng

TP. H Ch Minh, thng 11 nm 2010 Ti liu tham kho: [1] Lng B Mnh, Nguyn Thanh Thy, Nhp mn x l nh, Nh xut bn Khoa Hc v K Thut, 2003. [2] Image Processing Toolbox. [3] Trn Vit H, Trng Quang Thnh, Nhng Tc Quyn Vo nh S, Lun Vn Tt Nghip, i hc Bch Khoa TPHCM, 12/2004.

Phn 2 : Gii thut thit k video watermarking 2

SVTH: Trn Quc Vit - Dng Tn V



I.

KHI NIM V NN NH:

Mc ch ca vic nn nh s l m ha cc d liu v dng thu gn, ti thiu ha c s bits dng biu din nh ln cc sai khc do qu trnh nn gy ra. Tm quan trng ca vn nn nh c th thy r qua cc s liu c th: vic pht v lu d video khng c nn s cc k tn km v khng thc t. Mt khung 352288 cha 202,752 bytes thng tin, vic ghi video dng khng nn vi 15 khung mi giy s i hi 3MB, mt pht s cn 180MB dung lng, mt ngy-24 gi s cn 262GB. Ch vi vic s dng nn, 15 khung/giy cho 24 gi ch cn 1.4GB. vi mt tm nh en trng kch thc 512512 pixel, mi pixel biu din bi 8 bits (biu din mt trong 256 gi tr mc xm), cn khong 256Kbytes d liu. Vi nh mu cn gp 3 ln con s ny. Cc phng nn c phn thnh hai nhm: nhm khng tn hao v nhm c tn hao. Cc phng php nn khng tn hao cho php biu din nh vi cht lng hon ton ngang bng vi nh gc, tuy nhin cc phng php ny khng li dng c c tnh ring ca d liu nh v t l nn rt thp. Do , trong thc t, cc phng php nn c tn hao l cc phng php c s dng ch yu. Nn d liu nh li dng cc thnh phn d tha tng hiu qu m ha.

Hnh 1: Qu trnh m ha v gii mPhn 3: Gii thut thit k video watermarking 3 SVTH: Trn Quc Vit - Dng Tn V



1. Nn tn hao da vo DCT: Gii thut nn tn hao c bit n nhiu nht l gii thut nn dng DCT. y l gii thut nn c chun ha vi tn gi JPEG (joint photographic expert group).

Hnh 2: S khi gii thut nn nh JPEG

Hnh 3: S khi gii thut gii nn nh nn nh, ta chia nh thnh cc khi 88 (hoc 1616). Mi khi 88 ny s c x l ring bit qua cc bc ca qu trnh nn nh. Tnh ton DCT (discrete cosine transform) ca mi khi, mi h s trong s 64 h s bin i DCT c lng t ha da vo bng gi tr lng t c thit k k lng. Trong chun nn JPEG, mi h s DCT s c chia cho mt trng s Phn 3: Gii thut thit k video watermarking 4 SVTH: Trn Quc Vit - Dng Tn V



v tr tng ng trong mt ma trn lng t 88, sau lm trn v s nguyn gn nht.

Cij = round (

Dij Qij

)

(1-1)

Vi D- ma trn cc h s DCT, Q- ma trn lng t (kch thc 88) Thng thng mt ngi kh phn bit cc thnh phn tn s cao ca nh, do cc thnh phn ny s c chia cho cc trng s ln hn. JPEG nh ngha cc ma trn lng t theo cp cht lng t 1 n 100 (cp mt 100 c cht lng tt nht). Ma trn chun ha JPEG cp cht lng 50:

N k ,l

16 11 10 16 24 40 51 61 12 14 14 = 18 24 49 99 72 Hnh 4: Ma trn lng t JPEG

Vi cc cp cht lng k vi k50, ma trn lng t c nh ngha bi phng trnh sau:

Cij = round (

Dij Qij

)ery 7-eueueu

(1-2)

Sau khi lng t, cc h s bin i DCT s c sp xp theo mt chui zig-zag bt u t thnh phn DC, ri n thnh phn AC:

Phn 3: Gii thut thit k video watermarking

5




Hnh 5: Qu trnh bin i DCT Cui cng cc h s ny c chuyn thnh chui bit nh phn bng k thut m ha entropy. K thut m ha thng dng l RLC (run length coding) hay RLE (run length encoder). Dng m Huffman m ha cho cc symbol.


6




Hnh 6: V d v nn nh JPEG

Run length coding: nh vi cc mc xm lp li dc theo cc hng (hay theo cc ct) c th c nn bng cch gi li cc run ca cc gi tr mc xm ging nhau theo nh dng: Gi tr mc xm 1 Lp li 1 Gi tr mc xm 2 Lp li 2

i vi nh en trng (B/W image) s dng m runlength khc:

Hnh 7: Run length coding Huffman coding: Phng php m ha Huffman cung cp chiu di m bin thin vi chiu di code-word trung bnh cc tiu, s d tha t nht c th i vi ngun tin tc ri rc (tin tc y l cc gi tr mc xm). Discrete cosine transform (DCT): DCT thng c s dng trong nn nh nh trong h thng chun JPEG. nh ngha DCT:

Cij = round (

Dij Qij

)ery 7-eueueu7

(1-3)





Cij = round (

Dij Qij

)ery 7-eueueu

(1-4)

Bin i ngc DCT :

Cij = round (

Dij Qij

)ery 7-eueueu

(1-5)

Vic nn c thc hin bng khi m m rng DCT v Huffman. im bt li ca DCT l hm ca n th c nh khng th thch nghi khi d liu ngun thay i. 2. Nn nh bng gii thut phn tch tr ring: Phng php phn tch tr ring (SVD- singular value decomposition) c ng dng trong k thut nn nh. c im quan trng ca phng php ny l c th p dng cho bt k ma trn thc mn no. SVD phn tch mt ma trn A cho trc thnh ba ma trn U, S, V sao cho:

Cij = round (

Dij Qij

)ery 7-eueueu

(1-6)

Trong U, V l cc ma trn trc giao; S- ma trn ng cho Ma trn U l ma trn gm cc vector ring tri ca A, ma trn V l ma trn gm cc vector ring phi ca A, mi phn t ng cho ca ma trn S l mt tr ring ca A. Cc tr ring c sp xp trn ng cho chnh theo th t sau:

Cij = round (

Dij Qij

)ery 7-eueueu

(1-7)

Vi r l hng ca ma trn A, p=min{m,n}. Da vo cc tnh cht ca ma trn n v, ma trn ng cho, ma trn trc giao v ma trn chuyn v, t phng trnh trn ta tm c ma trn V v ma trn U. Cui cng ta phn tch ma trn A di dng:Phn 3: Gii thut thit k video watermarking 8 SVTH: Trn Quc Vit - Dng Tn V



A = (u1...u1...u1 )

1. . .

1

...

0

A v S l cc ma trn kch thc mn, U l ma trn m1, v V l ma trn nn. Bng cch phn tch ma trn nh A di dng A = US c th gim i nhng thng tin tha: (1-9) Cc tr ring c sp xp theo th t gim dn, do nhng s hng pha sau s c t nh hng n nh v c th b i cc s hng ny. , ta c th biu

din ma trn A bng t phn t hn. Nu hng ca ma trn A l r k. Tng gi tr k th cng d ly li watermark tuy nhin s phi tr gi cho cht lng ca nh do bin cc h s khc xa nhau.

Phn 4: Gii thut thit k video watermarking 11




Phn 4: Gii thut thit k video watermarking 12


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Bao Cao 4-10-2010 (Repaired)_quang