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10 장 기본 비디오 압축 기술. 10.1 비디오 압축 소개 10.2 움직임 보상에 기반한 비디오 압축 10.3 움직임 벡터를 위한 탐색 10.4 H.261 10.5 H.263. 10.1 비디오 압축 소개. 비디오는 시간 - 순서화된 프레임의 연속 ( 즉 , 영상 ) 으로 구성 . 비디오 압축에 대한 분명한 해결책은 이전 프레임에 기초한 예측 부호화 일 것임 . 압축은 영상들을 감산함으로써 진행 : 시간 순서대로 감산하고 , 나머지 오류를 부호화함 . - PowerPoint PPT Presentation
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10 10.1 10.2 10.3 10.4 H.26110.5 H.2632011-2*
10.1 2011-2* - (, ) .
.
: , .
.
10.2 2011-2* .
(temporal redundancy) . () , .
(MC: Motion Compensation) 1. ( )2. 3. , ,
2011-2* NN (macroblocks) .
N = 16. 4:2:0 , N = 8.
.
(Target frame) . / ()( (Reference frame)() ) . MV . 10.1 , (forward prediction) .
2011-2* 10.1: MV [-p, p] .
(2p+1)(2p+1) .
10.3 (MAD: Mean Absolute Difference) :
N - ,k l - ,i j - ,C(x+k, y+l) - ,R(x+i+k, y+j+l) - .
MAD(i, j) , MV = (u, v) (i, j) .2011-2*
2011-2* (sequential search): (2p+1)(2p+1) .( (Full search) )
, MAD (10.1) .
MAD (i, j) MV(u, v) .
. (, , ) . (2p+1)(2p+1) N2 3 O(p2N2).
2011-2* 10.1 :
2 2011-2* (logarithmic search): .
2 .
10.2 , 9 MAD- ; 1 .
MAD , , -(step-size)((offset)) .
, 9 2 . .
2011-2* 10.2: 2
10.2 : 2 2011-2*
, :2011-2*
2011-2* (: multiresolution) .
10.3: 0 3- , 1 2 2 , 2 .
, p , .
2011-2* 10.3: 3-
() k (uk, vk) , k-1 (2uk ,2vk) 33 . (uk-1, vk-1) k-1 :
( , ) k . ( , ) :
2011-2* 10.3 :
2011-2* 10.1
10.4 H.2612011-2*H.261: , .
, ISDN .
p64kbps , p 1 30 .( p64 )
150msec , .
ITU & H.261 2011-2*H.261 ITU .
1. H.221 64 1,920kbps (audiovisual) .
2. H.230 .
3. H.242 .
4. H.261 p64kbps (encoder)/(decoder).
5. H.320 p64kbps (narrow-band) .
2011-2* 10.2 H.261
2011-2* 10.4: H.261
H.261 2011-2* : -(I-) -(P-):
I- . JPEG I- . .P- : .( P- I- )P- (temporal redundancy removal) , I- (spatial redundancy removal) . , I- .
H.261 15 . , P=15.
(I-)2011-2* Y 1616 . Cb Cr 4:2:0 88 . 88 4 Y , 1 Cb , 1 Cr . 88 DCT . DCT . 10.5: I-
(P-) 2011-2* 10.6 H.261 P- :
, .
, (difference macroblock) .
88 DCT, , , .
P- ( ) .
, . , .
( ), (non-motion compensated) .
MVD :2011-2*
2011-2* 10.6: H.261 P-
2011-2*H.261 H.261 DCT , _(step_size) .
DCT DCT QDCT , DC :
:
scale [1, 31]
H.261 2011-2* 10.7 H.261 .
I, P1 P2 .
: ( ) .
10.3 10.4 .
2011-2* 10.7: H.261
2011-2* 10.7(): H.261
2011-2* 10.3: H.261 10.4: H.261
H.261 2011-2*1. : PSC (Picture Start Code) . TR (Temporal Reference) - .
2. GOB : H.261 113 , GOB(Group of Blocks) .
10.9 CIF QCIF GOB .
, CIF 352288 26 GOB . GOB (GBSC: Start Code) (GN: Group Number) . 10.8 H.261 : 4 : , GOB, , .
2011-2* , H.261 (identifiable) GOB .
GQuant MQuant( ) , GOB .
3. : (MB) GOB , (MQuant) 6 88 (4Y, 1Cb, 1Cr) .
4. : 88 , DC AC 0-(Run) 0 (Level) , EOB(End of Block) . Run [0, 63]. Level . [-127, 127], level 0.
2011-2* 10.8: H.261
2011-2* 10.9: H.261 GOB
10.5 H.2632011-2*H.263 (PSTN: Public Switched Telephone Networks) .
64kbps .
- , (- - ) .
2011-2* 10.5 H.263
H.263 & GOB (Group of Blocks)2011-2*H.261 , H.263 GOB(Group of Blocks) .
H.263 GOB H.261 , .
10.10 , QCIF 9 GOB , GOB 111MBs (17616) . 4CIF 18 GOB , GOB 442MBs (70432) .
2011-2* 10.10: H.263 GOB
2011-2*H.263 MV() , MV1, MV2, MV3 .( 10.11(a) )
MV(u, v) :
MV(u, v) , ( , ) , .
2011-2* 10.11 H.263 MV (MV1, MV2, MV3) GOB MV
- 2011-2* H.261 - (full-pixel precision) H.263 - (half-pixel precision) .
MV(u, v) u v [-16, 15.5].
10.12 , - (bilinear interpolation) .
2011-2* 10.12: H.263 - A, B, C, D: a, b, c, d:
H.263 2011-2*H.263 :1. :
.
, .
[-31.5, 31.5].
2011-2*2. - :
H.261 , H.263 DCT (VLC) .
H.261 , H.263 4 . .
3. :
, 16 8 .
4 (88 ) .
2011-2*4. PB- :
10.13 , H.263 PB- .
PB- PTYPE .
PB- .
, PB- B- . H.263 2 .
2011-2* 10.13: H.263 PB-PB I- P- P- I- P- P- B-
H.263+ H.263++2011-2*H.263+ : , , , .
H.263+ H.263 4 12 .
(RVLC: Reversible Variable Length Coding) .
(flexibility) GOB .
2011-2*H.263+ (Temporal), SNR (Spatial scalabilities) .
1 , B- P- PB- .
H.263+ (blocking effects) (deblocking filters) .
2011-2*H.263++ H.263 (ERRS :Enhanced Reference Picture Selection), (DPS : Data Partition Slice), .
ERPS - . (coding efficiency) (error resilience) .
DPS DCT .
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