transform-domain wyner-ziv codec for video
DESCRIPTION
Transform-domain Wyner-Ziv Codec for Video. 教師 : 楊士萱 老師 學生 : 李桐照 同學. OutLine. 1:Review of DSC 2:Wyner-Ziv Codec for Video 3:Turbo Coding 4:Future Work. Review of DSC. Distributed Source Coding. Compression of two or more correlated source - PowerPoint PPT PresentationTRANSCRIPT
Transform-domain Wyner-Ziv Codec for Video
教師 教師 : : 楊士萱 老師楊士萱 老師學生 學生 : : 李桐照 同學李桐照 同學
OutLine
1:Review of DSC
2:Wyner-Ziv Codec for Video
3:Turbo Coding
4:Future Work
Review of DSC
Source X
Source Y
Source Encoder X
Source Encoder Y
Joint Source Decoder
Divination X,Y
Distributed Source Coding
Compression of two or more correlated source
•The source do not communicate with each other (hence distributed coding)
•Decoding is done jointly (say at the base station)
Wyner-Ziv Codec for Video
DCTMk2 Level
QuantizerTurbo Encoder BufferW Xk qk
Bit-Plane 1...
Bit-Plane Mk
ExtractBit-Plane
Turbo DecoderReconstructIDCT
DCT
Request bits
Xk ’ qk’
Yk
Side Information
W ’
K
Wyner-Ziv Codec for Video DCTW Xk
K: coefficient number Xk: coefficient bands
ex: X1=A1A2A3A4
DCTMk2 Level
QuantizerTurbo Encoder BufferW Xk qk
Bit-Plane 1...
Bit-Plane Mk
ExtractBit-Plane
Turbo DecoderReconstructIDCT
DCT
Request bits
Xk ’ qk’
Yk
Side Information
W ’
K
Wyner-Ziv Codec for Video
假設 DCT 值域 :0~255
Ex: (DC 值對應 64) 0,3,…..255
64 區間因此用 6 bits 即可表示 DC 值
EX: q1=Q(A1),Q(A2),Q(A3),Q(A4)
XkMk2 Level
Quantizerqk
DCTMk2 Level
QuantizerTurbo Encoder BufferW Xk qk
Bit-Plane 1...
Bit-Plane Mk
ExtractBit-Plane
Turbo DecoderReconstructIDCT
DCT
Request bits
Xk ’ qk’
Yk
Side Information
W ’
K
Wyner-Ziv Codec for Video Bit-Plane 1
.
.
.Bit-Plane Mk
ExtractBit-Plane
qk
EX: q1=Q(A1),Q(A2),Q(A3),Q(A4)
Q(A1)=111100 Q(A2)=110111
Q(A3)=110011 Q(A4)=111011
DCTMk2 Level
QuantizerTurbo Encoder BufferW Xk qk
Bit-Plane 1...
Bit-Plane Mk
ExtractBit-Plane
Turbo DecoderReconstructIDCT
DCT
Request bits
Xk ’ qk’
Yk
Side Information
W ’
K
Wyner-Ziv Codec for Video
Turbo Encoder Buffer
Bit-Plane 1...
Bit-Plane Mk
Turbo Coding 採用 Systematic code type
Turbo Encoder -@ Message bits :1111
-@ Parity bits:
Buffer store:-@ Message bits
-@ Parity bits
Wyner-Ziv Codec for Video
Request bits
K
Buffer
Turbo Decoder
DCT
qk’
Yk
Buffer store:-@ Message bits -@ Parity bits
Normal:-@(Yk) Message bits -@ Parity bits
Error Probability >10^-3Request bits :-@ Message bits
DCTMk2 Level
QuantizerTurbo Encoder BufferW Xk qk
Bit- Plane 1...
Bit-Plane Mk
ExtractBit-Plane
Turbo DecoderReconstructIDCT
DCT
Request bits
Xk ’ qk’
Yk
Side Information
W ’
K
Wyner-Ziv Codec for Video
DCTMk2 Level
QuantizerTurbo Encoder BufferW Xk qk
Bit-Plane 1...
Bit-Plane Mk
ExtractBit-Plane
Turbo DecoderReconstructIDCT
DCT
Request bits
Xk ’ qk’
Yk
Side Information
W ’
K
Turbo Coding - Encoding
RSCRate:1/2
RSCRate:1/2
Interleaver
Puncture
Message bits m(i) m(i)
c1(i) c2(i)
Turbo Encoder
Interleaver type:
1:Block Interleaver
2:Random Interleaver*
3:S-Random Interleaver*
4:Prime Interleaver*
5:Convolutional Interleaver*
Turbo Coding - Encoding
RSCRate:1/2
RSCRate:1/2
Interleaver
Puncture
Message bits m(i) m(i)
Turbo Encoder
1 3 5 7 9
2 4 6 8 0Write in
Read out
Message bits: 1234567890
Interleaver
Read out bits:1357924680
DeInterleaver Write in
1 3 5 7 9
2 4 6 8 0Read out
Turbo Coding - Encoding
d(i)=m(i)+d(i-1)+d(i-2)
Register 1 Register 2
Recursive Systematic Convolutional
Message bits m(i)
d(i)
d(i-2)
d(i-1)
c0(i)
c1(i)
Turbo Coding - Encoding
RSCRate:1/2
RSCRate:1/2
Interleaver
Puncture
Message bits m(i) m(i)
Turbo Encoder
若不經過 Puncture 時 , 則
Rate=1/3
若經過 Puncture, 則我們可以調整傳輸資料使 Rate=1/2 提升傳輸效率
C1 bits A B C D
Pass Puncture
bitsA F C H
C2 bits E F G H
Turbo Coding - Encoding
RSCRate:1/2
RSCRate:1/2
Interleaver
Puncture
Message bits m(i) m(i)
Turbo Encoder
RSCRate:1/2
RSCRate:1/2
Interleaver
Puncture
Message bits m(i) m(i)
Turbo Encoder
0101001001
1110011000
0110111101
0100011101
Turbo Coding - Encoding
Estimative m
Decoder
Decision
Turbo Decoder
Decoder
DeInterleaver
DeInterleaver
Interleaver
Parity 1
Parity 2
Systematic code
Interleaver
Turbo Coding - Decoding
A Posteriori Probability (APP): Assume Tr=+1 or -1
P(Tr=i|x)=P(x|Tr=i)*P(Tr=i)/P(x)
Log-Likelihood Ratio (LLR):
L(Tr|x)=log[ P(Tr=+1|x)/P(Tr=-1|x)]
=log[P(x|Tr=+1)*P(Tr=+1)/ P(x|Tr=-1)*P(Tr=-1)]
= log[P(x|Tr=+1)/ P(x|Tr=-1)]+log[P(Tr=+1)/P(Tr=-1)]
=L(x/Tr)+L(Tr)
Turbo Coding - Decoding
Message Passing ConceptB CA D E F
1 11 1 1 1
B CA D E F
1 111 1 1
1 432 5125 4 3
:Extrinsic InformationCheck Nodes : A,…F
Turbo Coding - Decoding
所有英文字母的數目 =( 左相鄰字母告知的數目 +右相鄰字母告知的數目 )+自己
Overall Information = Extrinsic Information + Intrinsic Information
B CA D E F
1 111 1 11 432 5125 4 3
66 6666
Turbo Coding - Decoding
SISO DecoderPchannel
Pa prrori
Pextrinsic
Pa posteriori
P a prioir : L(Tr)
P channel : L(x/Tr)
P extrinsic : as other SISO Decoder’s Pa prioir
P a posteriori : Decision Message bits
Turbo Coding - Decoding
SISO decoder 1:MAP Rule2:Log-MAP 3:Soft Output Viterbi Algorithm*
Turbo Coding - Decoding
Turbo Coding - Error Detection
RSCRate:1/2
RSCRate:1/2
Interleaver
Puncture
Message bits m(i)m(i)
Turbo Encoder
Parity Check Encoder
傳統 Turbo Coding-Error Detection
方法 1: CRC 對於 Message 長度太短 , 會浪費過多 bits 在 CRC 上
方法 2: 奇 ( 偶 ) 同位元 對於 Message 長度太短 , 比較不會浪費 bits 在其上
Future Work
1: 了解 Turbo Decoder 原理
2: 寫出一個簡易型可以配合 DSC 系統的 Turbo Coding
3: 將 Turbo Coder 換成 LDPC