# Transform-domain Wyner-Ziv Codec for Video 教師 : 楊士萱 老師 學生 : 李桐照 同學.

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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 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

K: coefficient number X k: coefficient bands ex: X1=A1A2A3A4

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: q 1=Q(A1),Q(A2),Q(A3),Q(A4)

Wyner-Ziv Codec for Video EX: q 1 =Q(A1),Q(A2),Q(A3),Q(A4) Q(A1)=111100 Q(A2)=110111 Q(A3)=110011 Q(A4)=111011

Wyner-Ziv Codec for Video 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 Buffer store:-@ Message bits -@ Parity bits Normal:-@(Yk) Message bits -@ Parity bits Error Probability >10^-3 Request bits :-@ Message bits

Wyner-Ziv Codec for Video

Turbo Coding - Encoding

Interleaver type: 1:Block Interleaver 2:Random Interleaver* 3:S-Random Interleaver* 4:Prime Interleaver* 5:Convolutional Interleaver* Turbo Coding - Encoding

13579 24680 Write in Read out Message bits: 1234567890 Interleaver Read out bits:1357924680 DeInterleaver Write in 13579 24680 Read out Turbo Coding - Encoding

0101001001 1110011000 0110111101 0100011101 Turbo Coding - Encoding

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 Concept :Extrinsic Information Check Nodes : A,…F Turbo Coding - Decoding

P a prioir : L(Tr) P channel : L(x/Tr) P extrinsic : as other SISO Decoder’s P a prioir P a posteriori : Decision Message bits Turbo Coding - Decoding

SISO decoder 1:MAP Rule 2:Log-MAP 3:Soft Output Viterbi Algorithm* Turbo Coding - Decoding

Turbo Coding - Error Detection 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

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