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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.

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Presentation on theme: "Transform-domain Wyner-Ziv Codec for Video 教師 : 楊士萱 老師 學生 : 李桐照 同學."— Presentation transcript:

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

2 OutLine 1:Review of DSC 2:Wyner-Ziv Codec for Video 3:Turbo Coding 4:Future Work

3 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)

4 Wyner-Ziv Codec for Video

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

6 Wyner-Ziv Codec for Video 假設 DCT 值域 :0~255 Ex: (DC 值對應 64) 0,3,… 區間因此用 6 bits 即可表示 DC 值 EX: q 1=Q(A1),Q(A2),Q(A3),Q(A4)

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

8 Wyner-Ziv Codec for Video Turbo Coding 採用 Systematic code type Turbo Encoder Message bits :1111 Parity bits: Buffer Message bits Parity bits

9 Wyner-Ziv Codec for Video Buffer Message bits Parity bits Message bits Parity bits Error Probability >10^-3 Request bits Message bits

10 Wyner-Ziv Codec for Video

11 Turbo Coding - Encoding

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

13 Write in Read out Message bits: Interleaver Read out bits: DeInterleaver Write in Read out Turbo Coding - Encoding

14

15 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 bitsABCD Pass Puncture bits AFCH C2 bitsEFGH Turbo Coding - Encoding

16 Turbo Coding - Encoding

17 Turbo Coding - Decoding

18 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

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

20 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 Turbo Coding - Decoding

21 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

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

23 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

24 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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