transform-domain wyner-ziv codec for video

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