1

Department of Electrical Engineering,Stanford University

Anne Aaron, Shantanu Rane, David Rebollo-Monedero and Bernd Girod

Systematic Lossy Forward Error Protection

for Video Waveforms

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 2

Overview

Error Resilient Digital Video Broadcasting Systematic Lossy Forward Error Protection Embedded Wyner-Ziv Coding Improved Wyner-Ziv Video Codec

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 3

Error-Resilient Digital Video Broadcasting

Terrestrial broadcast

Cable TV

Satellite Broadcast

uplin

k

• Forward Error Correction (FEC) “Cliff” effect For graceful degradation,

Priority Encoding Transmission (PET) [Albanese, et al., 1996]

Layered representation incurs a rate-distortion penalty

• Forward Error Protection (FEP) Protects the video waveform Graceful degradation without

layered representation

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 4

Encoder

Related Work

Channel A

DecoderChannel DX X*

Y

• Bounds for systematic lossy source-channel coding

[Shamai, Verdu and Zamir, 1998]

• Enhancing analog transmission systems using digital side information [Pradhan and Ramchandran, 2001]

• Robust predictive coding [Sehgal and Ahuja, 2003]

Side information

uncoded

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 5

S*Reconstructio

n

Slepian-Wolf

Encoder

Slepian-Wolf

Decoder

Side information

Coarse Quantizer

Scalar Quantizer

Turbo Encoder

Turbo Decoder

Systematic Lossy Forward Error Protection

MPEG Encoder

MPEG Decoder with Error

Concealment

Err

or-P

rone

cha

nnelS S’

Protects the original video waveform “Lossy” protection

Wyner-Ziv Decoder

Wyner-Ziv Encoder

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 6

Results

Carphone: CIF, 50 frames @ 30fps 1 Mbps, 1% macroblock loss

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 7

Error Concealment only (No WZ bits)

Wyner-Ziv Coding (16 quantization levels, 0.75bpp)

Carphone: CIF, 1 Mbps, 1% macroblock loss

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 8

Embedded Wyner-Ziv Codec

MPEG Encoder

MPEG Decoder with Error

Concealment

Err

or-P

rone

cha

nnelS S’

S*Wyner-ZivEncoder A

Wyner-ZivDecoder A

S**Wyner-ZivEncoder B

Wyner-ZivDecoder B

• Graceful degradation of video quality• Does not require layered representation

… …

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 9

Results2-level Wyner-Ziv Codec

Carphone: CIF, 50 frames @ 30fps 1 Mbps, 1% macroblock loss

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 10

Systematic Lossy Forward Error Protection

MPEG Encoder

MPEG Decoder with Error

Concealment

Err

or-P

rone

cha

nnelS S’

Wyner-Ziv Decoder

Coarse Quantizer

Wyner-Ziv Encoder

Reconstruction

Slepian-Wolf

Encoder

Slepian-Wolf

Decoder

S*

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 11

Improved Wyner-Ziv Coder

Err

or-P

rone

cha

nnelMPEG

Encoder

MPEG Decoder with Error

ConcealmentS S’

MPEGEncoder

Common reference frame

MPEGEncoder

[Rane, Aaron, Girod (submitted to VCIP ’04)]

Parity symbols

R-SEncoder

R-SDecoder

Side information

S*

Wyner-Ziv Encoder

Wyner-Ziv Decoder

MPEGDecoder

Common reference frame

Fallback to coarse representation

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 12

Systematic Lossy FEP vs. FEC Foreman.cif

FECMain Stream @ 1.092 MbpsFEC (n,k) = (40,36) FEC bitrate = 120 KbpsTotal = 1.2 Mbps

Proposed SchemeMain Stream @ 1.092 MbpsWZ Stream @ 270 KbpsFEP (n,k) = (52,36)WZ bitrate = 120 KbpsTotal = 1.2 Mbps

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 13

1 Mbps + 120 kbps FEC(33.03 db)

Foreman: CIF, 50 frames, symbol error rate = 10-3

1 Mbps + 120 kbps FEP(38.40 db)

Aaron, Rane, Rebollo-Monedero, Girod: Forward Error Protection of Video Sept. 15, 2003 14

Summary

• A novel systematic lossy forward error protection scheme for error-resilient video broadcasting

• Wyner-Ziv coding applied to forward error protection• Advantages

More robust than FEC over a wide range of error ratesGraceful degradation without layered video representationBackward-compatible