An improved unequal error protection technique for the wireless transmission

of MPEG-4 Video

Bo Yan, Kam Wing NGThe Chinese University of Hong Kong

ICICS-PCM 2003

Presenter: Joungsik Kim

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Contents

Introduction Related Techniques The Proposed I-UEP Technique Simulation Results Conclusion

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Introduction To make the compressed bitstream more robust to channel e

rrors, the MPEG-4 video compression standard has incorporated several error resilience tools

Among these techniques, the traditional unequal error protection (T-UEP) technique is the most popular, which can protect the different parts on a MPEG-4 video p

acket (VP) with different channel coding rates based on rate-compatible punctured convolutional (RCPC) codes

However, this technique is not powerful enough for this application due to performance issues

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Related Techniques

Error-resilient Coding in MPEG-4 Video packet resynchronization Data partitioning (DP) Reversible variable length codes Header extension code (HEC)

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Video Packet Resynchronization

Using resynchronization marks to recover synchronization with the encoder

Maker k

Resync.maker

MBno QP HEC Combined motion and DCT data

Organization of the data within a Video Packet

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Data partitioning

Data partitioning mode To avoid discarding all the video data in the VP Motion part / Texture part

Separated by a motion boundary maker (MBM)

Resync.maker

MBno QP HEC Motion data MBM DCT data

COD1 MCBPC1 MVx1 MVy1 COD2 COD3 MCBPC3 MVx3 MVy3

Bits Components with data partitioning in the MPEG-4 VP

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RCPC Codes

Convolutional code The current output block depends on

Information bits in the current input block and one or more previous input blocks

Input Stream k

n

EncodeV blocksCoded Stream

Structure of a General Convolutional Code

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The relationship of the pth coded block to the input data block k-1 k-1

( ) (0) ( ) (1) ( 1)

j=0 j=0

k-1( 1) ( ( 1))

j=0

v-1 k-1( ) ( )

l=0 j=0

k-1 v-1( ) ( )

j=0 l=0

k-1(0)

j=0

, 0 1

[

p p pi ij j ij j

v p vij j

l p lij j

l p lij j

ij

C g d g d

g d

g d i n

g d

g g

(1) (2) 2

( 1) 1 ( )

( )

]

[ ( )]

ij ij

v v pij j

p

D g D

g D d

d G D

(n,k,v) code:

Puncturing Matrixes for Different Code Rate

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The T-UEP Technique T perform the T-UEP in the compressed video streams,

The “data partitioning tool” is exploited in the video packet For video packet, the information bits are divided into three pa

rtitions, each of which has a different sensitive channel errors

R1<R2<R2 To realize it, the Rate Compatible Punctured Convolutional (RCP

C) codes are used

VP Header DC DCT data AC DCT data

VP Header Motion data Texture data

I-VOP

P-VOP

R1 R2 R3

The Structure of T-UEP for I-VOP and P-VOP

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The Proposed I-UEP Technique

Focus on error protection in the motion data

Four different data types in the motion part COD: to indicate whether certain MB is coded or not MCBPC: variable field used to indicate the mode of the M

B MVx: the x component of the MV MVy: the y component of the MV

These four data types use different codebooks for variable-length decoding.

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1 0 0 0 1 0 0 0 1 1 0 0 1 1COD COD

0 0 0 0 1 0 0 0 1 1 0 0 1 1

MCBPC MVx MVy

COD MCBPC MVx MVy

Original:

After error:

error bit

The Changed Data Types by Bit Errors in the motion part

COD1 MCBPC1 MVx1 MVy1 COD2 COD3 MCBPC3 MVx3 MVy3 ……

COD1 MCBPC1 MVx1 MVy1COD2 COD3 MCBPC3 MVx3 MVy3 …………

Motion part

Motion partCode part

BeforeReorganizati

on

AfterReorganizati

on

Reorganize the Motion Part in the VP

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Thus the VP can be partitioned into four parts: VP header, COD part, Mode part and Texture part

R1<RCOD<RMode<R3

VP Header Motion data Texture data

R1 RMode R3

COD part

RCOD

The Structure of the I-UEP technique

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Simulation results

For T-UEP R1 = 1/3 R2 = 4/7 and R3 = 4/5

For I-UEP R1 = 1/3 RCOD = 1/2 RMode = 2/3 and R3 = 4/5

Foreman Sequence Simulation Result(a) T-UEP; (b) I-UEP

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Conclusion

The I-UEP proposed to strengthen the robustness of the transport of MPEG-4 video over wireless channels Reorganizes the components in the VP and

partitions it into four parts. Thus the COD bits can be more protected with

lower code rate than other bits in the motion part

After applying it, the decoded video quality can be improved significantly after transmission over noisy wireless channels