An improved unequal error protection technique for the wireless transmission of MPEG-4 Video Bo Yan, Kam Wing NG The Chinese University of Hong Kong ICICS-PCM 2003 Presenter: Joungsik Kim

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

3 Introduction  To make the compressed bitstream more robust to channel errors, 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 packet (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

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

5 Video Packet Resynchronization  Using resynchronization marks  to recover synchronization with the encoder Maker k Resync. maker MB no QPHECCombined motion and DCT data Organization of the data within a Video Packet

6 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 MB no QPHECMotion dataMBMDCT data COD 1 MCBPC 1 MV x1 MV y1 COD 2 COD 3 MCBPC 3 MV x3 MV y3 Bits Components with data partitioning in the MPEG-4 VP

7 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 Encode V blocks Coded Stream Structure of a General Convolutional Code

8  The relationship of the p th coded block to the input data block ( n,k,v ) code: Puncturing Matrixes for Different Code Rate

9 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 partitions, each of which has a different sensitive channel errors  R 1 <R 2 <R 2  To realize it, the Rate Compatible Punctured Convolutional (RCPC) codes are used VP HeaderDC DCT dataAC DCT data VP HeaderMotion dataTexture data I-VOP P-VOP R1R1 R2R2 R3R3 The Structure of T-UEP for I-VOP and P-VOP

10 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 MB  MV x : the x component of the MV  MV y : the y component of the MV  These four data types use different codebooks for variable-length decoding.

COD MCBPCMV x MV y CODMCBPCMV x MV y Original: After error: error bit The Changed Data Types by Bit Errors in the motion part COD 1 MCBPC 1 MV x1 MV y1 COD 2 COD 3 MCBPC 3 MV x3 MV y3 …… COD 1 MCBPC 1 MV x1 MV y1 COD 2 COD 3 MCBPC 3 MV x3 MV y3 …… Motion part Code part Before Reorganization After Reorganization Reorganize the Motion Part in the VP

12  Thus the VP can be partitioned into four parts:  VP header, COD part, Mode part and Texture part  R 1 <R COD <R Mode <R 3 VP HeaderMotion dataTexture data R1R1 R Mode R3R3 COD part R COD The Structure of the I-UEP technique

13 Simulation results  For T-UEP  R 1 = 1/3 R 2 = 4/7 and R 3 = 4/5  For I-UEP  R 1 = 1/3 R COD = 1/2 R Mode = 2/3 and R 3 = 4/5 Foreman Sequence Simulation Result (a) T-UEP; (b) I-UEP

14 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