Robust Compression and Transmission of MPEG4 Video

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Robust Compression and Transmission of MPEG-4
Video

• ACM Multimedia, Oct 1999
• Steven Gringeri ,Roman Egorov, Khaled Shuaib,
• Arianne Lewis and Bert Basch

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Outline

• Introduction
• Overview of MPEG-4 Standards
• Error Resilience Features in MPEG-4
• Error handling in Decoding MPEG-4
• MPEG-4 Video Performance Experiments
• Conclusions

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Introduction

• With variable length code,the transmission errors
  can cause the decoder to incorrectly determine a
  code words length leading to loss of
  synchronization between the decoder and the
  stream.
• Predictive coding techniques allow errors to
  propagate thus degrading video quality.

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Introduction(cont.)

• MPEG-4 standards define a set of special error
  resiliency tools to handle these issues.

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Overview of MPEG-4 Standards

• The MPEG-4 standards present a scene as a set of
  audiovisual objects.
• An MPEG-4 stream contains three major types of
  video object planes(I-VOP,P-VOP,B-VOP).

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Overview of MPEG-4 Standards(cont.)
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Overview of MPEG-4 Standards(cont.)

• MPEG-4 standards support object-based coding
  where each object in a video scene can be coded
  as a separate bit stream and where both natural
  and synthetic objects can be mixed.

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Overview of MPEG-4 Standards(cont.)
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Error Resilience Features in MPEG-4

• The MPEG-4 standards provide built-in error
  resilience capabilities to detect and localize
  errors, to recover data after errors, and to
  visually conceal the effect of errors.
• Resynchronization markers
• Data partition
• Header protection
• Reversible variable length code

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Error Localization

• Resynchronization markers

• Data partition

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Error Localization(cont.)
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Error Localization(cont.)
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Error Localization(cont.)
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Intra Frame Refresh
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Error Handling in Decoding MPEG-4

• When an error is detected in a video packet, the
  damaged macroblocks must be discarded.
• The simplest approach is to leave the affected
  region unchanged until the next undamaged intra
  coded macroblock is available.
• If motion information is undamaged,it can be used
  to estimate macroblock movement so that more
  accurate concealment can be performed.

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MPEG-4 Video Performance Experiments

• NM image

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Effect of Bit Errors on Video Quality
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Effect of Bit Errors on Video Quality(cont.)
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Effect of Bit Errors on Video Quality(cont.)
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Effects of Packet Size and Boundaries on Video
Quality
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Localizing Errors Using Packet Video
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Localizing Errors Using Packet Video(cont.)
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Error Correcting Codes

• BCH code (n,k)
• n n bits
• k protect k bits
• t the maximun number of errors that a code can
  correct

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Error Correcting Codes(cont.)

• PB post-decoder BER

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Error Correcting Codes(cont.)
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Conclusion