Title: Robust Compression and Transmission of MPEG4 Video
1Robust Compression and Transmission of MPEG-4
Video
- ACM Multimedia, Oct 1999
- Steven Gringeri ,Roman Egorov, Khaled Shuaib,
- Arianne Lewis and Bert Basch
2Outline
- Introduction
- Overview of MPEG-4 Standards
- Error Resilience Features in MPEG-4
- Error handling in Decoding MPEG-4
- MPEG-4 Video Performance Experiments
- Conclusions
3Introduction
- 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.
4Introduction(cont.)
- MPEG-4 standards define a set of special error
resiliency tools to handle these issues.
5Overview 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).
6Overview of MPEG-4 Standards(cont.)
7Overview 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.
8Overview of MPEG-4 Standards(cont.)
9Error 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
10Error Localization
- Resynchronization markers
11Error Localization(cont.)
12Error Localization(cont.)
13Error Localization(cont.)
14Intra Frame Refresh
15Error 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.
16MPEG-4 Video Performance Experiments
17Effect of Bit Errors on Video Quality
18Effect of Bit Errors on Video Quality(cont.)
19Effect of Bit Errors on Video Quality(cont.)
20Effects of Packet Size and Boundaries on Video
Quality
21Localizing Errors Using Packet Video
22Localizing Errors Using Packet Video(cont.)
23Error Correcting Codes
- BCH code (n,k)
- n n bits
- k protect k bits
- t the maximun number of errors that a code can
correct
24Error Correcting Codes(cont.)
25Error Correcting Codes(cont.)
26Conclusion