Abstract

This dissertation presents an error resilient H.263 video compression scheme over noisy channels. The start codes in the H.263 bit stream syntax, which inherently provide the resynchronization functionality for error handling, may cause significant error damage if they are incorrectly decoded. Therefore, we develop a video segment regulation algorithm at the decoder to efficiently identify and correct erroneous start codes and block addresses. In addition, a parity-embedded error detection technique is also implemented. At the encoder, the requisite parity-check codes for all macroblocks in the previous frame are embedded into the motion vectors and the quantized residual DCT coefficients of the current encoding frame. Then the decoder can effectively manipulate these embedded bits to enhance the error detection capability at the macroblock-layer. Finally, the precise error tracking technique is used to further reduce the error propagation effects. After performing the video segment regulation and the parity-embedded error detection, the decoder can report the accurate addresses of detected corrupt blocks back to the encoder via a feedback channel. With these negative acknowledgments, the encoder can precisely calculate and trace the propagated errors by examining the backward motion dependency for each pixel in the current encoding frame. With this precise tracking strategy, the error propagation effects can be terminated completely by INTRA refreshing the affected blocks. Simulation results show that the proposed scheme yields significant video quality improvements over the motion compensated concealment by gains of 4 to 6 dB PSNRs at bit rate around 32 kbps in the error-prone DECT environments. In particular, this scheme complies with the H.263 standard and has the advantages of low memory requirement and computation complexity that are suitable for practical real-time implementation.