| An robust still image compression algorithm and implementation of wireless video transmission is introduced. The improved self-synchronizing Huffman code is proposed to decrease the error propagation length in the compressed bit stream caused by errors during transmission. After regaining synchronization, the decoder may still not be able to align each symbol with its correct location due to the wrong number of previously decoded symbols in the error propagation region. A scheme to identify the probable error location and then move symbols towards their correct positions is also proposed by exploiting the correlation between coefficients of the current subband and their parent subband. Experiments under different error conditions are performed, and it is demonstrated that the proposed error resilient techniques provide more a robust codec with very little sacrifice in the coding efficiency. The proposed algorithm has been cited in the documentation of error resilience ad hoe group of the verification model of next generation still image compression standard, JPEG 2000. Secondly, error resilient compression and transmission algorithm tailored to media and standard is implemented. In order to minimize the effect of errors on perceptually important low frequency subbands without introducing much higher overhead for error resiliency in JPEG 2000, we propose that these low frequency subbands be coded by using reversible variable length codes (RVLC). Unlike arithmetic codes, RVLC allows two-way decoding. This results in the recovery of larger parts of the corrupted block in spite of the presence of errors. The remaining coefficients of the block can then be reliably reconstructed by using error concealment at the decoder. To examine the performance and the bottleneck of a wireless video transmission system over the cellular phone infrastructure, we build one system to demonstrate the feasibility and use a low overhead error control scheme to achieve robustness. |
