Robust image transmission using resynchronizing variable-length codes and error concealment

Resynchronizing variable-length codes (RVLC's) for large alphabets are desi gned by first creating resynchronizing Huffman codes and then adding an ext ended synchronizing codeword, and the RVLC's are applied to both JPEG and w avelet-based image compression. The RVLC's demonstrate the desired resynchr onization properties, both at a symbol level and structurally so that decod ed data can be correctly placed within an image following errors, The encod ed images, when subject to both structural and statistical error detection and concealment, can tolerate BER's of up to 10(-4) and are very tolerant o f burst errors, The RVLC-JPEG images have negligible overhead at visually l ossless bit rates, while the RVLC-wavelet overhead can be adjusted based on the desired tolerance to burst errors and typically ranges from 7 to 18%. The tolerance to both bit and burst errors demonstrates that images coded w ith such RVLC's can be transmitted over imperfect channels suffering bit er rors or packet losses without channel coding for the image data, or with le ss channel coding than would be required if the encoded image data could to lerate no bit errors. While the overhead is nontrivial for the RVLC-wavelet images and the lower-rate RVLC-JPEG images, the encoded bitstreams do not have the firm restrictions on numbers or spacings of bit errors that some e rror correcting codes have, and hence provide more graceful degradation.