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

Resynchronizing variable-length codes (RVLCs) for large alphabets are designed by first creating resynchronizing Huffman codes and then adding an extended synchronizing codeword, and the RVLCs are applied to both JPEG and wavelet-based image compression. The RVLCs demonstrate the desired resynchronization properties, both at a symbol level and structurally so that decoded data can be correctly placed within an image following errors. The encoded images, when subject to both structural and statistical error detection and concealment, can tolerate BERs of up to 10/sup -4/ and are very tolerant of burst errors. The RVLC-JPEG images have negligible overhead at visually lossless 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 with such RVLCs can be transmitted over imperfect channels suffering bit errors or packet losses without channel coding for the image data, or with less channel coding than would be required if the encoded image data could tolerate 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 error correcting codes have, and hence provide more graceful degradation.