Image and video wavelet coding for noisy channels
Nick Kingsbury, D.W. Redmill · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1997
We describe techniques of encoding compressed images and video such that the encoded bit stream is resilient to transmission errors which occur on typical noisy channels, particularly to and from mobile users. These errors may occur in the form of random bit errors, bursty bit errors or packet losses, or combinations of these, and the proposed techniques are shown to suffer only gradual and graceful degradation as the error rate increases. This contrasts markedly with the severe error sensitivity of conventional image compression standards, such as JPEG and MPEG. A key tool that we employ is the error resilient entropy code (EREC)6 which largely overcomes the problems of loss of synchronization and severe error propagation, inherent in most entropy coded data streams. Unlike traditional forward error correction methods, the error-resilient techniques which we employ do not add significant redundancy to the compressed data and therefore do not waste capacity or degrade the compression performance under good channel conditions. They are shown to work particularly well with wavelet compression because the localized image defects, which errors do cause, are less visible with wavelets than with DCT-based compression, due to the smoother boundaries of the wavelet basis functions.