Abstract: Variable-length codes are widely adopted for lossless data compaction in many digital video applications, e.g., videophone and high definition television (HDTV). However, error propagation is still a major concern for practical applications. In general, since there are no explicit word-boundaries in the variable- length coded data stream, a transmission error will cause the succeeding codewords to be decoded erroneously. One way to confine the error propagation is through the periodic use of synchronizing words that have a special bit pattern which can be recognized in the coded bit stream as long as there are no errors in the words itself. We call such codewords 'clear' codewords. A basic property of the clear codewords is that they cannot be formed by any concatenation of other codewords. These clear codewords are useful not only for the detection and confinement of errors but also for the multiplexing and demultiplexing of multiple variable-length coded bit streams. The construction of efficient variable-length codes with clear codewords is an interesting and important issue for many practical applications. In this paper, a systematic method is provided for the construction of such codes.!13
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