Variable-bit-rate HDTV codec with ATM-cell-loss compensation

A variable-bit-rate coding algorithm based on motion-adaptive discrete cosine transform (DCT) is investigated for asynchronous transfer mode (ATM) environments in broadband integrated-services digital networks (B-ISDN). The algorithm effectively reduces the bit rate, in particular, for HDTV-picture sources with little motion. Adaptive two-layered coding, an ATM cell matrix for error correction, and a block interleave for error concealment are proposed to keep picture quality high by compensating for ATM cell loss. A feedforward control scheme for variable-length coding (VLC), a multimode quantization that restricts peak bit rate and average bit rate, is also proposed for traffic control. Experimental hardware is shown to reduce the coding bit rate for pictures of HDTV conference applications to peak bit rate of 65-Mb/s and an average bit rate of 10-20-Mb/s in ATM environments.<
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