A hierarchical DCT-based system is presented that prioritizes and compresses high data rate video for transmission over cell-based ATM networks. The proposed system is both robust to cell loss, and efficient in bandwidth utilization. Cell loss due to network congestion can significantly deteriorate the visual quality of the received image. Various cell loss concealment techniques have been proposed in the literature. The system proposed here will significantly reduce complexity of cell loss concealment circuitry at the receiver.

ATM standards allow one bit for priorities; thus a two-level hierarchical scheme is examined. We also study performance for priorities greater than two. When the ATM network needs to drop cells due to congestion, the low- priority cells are dropped first. We assume that the high- priority cells are received without any cell loss whereas the low-priority cells are subject to a non-zero cell loss probability rate.

The transmission rate is the 130 Mbps H4 access rate. Due to this high rate, the coder is kept simple and only intrafield coding is considered. Variable length coding is utilized to noiselessly compress the data before transmission. Two lossless techniques are examined: adaptive Huffman coding and arithmetic coding. The codecs will be tested assuming a Markov source with varying orders of memory (as well as the memoryless case). Simulation results are used to judge performance of this hierarchical system.