39 – DV compression

Publisher Summary Digirtal Video (DV) denotes the compression and data packing scheme used in consumer digital video cassette (DVC) recorders and their professional derivatives. DV compression uses discrete cosine transform (DCT), quantization, and variable-length encoding (VLE) comparable to JPEG; however, DV does not conform to the Joint Photographic Experts Group (JPEG) standard. Optimizations have been made to accommodate interlaced scanning, constant bit-rate (CBR) operation, and other features related to videotape recording. Constant bitrate is achieved by dynamically altering the quantization matrices to avoid exceeding the available capacity. The main challenge of DV encoding is to determine suitable quantization matrices for a segment's AC coefficients, such that when all of the quantized coefficients are subject to variable-length encoding, the VLEcoded coefficients just neatly fit in the available space. The goal is to quantize the AC terms as finely as possible without exceeding the capacity of a segment. The chapter also discusses the challenge associated with DV encoding for determining suitable quantization matrices for a segment's AC coefficients