LZW Algorithm Builds a dictionary of symbol code pairs that usually is smaller that the original set of symbols. Can be made to be very fast. Discrete Cosine Transform Transforms data from spatial domain to frequency domain. Most software implementations use fixed-point arithmetic. Quantization Reduces the number of bits per sample, and is the source of most error.
Some frames hold delta information from other frames.
Symmetrical vs. Asymmetrical Symmetrical refers to codecs that have similar compression and decompression times. Asymmetrical codecs usually take much longer to compress, but decompress quickly. Developed by SuperMac Technology in the late 1980's. Supported by QuickTime, NetShow, others. Based on vector quantization.