Entries found for search: PCM
ADPCM : Adaptive Delta (Differential) Pulse Code Modulation. A type of split-band, time-domain audio compression algorithm for 16-bit digital audio based on describing level differences between adjacent samples. Different from conventional linear PCM by coding only level differences between samples, rather than the absolute level of each sample. According to the characteristics of the audio signal, ADPCM adapts the step size represented by each quantizing interval to accommodate rapid changes in level caused by high frequencies or transients, thereby providing an overall reduction in bit rate; the compression ratio is 4:1. There are at least two ADPCM standards: Microsoft and IMA/ADPCM, the latter popular for multimedia applications. See delta modulation, split-band, sub-band, transform coding.
PCM : Pulse Code Modulation. A technical term for sampling. Any digital method of encoding and decoding the amplitude of an audio signal. For example, an 8-bit PCM yields amplitude values of 0-255, and produces attendant sampling errors and quantization errors. PCM cards are always ROM, and contain only sampled waveforms, contained in a wavetable. See PWM, split-band. See also PAM.
PCM-F1 : A reference to the (discontinued) Sony digital recording system which used an EIAJ-format, 16-bit PCM processor to convert audio into a digital form that can be stored on consumer videotape. The first attempt at digital audio.
PCMCIA personal computer memory card international association. The preferred term is PC Card; a 32-bit implementation is called a cardbus. A credit-card-size interface commonly found in notebook computers. They are primarily used for modems and network interfaces (and storing programs in synthesizers); this specification has historically been inhospitable to audio devices even though a handful of successful advices do exist.