Pulse code modulation

Pulse-code modulation (PCM) refers to audio that is digitally recorded in discrete samples as opposed to being synthesized on the fly through a programmable sound generator, FM synthesis, or subtractive synthesis. PCM data can be stored in many different formats at different levels of quality, but, unlike synthesized music, the playback is essentially identical on all devices, the only difference can come from the quality of the speaker. However, the benefit of identical output on all devices comes at a cost of much larger files.

Versions

DPCM

In differential pulse-code modulation, not the actual pulses, but their distance to each other is stored, producing smaller but also muffled sounds.

The RP2A03 implements DPCM.

ADPCM

In adaptive differential pulse-code modulation, whenever a distance is particularly high or low, all further distances are scaled up or down, producing less muffled sounds at the same size.

X68000, Sound Blaster and WAV implement ADPCM.

BRR

The S-SMP's patented ADPCM variant is known as bit rate reduction.