Adaptive differential pulse-code modulation (ADPCM) is a variant of differential pulse-code modulation (DPCM) that varies the size of the quantization step, to allow further reduction of the required data bandwidth for a given signal-to-noise ratio.
[1] ADPCM was developed for speech coding by P. Cummiskey, Nikil S. Jayant and James L. Flanagan at Bell Labs in 1973.
When the ADPCM bitstream of each subband is obtained, the results are multiplexed, and the next step is storage or transmission of the data.
[6] As of 31 October 2024[update], FFmpeg include 50 built-in ADPCM decoders and 16 encoders, some catering to niche purposes.
For instance, "ADPCM Westwood Studios IMA" (adpcm_ima_ws) encodes and decodes the audio of the old Command & Conquer video games.