Adaptive differential pulse code modulation (ADPCM) is a compression and decompression algorithm that uses adaptive quantizers and adaptive predictors to compress sound data, typically speech. The implemented encoder takes 16‑bit pulse code modulation (PCM) data to produce a representation using 4‑bit ADPCM values.

The ADPCM implementation is not compliant with the G.726 standard or any other ADPCM standard. Therefore, it cannot be used to interface to other ADPCM compressors/decompressors. It does not include error correction, so it is not suitable for transmission over an imperfect link. However, the implementation is suitable for reducing audio storage overheads.

See Chapter 2 Adaptive Differential Pulse Code Modulation.