Audio Compression

This processing stage can compress and decompress audio samples using Adaptive Differential Pulse-Code Modulation (ADPCM). ADPCM was initially developed for speech coding, but often offers acceptable performance for music coding. It can be used to save a significant amount of bandwidth as it reduces 16-bit samples into 4-bit codes.

To use ADPCM, a compression instance must be created and added to an audio recording pipeline. On the playback audio device, a decompression instance must be created and added to the audio playback pipeline. This processing stage works for mono and stereo streams, but it must be specified when configuring the instance.

Note

The compression processing stage is compatible with packed audio samples using a bit depth of either 16, 24 or 32-bit and unpacked audio samples using a bit depth of either 16, 18, 20, 24 or 32-bit. Under-the-hood, the compression algorithm (ADPCM) necessitates 16-bit samples at its input. When used with a different format, the samples are converted to 16-bit before compression and extended back after decompression.