This is an implementation of the VADPCM codec. The VADPCM codec is often used by Nintendo 64 games—this includes both homebrew games made using LibDragon and commercial games made during the 1990s and 2000s with the proprietary SDK, LibUltra.
VADPCM is licensed under the terms of the Mozilla Public License Version 2.0. See LICENSE.txt for details.
The project is, as of September 2023, under active development. Version 1.0 is expected within the next six months.
VADPCM is a variant of ADPCM. It encodes blocks of 16 samples of audio into 9 bytes of data, giving 4.5 bits per sample. There are no settings or parameters to change the bit rate; the bit rate is always 4.5 bits per sample.
The audio quality of VADPCM is good, but this codec is not competitive with codecs like Opus, Vorbis, or even MP3.
VADPCM uses a codebook of second-order linear predictors, and encodes the residuals using 4 bits per sample. Each block of 16 samples shares the same predictor and scaling factor. The predictors in the codebook are stored in a vector format, which makes it easy to write a high-performance decoder using SIMD instructions. The Nintendo 64 has a coprocessor, called the Reality Signal Processor, with SIMD capabilities.