Yamaha ADPCM
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- Microsoft Audio ID: 0x0020
- Extension: spb,mmf
- Company: Yamaha
- Sample: http://samples.mplayerhq.hu/A-codecs/format-0x20-laugh.mmf
- ACM Codec: https://web.archive.org/web/20160323215457/http://smaf-yamaha.com/jp/tools/dl/Yamaha-ADPCM-ACM-Driver-100-j.zip
A variant of this codec is used by several Yamaha chips:
- Y8950(MSX-SOUND)
- YM2608（OPNA) [the external ADPCM channel only]
and may also be used on the following chips:
- YM2610(OPNB) [the external ADPCM_B channel only?]
- YMZ263B(MMA)
- YMZ280B(PCMD8)
A (possibly slightly changed) variant is used on the sound chip of Sega Dreamcast and NAOMI:
- Yamaha AICA Super Intelligent Sound Processor
The exact codec was also used by Yamaha SMAF MA-2 and onward):
- MA-2 (YMU759)
- MA-3 (YMU762)
- MA-5 (YMU765)
- MA-7 (YMU786)
The functionality of this codec is explained fairly extensively in two datasheets:
- Y8950 application manual: http://www.datasheetarchive.com/pdf/download.php?id=212962c2fe1b63fdc5ab320ca05ff3efefc925&type=M&query=y-8950
- YM2608 datasheet (Japanese): http://nemesis.hacking-cult.org/MegaDrive/Documentation/YM2608J.PDF
- Translated version of YM2608 datasheet: http://nemesis.hacking-cult.org/MegaDrive/Documentation/YM2608J%20Translated.PDF
The codec is almost a reference implementation of the codec described in Jayant's 1973 paper [1] (Table VIII, 'DPCM' column, B=4). This paper, along with its companion paper [2] originally coined the term "ADPCM".