TwinVQ (transform-domain weighted interleave vector quantization) is an audio compression technique developed by Nippon Telegraph and Telephone Corporation (NTT) Human Interface Laboratories (now Cyber Space Laboratories) in 1994. The compression technique has been used in both standardized and proprietary designs.
TwinVQ in MPEG-4 
TwinVQ is one of the object types defined in MPEG-4 Audio, published as subpart 4 of ISO/IEC 14496-3 (for the first time in 1999 - a.k.a. MPEG-4 Audio version 1). This object type is based on a general audio transform coding scheme which is integrated with the AAC coding frame work, a spectral flattening module, and a weighted interleave vector quantization module. This scheme reportedly has high coding gain for low bit rate and potential robustness against channel errors and packet loss, since it does not use any variable length coding and adaptive bit allocation. It supports bitrate scalability, both by means of layered TwinVQ coding and in combination with the scalable AAC.
Note that some commercialized products such as Metasound (Voxware), SoundVQ (Yamaha), and SolidAudio (Hagiwara) are also based on the TwinVQ technology, but the configurations are different from the MPEG-4 TwinVQ.
TwinVQ as a proprietary audio format 
A proprietary audio compression format called TwinVQ was developed by Nippon Telegraph and Telephone Corporation (NTT) (in NTT's Human Interface Laboratories) and marketed by Yamaha under the name SoundVQ. The NTT also offered a TwinVQ demonstration software for non-commercial purposes - NTT TwinVQ Encoder and TwinVQ Player, encoder API, decoder API and header file format. The filename extension is .vqf.
TwinVQ uses Twin vector quantization. The proprietary TwinVQ codec supports constant bit rate encoding at 80, 96, 112, 128, 160 and 192 kbit/s. It was claimed that TwinVQ files are about 30 to 35% smaller than MP3 files of adequate quality. For example, a 96 kbit/s TwinVQ file allegedly has roughly the same quality as a 128 kbit/s MP3 file. The higher quality is achieved at the cost of higher processor usage.
Yamaha marketed TwinVQ as an alternative to MP3, but the format never became very popular. This could be attributed to the proprietary nature of the format—third party software was scarce and there was no hardware support. Also the encoding was extremely slow and there was not much music available in TwinVQ format. As other MP3 alternatives emerged, TwinVQ quickly became obsolete.
The proprietary version of TwinVQ can be also used for speech encoding. Compression technology specifically designed to handle voice compression was published by NTT. The NTT TwinVQ implementation supported sampling frequencies from 8 kHz or 11.025 kHz and bit rate from 8 kbit/s.
Software support 
The Format Developers -
NTT in Japan is said to have once offered (on its website) a player/encoder for download (citation needed). This was not as successful as the Yamaha version (see below) and, nowadays, is almost impossible to find (citation needed).
Co-Developer, Yamaha's own encoder/player (that is no longer maintained) is called K-Jöfol in Japan - and its International-English equivalent is called SoundVQ, that can be downloaded here -
SoundVQ - Ver 251 (filename: vqp251b1e.exe) http://www.sonicspot.com/soundvqplayer/soundvqplayer.html
SoundVQ - Ver 252 (filename: vqp252b1e.exe) (final release) https://mega.co.nz/#!WdtGTJbY!GPr4iHLWXjsWeADnVjteXSSq8wMpIN2nUpfev3IYK98
(For Windows 2000, Windows XP and some versions of Windows Vista). (Please mirror above download for archival purposes)
Other Developers -
The format was reverse-engineered in 2009 by the FFmpeg project and decoding of vqf files is supported by the open-source libavcodec library, which makes it supported in, for example, VLC media player.
Some older versions of Nero Burning ROM are able to encode to TwinVQ/VQF.
For users of GNU/Linux or similar systems, there is an XMMS plugin.
Some CD-Ripping/Converter software also support encoding to .vqf format, for instance FairStars CD Ripper as well as a companion program called Fairstars Audio Converter.
See also 
- MPEG-4 Audio FAQ - ISO (1998)
- MPEG-4 Natural Audio Coding - scalability in MPEG-4 natural audio, TwinVQ, Audio profiles and levels
- What Is VQF? - an article on the historical VQF website (2000)
- VQF on Hydrogenaudio Knowledgebase (2006)
- The historical NTT TwinVQ website - by Nippon Telephone and Telegraph (2002), (2008)
- Informations about TwinVQ on MP3' Tech (2001)
- XMMS VQF Plugin at Freecode (2002-07-12)
- Winamp VQF Plugin (2000-07-27)
- Nippon Telegraph and Telephone Corp. (1995). "R&D activities of NTT's Research and Development Headquarters in 1994 - An Integral Multimedia Capability - Compression Encoding of Music with TwinVQ (archived website)". Archived from the original on 1997-10-09. Retrieved 2010-08-06.
- NTT (1996). "Welcome to the home of TwinVQ! (archived website) (Japanese)". Archived from the original on 2000-08-30. Retrieved 2010-08-06.
- "AES E-Library - Transform-Domain Weighted Interleave Vector Quantization (TwinVQ)". Audio Engineering Society. 1996. Retrieved 2010-08-06.
- "Our research of Audio". NTT HI Labs. 1997. Archived from the original on 1999-01-28. Retrieved 2010-08-06.
- ISO (1999). "ISO/IEC 14496-3:1999 - Information technology -- Coding of audio-visual objects -- Part 3: Audio". ISO. Retrieved 2009-10-09.
- D. Thom, H. Purnhagen, and the MPEG Audio Subgroup (1998-10). "MPEG Audio FAQ Version 9 - MPEG-4 - an introduction to MPEG-4 Audio". chiariglione.org. Retrieved 2009-10-06.
- ISO/IEC JTC 1/SC 29/WG 11 (1999-07), ISO/IEC 14496-3:/Amd.1 - Final Committee Draft - MPEG-4 Audio Version 2 (PDF), retrieved 2009-10-07
- Heiko Purnhagen (2001-06-01). "The MPEG-4 Audio Standard: Overview and Applications". Heiko Purnhagen. Retrieved 2009-10-07.[dead link]
- ISO/IEC JTC1/SC29/WG11 N2203 (1998-03). "MPEG-4 Audio (Final Committee Draft 14496-3)". Heiko Purnhagen. Retrieved 2009-10-07.[dead link]
- Business Wire (1996-12-11). "Voxware expands technology offerings & signs licensing agreement with NTT.". The Free Library. Retrieved 2009-10-06.
- Business Wire (1997-05-13). "IBM Licenses Voxware's MetaSound Technology for Use in Multimedia Products.". The Free Library. Retrieved 2009-10-06.
- YAMAHA CORPORATION (2000). "Yamaha SoundVQ". Archive.org. Archived from the original on 2003-02-27. Retrieved 2009-10-06.
- YAMAHA CORPORATION (1997). "Yamaha "SoundVQ"". Archived from the original on 1998-12-07. Retrieved 2010-08-06.
- NTT-East Multimedia Business Department (2000-03-31). "About TwinVQ". Archive.org. Archived from the original on 2000-08-17. Retrieved 2009-10-06.
- "Music compression technology "TwinVQ" (archived website) (Japanese)". 1996. Archived from the original on 1997-06-27. Retrieved 2010-08-06.
- "About TwinVQ (archived website) (Japanese)". 1997. Archived from the original on 1997-07-25. Retrieved 2010-08-06.
- NTT-East Multimedia Business Department (2008). "TwinVQ Software". Archive.org. Archived from the original on 2008-04-19. Retrieved 2009-10-07.
- NTT-East Multimedia Business Department (2002). "TwinVQ - libraries and sample programs". Archive.org. Archived from the original on 2002-12-27. Retrieved 2009-10-07.
- NTT-East Multimedia Business Department (2000). "TwinVQ F.A.Q.". Archive.org. Archived from the original on 2000-08-19. Retrieved 2009-10-06.
- NTT (1998-03-24). "TwinVQ (archived website)". Archive.org. Archived from the original on 1998-04-30. Retrieved 2009-10-06.
- MultimediaWiki (2009). "VQF". MultimediaWiki. Retrieved 2009-10-07.
- "TwinVQ F.A.Q. (archived website) (Japanese)". 1997. Archived from the original on 1997-07-25. Retrieved 2010-08-06.
- "TwinVQ decoder source-code". Retrieved 2009-08-23.