Compression of human speech is a specialized form of audio compression. Greater levels of compression can be achieved by modeling the human vocal tract, and taking advantage of redundancy in human speech. See special area for the G.7xx audio speech codecs (G.721, G.722, G.726, etc.).
This is a list of ITU-T Recommendations on "Transmission systems and media, digital systems and networks" (Series G). It contains an index for the G.7xx audio codecs family. One can check the status of documents, see their contents and buy them online.
Created: 30/01/2006
by Maxim SmirnovMore...
This company makes the AMBE-2020, a Vocoder chip that compresses speech down to a miniscule 4 Kbps. They have an additional product library of low bit-rate codes both in hardware and software.
Created: 21/11/1999
by Mark NelsonMore...
These folks offer some seminars on communcations (at Arisona State University). On their page, if you go to the links to free software, you will find Matlab code for CELP and LPC Vocoders (FS-1016 and lpc10e). This same page also has a wide variety of links for speech coding stuff.
Created: 31/12/1999
by Mark NelsonMore...
HawkVoice is a game oriented, multiplayer voice over network API released under the GNU Library General Public License (LGPL), with
support for Linux/Unix and Windows 9x/ME/NT/2000. It is designed to be a portable, open source code alternative to DirectPlay(R) Voice in DX8.
Created: 09/03/2001
by Mark NelsonMore...
GSM provides telephone quality speech at a compressed rate of 13 Kbps. Compare this to the 64 KBps required by standard u-law and A-law codes. This site gives lots of info about the GSM format, along with free source code.
Created: 21/11/1999
by Mark NelsonMore...
This site contains the comp.speech FAQ, and also has links to their ftp site, which contains software for speech codecs.
Created: 21/11/1999
by Mark NelsonMore...
This project is an attempt to port the free Speex voice codec to a pure Java implementation.
Version 0.9.4 is shipping as of June, 2004.
Created: 27/06/2004
by Mark NelsonMore...
The Speex project aims to build a patent-free, Open Source/Free Software voice codec. Unlike other codecs like MP3 and Ogg Vorbis, Speex is designed to compress voice at low bitrates in the 8-32 kbps/channel range. Possible applications include VoIP, internet audio streaming, archiving of speech data (e.g. voice mail), and audio books. In some sense, it is meant to be complementary to the Ogg Vorbis codec.
Speex 1.1.5 was released in April, 2004.
Created: 25/04/2004
by Mark NelsonMore...
OTR stands for "Old Time Radio". The owners of this project want to be able to listen to classic mono AM radio recordings on their Sharp PDAs.
Created: 23/07/2003
by Mark NelsonMore...
Hawk Software is now selling a pair of codecs, LPC-10 and OpenLPC, that are suitable for Windows CE, CELinux, and other 32-bit embedded platforms. More are planned for future releases.
Created: 08/07/2003
by Mark NelsonMore...
This product takes your text, converts it to speech, then stores the result in one of several compressed formats, including MP3, Ogg Vorbis, and G.721.
Created: 07/06/2003
by Mark NelsonMore...
The EasyAudio ActiveX Control adds speech handling capabilities to your Win32 program. Listed features include nice things such as support for popular codecs including G.729, G.711, and ADPCM, unicast and multicast support, AGC, jitter buffer management, and noise reduction. The web page gives a price of $1000 for the control, and $2000 for the source code. I hope that big price tag includes free distribution rights, but the web site is woefully short on license information.
Version 3.0 is shipping as of March, 2003.
Created: 16/03/2003
by Mark NelsonMore...
A nice set of links to AudioCoding information. Since this is a Wiki site, it is highly collaborative - registered users can provide updates and modifications to the site at will. (I think.)
Created: 13/12/2002
by Mark NelsonMore...
Nellymoser is the leading provider of proprietary speech and audio software technology and solutions in the areas of compression, modification, synchronization and conversion. Our products improve speech and audio quality and efficiency in bandwidth-constrained environments while creating more immersive, interactive environments for your applications and services.
Created: 09/12/2002
by Mark NelsonMore...
The Asao libraries from Nellysoft have been designed specifically to address the need for a very small footprint, low bandwidth speech and audio compression. Asao will operate at a variety of bit rates (12/16/24/32 Kbps). This new technology can be rapidly harnessed for applications such as streaming over mobile data networks, Internet radio and embedded platforms such as toys and other consumer devices.
Created: 09/12/2002
by Mark NelsonMore...
The Sase libraries fron Nellysoft offer flexible compression options for both embedded and data packets based compression implementations It can operate in either a single bit rate or a multi-rate mode, offering compression rates (1.8/3.2/6.4 Kbps) to suit your application or the changing environment of packet based networks. Sase has the ability to switch bit rates on-the-fly to better handle changing network condition. At 3.2 Kbps Sase offers near toll quality, as you would expect when more bits are added the speech quality improves at 6.4 Kbps.
Created: 09/12/2002
by Mark NelsonMore...
The voice recording applet SDK is designed for the web developers and allows to record the voice from web site, to compress it and to send to the web server via HTTP. To playback the recorded voice from the server the embedded voice streaming player or a separate player as a voice streaming applet can be used. Both applets are designed in Java 1.1 and has a JavaScript interface.
Created: 15/09/2002
by Mark NelsonMore...
Source code for A 2.4 Kbps MELP coder. Target is Sun OS4. Phil Frisbie did the detective work needed to determine that the MELP coder is now owned by ASPI, so if you want to use it, you need to talk to them about licensing. See them at www.aspi.com.
Created: 05/03/2002
by Mark NelsonMore...
UCSB research activities, including speech coding, audio compression, video coding. Lots of links to demos and publications.
Created: 22/02/2002
by Mark NelsonMore...
This is the home page for the IETF group that reviews RTP packetization standards. Links on this page for all the drafts you can imagine for sending video and audio over RTP streams.
Created: 27/01/2002
by Mark NelsonMore...
A company named Effnet Inc. is licensing a version of CRTP, a protocol that compresses packet headers in RTP streams. With small VOIP packets this can provide substantial savings.
Created: 08/01/2002
by Mark NelsonMore...
Atlanta Signal Processor, Inc., is nice enough to host his paper on their site. It gives a brief overview of the MELP Vocoder algorithm.
Created: 15/12/2001
by Mark NelsonMore...
Apple has published a tech note describing the differences between these two file formats, which on the face of it ought to be identical.
Created: 14/09/2001
by Mark NelsonMore...
An ftp site with various speech codecs, including G.722, GSM, G.711, G.723, G.721, CELP, and LPC. Licensing and ownership of the C source varies.
Created: 06/07/2001
by Mark NelsonMore...
Zarak Systems will perform Quality of Service testing using PSQM, the Perceptual Speech Quality Measurement. This web page will tell you a little bit about what that means to you.
Created: 11/06/2001
by Mark NelsonMore...
Some speech samples that have been encoded at various rates using various codecs. If you've never heard speech encoded at 1.4 Kbps, here's a chance to check it out.
Created: 08/05/2001
by Mark NelsonMore...
The DSP Group makes a codec called TrueSpeech. You can get a copy of the player for free here to check out the 8.5 KBps audio it makes possible.
Created: 24/09/2000
by Mark NelsonMore...
This freeware program is designed to perform Internet telephony. It incorporates source for a couple of interesting speech codec, which is why it gets a link in the library.
Created: 24/09/2000
by Mark NelsonMore...
IstraSoft appears to make some speech codecs, supplied as Windows DLLs. Plus some discussion on their web page re: English phonetics.
Created: 27/08/2000
by Mark NelsonMore...
Descriptions of various speech codecs, include G.711, G.721, GSM, and CELP. Each codec gets a brief description plus pointers to additional material and source code.
Created: 20/08/2000
by Mark NelsonMore...
A project at Cambridge University that led to a low bit rate speech coder that was used in the HP 620LX Palmtop PC.
Created: 15/07/2000
by Mark NelsonMore...
This site advertises a bunch of nifty looking codecs, including TELP, JPEG, Speech, MPEG, and wavelet compressors. I can't quite determine exactly what form the products come in.
Created: 03/06/2000
by Mark NelsonMore...
Nuera makes a couple of speech multiplexers that use CELP compression. You probably won't be interested in these unless you've got a T1 line that is bursting at the seams.
Created: 03/06/2000
by Mark NelsonMore...
Has free codecs download, including G.729A. VoiceAge allows developers to freely use their G.729(A) codec object code for non-commercial purposes. This initiative provides you with an opportunity to work with the G.729(A) codec for free while developing products or applications.
Our technology served as the foundation for numerous voice compression products used by voice portal and large multinationals in their efforts to better meet the quality requirements that end users. As example voice email, voice chatting, voice annotation in web site. Our technology is already integrated into software by companies such as Microsoft with its Netshow® software and in its Mediaplayer®, and RealNetworks within its RealAudio® and RealVideo®. In addition, over the last decade this compression technology (over 100 patents) was positioned in several International Telecommunication standards, notably: GSM ,PCS, TDMA ,CDMA, TETRA, G.729 . VoiceAge’s compression technology is well positioned at cross road of internet and voice for next-generation of voice portal.
Created: 23/01/2000
by Mark NelsonMore...
These folks at UCSB are encoding speech at 2.8 Kbps. It sounds very good considering the bit rate. Links here to a presentation and an abstract, as well as some samples.
Created: 13/01/2000
by Mark NelsonMore...
On these web pages I try to give an idea of the principles involved in speech coding, and details of commonly used coders. Also links are given to other related pages, and the source code of some common speech codecs.
Created: 01/01/1970
by Mark NelsonMore...
