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Revision as of 20:45, 3 December 2010
| Developed by | Xiph.Org Foundation |
|---|---|
| Type of format | Audio |
| Contained by | Ogg |
| Standard | Documentation |
| Developer(s) | Xiph.org Foundation, Jean-Marc Valin |
|---|---|
| Preview release | 0.9.1
/ November 8, 2010 |
| Operating system | Cross-platform |
| Type | Audio codec, reference implementation |
| License | 3-clause BSD |
| Website | celt-codec.org |
CELT (Constrained Energy Lapped Transform) is an open, royalty-free audio compression format and a free software codec for use in low-latency audio communication. It's a lossy codec, meaning quality is permanently degraded to reduce file size.
CELT is meant to bridge the gap between Vorbis and Speex for applications where both high quality audio and low delay are desired.[1] It is suitable to carry both speech and music. It borrows ideas from the CELP algorithm, but avoids some of its limitations by operating in the frequency domain exclusively.[1]
In December 2007, a first development version of CELT was published.[2] The latest version of CELT is 0.9.0, released on November 6, 2010.[3]
In July 2009 the CELT codec was submitted as an IETF draft.[4][5] In May 2009, a draft of RTP payload format for the CELT Codec was published.[6] In September 2010 a draft of the Opus codec which uses SILK and CELT was submitted to the IETF.[7]
Technical details
CELT can use sampling rates from 32 kHz to 48 kHz and above, adaptive bit-rate from 32 kbit/s to 128 kbit/s per channel and above. CELT supports mono and stereo and it is applicable to both speech and music. It uses ultra-low algorithmic delay (as low as 2 ms; scalable, typically from 3 to 9 ms). There are no known intellectual property issues and it is free software/open-source.[4][1]
Software
In January 2009 support for CELT was added to the Ekiga[8] and FreeSWITCH[9] VoIP programs.
CELT is also supported or used by:[10]
- Gablarski[11]
- GStreamer
- jack-audio-connection-kit (netjack)
- liboggz
- Mumble (starting with version 1.2)
- NexGenVoIP
- Radio CHNC
- RoarAudio
- Soundjack
- Teamspeak 3
See also
References
- ^ a b c Xiph.Org The CELT ultra low-delay audio codec - home page, Retrieved 2009-09-01
- ^ Xiph.Org (2007-12-08) CELT releases - celt-0.0.1.tar.gz, Retrieved 2009-09-01
- ^ Xiph.Org CELT News, Retrieved 2010-11-06
- ^ a b CELT IETF draft
- ^ IETF - AVT Working Group (2009-07-04) Constrained-Energy Lapped Transform (CELT) Codec, Retrieved 2009-09-01
- ^ IETF - AVT Working Group (2009-05-08) RTP Payload Format for the CELT Codec, Retrieved 2009-09-01
- ^ Definition of the Opus Audio Codec
- ^ Ekiga 3.1.0 available
- ^ FreeSWITCH: New Release For The New Year
- ^ Software that uses or supports CELT
- ^ www.gablarski.org