The CELT ultra-low delay audio codec
Overview
The CELT codec is an experimental audio codec for use in low-delay speech and audio communication.
The Technology
CELT stands for "Code-Excited Lapped Transform". It applies some of the CELP principles, but does everything in the frequency domain, which removes some of the limitations of CELP. CELT is suitable for both speech and music and currently features:
- Ultra-low latency (typically from 3 to 9 ms)
- Full audio bandwidth (44.1 kHz and 48 kHz)
- Support for both voice and music
- Stereo support
- Packet loss concealment
- Constant bit-rates from 32 kbps to 128 kbps and above
- A fixed-point version of the encoder and decoder
The CELT codec is meant to close the gap between Vorbis and Speex for applications where both high quality audio and low delay are desired.
Getting Involved
CELT is still in very early phase. At this point, two ways of getting involved are: helping design the algorithm (requires strong DSP knowledge) or building applications using CELT and maybe help define future directions the codec will take.
If you have questions or are interested in contributing to the project, you can also contact the Project Lead, Jean-Marc Valin.
Headlines
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Version 0.3.2 released
16 May, 2008
Version 0.3.2 is out. This consists mainly of quality tuning. We've also completed some listening tests based on that version for the Comparison page.
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Version 0.3.1 released
26 April, 2008
Version 0.3.1 is now released. CELT is now a lot faster and can run in real-time on a PC with less than 10% CPU.
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Domain is up
18 March, 2008
Just registered celt-codec.com and celt-codec.org for this project. Now working on the website