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Keep in mind that CELT is still a work in progress. Neither the API/ABI, nor the bit-stream are stable. Since CELT is still in development, most new releases (even minor ones) change the bit-stream, so compatibility is not preserved. Once version 1.0 is released the bitstream will be frozen and future revisions will be compatible. Also, while we do not expect it to set your house on fire, we cannot guarantee that it won't. So be warned! That being said, we're interested in feedback (bug reports, feature requests, comments) from people trying to use it.

Source code repository

CELT is hosted in Git and you can grab the latest code by typing:

git clone git://git.xiph.org/celt.git or
git clone http://git.xiph.org/celt.git

Latest development releases

0.7.1

CELT 0.7.1 improves the quality of the packet loss concealment (PLC), but does not change the rest of the codec. For this reason it is the first release not to break bit-stream compatibility with the previous release (0.7.0). But I promise not to do it again, the next CELT release will likely break compatibility once again. Note that the PLC improvements have not been completely converted to fixed-point yet, so the fixed-point still uses the old PLC. Last thing, the default name of the library was changed to libcelt0.so to make it easier to do the transition when the final 1.0 release comes out (with frozen bit-stream and API).

0.7.0

CELT 0.7.0 again improves the stereo quality, reduces artefacts at low bitrates (birdies and speech roughness) and fixes many bugs. In addition to the usual bitstream incompatibilities, the API has also changed in this release.

0.6.1

CELT 0.6.1 improves the stereo quality, especially at lower bit-rates. This breaks bit-stream compatibility again, but only for stereo this time.

0.6.0

This release brings in many quality improvements, including better stereo coupling, better handling of transients, and better handling of highly tonal signals. In addition, packet loss robustness has been improved through the optional use of independent (intra) frames. CELT now supports a larger dynamic range, suitable for encoding 24-bit audio (float version only). There is also a very early VBR implementation. The 0.6.0 testing page has more information about this release.

0.5.2

Version 0.5.2 has just been released with a few fixes over 0.5.1. On top of that, the pitch prediction was both improved and simplified. The other main change is a new bit allocation algorithm with better rounding and fine energy allocation. These changes resulted in considerable quality improvements at the smallest frame sizes. As with most prior releases this release breaks compatiblity with older bitstreams. The 0.5.2 testing page has more information about this release.

0.5.1.3

This is an update of the original 0.5.1 release that renames exported library/header symbols and header install locations from 'celt*' to 'celt051*' in order to assist in packaging and deploying compatability versions of this prerelease alongside later, incompatible versions of celt. In addition, this release contains fixes to all bugs known to affect the original 0.5.1 release.

0.5.1

This release fixes a number of issues with 0.5.0. Several cases where the encoder could fail have been fixed, including one that could cause memory corruption (and possibly a segfault). In addition, the VQ search has been improved, which results in a small CPU reduction, while fixing some quality problems with low frequency tones. Other than that, there should be no significant quality changes.

Older development releases

These are older releases, provided mainly for historical reasons.