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—The CELT codec has been merged into the IETF Opus codec and is now obsolete—


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

The repository can be viewed online at http://git.xiph.org/?p=celt.git.

Latest development releases


CELT 0.11.1 fixes two minor bugs with 0.11 that affect the bit-stream. The quality should improve (very) slightly, but not enough to be noticeable in most cases. Several Opus-related bugs have also been fixed.


CELT 0.11 introduces API changes that should be close to the final API. The bit-stream is also in "soft-freeze" meaning there is an attempt to keep it fixed, but some bugs may force changes. There are also some minor quality improvements, mostly at high bit-rate.


CELT 0.10.0 again brings many quality improvements, mostly through better bit allocation. It also fixes many bugs and regressions, most notably with VBR support. The bit-stream is not compatible with version 0.9.x. See Monty's CELT demo page for more details on recent (and less recent) CELT development.


CELT 0.9.1 greatly improves the packet loss concealment. This change is especially dramatic in fixed point mode. The 0.9.1 bit-stream is compatible with 0.9.0.

Older development releases

These are older releases, provided mainly for historical reasons.

—The CELT codec has been merged into the IETF Opus codec and is now obsolete—