caudec (pronounced: /kɔːdɛk/, as in caught, and a deck of cards) is a command-line utility for GNU/Linux and OS  that transcodes (converts) audio files from one format (codec) to another. It leverages multi-core CPUs with lots of RAM by using a ramdisk, and running multiple processes concurrently (one per file and per codec). It is Free Software, licensed under the GNU General Public License. See what it looks like, download it, install it.


  • caudec is fast. Encoding Pink Floyd's The Wall (81 minutes, 26 tracks - arguably classier than ABBA, but caudec doesn't discriminate) from WAV to FLAC --best is done at 183x real time on a Core i7 @ 2.2 GHz with 8 processes, versus 46x with one process. FLAC -5 encodes at 532x, TAK -p2 at 705x.
  • Supported input formats / codecs: WAV, AIFF, CAF, FLAC, WavPack, Monkey's Audio, TAK, Apple Lossless (ALAC).
  • Supported output formats / codecs: WAV, AIFF, CAF, FLAC, Flake, WavPack, Monkey's Audio, TAK, Apple Lossless (ALAC), lossyWAV, LAME, Ogg Vorbis, Nero AAC, qaac, Musepack, Opus.
  • Support for high quality resampling and downmixing / upmixing to stereo, with SoX.
  • Optimized I/O: input files are copied onto a ramdisk sequentially, so as to get the best performance out of the underlying medium (e.g. a hard drive). Transcoding however is done concurrently. Example: file 1 gets copied. When that's done, transcoding of file 1 starts. Meanwhile, file 2 gets copied, etc… Very little time is lost reading the files.
  • Transcoding to several different codecs at once is possible. In that case, decoding of input files is done only once.
  • Multiple instances of caudec can be run concurrently while sharing ressources.
  • Metadata is preserved (as much as possible) from one codec to another.
  • Multiprocess Replaygain scanner (except for Opus and Musepack)
  • Uses existing, popular command line tools and encoders / decoders.

Intended Usage

caudec is most useful when dealing with one album at a time (with 1, 2 or 3 discs, with each track as a separate file). Handling of multiple albums is done via scripting. caudec cannot efficiently deal with very large files (recordings that are several hours long), or very large numbers of files (messy collections with a single directory and thousands of files). Those are known limitations, and they are not within the scope of this program. See version notes.

User Feedback

Please report any bugs that you may find, if they're not already listed. Feature requests are welcome as well. Alternatively, you can contact me directly (see below).


You may use caudec's logo to illustrate an article or blog post, as long as you make sure to mention caudec by name and link to this website. All other rights reserved.

Rockbox Themes

Aside from caudec, I enjoy designing Rockbox themes for the iPod Classic, Sansa Fuze+ and Clip+.

Rockbox Themes


I idle in #caudec on Freenode. To contact me by e-mail, click here (optionally use my PGP / GnuPG public key, OTR fingerprint). Here's my online resume (in French). If you find caudec particularly useful, please consider making a small donation.