FLAC stands for Free Lossless Audio Codec. FLAC is a popular audio compression codec that is lossless. Unlike lossy codecs such as MP3 and M4A, it does not remove any information from the audio stream and is suitable for both everyday use and also for archiving your entire audio collection. The FLAC format is currently well supported by many software and hardware audio products.

On January 29th, 2003, Xiphophorus (now called the Xiph.org Foundation) announced the incorporation of FLAC under their xiph.org banner, to go along with Ogg Vorbis, Ogg Theora, and Speex.

Contents

1 The Project 2 Comparisons 3 See also 4 External links

The Project

The FLAC project consists of:

• the stream format
• libFLAC, a library of reference encoders and decoders, and a metadata interface
• libFLAC++, an object wrapper around libFLAC
• flac, a command-line wrapper around libFLAC to encode and decode .flac files
• metaflac, a command-line metadata editor for .flac files
• input plugins for various music players (Winamp, XMMS, foobar2000, musikCube, and many more)

"Free" means that the specification of the stream format is in the public domain (xiph.org reserves the right to set the FLAC specification and certify compliance), and that neither the FLAC format nor any of the implemented encoding/decoding methods are covered by any patent. It also means that the sources for libFLAC and libFLAC++ are available under Xiph.org's BSD license and the sources for flac, metaflac, and the plugins are available under the GPL.

Comparisons

FLAC is distinguished from general lossless algorithms such as ZIP and gzip in that it is specifically designed for the efficient packing of audio data; while ZIP may compress a CD-quality audio file 20–40%, FLAC achieves compression rates of 30–70%.

While lossy codecs can achieve ratios of 80–90+%, they do this at the expense of discarding data from the original stream. FLAC uses Linear prediction to convert the audio samples to a series of small, uncorrelated numbers (known as the residual) which are stored efficiently using Golomb-Rice coding. It also uses Run-length encoding for blocks of identical samples such as silent passages. FLAC's technical strengths versus other lossless codecs lie in its ability to be streamed, as well as a fast decode time that is independent of compression level.

FLAC has become the preferred lossless format for trading live music online. It has a smaller file size than Shorten, and unlike MP3, it's lossless, which ensures the highest fidelity to the source material, which is important to live music traders. It has recently become a favorite trading format of non-live lossless audio traders as well.

FLAC compiles on many platforms: most Unices (including Linux, *BSD, Solaris, and Mac OS X), Windows, BeOS, and OS/2. There are build systems for autoconf/automake, MSVC, Watcom C, and Project Builder.

See also

• Lossless data compression
• Lossy data compression
• Audio data compression

External links

• Project homepage
• etree Wiki flac page
• Unofficial FLAC installer for Windows
• Adobe Audition FLAC filter allows Adobe Audition to read and save FLAC files.
• MacFLAC GUI frontend to encode/decode FLAC on Mac OS X
• xACT, based on MacFlac, is a Mac OS X GUI for shorten, shntool, flac, and monkey's audio
• iRecordMusic, records Internet audio streams to FLAC, Ogg Vorbis, MP3, AAC, and more... on Mac OS X
• FLAC Codecs for Windows media player or other directshow applications.
• VUPlayer free audio player for FLAC audios. Also converts files to/from the FLAC audio format.