FLAC |
FLAC stands for Free Lossless Audio Codec. FLAC is a popular Free software audio compression Codec that is lossless data compression. Unlike lossy data compression codecs such as MP3 and Advanced Audio Coding, it does not remove any information from the audio stream and is suitable both for everyday playback and for archiving audio collections. 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.
=The project=
The FLAC project consists of:
Free means that the specification of the stream format can be implemented by anyone without prior permission (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 reference implementation is .
In its stated goals, the FLAC project encourages its developers not to implement copy prevention features of any kind.[http://flac.sourceforge.net/goals.html]
=Comparisons=
FLAC is distinguished from general lossless algorithms, such as ZIP file format and Gzip, in that it is specifically designed for the efficient packing of audio data: while ZIP may compress a CD-quality audio file by ten to twenty percent, FLAC achieves compression rates of thirty to fifty percent.
While lossy codecs can achieve ratios of eighty percent or more, they do this by 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 coding. It also uses run-length encoding for blocks of identical samples, such as silent passages. The technical strengths of FLAC compared to other lossless codecs lie in its ability to be streamed and in a fast decode time, which is independent of compression level.
FLAC has become the preferred lossless format for trading live music online, although others, such as Monkey s Audio, are frequently used as well. It has a smaller file size than Shorten; and it is lossless, which is important to live-music traders. It has recently become a favorite trading format among traders of non-live lossless audio as well.
FLAC is also a popular archive format for owners of compact disc and other media who wish to preserve their valuable audio collections. If the original media is lost, damaged, or worn out, a FLAC copy of the audio tracks ensures that an exact duplicate of the original data can be recovered at any time, a restoration impossible from a lossy archive (e.g., MP3) of the same data. The optional creation of a CUE file makes the CD perfectly identical to the original CD.
The Hydrogenaudio Wiki features a very thorough [http://wiki.hydrogenaudio.org/index.phptitle=Lossless_comparison comparison] of lossless codecs, including FLAC.
= Technical =
FLAC supports only fixed-point samples, not floating-point. This is to eliminate any rounding errors to ensure bit-perfect reproduction. It can handle any PCM bit resolution from 4 to 32 bits per sample. It supports any sampling rate from 1 Hz to 655,350 Hz in 1 Hz increments.
FLAC compiles on many platforms: most Unices (including Linux, *BSD, Solaris Operating Environment, and Mac OS X), Microsoft Windows, BeOS, and OS/2. There are build systems for Autoconf/Automake, MSVC, Watcom, and Project Builder.
=See also=
*Lossless data compression *Lossy data compression *Audio data compression *Monkey s Audio
= External links =
*[http://wiki.etree.org/index.phppage=FLAC etree.org wiki] *[http://flac.sourceforge.net/ FLAC Project homepage] *[http://www.hydrogenaudio.org/forums/index.phpshowtopic=34401 List of programs that support the FLAC format] compiled by the Spread FLAC campaign. *[http://members.home.nl/w.speek/comparison.htm Comparison of FLAC and other lossless audio codecs] *[http://www.bobulous.org.uk/misc/audioFormats.html Speek s comparison of lossless and lossy audio formats]: Compression times and ratios using FLAC, Wave, Ogg Vorbis, and MP3 formats. *[http://web.inter.nl.net/users/hvdh/lossless/lossless.htm Comparison of lossless formats] by Hans Heiden|
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