File Extension FLAC

Free Lossless Audio Codec, FLAC, is an audio file format similar to MPEG Layer 3 (MP3). The major difference is that there is no loss of quality. Even though the ZIP format works this way, FLAC offers much better compression since it is made for audio files.

It is the fastest most commonly used audio codec, apart from being the only non-proprietary one of its kind. Its application programming interface (API) is well documented. It supports tagging, fast seeking and cover art. Most OSs (Operating systems), Linux, BSD, IRIX, OS X, Solaris, BeOS, OS/2, Windows and Amiga included support FLAC.

The description ‘free’ means much more than availability at zero cost. It also means that the specification is completely available to members of the public, for any purpose. The stated format and its implemented encoding or decoding methods are not patented. Under any existing open source license, users can access the source code. The lossless capability is achieved through bit-for-bit encoding. Each frame has a sixteen-bit cyclic redundancy check used in detecting any transmission errors. Integrity is maintained via the use of MD5 signatures of the unencoded audio file data. Comparing the two is the best way to check for integrity during testing and decoding. Since the file format is asymmetric, favoring decode speed, FLAC is fast. The decode algorithm requires integer arithmetic, making it less computer sensitive when compared to a majority of perceptual codecs. Most hardware allows for real time decoding. Flexible metadata is another primary feature of FLAC, as applications can prepare specialized metadata on registering their identification. This makes it easy to define and implement new blocks of metadata that can be of use in the future without having to break older decoders and streams.

With reference to storage, FLAC enables efficient archiving. The format is open and eliminates the common problem of generation loss that plagues conversion. Despite the MD5 signatures and the CRCs, there is an additional ‘verify’ option, which decodes encoded streams parallel to the whole encoding process. Comparison of values follows. If there is a mismatch, the process aborts, reporting an error. These features also enable CD archiving using ‘cue sheet’ metadata blocks. These give computer users a chance to store a CD’s content table as well as index and track points. The last main feature of FLAC is that the format is error resistant. This is due to the framing method used. Stream errors limit frame damage where errors occur.