What is FLAC?

Audio Format Description

FLAC works like ZIP does in the sense that it compresses information, only that it's for audio. FLAC's compression ratio is about 2:1. It is also similar to MP3 with the difference that it is lossless, meaning that the audio may be compressed without any loss of information or audio quality.

A prominent feature of FLAC is that it is streamable. That is, each FLAC frame contains all the necessary data to decode it without relying on the previous or the following frame. Each frame also contains 16-bit CRC of data to detect transmission errors, which is what prevents loss of any information and ensures bit-perfect reproduction. FLAC can handle any PCM (audio data) bit resolution from 4 to 32 bits per sample and any sampling rate from 1 Hz to 1,048,570 Hz in 1 Hz increments. It can also handle up to 8 channels, which can be grouped in cases such as stereo and 5.1 channel surround which allows an increase in compression.

Besides the frame CRCs and the MD5 signature, FLAC also has a verify option to decode the encoded stream in parallel to the encoding process. This compares the result to the original and aborts any error in case of a mismatch. This feature makes FLAC most suitable for audio archiving.

FLAC supports tagging, cover art and fast seeking, and is itself supported by most operating systems – like Unix and Unix-like (including Linux, BSD, Solaris, IRIX, and Mac OS X), Windows, Amiga, BeOS, and OS/2 operating systems. Most consumer electronic devices – including portable players, home stereo equipment, and car stereo – support FLAC. FLAC files can be played on these devices just like MP3 files.

Authored by Josh Coalson, FLAC has now been incorporated by Xiph.Org Foundation.

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