FLAC Questions

FLAC.ORG presents FLAC Questions

What is a FLAC file?

FLAC files are lossless audio files that preserve the full quality of the original audio source. FLAC files can be made from live concerts, CDs and other recorded music, or just about any kind of audio you can imagine. The beauty of FLAC is that the format itself is free, without any underlying patents, plus the audio is compressed but maintains all the full quality of the source audio. FLAC is currently quite popular, and is used by many people to archive their entire music collection in digital format. FLAC is an acronym for Free Lossless Audio Codec and its file extension is .flac

Another benefit in using FLAC files, is that you can easily transcode to another audio format (i.e. MP3 or M4A/AAC) at any time. Since FLAC is an open, free format, this ensures your hard work in digitizing your audio collection from records and CDs will be accessible for years to come.

The FLAC file format and specifications have been released to the Public and may be freely used without payment of any licensing royalties. To better help FLAC's acceptance, FLAC is under the Xiph.org banner of audio codecs, which includes the popular Ogg Vorbis lossy audio file format.

Notable features of FLAC (derived from info on FLAC author's web site):

* Lossless: The encoding of audio (PCM) data incurs no loss of information, and the decoded audio is bit-for-bit identical to what went into the encoder. Each frame contains a 16-bit CRC of the frame data for detecting transmission errors. The integrity of the audio data is further insured by storing an MD5 signature of the original unencoded audio data in the file header, which can be compared against later during decoding or testing.

* Fast: FLAC is asymmetric in favor of decode speed. Decoding requires only integer arithmetic, and is much less compute-intensive than for most perceptual codecs. Real-time decode performance is easily achievable on even modest hardware.

* Hardware support: Because of FLAC's free reference implementation and low decoding complexity, FLAC is currently the only non-proprietary, free lossless codec that has any kind of hardware support.

* Streamable: Each FLAC frame contains enough data to decode that frame. FLAC does not even rely on previous or following frames. FLAC uses sync codes and CRCs (similar to MPEG and other formats), which, along with framing, allow decoders to pick up in the middle of a stream with a minimum of delay.

* Seekable: FLAC supports fast sample-accurate seeking. Not only is this useful for playback, it makes FLAC files suitable for use in editing applications.

* Flexible metadata: New metadata blocks can be defined and implemented in future versions of FLAC without breaking older streams or decoders. There are metadata types for tags, pictures, cue sheets, and seek tables. FLAC now supports embedded Album Art and Lyrics.

* Suitable for archiving: FLAC is an open format, and there is no generation loss if you need to convert your data to another format in the future. In addition to the frame CRCs and MD5 signature, flac has a verify option that decodes the encoded stream in parallel with the encoding process and compares the result to the original, aborting with an error if there is a mismatch.

* Convenient CD archiving: FLAC has a "cue sheet" metadata block for storing a CD table of contents and all track and index points. For instance, you can rip a CD to a single file, then import the CD's extracted cue sheet while encoding to yield a single file representation of the entire CD. If your original CD is damaged, the cue sheet can be exported later in order to burn an exact copy.

* Error resistant: Because of FLAC's framing, stream errors limit the damage to the frame in which the error occurred, typically a small fraction of a second worth of data. Contrast this with some other lossless codecs, in which a single error destroys the remainder of the stream.

How to Play a FLAC file

In order to play FLAC files you need either audio software or hardware capable of playing FLAC encoded files. Many FLAC supporting devices and programs exits and are being created to handle this very popular lossless audio format. Check the list under support to see if your favorite audio player supports FLAC files. Many support FLAC "out of the box" (i.e. natively), but others require a third-party plugin.

More and more native FLAC playback devices are being released now, so you shouldn't have too much of a problem finding a software program or hardware device that supports FLAC. One of the advantages of going with a free, open source audio codec like FLAC is that many programs and devices will support FLAC, both now and in the future.

To play your FLAC file(s), follow the instructions for your particular software or hardware and select the FLAC files you want to play. If all goes well, you should start hearing pristine digital audio quality that is identical to the original audio source the FLAC file was created from. Enjoy!

How to Convert a FLAC file

Converting FLAC files to other digital audio formats is relatively easy with the many software tools now available. Another name for this process is called transcoding, and it is usually quite easy to do as more programs have begun to support FLAC natively. You can convert from lossless FLAC audio quality to another lossless codec/format or to one of many lossy audio formats such as as the popular MP3 and M4A (AAC) formats.

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