What is FLAC?

R. Kayne

FLAC stands for Free Lossless Audio Codec, a leading compression technique that preserves original audio quality while reducing file size. It is an open-source, royalty-free format that has been adopted widely for its many advantages in digital audio reproduction.

Handheld MP3 player.
Handheld MP3 player.

Compression techniques take large files, such as WAVE (.wav), and reduce the data bits while preserving as much of the audio landscape as possible. A well-known audio compression format is MP3 (.mp3), which slim down bulky WAVE and compact disk (.cda) files to a fraction of their original size, making it an ideal format for portable audio players. The MP3 format allows a vast library of songs to fill a very small storage footprint, but there is a trade-off in audio quality.

FLAC stands for Free Lossless Audio Codec, a leading compression technique that preserves original audio quality while reducing file size.
FLAC stands for Free Lossless Audio Codec, a leading compression technique that preserves original audio quality while reducing file size.

FLAC surpasses MP3 quality by preserving the original soundscape in exact detail. The format reduces the original file size by roughly 30 to 60% with no loss of quality, making it a lossless format. This differs from the MP3 format, which is a lossy format, or a format that loses quality in the conversion process.

One of the great strengths of FLAC is its very fast decoding time, or ability to stream even on modest hardware. Technical specifics in the framed architecture also allow it to be error resistant, in that each frame has the information it needs to decode itself. If a frame is corrupted, the data lost in the stream is a mere blip. This differs from other types of lossless formats where the entire stream would essentially become corrupted.

Another feature of this format is that it can handle up to eight channels of audio for preserving surround sound recordings. FLAC is also a good choice for archiving audio CDs, as a person can always convert the file to a different format in the future. A further advantage is that it supports replaygain, a technique for ensuring that recorded sound files play at the same volume level.

The only real disadvantage of FLAC files is that the compression ratio is not as steep as other codecs, which means that the files will be somewhat larger. With all of the advantages that this format has, however, this is a happy trade off for many audiophiles.

Considering the falling prices of flash cards, portable players, and storage devices, the format will likely only gain support. The files can play on many media players, although not all.

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Discussion Comments


iPod's don't support FLAC.


@sammyG: What you seem to be ignoring is the fact that by ripping to FLAC, you are essentially "future proofing" your digital music collection. External hard drives, etc. are dirt cheap now, so what on earth is the benefit of archiving your music in a lossy format? You might well regret it at a later date when your equipment does improve and you can tell the difference more obviously.

For the record, I was incredibly sceptical about being able to notice a difference between flac and, for example, 320kbps mp3, but I decided to rip my collection into flac anyway (for the reasons stated above). Once you get used to listening to flac files, you can usually tell when you've played an mp3 instead. Drums and hi-hats in particular don't seem anywhere near as "crisp". Just my opinion!


I'm anon147715, just a follow-up. I did mix up the order of comments below (assumed "since when could you play FLAC on an Ipod?" was the most recent in response to Jaybird's comment). Sorry about going off a tangent about mp4. Hope the info still helps.


Thank you for this post. I've been searching for a summary on flac and this pretty much nails it. Using FLAC has saved me great deal of time transferring recordings over the internet compared to wav.

Just to clarify the other comments above, mp4 is the format container and FLAC, Apple Lossless, AAC etc is the audio encoding tho FLAC uses its own container/extension, i.e. flac.

Jaybird: If you want to be technical, Apple/iTunes uses AAC (a lousy audio encoder) which stores audio data in .m4a format (MPEG-4 audio), which is smaller has better audio quality compared to mp3. Apple also has their own novel lossless encoder (similar to FLAC) with the newer iTunes which also stores the audio data in .m4a format. For other devices/player and in general, the standard extension and referral is still mp4.


I believe there is a big audible difference using flac files compared to mp4 in the detail, depth of field /imaging of music files. I am using good quality equipment to play through but even listening through my n8 nokia it is well worth having your favorites loaded in flac format and playing through folderplay.


anon71388: please don't confuse others. if you're not sure about the audio format don't post comment. Ipod can support flac format. please do research before commenting.


I think that the common music consumer simply cannot tell the difference between a compressed MP3 file and a FLAC file. Honestly, you have to have very nice audio equipment, including quality amplifiers and speakers to even achieve an audible quality difference.

Maybe if you are a true audiophile you could make use of the FLAC file format but otherwise I would have to say that one should stick with high bit rate MP3s.


Since when could you play FLAC on an iPod?

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