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Beginners Guide To File Formats

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Beginners Guide To File Format Options

This is one of those topics that people can get very strong opinions on, so lets try to tread carefully here!

There are many different file formats in use - WAV, MP3, FLAC, AAC, WMA and more - in many cases with multiple flavours. You may also see the term "codec" used almost as a synonym - it really refers to the program that creates or reads the file format, but it comes to much the same thing. See Codec comparison for a list of the main options and their features.

Search the forums for a variety of threads and opinions on this topic.


The key features are:

Compressed or not?

Most formats try to make the file size as small as possible by losing unnecessary bits. WAV and the less common AIFF don't and consequently have the largest files. Everything else compresses to one extent or another.

Lossless or Lossy?

A Lossy format is one which is prepared to throw information away in pursuit of smaller file sizes. Obviously they try hard not to make it too obvious, and some are very smart. MP3 is always lossy.

A Lossless format is one which doesn't lose any information compared to the original (in the same way that ZIP works, for example). WAV and FLAC are always Lossless.

To confuse us, some formats such as WMA have lossy and lossless variations. Apple has two formats: AAC (lossy) and Apple Lossless (sometimes incorrectly called AAC Lossless).

If you would like to know more about audio compression have a look at http://en.wikipedia.org/wiki/Audio_data_compression


Is measured in kbits/sec and simply says how much data there is in a stream. The higher the bit rate, the higher the quality. For example a 320kbit/s MP3 is generally held to be of very high quality, 128kbit/s more ordinary. Beware - you can't directly compare two different formats in this way, as the sound quality depends also on the ability of the encoder to get the important bits right. So a 128kbit/s WMA is likely to sound better than a 128kbit/s MP3.

"VBR" (variable bit rate) means that the encoder is trying to be extra smart, turning up the bit rate when it thinks it will make a difference. "CBR" means "constant bit rate".

Low bitrates are good because they mean smaller files on your server and less bandwidth used on your network. On the other hand they are bad because they can sound very poor indeed. Make your own choice!

For best quality, of course, stick to one of the lossless formats - they should all sound exactly the same. Their bitrates should be "roughly" similar for a given piece of music, though if you look around you will find studies pointing out the modest differences in their efficiency.

Squeezebox Server can be configured to limit the bitrate for certain players if their network connection is bad.

Native or Transcoded?

In the SqueezeCenter/Squeezebox world, this can be an important difference. The various models of Squeezebox can handle different file types internally, so given (for example) an MP3 file can decode it into music within the box. Other file types can't be handled within the Squeezebox and are "transcoded", i.e. decoded in SqueezeCenter into another format that the Squeezebox does know how to handle (see also: Transcoding). SqueezeBox players natively handle the following formats:

Lossless: AIFF, PCM, FLAC, WAV

Lossy: MP3, OGG and WMA (except WMA Lossless):

Some earlier models just MP3. See Hardware comparison.

Another significant difference for a Squeezebox is that you can fast-forward or rewind with a format that can be played natively, but not one that is being transcoded.


If you want to be able to play your files in multiple places (eg on Squeezebox, on a software player, on a portable "MP3" player) then you'd ideally like to have one format to do all of them. So check what your players will play!

However, don't get too hung up on this: there may be no acceptable compromise between "top quality" for your home audio listening and "small size" for your portable. Many people deliberately rip into multiple formats at once for the different uses (there are tools to make this easy. Search for EAC or dbpoweramp). Or, as a variation on this, use a script which regularly converts from the master set of files (lossless, e.g. FLAC) into a lossy set for portables (e.g. MP3). Search the forums for Flac2mp3.


You will almost certainly want your music files to contain information (e.g. Artist, Album, Title etc) in Tags. Most file formats will manage this - but not WAV or AIFF. A free program that a lot of Squeezebox users use to check and correct tags is MP3tag. It's very powerful so be careful but can save you a lot of time getting your music tagged correctly.


  • Always use a lossless codec for archival unless you enjoy ripping.
  • FLAC is a good all-round choice: lossless with native support in recent Squeezeboxes'.
  • If you want to use the same files in an iPOD, consider MP3, AAC or Apple Lossless. MP3 has an advantage for the squeezebox as it is a native format.
  • Lame (Lame Ain't an MP3 Encoder) is considered by most knowledgeable people to be the best high quality MP3 encoder. Hydrogenaudios' Lame Site for everything you need to know about Lame MP3 and a lot you probably don't want to know.
  • Similarly if you have a need to use the same files in another player, go with what works in most places for you.
  • Don't forget that its fairly easy to change from one lossless format to another - so if in doubt, pick one! You can change your mind later without losing quality. But if you start with a lossy format, you can never get back to the original without re-ripping
  • High bit rate (190kbs and up) VBR MP3's are considered to be transparent to a majority of the people, meaning that in "blind listening tests a majority of people can't tell the difference between them and the originals. You may have an exceptional ear, so listen and find your transparency level. A lot of people may be surprised to find 128kbs VBR MP3 and AAC files to be transparent to their ears. Not all songs are created equal. You may find a particular part of a particular song has a noticeable buzz or other distortion. Don't be afraid to re-rip that song to a lossless codec later.
  • Don't be afraid to rip in multiple formats for different uses. You should be able to automate this easily. Both EAC (exact audio copy) and dbpoweramp [1] can be configured to rip to 2 or more formats at the same time. With current storage prices, this makes it very easy to have a library for home listening and one for your portable audio player.
  • Remember, in the end it comes down to your ears, not what somebody else tells you. Don't let pride get into the mix. If 128kbs is transparent to you, use it. It's to your advantage as it will take up much less space leaving room for more great music!

Other Resources

Contributors: Ceejay, Nonreality ...

Media formats (codec comparison)
AAC - AAC+ - Apple Lossless - CD - DVD - FLAC - M3U - MP3 - Ogg Vorbis - WAV - WMA