A Guide To Audio File Formats
There’s a myriad of audio file formats – but what’s the difference between them?
If you’ve used any kind of audio software at all, whether it is a full audio recording package, or a an music file manager, such as iTunes, you’ll be aware that there is a large number of different file formats. WAV, AIFF, MP3, FLAC… the list goes on and on.
But when you’re using a software package, and you’re suddenly faced with a huge list of potential file types to save to, you may well wonder ‘what are all these audio file formats for?’
Codecs and File Formats
Sometimes the term ‘codec’ is mistakenly used to describe an audio file format. This isn’t correct. A codec is algorithm or ‘library’ used to encode and decode the audio data. Think of it sort of like a cipher used to understand a code, or translate something into code.
The file format is sometimes called the wrapper, as it ‘wraps’ this raw data with a ‘container’ that may also comprises file settings, which may vary according to file type. For example, an MP3 can contain metadata such as song names, album names, sleeve art and more.
Lossy come home… (ouch!) – uncompressed vs. lossless vs. lossy audio file formats
All audio files can be divided into three categories: uncompressed, lossless, and lossy.
Uncompressed audio file formats – WAV, AIFF
These are those that do not employ any compression algorithms to make the file smaller. Thus, there is no loss of quality. The most popular two uncompressed formats are WAV and AIFF. Both are based on PCM (Pulse Code Modulation), using very similar technology, but slight changes in data storage.
Both are of high quality, but have large file sizes. Typically, a CD quality (16-bit 44.1kHz stereo) file will occupy 10mb for every 1-min of length.
The high quality, and simplicity of these files makes them easy to edit and process. Thus, these are generally the first choice in professional audio applications.
BWF (broadcast WAV) extends this format by adding better provision for embedding metadata. This makes it a good option for archiving files.
Lossless audio file formats – FLAC, ALAC, APE
This generally refers to those file formats that compress the file (making it smaller), but preserving the audio quality of the original file.
So, in situations where data has to be kept to a minimum, but without compromising on quality, these file formats can be used. Typically, a FLAC file is around half of the size of the size of a WAV or AIFF of equivalent sample rate.
The advantage of these file types is that they can be converted to and from WAVs or AIFFs with no loss of quality.
Lossy audio file formats – MP3, WMA, AAC, Vorbis
These compress the file but at the expense of some audio quality. There are a number clever tricks employed by these formats to compress the files. For example, an MP3 uses algorithms based on psychoacoustic theories to analyse frequencies that are masked, and removes them.
As a result, file lossy formats can compress files to a tiny size. Typically, a stereo MP3 at 128kbps will be around 1/10 the size of a WAV or AIFF equivalent at CD quality.
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