Words from the Glossary
As we continue our exploration of terms from our glossary, this month we're taking a look at audio file formats.
Audio File Formats
This month's terms:
audio file formats, codec
Uncompressed audio file formats: WAV (.wav), AIFF (.aif), BWF (.bwf), and AU (.au).
Lossless compressed audio file formats: FLAC (.flac), Monkey's Audio (.ape), WavPack (.wv), True Audio, (.tta), ATRAC Advanced Lossless, Apple Lossless (.m4a), MPEG-4 ALS, MPEG-4 SLS, MPEG-4 DST, Windows Media Audio Lossless (.wma), and Shorten (.shn).
Lossy compressed audio file formats: MP3 (.mp3), Ogg Vorbis (.ogg), Musepack (.mpc), Advanced Audio Coding (.aac), ATRAC, RealAudio (.ra), and Windows Media Audio Lossy (.wma).
First of all, lets clear up the difference between a codec and an audio file format. A codec, which is short for code-decode, is a method of encoding audio in a digital form. An audio file format is the method by which such data is stored as a file on a computer. The format specifies how the file is to include the encoded audio and usually the format for a header with such information as title, artist, and what codec was used. For example, a WAV file (sometimes called a WAVE file) is a file format that can use several codecs, such as PCM and MPEG-3. The confusion arises when the codec and the file format are called the same thing, such as an MP3.
You are probably familiar with the MP3 format. Because it was essentially the first internet audio format, it has become the de facto standard. However, the MP3 format has a number of short-comings, especially audio quality at lower bit rates. As the bit rate goes down, the file size gets smaller, but the audio quality also decreases. For this reason, several competing formats have been developed in an effort to improve the audio. Some of those formats you have probably never heard of ... and likely never will come across. Others have made real inroads at becoming the new audio standard. However, none of them has yet replaced the MP3.
In the recording studio, only uncompressed audio files are used. Typically, these are one of three formats. The Wave Audio Format (WAV) was originally used only on PCs, but now is used on both PC and MACs. The Audio Interchange File Format (AIFF) was developed by Apple, but likewise can be found on both platforms. The Broadcast Wave Format (BWF) is a version of the WAV format that was developed by radio broadcaster and includes additional metadata useful to broadcasters. As you can imagine, only an uncompressed file is and should be used in the recording process. Such files later can easily be converted to other formats for posting on the internet or other uses.
In an effort to create smaller files without sacrificing audio quality, the lossless codecs were developed. While they preserve audio quality their ability to reduce file size is not as impressive as the MP3 and others of that ilk. Typically the file size reduction is only on the order of 30 to 50%. With the continued increase in hard drive size (now measured in terabytes), one has to wonder if we will need to compress files at all in the future.
If you are observant, you may have noticed that some of the formats appear in both the lossy and lossless categories. Because a file format can contain more than one codec, it can be a member of both groups. For example, Microsoft has added a lossless version to its WMA audio file in an effort to compete with lossless formats from Apple and others.