MIDI files are easy: .mid or .smf. Audio files, however, come in a dizzying array of formats. When you begin to utilize audio files in your music sequences, podcasts, movies, and websites, you’ll have to know the most common audio file formats and the advantages of choosing one format over the other. This post will hopefully provide you with some useful information on the various audio file formats out there and the compatibility issues that you might run into while using them.
First, it is important to know how computers capture audio. To simplify the operation, audio is captured using a process known as PCM: Pulse Code Modulation. This process takes many tiny samples of a sound wave (like pictures) which are then converted to a series of 1’s and 0’s - binary code. For a great diagram of this process, click HERE.
Second, there are two different formats of digital audio. The first, uncompressed, uses every single one of those samples and usually the files sizes are pretty large (10MB per recorded minute). There are two major uncompressed file formats: .WAV for Windows computers and .AIFF for Apple computers (although you can successfully play both files types on both platforms). Most sequencers and movie editing software can import .wav and .aiff file formats. The main thing to remember with them is that they are pretty large files. The second format is called compressed and here, there are two different types of compression: lossless and lossy.
Lossless compression means just that: the files are squashed so that they can reduce their file size, but the original audio data is still there. Lossy compression actually cuts out some of the audio data (most often silence or sounds out of hearing range). Lossless compression file formats are mostly proprietary, which means that you can only play them on a certain audio player: Windows Media Lossless, Apple Lossless: ALAC, or Real Audio: .ra. I usually avoid using these file types in my music projects because they are often unreadable by the software because of this proprietary aspect.
Lossy compression file formats are much more common. These formats include: .MP3, .AAC, .WMA, Ogg Vorbis, .M4A, and others. These audio files are compressed to 1/10th the size of the original uncompressed audio file with only a small difference in quality. These file formats are used quite often in a wide variety of software applications. It is important to note that in addition to the lossy files formats, there are also protected audio file formats, including Apple’s .m4p and Protected WMA files. These files are not usable in most sequencing programs. In order to use them you’ll need to “crack the DRM” which is illegal - albeit possible.
Third, the type of audio file you use often depends on the computing platform you use: Mac or PC. Many of the files mentioned above can easily be played on either platform by downloading the respective player. All of these files can be burned onto a CD and played back on a standard CD player (one that is capable of playing digital audio files). As far as software is concerned, if you are on a Mac you can bet that the software will “get along” with Apple friendly formats and might have some problems with Windows formats, and vice versa. Every software program has a technical specifications sheet that will list the file formats it can utilize.
Hopefully this post has provided you with some insight into the world of audio file formats. There are scores of other formats that I didn’t mention. For a full listing of the available file formats, I have found that the Wikipedia entry is pretty accurate.
I welcome your comments, questions, and suggestions.