If you use iTunes or if you buy and download digital music, you’ll have come across a number of terms and abbreviations that describe digital audio files. This alphabet soup can be quite confusing. What are codecs or audio file formats? What is a bit rate, and what’s a sample rate? What does it mean when music is “high-resolution?”
This article covers what you need to know about digital audio files. I’ll tell you the difference between lossy and lossless files, I’ll explain why bit rates matter (or don’t), and I’ll help you understand the various file formats you may encounter.
Compression: lossy and lossless
When you buy a CD, the audio on the disc is uncompressed. You can rip (or import) CDs with iTunes or other software, turning the CD’s audio into digital audio files to use on a computer or a portable device. In iTunes, you can rip in two uncompressed formats: WAV and AIFF (other software allows for other formats). Both formats simply encapsulate the PCM (pulse-code modulation) data stored on CDs so it can be read as audio files on a computer, and their bit rate (you’ll learn what the bit rate is below) is 1,411 kbps.
WAV and AIFF files can be quite large. As such, digital audio files are compressed to save space. There are two types of compression: lossless and lossy. Lossless includes formats (or codecs, short for coder-decoder algorithms) such as Apple Lossless and FLAC (the Free Lossless Audio Codec). Lossy includes the ubiquitous MP3 and AAC formats. (AAC, which stands for Advanced Audio Coding, is, in reality, the MP4 format, the successor to the older MP3. While Apple adopted it early on in iTunes, Apple was not involved in its creation, and has no ownership of this format.)
You may see other audio formats too, though they are less common. These include Ogg Vorbis, Monkey’s Audio, Shorten, and others. Some of these codecs are lossy, and some are lossless. However, if you use iTunes and Apple hardware, you’ll only encounter WAV, AIFF, MP3, AAC, and Apple Lossless, at least for music.
When you rip or convert an uncompressed audio file to a lossless format, and then play that file, it is a bit-perfect copy of the original (assuming the data was read correctly from a CD). As such, you can convert from one lossless format to another with no loss of quality.
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