I regularly get questions about lossless audio files, or files compressed in a lossless format, for my Ask the iTunes Guy column. These questions come from people who seek to listen to the best quality audio files with iTunes. But many iTunes users don’t know what these files are.
In this article, I’m going to explain what lossless audio files are, how to create them, why you might want to use them, and why you might not.
What is compression?
Let’s start with a simple question: what is compression? You’ve probably familiar with Zip compression, which lets you shrink the size of a Word file or a PowerPoint presentation for storage or to send to someone by email. When you unzip—or decompress—the archive, the resulting file contains the exact same data as in the original. This seemingly magical compression algorithm looks for redundancies in data, and writes a sort of shorthand, saving a great deal of space.
With audio files, there are two types of compression: lossy and lossless. The former is the way files such as MP3s and AACs are shrunk to one-quarter, even one-tenth the size of the original files. This type of compression removes data for sounds that you can’t hear, as well as using other “psychoacoustic” techniques to compact the files.
Lossless compression for audio files allows you to take an original music file—on a CD, for example—and shrink it to save space, yet retain the same quality. It’s not as small as a lossy compressed file, but when you play it back, the file is decompressed on the fly, and the resulting data is exactly the same as the original. This is similar to the way a Zip file of a Word document containing the text of Moby-Dick has all the same words when it’s uncompressed.
iTunes handles several audio file formats:
WAV and AIFF are uncompressed audio files, which encapsulate the data on a CD (or converted from a studio master) in a way that the files can be read on a computer.
Apple Lossless is a lossless format, which retains the full quality of the uncompressed audio, yet uses much less space; generally about 40 to 60 percent less than WAV or AIFF files.
AAC and MP3 are both lossy compressed formats. AAC is actually the MP4 standard, the successor to MP3.
You choose which format you use to rip CDs and convert files in iTunes in the General preferences. Click Import Settings, then make your choice.
These different formats have different bit rates, and, as such, result in files of different sizes. Here’s an example; I ripped a song in three different formats:
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