Music Served: Extracting Music from your PC MP3? FLAC? AAC? AIF? WAV?

Sidebar: MP3? FLAC? AAC? AIF? WAV?

Readers continually ask us which file format they should rip their CDs to. Low-bit-rate MP3s are tempting to many because they maximize the number of songs that can be stored on a given hard drive. On the other hand, the AIF and WAV formats are claimed to be of true "CD quality." Is this true? And what about FLAC and ALC?

In March 2008 I wrote an article on this subject. I urge you to read it, but in a nutshell: For serious listening, we do not recommend any of the lossy-compressed formats—MP3, AAC, WMA—at any bit rate. AIF and WAV are, respectively, Apple- and Windows-based standards of describing the CD's audio data; both are uncompressed and both are true "CD quality" and therefore recommended.

The AIF or WAV file that represents a three-minute song on a CD is typically 30–40 megabytes in size. This file can be squashed down to 3–4MB by using MP3 encoding at 128kbps, but to achieve this degree of compression, real audio information must be eliminated—hence the term lossy compression. Data are not discarded arbitrarily; instead, the MP3 codec examines the musical spectrum in each slice of time and, using a model of human hearing, decides what can be safely discarded. If this codec has been properly implemented with the right psychoacoustic assumptions, the musical information represented by the lost data may not be missed by most listeners most of the time. But it most certainly will be missed by some listeners with some music some of the time. And at some time, that listener will definitely be the person who has ripped all his CDs as low-bit-rate MP3s and then got rid of the discs!

So to us at Stereophile, the question of which lossy codec is "the best" is moot. There seems little point in spending large sums of money on superbly specified audio equipment if you're going to play sonically compromised, lossy-compressed music on it.

We recommend that, for serious listening, audiophiles use uncompressed audio file formats such as WAV or AIF—or, if file size is an issue because of limited hard-drive space, a lossless format such as FLAC, WMA Lossless, or ALC. These will be audibly transparent to all listeners at all times with all kinds of music through all systems. If you simply must use lossy coding, use AAC at its highest bit rate of 320kbps rather than MP3.

Lossless compression is benign in its effect on the music. Similar to LHA or WinZip computer data crunchers, lossless compression packs the data more efficiently on the disk, but the data read out are identical to the data that went in. Lossless compression can give you a reduction in file size of 40–60% of the original, which is why something like FLAC is often used by music servers.—John Atkinson