Reading this forum gave me the idea of doing some tests on Apple Lossless encoded files to see exactly how lossless they really are. One user reported using the UNIX command "diff" on an original WAV file and a WAV file converted from an ALAC file converted from the original WAV file. His results were identical. I decided to repeat the procedure, but testing AIFF files as well.

The results were quite interesting.

While the original WAV and the 3rd generation WAV reported identical, the original AIFF and 3rd generation AIFF files did not. In fact, file sizes differed by 6 bytes, the alac2aiff file being larger. I've also tested iTunes converting WAV to AIFF and then back to WAV, and vice versa. Those proved to be identical.

Any ideas explaining the behavior? Thanks.

Tests were done in the latest iTunes on a Mac platform. iTunes version 7.0.2

WAV and AIFF files have headers and other metadata that can differ even if the actual sound signal doesn't, so always export the raw signal before doing such a comparison (you can use pretty much any audio editor for this, if you haven't got one yet Audacity can probably do this, although I haven't checked).