I've noticed an oddity with Apple Lossless file sizes when dealing with mono audio files.

For example, I have a stereo WAV file of a mono song, which is 15.6MB. If I convert it to a mono WAV file, it shrinks down to what you'd expect: 7.8MB, exactly half as much.

Using dBPowerAmp, if I convert the stereo WAV file to a stereo FLAC file, it's 8.1MB. If I convert it to a mono FLAC file, it's 5.4MB.

However, if I convert it to a Apple Lossless file, the file size is 8.1MB. There appears to be no provision for converting to a mono ALAC file within iTunes. However, when I tried to use the "Channel Count" feature within dBPowerAmp to force the conversion to 1 channel, I get intermittent glitches in the file (which is smaller than 8.1MB).

My suspicion is that Apple did not build in any provision for mono-only files within their Lossless spec. Anybody know anything about this, or can point to specifications on the web that would go into this in detail?

I remember reading something about this about 4 months ago in that people were trying to encode mono speech using Apple lossless. They were encountering error after error. They then changed it to a stereo file (the mono file being duplicated in both the left and right channel) and they were able to encode it just fine. Maybe someone can provide more insight or provide you with a link. I think it is normal though but I could be wrong.

Yeah, that's what I'm hearing as well. It looks like this is a bug within Apple Lossless (and/or QuickTime).

Didn't FLAC automatically detects if a stereo file is actually mono and saves space accordingly?