I'm about to re-rip all my CDs, using Apple Lossless encoding, hopefully to avoid having to re-rip them again in the future. I've build a server with plenty of space, so I want to store some compressed versions of the tracks, in addition to the lossless originals. (I need smaller versions for an iPod.)

It looks like I should be able to use the qt_export utility from the qt_tools package, written by David Van Brink, to easily convert the lossless files into MPEG-4 audio files.

The command I used to process my lossless files was:

for FILE in *; qt_export --loadsettings=../../qt_export.dat "$FILE" "ipod-$FILE"; done

The settings file instructs qt_export to use the mp4a compressor at 192 kbs, stereo.

In fact, it seemed to work so well that I had processed several albums before I tried to use one of the AAC-compressed files. iTunes won't open the file, and QuickTime Player gives an error: "An Audio Elementary Stream Descriptor is corrupted."

Any suggestions on what I'm doing wrong, or how to easily convert batches of Apple Lossless encoded files?

Why don't you just use iTunes? First rip all the files to lossless, then select all the files you want, right click, convert selection to AAC.

Better yet, rip all your files to lossless, then do the following: create a "smart playlist" that sorts by "kind: Apple Lossless," click on the playlist once created, hit cmd-A to select all the tracks, then right-click (or ctrl-click) to convert all to AAC. This is assuming that you may have other non-lossless files laying around; if not , you don't even have to create a playlist: just go into the library and hit cmd-A to select everything.

This may address half of a problem for some people. In my case, I've already ripped several dozen CDs to compressed format (AAC). I don't necessarily want to re-rip all of those right away.

I have recently made the decision to rip from now on to lossless. I have also decided to backup my collection on an external drive.

Consequently, I'm looking for a way to rip the remaining CDs to Lossless, yet keep my Lossless and compressed files separate. The reason for this is I don't have a digital jukebox (iPod or equivalent). But if/when I get one, I will need a way to know exactly which CDs are in lossless so they can be converted easily to the appropriate compressed format. When converting from lossless to compressed, iTunes places the compressed file in the same folder as the lossless version. This creates a costly storage inefficiency: you don't need both a lossless and compressed versions of a given track on your computer at the same time.

Solution summary:
1) create a separate folder to store lossless files separate from compressed
2) perform a backup to exernal disk before syncing with digital jukebox

The proposed solution is to create a new folder named "Lossless Rips." This folder can be located in my Music folder or elsewhere; it doesn't necessarily have to be located in the iTunes folder. Once a CD is ripped to lossless, find that new file folder within the iTunes folder and move it to the "Lossless Rips" folder. iTunes updates the path to the song files within iTunes so they can still be played from the library or any playlists you've created.

In future, to convert Lossless tracks to compressed (AAC or MP3) for purposes of syncing with a digital jukebox, create a "smart playlist" selecting "Kind" and specifying "lossless," as suggested by Cygnus X1, select all items in the playlist and convert to AAC. iTunes automatically creates new subfolders within the iTunes folder for each CD and places the compressed version of each track in the appropriate subfolder.

As a result of this process, compressed files will all be located together in the iTunes folder, and Lossless will remain separate in the "Lossless Rips" folder.

As for backup, if a onetime backup of both the iTunes (with compressed files) and Lossless Rips folders is done before converting any lossless files to compressed files, and if going forward all new CDs are converted to Lossless, then all that needs to be backed up in the future is the "lossless rip" folder.

Of course, if in future the CDs that were originally ripped to a compressed format are re-ripped to lossless, the compressed version of the music tracks can be deleted from the backup disk and the main comuter once they are added to the disks in lossless format.