iTunes cannot convert Apple Lossless tracks to 128 kbps AAC files when sync'ing with iPhone I'm using the Convert higher bit rate songs to 128 kbps AAC option in iTunes when sync'ing music to my iPhone.

iTunes is complaining about three tracks from an album I recently ripped every time I sync my phone. It claims they can't be converted (I rip as Apple Lossless). Unfortunately there's not much in the way of detailed information in the error messages iTunes is giving me.

Does iTunes maintain a parallel, down-sampled, library on disk when I check this option? Could I downsample my Apple Lossless files myself, save them in this parallel library, and stop iTunes from trying to do the conversion on sync? I took a look in my iTunes Media folder for a parallel library but couldn't find anything.

Is the conversion done as the songs are transferred to my iPhone and the converted files live no other place than on my phone?

This is iTunes 10 on OS X 10.6 with an iPhone 3GS.
I had a similar problem with few of my tracks. The conversion is done live, while syncing. Basicly the problem is with the particular sound track, not the lossless codec (ALAC) itself. I used a third party utility to re-encode the original (keeping it to ALAC) and then iTunes managed to re-encode the track back to 128kBit AAC. Hope this helps.


  Does iTunes maintain a parallel, down-sampled, library on disk when I check this option? 


No - re-encoding is done live, that's why it's so slow.