I only recently learned about iTunes being able to transcode music into 128kbit/s AAC on the fly, while syncing to the iPhone. Quite useful, since I’m keeping my music in 256 or 320 kbit/s MP3. Using the lower bitrate AAC on the iPhone still gives me decent quality on the go, while saving space for more music and apps.
Only one annoying problem: over the years and moving the music library from machine to machine, some files got corrupted. When I come across one during playback and I’m sufficiently annoyed by the problem, I’ll simply delete it and re-rip it, or buy a copy from the store. However, when iTunes tries to transcode all the files I want synced to my iPhone, it stumbles over files with encoding problems, and stops syncing. And the error message doesn’t even identify the file it’s having problems with, only the song title. Bummer.
iTunes does not appear to have a way to check and mark files with encoding problems, so you have to rely on identifying problematic files by playing them. Not very convenient. Luckily, I found MP3 Scan+Repair, a Mac program that will check a batch of files, identify broken ones, and even try to repair them.
You can drag files from the Finder or iTunes into MP3sar’s main window, and it will immediately start scanning them. Using the display filter buttons in the toolbar, you can show only the problematics files, select them, and let the program try and repair them. In my limited testing so far, M3SAR does a good job of identifying and repairing the files, even if some problems will only fix the file format, but not remove audible errors. But for being able to quickly see which of the twelve different versions of My Funny Valentine is stopping iTunes from syncing my iPhone is absolutely worth it.