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Ask the iTunes Guy: Missing audio files, classical music, and .m4a files

Kirk McElhearn | June 22, 2015
You've got some music files on your Mac, and they all look alike in the Finder. If you want to find which ones are AAC files and which are Apple Lossless, what do you do? Well, I've got the answer. I also discuss the Case of the Missing Audio Files, and look at some possible ways to view classical music in iTunes.

You've got some music files on your Mac, and they all look alike in the Finder. If you want to find which ones are AAC files and which are Apple Lossless, what do you do? Well, I've got the answer. I also discuss the Case of the Missing Audio Files, and look at some possible ways to view classical music in iTunes.

What kind of file is this?

Q: How can I tell if a file with an .m4a extension is a lossy AAC file or an Apple Lossless file?

It's a bit annoying that Apple uses the same file extension for both lossy and lossless files, especially because AAC is part of the MP4 specification, and Apple Lossless is not.

If you're looking at a file in the Finder, it's not that easy to tell one from the other. The Kind that the Finder shows for both files is Apple MPEG-4 Audio. In the screenshot to the right, you can't tell that the file on the left John Foxx's "No One Driving"is an AAC file, and that Yes's "I've Seen All Good People" is lossless. You can see the difference in the file size, which is a good indicator, but you need to mentally calculate the ratio of the size and duration.

Within iTunes, you can tell which files are lossless in other ways, such as by displaying the Bit Rate column in list views. Lossless files have higher bit rates, generally above the highest AAC bit rate of 320 kbps. You can also make a smart playlist to find all your Apple Lossless files. Use the condition Kind Contains Apple Lossless.

There's one more way you can tell these files apart: that involves using Terminal. There's a little-known command called afinfo that gives you a lot of information about a music file. Open Terminal (it's in your /Applications/Utilities folder), type afinfo, then a space, and then drag an audio file from the Finder to the Terminal window. Press Return, and Terminal will display information about the file. Near the top, you'll see something like this:

Data format: 2 ch, 44100 Hz, 'alac' (0x00000001) from 16-bit source, 4096 frames/packet

In the last line, you can see that the file is alac, or Apple Lossless Audio Codec.

A lossy, AAC file will display this:

Data format: 2 ch, 44100 Hz, 'aac ' (0x00000000) 0 bits/channel, 0 bytes/packet, 1024 frames/packet, 0 bytes/frame

Where did my files go?

Q: Somehow, over time, hundreds of files (from a library of maybe 5000 songs) have been deleted from my iTunes library folder. I have scores of empty folders that once contained all the tracks of albums. For other albums, just one, two or more files are gone. I back these files up daily, but the problem is that I'm not aware when files suddenly disappear, so the backups often delete files in order to conform with what is in the (new) iTunes library. I don't see anything that links those files that are lost; it seems entirely random. What can I do about this?

 

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