Question: I download lots of lectures from iTunes U. The problem is, they usually come with video and there is no audio-only version for many.

How can I, using any software available for Snow Leopard, free or paid, extract the audio from a series of video files and end up with a series of audio files?

Any ideas?

Answer: 
I suggest using [Max](http://sbooth.org/Max/) or [ffmpegx](http://www.ffmpegx.com/), which is a GUI for ffmpeg.

You can also use ffmpeg from the shell:

```
for f in *.mp4; do ffmpeg -i "$f" -vn -c copy "${f%mp4}m4a"; done

```

`-vn` (video none) removes video streams and `-c copy` disables re-encoding the audio. You can install ffmpeg with `brew install ffmpeg` after installing Homebrew.
You can import the clip into iMovie, then export it as an AIF audio file using the iMovie Share menu's Quicktime export feature. Then you can import the AIF file into iTunes. Once it's in iTunes, you can create a much more compact MP3 version. All rather cumbersome. Too bad iTunes U doesn't just upload audio versions of all the lectures. The video files are big and unwieldy and difficult to use on an iPod.