If you want to extract the audio from a video you found online, for example from YouTube, there are some easy way. You'll need to download first the FLV video, as explain on another blog entry (
Saving YouTube Videos on Mac OS). If the format is not FLV, skip this part and go directly to the second method described below.
Once you have the FLV file, here there are two ways to extract the audio:
Alternative 1: Split the audio directly from the FLV video
Download the free program
iExtractMP3, run the program and drag and drop the FLV file on it.
Alternative 2. Use iTunes to transform the audio into AAC
Having a MPEG video (extension .m4v, .mov or similar), locate the file on your disk first.
Then open iTunes (the video doesn't need to be in your iTunes library), and go to “Advanced” in the menu bar. While the menu is open, press the option key in the keyboard, that will show the hidden option “Convert to AAC...” instead of the greyed out “Create AAC Version”.
Select “Convert to AAC...” and iTunes will allow you to select the video file to transform. Once selected, iTunes will extract the audio, creating a new music item on the Music section. You will be able to find it also in the “Recently Added” playlist.
References:
http://www.fraction.jp/log/archives/2008/01/18/FLVMP3Extractor
or in English:
http://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=ja&tl=en&u=http%3A%2F%2Fwww.fraction.jp%2Flog%2Farchives%2F2008%2F01%2F18%2FFLVMP3ExtractorLabels: AAC, Audio, iTunes, MP3, Safari, Video