You will be getting a separate AC3 file provided as part of the conversion if you selected the 'Extract 5.1ch Audio' option under Advanced Preferences.
This is a 5.1 channel audio file (assuming your camera records 5.1 channel audio) which can be used with Final Cut to edit a surround sound audio track.
AC3 audio
You will be getting a separate AC3 file provided as part of the conversion if you selected the 'Extract 5.1ch Audio' option under Advanced Preferences.
This is a 5.1 channel audio file (assuming your camera records 5.1 channel audio) which can be used with Final Cut to edit a surround sound audio track.
Our instructions on how to do this using Final Cut Pro and Compressor can be found here:
http://shedworx.com/hd-information/surround-sound
If you are not interested in surround sound editing, you can switch off the option that creates this file.