How can I convert AC3 audio files to AAC?

I had a friend with a BluRay drive extract the audio from my copy of a concert BluRay disc into AC3 files which he returned to me, but now I'm not sure what the best way would be to convert those AC3 files into AAC files.

I've read that it's not possible to go directly from AC3->AAC, but instead have to use WAV as an intermediary; AC3->WAV->AAC. I can probably figure out how to do this, but why should I be the one to make two steps? Is there software already available (free preferred, but not required) that will simply let me plug in an AC3 file and get an AAC equivalent out?

When I say AAC equivalent, that means identical channel setup to the source AC3 files by default, but perhaps also preferences to constrain it to 2 channel or anything else I'd like.

I've already tried using Handbrake and Max to no avail.

Solution 1:

VideoLAN can do this. Select "Streaming/Transcoding Wizard" from the File menu. Choose "Transcode/Save to file". On the next page click "Choose" and open your AC3 file. On the next page tick "Transcode audio" and choose "MPEG 4 Audio" and choose the desired bitrate. Click "Next", choose "MPEG 4 / MP4", click "Next" again and "Choose..." where to save the file. "Next" and "Finish".

The file VideoLAN creates has the extension .mp4, change it to .m4a and there you go.

Solution 2:

Would using Automator to run Apple- or shell-scripts that call ffmpeg be a workable solution? This site has some ideas on AC3 to MP3 using ffmpeg. The first comment mentions this which seems pretty close:

ffmpeg -i audio.ac3 -acodec libmp3lame -ar 48000 -ab 256k -ac 2 output.mp3

Solution 3:

I was playing with this problem today and while I didn't find a batch process solution, I did learn something that may me useful to others faced with this problem.

If you install the Perian QuickTime components, QuickTime Player X will open and play AC3 files. Unfortunately, it will not export them. However, if you use QuickTime Player 7 Pro (again, with Perian installed) you can export an AC3 file into an AIFF or WAV format. Once you have the file saved in one of those formats, it is trivial to create an Automator Droplet (or service) to convert the files into an AAC/MP4 format.

image of Encode to iTunes Plus workflow in Automator

Solution 4:

The Audacity 1.3 beta claims to import AC3 files and will export M4A/AAC so long as the ffmpeg libraries are installed.

I can tell you the software opens cleanly and imports an AAC file, but I have no AC3 files with which to test it.

Solution 5:

It's not pretty, but if you'd prefer a GUI app, Audio Converter should do what you need. It's 99¢ on the App Store, or free from their site.