Just a tip, some folks are trying to take a single audio track and convert it into a multiple Audio Tracks. Here is a method used by Wilky13, transcribing:
Summary: I want an mp4 file with stream 1: H.264 video, stream 2: 2-ch AAC audio, stream 3: 6-ch AC3 audio. I am modifying the default MP4 High Quality profile.
Got handbrake working with:
handbrake-audio=-E faac,ffac3 -R auto -B 384
handbrake-audioac3=-E faac,copy:ac3
handbrake-AudioOptimized=true
Got ffmpeg working with:
ffmpeg-audio=-map 0:1 -map 0:1 -c:a:0 aac -ab 192k -ac 2 -c:a:1 ac3 -ab 192k
ffmpeg-audioac3=-map 0:1 -map 0:1 -c:a:0 aac -ab 384k -ac 2 -c:a:1 copy
ffmpeg-AudioOptimized=true
This is the basic construct, you can modify as appropriate. Refer to the Advanced Commands documentation and Profile Basics documentation to understand the differences between audio and audioac3