Converting 5.1 audio to stereo and keeping both tracks

Solution 1:

I was able to pull this off by using the following command. I'm not experienced with FFmpeg though, so I'm probably doing something wrong. Any suggestions at all? I don't even think the "96k" part is working.

Updated working command:

ffmpeg -i "input.mkv" \
-map 0:0 -map 0:1 -map 0:1 \
-c:v copy \
-c:a:0 aac -b:a:0 192k -ac 2 \
-c:a:1 copy \
"output.conv.mkv"

Edit: Just thought I should mention, I originally used libfaac (with 96k bit rate), but actually meant to use libfdk_aac here. I changed it to aac in case anyone wants to use this command as is and have good quality. By the way, FFmpeg documentation says libfdk_aac > aac > libfaac.

Solution 2:

Use ffmpeg as follows

ffmpeg -i input -vn -c:a aac -ac 2 stereo.mp4

ffmpeg -i input -i stereo.mp4 -c copy -map 0:v -map 1:a -map 0:a dualaudio.mp4