Convert 7.1 audio to 5.1, leaving video alone
bartron on 1/1/2021
Since Roku can't play audio from 7.1 DTS audio, the quick way is to use FFMPEG to convert the audio to AC3 5.1, leaving the video alone. The command for that is:
ffmpeg -i input.mkv -c:v copy -c:a ac3 output.mkv