Use the map command to remove streams from media files.

• The stream index begins at 0, so, for example, to remove the first stream in the file you would use -map -0:0, to remove the second stream you'd use -map -0:1:

ffmpeg -i "input.mkv" -map 0 -map -0:1 -c copy "output.mkv"

Streams can also be removed by type

For example, to remove the second video stream you'd use -map -0:v:1, to remove the second audio stream you'd use -map -0:a:1 and to remove the second subtitle stream you'd use -map -0:s:1.

You can use these commands together to do them all at once:

ffmpeg -i "input.mkv" -map 0 -map -0:v:1 -map -0:a:1 -map -0:s:1 -c copy "output.mkv"

You can automate this process on your files using the following Tdarr Plugins:

To remove subtitle streams:

Tdarr_Plugin_x7ab_Remove_Subs

To remove audio streams based on language:

Tdarr_Plugin_MC93_Migz3CleanAudio