The command I usually use in case of single audio stream mkv files to convert them to mp4 is:
ffmpeg -i location of mkv file\movie.mkv -c copy location of my usb stick\blablabla.mp4`
But when I did this command with an mkv file that had two audio sources, I ended up with no sound at all on TV and only English audio on PC, when I needed the Hungarian version. What is the command that converts mkv to mp4 while keeping only the audio source specified by me? If it's any help VLC says that audio track #2 is the Hungarian version.