ffmpeg -i "input.mkv" -vn -acodec copy audio.mp3
ffmpeg -i "input.mkv" -vn -map 0:a -acodec copy audio.mp3
ffprobe -v quiet -print_format json -show_format -show_streams "audio.aac"
ffprobe -v error -select_streams a:0 -show_entries format=bit_rate -of default=noprint_wrappers=1:nokey=1 "audio.aac" | uniq
ffprobe -v quiet -print_format json -show_format -show_formats "input.mkv"
ffprobe -v error -hide_banner -select_streams v:0 -show_frames "input.mkv"
ffmpeg -i "input.mkv" -c copy -map 0:a -f null -