ffmpeg -ss 00:25:13 -i "Input.mkv" -c copy -t 00:01:31 -c:v libx264 -map 0:v:0 -map 0:a:1 -c:a aac "Output.mp4"
-ss 00:25:13
when to start-t 00:01:31
how lonh to cut-map 0:v:0
to select video stream-map 0:a:1
to select audio stream-c:v libx264
convert to mp4-c:a aac
convert audio to aac codec