Extract audio from a movie
ffmpeg -i infile.mkv outfile.mp3
Convert WAV to MP3
ffmpeg -i infile.wav outfile.mp3
Extract subtitles from movie with ffmmpeg
ffmpeg -i Movie.mkv -map 0:s:0 subs.srt
i: Input file URL/path. -map: Designate one or more input streams as a source for the output file. s:0: Select the subtitle stream.
his would download the first subtitle track. If there are several, use 0:s:1 to download the second one, 0:s:2 to download the third one, and so on
Crop an MP3 from x to x+n
Take a look at the -t and -ss arguments. They should do what you want.
Restrict the transcoded/captured video sequence to the duration specified in seconds. hh:mm:ss[.xxx] syntax is also supported.
Seek to given time position in seconds. hh:mm:ss[.xxx] syntax is also supported.
ffmpeg -ss 30 -t 70 -i inputfile.mp3 -acodec copy outputfile.mp3 should do the trick for the range you mentioned (30s-100s).