This is a quick “cheat sheet” for myself…

Python

• generate TOTP given seed: python -c "import pyotp;print(pyotp.TOTP('seed').now())"

ffmpeg

• extract specific portions of video w/o re-encoding: ffmpeg -i <input> -ss <seek timestamp> -t <duration> <output>
  • -ss <seek timestamp>: the timestamp (in h:m:s.ss format) to start from
  • -t <duration>: the duration of the extracted clip (in h:m:s.ss format)
  • note that multiple -ss <seek timestamp> -t <duration> <output> can be appended to do multiple extractions in one pass

• remove embedded closed captions from video stream (e.g. example ffprobe output below): ffmpeg -i <input> -c copy -bsf:v 'filter_units=remove_types=6' <output>

    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1072 [SAR 1:1 DAR 120:67], Closed Captions, 2150 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)   Metadata:     handler_name : VideoHandler     vendor_id : [0][0][0][0]

• removing or re-ordering audio and subtitle tracks: ffmpeg -i <input> -map 0:v:0 -map 0:a:<index> -map 0:s:<index> -c copy <output> (assuming only single input and single video stream, all <source> entries for the -map <source>:<type>:<index> parameters is always 0)
  • -map 0:a:<index>: zero-based index of the audio track (i.e. even if multiple audio streams exist, and/or the first audio track is stream #0:n, the first audio track’s index is still “0“); multiple entries can be used, with the new order based on the order the -map parameter appears
  • -map 0:s:<index>: zero-based index of the subtitle track (i.e.even if multiple subtitle streams exist, and/or the first subtitle track is stream #0:n, the first audio track’s index is still “0“); multiple entries can be used, with the new order based on the order the -map parameter appears
  • any un-mapped streams will be ommitted in the output (i.e. if you left out the -map 0:v:0, there will be no video stream)

• removing or switching default audio and subtitle tracks: ffmpeg -i <input> -c copy <output> -dispositions:<type>:<index> 0 -dispositions:<type>:<index> default <output>
  • -dispositions:<type>:<index> 0: remove stream <index> as the default stream for <type>
  • -dispositions:<type>:<index> default: set stream <index> as the default stream for <type>
  • note that the <index> is based on the output streams  order (e.g. if placed after other -map parameters)