Trim an audio or video file using ffmpeg

crop

#!/bin/bash

function help {
  echo "$(basename $0) - Trim an audio or video file using ffmpeg
Works with all formats supported by ffmpeg.
Seeks to the nearest frame positions by re-encoding.
Does not overwrite pre-existing output files.
Reduces file size procduced by OBS Studio by >80%.

Usage:
  $(basename $0) "dir/file.mkv" START [END]

START and END have the format [HH:[MM:]]SS[.XXX]
END defaults to end of audio/video file

Examples:
  $(basename $0) 'dir/file.mkv' 15      # Crop from 15.0 seconds to end
  $(basename $0) 'dir/file.mkv' 3.25 9  # Crop from 3.25 seconds to 9 seconds
"
  exit 1
}


if [ -z "$2" ]; then help; fi

if [ "$1" == -f ]; then
  shift
  OVERWRITE=-y
else
  OVERWRITE=-n
fi

FNAME="$1"
ORIGINAL_FN=${FNAME%.*}
EXT=${FNAME##*.}
COPY_FNAME="${ORIGINAL_FN}.crop.$EXT"

START="$2"
if [ "$3" ]; then 
  TO="-to $3"
else
  unset TO
fi

ffmpeg \
  "$OVERWRITE" \
  -i "$FNAME" \
  -ss "$START" $TO \
  -acodec copy \
  "$COPY_FNAME"