Compress mp4 video

compress-mp4.sh

#!/usr/bin/bash
# ffmpeg script to compress video files,
#   taken from https://unix.stackexchange.com/questions/28803/how-can-i-reduce-a-videos-size-with-ffmpeg
#
# USAGE
#   compress-mp4.sh INPUT OUTPUT [SUFFIX]
#
# ARGUMENTS
#   INPUT   Path to the source video file (any format ffmpeg can read).
#   OUTPUT  Path for the compressed output file.
#   SUFFIX  Optional label appended before the extension of OUTPUT.
#           When provided the script rewrites the output filename as:
#             <basename>-<SUFFIX>.<ext>
#           and skips compression if INPUT already ends with -<SUFFIX>.<ext>
#           (useful for idempotent batch loops).
#
# EXAMPLES
#   # Basic 720p compression
#   compress-mp4.sh recording.mp4 recording-small.mp4
#
#   # With suffix: writes recording-720p.mp4
#   compress-mp4.sh recording.mp4 recording.mp4 720p
#
#   # Re-running with the same suffix is a no-op (input already has the suffix)
#   compress-mp4.sh recording-720p.mp4 recording.mp4 720p
#
# FFMPEG SETTINGS
#   Codec   : libx265 (H.265/HEVC) — ~40-50 % smaller than H.264 at equal quality
#   CRF     : 28  (x265 default; lower = better quality/larger file; range 0-51)
#   Preset  : medium (speed/compression tradeoff; slower = smaller file)
#   Audio   : copied without re-encoding (-c:a copy)
#   Scale   : 720p height, width auto-calculated and rounded to nearest even number
#             (-vf "scale=-2:720")
#
# TIPS
#   • Lower CRF (e.g. 24) for higher quality; raise it (e.g. 32) for smaller files.
#   • Change -preset to 'slow' or 'veryslow' for better compression at the cost of time.
#   • Remove -vf scale if you want to keep the original resolution.
#   • Use -c:a aac -b:a 128k instead of -c:a copy to also compress audio.

if [[ "${1:-}" == "-h" || "${1:-}" == "--help" || $# -lt 2 ]]; then
  sed -n '/^# USAGE/,/^[^#]/{ /^[^#]/d; s/^# \?//; p }' "$0"
  [[ $# -lt 2 ]] && exit 1
  exit 0
fi

outfile="${2}"

if [ -n "$3" ]; then
  extension="${outfile##*.}"
  filename="${outfile%.*}"
  outfile="${filename}-${3}.${extension}"

  if [[ "${1}" == *"${3}.${extension}" ]]; then
    echo "Input file already ends with ${3}, skipping compression"
    exit 0
  fi
fi
  
if [ -f "${outfile}" ]; then
  echo "File exists: ${outfile}"
  exit 1
fi

ffmpeg -i "${1}"  -c:v libx265 -crf 28 -preset medium -c:a copy -vf "scale=-2:720" "${outfile}"