Detect and split video to scenes with ffmpeg

split-to-scenes.sh

# Splits video to separate scenes files
# Inspired by https://stackoverflow.com/a/38205105

#!/bin/bash

file=""
out="./"
diff=0.4
bitrate="512k"
trim=0
stripaudio=""

usage () {
  echo "Usage: $(basename $0) [[[-o folder] [-d ratio]] | [-h]] -f file.mp4"
  echo
  echo "Options:"
  echo "-f, --file          Input file"
  echo "-o, --out           Outpup files folder path, default"
  echo "                    to current folder"
  echo "-d, --diff          Number from 0 to 1, default to 0.4."
  echo "                    Scene change difference factor"
  echo "-b, --bitrate       Bitrate to encode parts, default to 512k"
  echo "-t, --trim          Trim last given seconds number, default 0"
  echo "-sa, --strip-audio  Strip audio"
  echo "-h, --help          Display this help message"
  echo
  echo "Example: split.sh -d 0.5 -o /tmp/parts -f file.mp4"
  echo "Splits file.mp4 file to scenes with change more than 0.5"
  echo "and saves output parts to /tmp/parts folder"
}

if [ "$1" = "" ]; then
  usage
fi

while [ "$1" != "" ]; do
  case $1 in
    -f | --file )
      shift
      file=$1
      ;;
    -d | --diff )
      shift
      diff=$1
      ;;
    -o | --out )
      shift
      out=$1
      ;;
    -b | --bitrate )
      shift
      bitrate=$1
      ;;
    -t | --trim )
      shift
      trim=$1
      ;;
    -sa | --strip-audio )
      stripaudio="-an"
      ;;
    -h | --help )
      usage
      exit
      ;;
    * )
      usage
      exit 1
  esac
  shift
done

cut_part () {
  duration_flag=""
  if [ "$3" != "" ]; then
    duration_flag="-t"
  fi
  ffmpeg -loglevel error -hide_banner -ss $1 $duration_flag $3 -i $file \
    -vcodec libx264 -movflags faststart -b $bitrate $stripaudio \
    -y $out/`printf "%04d_%s" $2 $filename` < /dev/null
}

filename=`basename $file`
mkdir -p $out
timefrom=0
i=1
while read -r timestamp; do
  duration=`bc <<< "$timestamp-$timefrom-$trim" | awk '{printf "%f", $0}'`
  cut_part $timefrom $i $duration
  timefrom=$timestamp
  i=`expr $i + 1`
done < <(
  ffmpeg -i $file -filter:v "select='gt(scene,$diff)',showinfo" -f null - 2>&1 | \
    grep Parsed_showinfo | grep pts_time:[0-9.]* -o | grep "[0-9]*\.[0-9]*" -o
)

if [ $timefrom != 0 ]; then
  cut_part $timefrom $i
fi

Thanks folks, I'm happily slicing up old home video tapes with this script.

Thanks to nielsbom for the hardware acceleration tip, I found the equivalent to h264_videotoolbox for my nvidia-GPU available in WSL is h264_nvenc and get about an 8x speedup.

With each tape there's usually a few scenes that I want to merge back together, so I wrote a script to run after this one; if I've identified that, say, all the videos from 0010_xyz.mp4 until 0018_xyz.mp4 should be one video, I can run the following:

./merge.sh 0010_xyz.mp4 0018_xyz.mp4

and the script will produce the intermediate list.txt of filenames to pass to ffmpeg's concat and write to file 0010-0018_xyz.mp4. it doesn't delete the input files of course, I do that manually after confirming the merge looks good.

https://gist.github.com/jazzyjackson/bf9282df0a40d7ef471e6676f282831e

And in case the scene splitting script missed something I need to split up manually, I can recommend this fun little utility that lets you seek, set markers, and split scenes without leaving your terminal: https://github.com/wong-justin/vic

Cheers