Detect black scenes and split with ffmpeg remux

black_split.sh

#!/usr/bin/env bash

# Splits video to separate scenes files when full black frames are found in the video
#
# Author: Werner Robitza
#
# Forked from: https://gist.github.com/davidwebca/e26186b8f4c6795b19c043fffb6f9861
# Inspired by https://gist.github.com/achesco/4dc2ebf13378a0a61fc26c7fe01f539e
# Who got inspired by https://stackoverflow.com/a/38205105

set -e

file=""
out="./"
stripaudio=""
add=0.00
trim=0.00
dur=2.00
ratio=0.98
th=0.10

usage () {
  echo "Usage: $(basename $0) [[[-o folder] [-d black duration]] | [-h]] -f <input>"
  echo
  echo "Options:"
  echo "-f, --file          Input file"
  echo "-o, --out           Output files folder path, defaults to current directory"
  echo "-d, --dur           Duration for black detection in seconds. 0.05 default (practical single frame)"
  echo "-r, --ratio         ffmpeg pic_th : Set the threshold for considering a picture black. Default: $ratio"
  echo "-th, --threshold    ffmpeg pix_th : Set the threshold for considering a pixel black. Default: $th"
  echo "-t, --trim          Substracts to splitting timestamp in seconds. Default: 0"
  echo "-a, --add           Adds to splitting timestamp in seconds. 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 black frames for more than 0.5 seconds"
  echo "and saves output parts to /tmp/parts."
}

cleanup() {
  rm -f ffout timestamps
}

trap 'cleanup' EXIT SIGINT SIGTERM

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

while [ "$1" != "" ]; do
  case $1 in
    -f | --file )
      shift
      file=$1
      ;;
    -d | --dur )
      shift
      dur=$1
      ;;
    -r | --ratio )
      shift
      ratio=$1
      ;;
    -th | --threshold )
      shift
      th=$1
      ;;
    -o | --out )
      shift
      out=$1
      ;;
    -t | --trim )
      shift
      trim=$1
      ;;
    -a | --add )
      shift
      add=$1
      ;;
    -sa | --strip-audio )
      stripaudio="-an"
      ;;
    -h | --help )
      usage
      exit
      ;;
    * )
      usage
      exit 1
  esac
  shift
done

cut_part () {
  printf -v fileout "$out/%04d_%s" "$2" "$filename"
  if [[ "$3" != "" ]]; then
    echo "Cutting from $1 for $3 seconds, writing to $fileout ..."
    ffmpeg -nostdin -y -loglevel error -hide_banner -i "$file" -ss "$1" -t "$3" "$fileout"
  else
    echo "Cutting from $1 until end, writing to $fileout ..."
    ffmpeg -nostdin -y -loglevel error -hide_banner -i "$file" -ss "$1" "$fileout"
  fi
}

cd "$(dirname "$0")" || exit 1

filename=$(basename "$file")
mkdir -p "$out"
timefrom=0
i=1

echo "Running blackdetect filter ..."

ffmpeg -i "$file" -vf "blackdetect=d=$dur:pic_th=$ratio:pix_th=$th" -f null - 2> ffout
black_start=( $(grep blackdetect ffout | grep black_start:[0-9.]* -o | grep "[0-9]*(\.[0-9]*)?" -oE) )
black_duration=( $(grep blackdetect ffout | grep black_duration:[0-9.]* -o | grep "[0-9]*(\.[0-9]*)?" -oE) )
> timestamps
for ii in "${!black_start[@]}"; do
  half=$(bc -l <<< "${black_duration[$ii]}/2")
  middletime=$(bc -l <<< "${black_start[$ii]} + $half")
  echo "$middletime" | LC_ALL=en_US.UTF-8 awk '{printf "%f", $0}' >> timestamps
  echo "" >> timestamps
done

echo "Found the following timestamps: "
echo
cat timestamps
echo

while read -r timestamp; do
  duration=$(bc -l <<< "$timestamp-$timefrom+$add-$trim" | LC_ALL=en_US.UTF-8 awk '{printf "%f", $0}')
  cut_part "$timefrom" "$i" "$duration"
  timefrom=$(bc -l <<< "$timestamp+$add-$trim" | LC_ALL=en_US.UTF-8 awk '{printf "%f", $0}')
  i=$((i+1))
done < timestamps

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