#!/bin/bash
# set -Eeuo pipefail
# Splits video to separate scenes files
# Source: https://gist.github.com/achesco/4dc2ebf13378a0a61fc26c7fe01f539e
# Inspired by https://stackoverflow.com/a/38205105

# The "-c:v h264_videotoolbox \" argument makes it work faster on Apple Silicon
# computers.
# ❗The bitrate argument is overriden in this version, we look at the original bitrate.

file=""
out="./"
diff=0.4
bitrate="512k"
trim=0
stripaudio=""
script_name=$(basename "$0")

usage () {
  echo "Usage: $script_name [[[-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 [ "$3" != "" ]; then
    duration_flag="-t"
  fi
  output_file="$out"/$(printf "%04d_%s" "$2" "$filename_without_spaces")
  echo "Creating ${output_file}"
  ffmpeg \
    -loglevel error \
    -hide_banner \
    -ss "$1" \
    $duration_flag "$3" \
    -i "$file" \
    -vcodec libx264 \
    -c:v h264_videotoolbox \
    -movflags faststart \
    -b "$bitrate_ffprobe" \
    $stripaudio \
    -y "$output_file" < /dev/null
}

filename=$(basename "$file")
filename_without_spaces="${filename// /_}"

bitrate_ffprobe=$(ffprobe -v quiet -select_streams v:0 -show_entries stream=bit_rate -of default=noprint_wrappers=1 "$filename" | cut -d"=" -f 2-)

mkdir -p "$out"
timefrom=0
i=1
echo "finding parts..."
while read -r timestamp; do
  duration=$(bc <<< "$timestamp-$timefrom-$trim" | awk '{printf "%f", $0}')
  cut_part "$timefrom" "$i" "$duration"
  timefrom=$timestamp
  echo from "$timefrom" for "$duration" seconds
  i=$(( i + 1))
done < <(
  ffmpeg -i "$file" -c:v h264_videotoolbox -filter:v "select='gt(scene,$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