Use ffmpeg to create a supercut from a directory of videos

supercut.sh

#!/bin/bash

set -euo pipefail

output_video=$1

# find good value that aligns with keyframes:
#   ffprobe -loglevel error -select_streams v:0 -show_entries packet=pts_time,flags -of csv=print_section=0 -i FortV0001-0240.mp4
seconds_per_video=$2

mkdir -p ./cuts
if [[ $(ls -A ./cuts) ]]
then
  rm ./cuts/*
fi
if [[ -f ./cuts.txt ]]
then
  rm ./cuts.txt
fi
if [[ -f "${output_video}" ]]
then
  rm "${output_video}"
fi

files="$(ls -1 ./videos | egrep '\.mp4$')"
num_files="$(ls -1 ./videos | egrep '\.mp4$' | wc -l)"

video_index=0
video_start=0
rounding_helper=0.01
total_seconds_per_video=10
frames_per_second=24

for file in ${files}
do
  # TODO handle when video_start + seconds_per_video > total_seconds_per_video

  echo "file" $file
  echo "video index" $video_index
  echo "video_start" $video_start

  if (( $(echo "(${video_start} + ${seconds_per_video}) <= ${total_seconds_per_video}" | bc -l) ))
  then
    start_time=$(echo "${video_start} + ${rounding_helper}" | bc -l | awk '{printf "%f", $0}')
    ffmpeg -hide_banner -loglevel error -ss "${video_start}" -i "./videos/${file}" -t "${seconds_per_video}" -c copy -avoid_negative_ts 2 "./cuts/${video_index}.mp4"
    echo "file cuts/${video_index}.mp4" >> "./cuts.txt"
    video_index=$((${video_index} + 1))
  else
    overflow_time=$(echo "${video_start} + ${seconds_per_video} - ${total_seconds_per_video} + ${rounding_helper}" | bc -l | awk '{printf "%f", $0}')
    leftover_time=$(echo "${seconds_per_video} - ${overflow_time} + ${rounding_helper}" | bc -l | awk '{printf "%f", $0}')

    echo "leftover_time" $leftover_time
    ffmpeg -hide_banner -loglevel error -ss "${video_start}" -i "./videos/${file}" -t "${leftover_time}" -c copy -avoid_negative_ts 2 "./cuts/${video_index}.mp4"
    echo "file cuts/${video_index}.mp4" >> "./cuts.txt"
    video_index=$((${video_index} + 1))

    echo "overflow_time" $overflow_time
    ffmpeg -hide_banner -loglevel error -ss "0" -i "./videos/${file}" -t "${overflow_time}" -c copy -avoid_negative_ts 2 "./cuts/${video_index}.mp4"
    echo "file cuts/${video_index}.mp4" >> "./cuts.txt"
    video_index=$((${video_index} + 1))
  fi

  video_start=$(echo "scale=0; (${video_start} + ${seconds_per_video}) % ${total_seconds_per_video}" | bc -l | awk '{printf "%f", $0}')
done

ffmpeg -hide_banner -loglevel error -f concat -i ./cuts.txt -c copy "${output_video}"

supercuts.sh

#!/bin/bash

set -euo pipefail

filename_prefix=$1
seconds_per_video_list=$2

for seconds_per_video in ${seconds_per_video_list}
do
  ./supercut.sh "${filename_prefix} (${seconds_per_video}s per).mp4" "${seconds_per_video}"
done