A script to loop an mp4 video similarly to Instagram's boomerang

boomerang.sh

#!/usr/bin/env bash
set -o errexit
set -o nounset

if [[ "$#" -ne 2 ]]; then
  echo "Usage: ./boomerang.sh src_file out_file"
fi

SRC=$1
OUT=$2
REV_SRC="${SRC/.mp4/.rev.mp4}"
LIST="part_list.txt"

touch $LIST

ffmpeg -i $SRC -vf reverse $REV_SRC

echo "file '$SRC'" >> $LIST
echo "file '$REV_SRC'" >> $LIST

ffmpeg -f concat -safe 0 -i $LIST -c copy $OUT

rm $REV_SRC $LIST