ffmpeg commandline crossfade-looped video

crossfadevideo.sh

#!/bin/bash
[[ ! -n $3 ]] && { echo "Usage: crossfadevideo <input.mp4> <fade in seconds> <output.mp4>"; exit; }
input="$1"
fade="$2"
duration="$(ffprobe -v error -select_streams v:0 -show_entries stream=duration -of default=noprint_wrappers=1:nokey=1 $1 )"
duration="$(echo "$duration-($fade)" | bc)"
[[ ${duration:0:1} == "." ]] && duration="0$duration"
output="$3"
set -x
ffmpeg -i "$input" -filter_complex '
[0]split[body][pre];
[pre]trim=duration='$fade',format=yuva420p,fade=d='$fade':alpha=1,setpts=PTS+('$duration'/TB)[jt];
[body]trim='$fade',setpts=PTS-STARTPTS[main];
[main][jt]overlay' "$output"

Fixed duration calculation typo