#!/bin/bash

output=output.mp4
metadatafile=FFMETADATAFILE
total_duration=0.0
prev_duration=0.0
prefix="PPL Training  Principles of Flight "

# first extract output metadata
test METADATAFILE && rm $metadatafile
ffmpeg -i $output -f ffmetadata $metadatafile
echo >> $metadatafile

# get chapters configuration
for f in *.mp4
do
	test "$f" == "$output" && continue
	noext=${f%%.mp4}
	duration=$(ffprobe "$f" -show_entries format=duration -v quiet -of csv="p=0")
	total_duration=$(echo $duration + $total_duration | bc)

	cat <<-EOF >> $metadatafile
	[CHAPTER]
	TIMEBASE=1/1000
	START=$(echo \($prev_duration \* 1000\) / 1 | bc)
	END=$(echo \($total_duration \* 1000\) / 1 | bc)
	title=${noext##$prefix}

	EOF

	prev_duration=$total_duration
done