#!/bin/sh

usage () {
	cat <<EOF>&2
Usage: ${0##*/} MODE

This script was generated with tc-video-custom.

It transcodes the embedded list of files using FFmpeg. MODE will specify what
kind of output you want. Edit this file to fit your needs and learn more about
FFmpeg.

Modes:

  -f:   Full video.
  -s:   Sample of 5 minute starting at 1 minute.
  -S N: Sample of N minutes starting at 1 minute.

EOF
}

SAMPLE=""
OPT_PROCESS=false
while getopts ":hfsS:" opt; do
	case $opt in
	h)
		usage
		exit ;;
	f)
		OPT_PROCESS=true ;;
	s)
		SAMPLE="-ss 60 -t 300"
		OPT_PROCESS=true ;;
	S)
		SAMPLE="-ss 60 -t $((60*$OPTARG))"
		OPT_PROCESS=true ;;
	\?)
		usage
		exit 1 ;;
	esac
done

shift $(($OPTIND - 1))

if ! $OPT_PROCESS; then
	usage
	exit
fi

if ! command -v ffmpeg >/dev/null 2>&1; then
	echo >&2 "'ffmpeg' not found"
	exit 1
fi

transcode () {
	## You can choose here to process all files at the same time. Useful if you
	## need to remux streams or to concatenate.
	# ffmpeg -i ###FILELIST \
	ffmpeg -nostdin $SAMPLE -i "$@" \
		-c:v libx264 -preset slow -crf 20 \
		-c:a libvorbis -b:a 192k -ac 2 \
		-c:s copy \
		-dn \
		-map 0 \
		"${1%.*}-$(date '+%F-%H%M%S').mkv"
}

set -- ###FILENAMES

## Choose to process all files one after another.
for i ; do
	transcode "$i"
done

## Or all files at the same time. You have to change the ffmpeg input in the
## function.
# transcode

################################################################################
## USE CASES
##
## Exchange stream 1 an 2 by first removing them, then reading them in the
## desired order.
##
##   -map -0:1 -map -0:2 -map 0:2 -map 0:1
##
## Change audio stream 1 title and remove audio stream 2 title:
##
##   -metadata:s:a:0 title="FR: OGG Stereo" -metadata:s:a:1 title=""
##
## Demux audio:
##   -vn -sn -c:a copy -map 0:1
##
## Dump audio to an ogg file:
##   -vn -c:a libvorbis -b:a 192k
##
## Add a delay to audio (assuming stream 0 is video and stream 1 is audio)
##   -i "$1" -itsoffset 0.300 -i "$1" -map 0:0 -map 1:1
##
## Insert stream 3 from file2 between all non-audio streams and audio streams of
## file1:
##   -i "file1" -i "file2" -map -0:a map 1:3 -map 0:a
##
## Concatenate files. See <https://trac.ffmpeg.org/wiki/Concatenate> for more
## details.
##
##   -f concat -i list.txt -c copy out.ext
##
## with `cat list.txt`:
##   file 'file1'
##   file 'file2'
##
## With different codecs:
##
##   -filter_complex '[0:0] [0:1] [1:0] [1:1] concat=n=2:v=1:a=1 [v] [a]' -map '[v]' -map '[a]'
##
################################################################################

################################################################################
## SOUND
##
## You should consider mixing down audio to 2 channels with '-ac
## 2'. This greatly reduce file size and avoid any confusion for playback, which
## is often the case when converting DTS to any other format because DTS has
## embedded channel description which is not available in other formats.
################################################################################

################################################################################
## X264 OPTIONS
##
## x264 presets (-preset <preset>).
##   preset ~= speed and quality*size ~= 1/speed
##   ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslow, placebo
##   Recommended values: faster -- slow
##   slow is approx. two times slower than fast, and reduces the size by approx. 10%.
##
## x264 overall quality (-crf) is a logarithmic scale.
##   18 is near perfection.
##   22 is really good compression, while a bit more blurry than the original.
##   20 is a good compromise.
##
## x264 tuning (-tune <preset>).
##   Possible values: film, animation, grain, ...
##   See x264 --fullhelp.
##   No tuning by default.
##
## x264 options (-x264opts me=<value>).
##   Possible values: hex, umh...
##   me=umh is default.
################################################################################

################################################################################
## FALLACIOUS INPUT
##
## In general, FFmpeg is not so good at copying fallacious streams. Reecoding
## video and audio streams helps a lot.
##
## "Can't write packet with unknown timestamp"
##   Put '-fflags genpts' before the input command.
################################################################################

################################################################################
## MISC
## To check what ffmpeg supports:
##   $ ffmpeg -codecs
##   $ ffmpeg -formats
##
## Useful guides:
##   x264: http://ffmpeg.org/trac/ffmpeg/wiki/x264EncodingGuide
##   ID3 details: http://en.wikipedia.org/wiki/ID3
################################################################################