#!/bin/bash

# muxsa-pngaac2mp4
#
# part of muxsa, https://git-nks-public.tik.uni-stuttgart.de/edu/muxsa
#
# this script tells ffmpeg (https://ffmpeg.org/) to read
# a series of slides in png file format (created with muxsa-kvm2png),
# a soundtrack.aac (recorded with audacity), and
# a ffmpeg concat multiplexer sequence file (created with muxsa-al2fc)
# and multiplex everything together
# into a mp4 video of the slideshow with background narration

# MIT License
#
# Copyright (c) 2023 Sebastian Kiesel <sebastian.kiesel@tik.uni-stuttgart.de>
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the "Software"),
# to deal in the Software without restriction, including without limitation
# the rights to use, copy, modify, merge, publish, distribute, sublicense,
# and/or sell copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
# OTHER DEALINGS IN THE SOFTWARE.

############################################################################
# see https://trac.ffmpeg.org/wiki/Slideshow

echo "This is muxsa-pngaac2mp4."

# first, we need to define 3 file names - check command line, then defaults:
# SLIDES_IN - concat multiplexer control file with png slide names
# AUDIO_IN  - one .wav or .m4a sound file, or concat file with several wav/m4a
# VIDEO_OUT - mp4 output

while getopts "a:s:o:" OPTION ; do
    case "$OPTION" in
    a)
        if [ -r "$OPTARG" ] ; then
            AUDIO_IN="$OPTARG"
        else
            echo "error: AUDIO_IN file $OPTARG does not exist. abort."
            exit 1
        fi
        ;;
    s)
        if [ -r "$OPTARG" ] ; then
            SLIDES_IN="$OPTARG"
        else
            echo "error: SLIDES_IN file $OPTARG does not exist. abort."
            exit 1
        fi
        ;;
    o)
        VIDEO_OUT="$OPTARG"
        ;;
    *)
        echo "Incorrect options provided - ignored"
        ;;
    esac
done
shift "$((OPTIND-1))"
# backward compatibility: before getopts we only accepted OUT as parameter
if [ -z "$VIDEO_OUT" -a -n "$1" ] ; then
    VIDEO_OUT="$1"
fi
# last resort: default output file name
if [ -z "$VIDEO_OUT" ] ; then
    VIDEO_OUT="out.mp4"
fi

if [ -z "$AUDIO_IN" -a -r "soundtrack.m4a" ] ; then
    echo "Setting AUDIO_IN to default file name soundtrack.m4a"
    AUDIO_IN="soundtrack.m4a"
fi
if [ -z "$AUDIO_IN" -a -r "soundtrack.wav" ] ; then
    echo "Setting AUDIO_IN to default file name soundtrack.wav"
    AUDIO_IN="soundtrack.wav"
fi
if [ -z "$AUDIO_IN" -a -r "audio.concat" ] ; then
    echo "Setting AUDIO_IN to default file name audio.concat"
    AUDIO_IN="audio.concat"
fi
if [ -z "$AUDIO_IN" ] ; then
    echo "No input audio file given and no default file name found. abort."
    exit 1
fi

if [ -z "$SLIDES_IN" -a -r "slides.concat" ] ; then
    echo "Setting SLIDES_IN to default file name slides.concat"
    SLIDES_IN="slides.concat"
fi
if [ -z "$SLIDES_IN" ] ; then
    echo "No input slides file given and no default file name found. abort."
    exit 1
fi

# now we got all input and output file names

# depending on the type of the audio input, we need to give different options
case "${AUDIO_IN##*.}" in
    m4a|M4A|aac|AAC)
        AUDIO_SOURCE_OPTS="-i"
        AUDIO_CODER_OPTS="-c:a copy"
        ;;
    concat|CONCAT|sequence|SEQUENCE|seq|SEQ)
        AUDIO_SOURCE_OPTS="-f concat -i"
        AUDIO_CODER_OPTS="-c:a aac -b:a 128k"
        ;;
    *)
        AUDIO_SOURCE_OPTS="-i"
        AUDIO_CODER_OPTS="-c:a aac -b:a 128k"
        ;;
esac

# time to start ffmpeg
# no "quotes" around the $..._OPTs on purpose
set -ex
ffmpeg -f concat -safe 0 -i "$SLIDES_IN" $AUDIO_SOURCE_OPTS "$AUDIO_IN" \
    -vsync cfr -vf fps=25 \
    -c:v libx264 -preset slow -tune stillimage -crf 23 -pix_fmt yuv420p \
    $AUDIO_CODER_OPTS \
    -movflags +faststart -brand mp42 "$VIDEO_OUT"

############################################################################