#!/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." 

OUTFILE="out.mp4"
if [ "$1" ] ; then
    OUTFILE="$1"
    # make sure that file ends on .mp4
    OUTFILE="${OUTFILE%%.mp4}.mp4"
fi

if [ ! -f slides.concat ] ; then
    echo "error: file slides.concat missing. abort."
    echo "consider using muxsa-al2fc for creating one."
    exit 1
fi

if [ -f soundtrack.m4a ] ; then
    AUDIOFILE="-i soundtrack.m4a"
    AUDIOOPTS="-c:a copy"
else
    if [ -f soundtrack.wav ] ; then
        AUDIOFILE="-i soundtrack.wav"
        AUDIOOPTS="-c:a aac -b:a 128k"
    else
        if [ -f audio.concat ] ; then
            AUDIOFILE="-f concat -i audio.concat"
            AUDIOOPTS="-c:a aac -b:a 128k"
        else
            echo "neither soundtrack.m4a, .wav, nor audio.concat found. abort."
            exit 1
        fi
    fi
fi

ffmpeg -f concat -i slides.concat ${AUDIOFILE} \
    -vsync cfr -vf fps=25 \
    -c:v libx264 -preset slow -tune stillimage -crf 23 -pix_fmt yuv420p \
    ${AUDIOOPTS} \
    -movflags +faststart -brand mp42 "${OUTFILE}"

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