src/ppm2mp4

#!/bin/bash

AVCONV="`which avconv 2> /dev/null`"
if test -z "$AVCONV"; then
    AVCONV=`which ffmpeg`
fi

while test $# -gt 0; do
    case $1 in
	-r) shift; rate="-r $1" ;;
	-*) options="$options $1" ;;
	*)  file="$1"
    esac
    shift
done

if test -z "$file"; then
    echo "usage: ppm2mp4 [OPTIONS] FILE" >&2
    exit 1
fi

if test -z "$AVCONV"; then
    echo "ppm2mp4: warning: could not find 'avconv' or 'ffmpeg'" >&2
    echo "ppm2mp4: the output will just be concatenated PPM files" >&2
    command="cat > $file"
else
    # -crf 18 low compression/high quality, 28 high compression/low quality
    # see https://trac.ffmpeg.org/wiki/Encode/H.264
    # -r 15  '15 frames/sec'
    command="$AVCONV -f image2pipe -vcodec ppm $rate -i - -c:v libx264 -preset slow -tune zerolatency -crf 18 -vf format=yuv420p -y -f mpegts $options $file"
fi

if test -d "$TMPDIR" ; then
    log=`mktemp $TMPDIR/ppm2mp4.XXXXXX`
else
    log=`mktemp /tmp/ppm2mp4.XXXXXX`
fi

if $command 2> $log; then :
else
    cat $log >&2
    rm -f $log
    exit 1
fi

# we reformat to create a standard (and more compressed) mp4 file
if $AVCONV -i "$file" -crf 18 -movflags +faststart $log.mp4 2> $log; then
    mv -f $log.mp4 "$file"
else
    cat $log >&2
    rm -f $log $log.mp4
    exit 1
fi    
rm -f $log

exit 0