makemp4.sh

#!/bin/sh

frames=/tmp/makemp4-frames

rm -r $frames
mkdir $frames

for i in {1..3}; do
    for file in *.png; do
        cp $file "$frames/$i-$file"
    done
done

ffmpeg -pattern_type glob -i "$frames/*.png" -f mp4 -y -vcodec libxvid -qmin 3 -qmax 5 -g 300 -flags +mv4 output.mp4