#!/bin/bash

last=cat-wow.png

while true; do
    ffmpeg -v 0 -i rtsp://pi2:8554/ -f image2 -vf "select='eq(pict_type,PICT_TYPE_I)'" -vsync vfr -vframes 1 -y cat-new.png 
    now=cat-`date +\%F-\%T`.jpg

    compare -fuzz 8% -compose src $last cat-new.png cat-comp.png
    size=`stat -c%s cat-comp.png`

    if [ $size -gt 8000 ] ; then
	echo "change!  $size  $last  $now"
	convert cat-new.png $now
	last=$now
    else
	echo "no change: $size  $last  $now"
    fi
done