#!/bin/bash

last=wow.png

while true; do
    ffmpeg -v 0 -i rtsp://192.168.120.180:8554/ -f image2 -vf "select='eq(pict_type,PICT_TYPE_I)'" -vsync vfr -vframes 1 -max_error_rate 0 -y darkroom-new.png 
    now=darkroom-`date +\%F-\%T`.jpg

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

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