#!/bin/bash

last=''
cur=''
threshold=20.0

for fname in frames/*; do
    last=$cur
    cur=$fname

    if [[ $last == '' ]]; then
    continue
    fi

    diff=$(compare -metric PSNR $cur $last null 2>&1)

    if [[ $(echo "$diff < $threshold"|bc) -eq 1 ]]; then
    echo "$fname changed"
    fi
done