#!/bin/sh
start_time=00:00
duration=1
palette="/tmp/palette.png"
filters="fps=3,scale=320:-1:flags=lanczos"
ffmpeg -v warning -ss $start_time -t $duration -i $1 -vf "$filters,palettegen" -y $palette
ffmpeg -v warning -ss $start_time -t $duration -i $1 -i $palette -lavfi "$filters [x]; [x][1:v] paletteuse" -y $2