#!/bin/bash
mkdir -p images
shopt -s nocaseglob nullglob

for f in *.mp4 *.mkv *.avi *.mov *.webm *.flv *.wmv; do
    name="${f%.*}"
    ffmpeg -ss 00:00:20 -to 00:00:35 -i "$f" -vf "fps=1,scale='if(gt(iw,ih),640,-2)':'if(gt(iw,ih),-2,640)'" -q:v 3 "images/${name}_x%04d.jpg"
done