ffmpeg -re -f concat -i <(printf "file '%s'\n" /path/*.flv | shuf) -i overlay.png -filter_complex "[0:v] overlay" -c:v h264 -preset veryfast -profile:v main -b:v 2000k -minrate 2000k -maxrate 2000k -bufsize 2000k -g 80 -c:a copy -f flv ServerAddress