#!/bin/bash

set +e

reencode() {
    local E=${2##*.}
    ffmpeg  -i "$2" -vf scale="-1:'min(ih,720)'" -c:v hevc_nvenc -b:v 1M -c:a aac -b:a 256K -y "$1.$E"
    local newsize=$(stat -c %s "$1.$E")
    local oldsize=$(stat -c %s "$2")
    if [ $newsize -lt $oldsize ]; then
        mv "$1.$E" "$2"
    else
        rm "$1.$E"
    fi
}

export -f reencode

find -size +100M -and \( -iname '*.mkv' -or -iname '*.mp4' \) | parallel -j 4 --progress --eta "reencode {#} {}"