#!/bin/sh
duration=$(ffprobe -i $1 -show_entries format=duration -v quiet | grep -o '[0-9]*' | head -1)
number=$(echo "scale=1;3/$duration*8" | bc)
bitrate="${number}M"
ffmpeg -i $1 -pass 1 -c:v libvpx -crf 4 -b:v $bitrate -an -y -f webm /dev/null
ffmpeg -i $1 -pass 2 -c:v libvpx -crf 4 -b:v $bitrate -an -f webm $2