High quality MP4 to WebM

mp4-to-webm.ps1

$Dir = get-childitem . | where {$_.extension -eq ".mp4"}
Foreach ($file in $Dir){
    $output = $file | % {$_.BaseName}
    $input = $file
    .\ffmpeg.exe -i "$input" -an -c:v libvpx -pix_fmt yuv420p -threads 4 -slices 8 -lag-in-frames 16 -auto-alt-ref 1 -ac 2 -c:a libvorbis -qmin 17 -crf 17 -qmax 17 -qcomp 1 -b:v 0 -qscale:a 10 -pass 1 -passlogfile "C:\Users\Calvin\AppData\Local\Temp\75b67ed3-075e-4eb7-b783-41b40406e7c4" -f webm -y "NUL"
    .\ffmpeg.exe -i "$input" -c:v libvpx -pix_fmt yuv420p -threads 4 -slices 8 -lag-in-frames 16 -auto-alt-ref 1 -ac 2 -c:a libvorbis -qmin 17 -crf 17 -qmax 17 -qcomp 1 -b:v 0 -qscale:a 10 -pass 2 -passlogfile "C:\Users\Calvin\AppData\Local\Temp\75b67ed3-075e-4eb7-b783-41b40406e7c4" -f webm -y "$output.webm"
}