haliphax

I adapted a PowerShell script by Tim Van Wassenhove that recurses through a given directory, searching for various types of audio files. These files are then converted to MP3 using VLC Player's command-line interface. My adjustments to Tim's original script include some string handling bits that ensure filenames with potentially dangerous characters (apostrophes in the case of the VLC command line, and square brackets in the case of the Remove-Item call) are taken care of.

mp3convert.ps1:

function ConvertToMp3(
	[switch] $inputObject,
	[string] $vlc = 'C:\Program Files (x86)\VLC\vlc.exe')
{
	process {
		Write-Host $_
		$codec = 'mp3'
		$newFile = $_.FullName.Replace("'", "\'").Replace($_.Extension, ".$codec")
		&"$vlc" -I dummy "$_" ":sout=#transcode{acodec=$codec,vcodec=dummy}:standard{access=file,mux=raw,dst=`'$newFile`'}" vlc://quit | out-null
		# Uncomment the next line when you're sure everything is working right
		#Remove-Item $_.FullName.Replace('[', '`[').Replace(']', '`]')
	}
}

function ConvertAllToMp3([string] $sourcePath) {
	Get-ChildItem "$sourcePath\*" -recurse -include *.wma,*.aac,*.ogg,*.m4a | ConvertToMp3
}

To use:

. C:\mp3convert.ps1
ConvertAllToMp3 C:\Music

Note: If you're going to kill the process, make sure you kill it from the PowerShell environment, and not from the VLC environment! If you kill it from the VLC environment and you've enabled the Remove-Item line, the file it's currently working on will be deleted!

If you want to take this process a step further and copy ID3 tags, check out Andrew Connell's blog post.