I cant find information on How to get audio with AviSynth script using DirectShowSource

If I get a Video.mpg in AviSynth script
DirectShowSource("c:\Video.mpg") I get no Audio
If I take that test.avs and open it with GraphEdit I only have Video Stream.

If I do the same but with an avi source I get Audio and Video Stream.

On the help.doc it says I could open mp3 too with DirectShowSource but no luck.

Do I need any codec for this to work I have installed Tsunami-Filter-Pack and Nimo Codec Pack