No sound when using Avisynth with x264/mp4

[MADestruction]

I got some x264 files that play just fine in WMP but I want to be able to watch them in black and white on the fly. I'm an encoding noob so my first script looks like this:

file.avs

DirectShowSource("D:\*************1080.mp4", fps=30, audio=true)
greyscale()

the avs file plays fine with WMP but there is no sound.

I have the Haali media splitter installed.

[jagabo]

I got some x264 files that play just fine in WMP but I want to be able to watch them in black and white on the fly.

Just turn the saturation down in the player. For example in Media Player Classic Home Cinema: