Equivalent to CCE's low pass filter in AviSynth?

From the CCE manual:
"It is a low pass filter to cut out the higher frequency components at specific frequencies. It tends to make the image blur or smooth."



Firstly, I'm not sure why the deafult is 4.5MHz when DVDs have an equivalent "analogue" resolution of ~ 6.75MHz?

But let's say I have a capture from an analogue format such as VHS (3MHz) or laserdisc (5MHz). Anything above these frequencies would be random noise and not real detail? So you could in theory run the video through a low pass filter which will smooth the image withou actually removing detail?

Is there anything in Avisytnh that can do this? The closest I could find is Defreq, but that seems to be designed for something different.