Virtualdub Filters - CLean up Blockiness and Deinterlace Better Way?

[doggyofone]

I've done some reading and am working with a ~700 mb avi that was blocky and I believe need deinterlacing. I ran VD with the smooth deinterlace filter and I've taken the deinterlaced avi and am running the MSU Deblocking filter. The avi looks better after deinterlace and I'm hoping the deblock will help. I used Divx 5.2.1 to compress.
Question - is there a better way to clean up an avi than I've used? I have other encoders that deinterlace, but I don't believe they deblock.
Can you run multiple filters in VB - deinterlace and deblock at the same time?

[guns1inger]

MSU Smart Deblock is probably the best deblocker for Vdub. I would be surprised however if your 700mb avi needed deinterlacing. Most avi files of that size are already progressive, and attempting to deinterlace them again will only throw away much needed information.

On what do you base your assumption that deinterlacing is required ?

[doggyofone]

The video looked a lot like the examples shown in the "What is de-interlacing" guide I got from 100 fps.com. The resulting avi looked better to me, but was still blocky. Hard to say watching on a PC vs through a standalone. I ran MSU to see if it improves.
How can I determine if it was progressive?