Glitches in mpeg after capture and conversion

[Headbanger's Ball]

I have captured a 90 minute concert from VHS using Dazzle's DVC 100 (which uses DVC200 drivers) and rendered an mpeg using Dazzle's MovieStar5 program. When I check the file, I notice that every now and then I get a strange 'blocking' of the picture. It looks like satellite TV does when it rains a little. Blocks trickle down the screen. This doesn't occur all the time but several times during the 90 minutes. I can live with it but am considering making DVDs for other people (home movies to DVD stuff) and don't think this is acceptable.
My question is: Is this a quirk in the capture/render part of the creation? And can the blocky frames be removed without causing me a nightmare of audio problems? I just want a clean picture start to finish.
All software used in the creation is up to date (including DirectX) and I have tried to capture using VirtualDub but it gave me errors.
Other info: Nothing else is running while the capture/render process happens to interfere with the programs or hog up RAM. And my system is quite capable of handling the task.
Thanks for replies.

[cmacleo]

Are the glitches in the source file/file you capture to (say an AVI). If so you are having some noise in the capture process, often due to a fault in the source media. You could clean it up using VirtualDub and mask the bad frames (this is a bit time consuming)

If the glitches are only in the rendered mpg file then it is an encoding issue, probably some type of bit rate shortage. I am not familiar with your programs but try altering your bit rate settings for the encode process.

[DJRumpy]

Your probably experiencing macroblocking, due to poor motion detection, or bitrate shortage. It seems like I remember the Dazzle hardware MPEG cards did a pretty decent job for quality, but it's still capturing directly to MPEG, with all that entails. You could try increasing your bitrate.

[Headbanger's Ball]

From what you've both said, it could be a combination of both motion detection and bitrate shortage. The glitches occur when there is a fast motion of the camera or a cut-away but it also happens in the middle of no motion but less frequently.
The capture/render program Dazzle provides with their device is limited in their settings. I'll see what I can tweak but don't think I can do anything short of running the mpeg in TMPGenc to correct the blocks...adding hours to the project.
Thanks