VirtualDub: Frames Look Worse in Preview Window?

Jellygoose · #1 07-30-2003, 06:13 AM

Hi all...

Yesterday, I compared 2 m1v files through VirtualDub-MPEG2, and took snapshots of some frames to compare the image quality.
When I skip through the frames manually, almost all pictures look very clean and without any blocks. When I hit Space (PLAY), and then hit Space(STOP) again, the very same frame would look a lot worse, with blocks in it.

This way I think is a lot more the way it SHOULD look, by comparing the 2 streams in PowerDVD.
What's the reason for this, and why is VirtualDub doing this filtering?

Jellygoose · #2 07-31-2003, 06:34 AM

So does someone know of a way to solve this with some setting in VDUB maybe?

kwag · #3 07-31-2003, 10:28 AM

Hi Jellygoose,

I don't know exactly what the reason is, but it could be the frame you stop at that moment ( I, B or P frame.)
The way I compare two files, is that I create an .avs script to load both sources, and then I stack them vertical. This way, when you scroll in Vdub, and you do a "Copy current frame to clipboard", you take the identical frame from both streams, and paste that into Windows paint. Then you can compare both. I use something like this:

Code:

clip1 = avisource("k:\source_1.avi") 
clip1 = clip1.Subtitle("Source 1 title") 

clip2 = avisource("k:\Source_2.avi") 
clip2 = clip2.Subtitle("Source 2 title") 


StackVertical(clip1, clip2, clip3) 
Levels(0, 1.5, 255, 16, 255) 
ConvertToRGB()

-kwag

Jellygoose · #4 07-31-2003, 11:57 AM

Yes that is very less complicated. So do you create uncompressed AVIs of your .m1v files before you load them in your AVS script?

However I want you to try this.
Load a Sample .m1v File into VirtualDub and press Play. Then press stop again on a random scene. Look at the frame. Now press right on your keyboard and after that left again, so that you are back at the frame you looked at before.
You'll see what I mean!