HiRes stills and line jitter-interesting results

farss wrote on 12/28/2004, 5:41 AM
As some of you know I (and many others, even users of other NLEs) have been grappling with this issue. All manner of solutions have been put forward and certainly they all kill the problem, some of them would either take the patience of a saint or else knock the resolution around.
The most obvious tool that Vegas provides is gaussian blur, a tiny amount (0.001) in the vertical direction certainly cures the problem but even though my source is mostly 3000x2000 the loss of resolution is noticeable. Now that to me seemed odd. So I'm thinking that Vegas calculates the blur radius based on project settings rather than source resolution.
To tes this I dropped the same still image into a 1080 project applied 0.001 vertical GB. Then took that into a PAL DV project.
Firstly, line jitter is gone. Secondly through my bleary eyes the result looks better than putting the same still into the same (PAL DV) project and applying the 0.001 GB. I've done a split screen check on both halves of the image (it's damn hard to judge these things at that res with real images) and both halves show better res on the 1080 uncompressed source.
Now this seems a pretty simple fix, well apart from trying to find space for over an hour of 1080 uncompressed video.
I'm hoping someone can tell me if this kind of makes sense, I'd love to know when I set GB to 0.001 just what the 0.001 is being calculated against and at what point in the processing chain. Is the radius 0.001 x 576 px in a PAL DV project?
If so then that should mean for a 1080i project it's 0.001 x 1080.
In order to avoid chewing up terrabytes of storage I'm going to try going direct from 1080 to mpeg-2 at 720x576.
Any thoughts much appreciated. Maybe we've got this sucker licked.

Comments

rmack350 wrote on 12/28/2004, 9:36 AM
That's very interesting. The obvious next question is what happens if you apply the blur to the original file in photoshop? This is something you could do in a photoshop batch file like: Select All, Copy, Paste (making a new layer so that you don't alter the original layer), Gaussian Blur, Save.

'Course I'm too lazy to just try it...

Rob Mack

farss wrote on 12/28/2004, 12:19 PM
Well you can achieve the same thing in PS except I can't find a PS filter that blurs vertically only. Must also say I haven't got my brain around running scripts with PS, no doubt one day I should make the effort.
Bob.
SonyDennis wrote on 12/28/2004, 8:15 PM
I hope you are also using "Best" quality rendering, because the downscaling algorithm there works best for hi-res stills.

///d@
rmack350 wrote on 12/28/2004, 8:38 PM
Yes, I wondered about that after writing. Gausian blur has no directionality but motion blur does and at your high resolution it can be pretty subtle.

Photoshop actions are pretty easy and once you've used them you'll be slapping your head wondering how you managed without them. Once you've recorded an action you can go to the file menu and hunt down the batch command. It can run an action on everything in a folder, or everything that's open, etc. I use it for shots of BIOS screens. I take maybe 200 shots and color correct, blur or sharpen, crop, resize, then save in a new folder. Meanwhile I go get a glass of water. So, since water is good for you, so are photoshop actions!

Rob Mack
rmack350 wrote on 12/28/2004, 8:41 PM
Best uses bicubic interpolation which is best for anything that is being resized in Vegas or any other app. Maybe that's why we call it "Best".

Just wanted to make the point for other readers.

Rob Mack
farss wrote on 12/29/2004, 12:46 AM
Thanks for the heads up on that one, I just did a test encode and the jitter is gone and the images look pretty good still. I'll run it again at 'Best'.
I'll perhaps not see much difference as my DVD player has died and I'm only going composite into the 16:9 TV.
I'm going to check the final result on a studio 16:9 monitor in a few days.
Hells Bells, all this grief and the client is giving this DVD away as a freebie with a CD!