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Rendered output has the jitters

Posted: Sat, 5th Nov 2005, 9:04pm

Post 1 of 4

jimwoodruff

Force: 600 | Joined: 2nd Nov 2005 | Posts: 5

CompositeLab Pro User Windows User

Gold Member

I'm getting less than ideal results with a chromakey using Chromanator -- or more accurately -- I'm getting less than ideal quality when output to DV format. Both the foreground and background clips were captured using Vegas 5.0c to the Vegas DV codec, from DVCAM tape.

After importing the clips into Chromanator and tweaking the key until I was seeing a good clip in the workspace, I rendered to a DV/DVCPRO Quicktime codec. I then imported the render into Vegas to add a graphic tag on the 30 clip.

The chromakeyed subject in the video (a waist up shot of a company CEO) walks toward the camera a couple of steps and in doing so he "rocks" right and left somewhat. It's during this motion that the rendered chromakey "strobes" pretty badly in the final output to standard DV video.

At first I thought it might be a field order issue, but it was rendered at the standard DV/NTSC "lower field first". But, I tried upper field first as well as progressive and all of them strobed quite a bit -- too much to use. I even tried a Windows uncompressed AVI as an output format and I get the same "strobing" video when the subject moves from side to side.

I then used the Chromakey plugin that comes standard with Vegas and while the key isn't as good as Chromanator, the output is perfectly stable, with no strobing at all.

Anyone ever see this and have a suggestion as to how to get rid of the jitters?

Thanks! smile
Posted: Sun, 6th Nov 2005, 11:30am

Post 2 of 4

Hendo

Force: 13107 | Joined: 16th Sep 2004 | Posts: 848

VisionLab User VideoWrap User PhotoKey 5 Pro User MuzzlePlug User PowerPlug User PhotoKey 3 Plug-in User FXhome Movie Maker FXpreset Maker Windows User MacOS User

FXhome Team Member

jimwoodruff wrote:

It's during this motion that the rendered chromakey "strobes" pretty badly in the final output to standard DV video.
It may help if you can upload a few seconds of both the original video (where the actor moves side-to-side) and also your Chromanator keyed version which has the strobing. Just a few seconds or so of each. That way the FXhome guys can see the issue for themselves.
Posted: Sun, 6th Nov 2005, 3:43pm

Post 3 of 4

jimwoodruff

Force: 600 | Joined: 2nd Nov 2005 | Posts: 5

CompositeLab Pro User Windows User

Gold Member

Thanks for the reply.

I was creating the sample files to upload and thought I'd try the Chromanator Directshow DV render format. When I used the resulting file within Vegas in the same manner as the previous files I don't get the stobe effect when the keyed subject moves back and forth. So, I'm guessing it might be a codec issue. I also noted that the Directshow DV is 30 FPS (multimedia) whereas all the other DV formated files are 29.970 FPS (correct for NTSC.)

But, no matter what render format I've used up till now, I still have to render the imported AVI from the Vegas timeline to get a "standard" NTSC DV file for export to DV tape. Does anyone know what format / codec / settings that I can use to render from Chromanator that will not require re-rendering from the Vegas timeline? It not only slows things down, but re-encoding the file can't be good for the final quality.

Thanks again.

Jim
Posted: Mon, 7th Nov 2005, 3:55am

Post 4 of 4

jimwoodruff

Force: 600 | Joined: 2nd Nov 2005 | Posts: 5

CompositeLab Pro User Windows User

Gold Member

Well, after some more testing, I think I might have found what was causing the jitters in my renders.

The default project for NTSC DV in Chromanator has the frame rate set at 30.00 fps, but it should be 29.970.

So, using the custom project settings, I created a new project and changed the frame rate to 29.970. Imported my DVCAM AVI clips into Chromanator and setup the key again. I then rendered out a QuickTime DV/DVCPRO file and the jittering seems to be gone now when output from the Vegas timeline as an NTSC DV file...

Hopefully it was that simple? smile