What is this distortion?

TimTyler wrote on 10/22/2002, 12:23 AM
Please view http://timtyler.com/frames.jpg

This is four consectutive partial frames (shot of a car driving left to right) taken from a DV tape of a film transfer.

The effect in frames 2 and 3 does not appear on the DV master. The capture was made using default settings in Sonic Foundry Video Capture v3, which is part of VV3c.

Am I doing something wrong?

Comments

Chienworks wrote on 10/22/2002, 6:47 AM
Those are interlacing artifacts. Have you changed your project properties at all from the default? They should be set to 29.97fps, lower field first. Are you changing the velocity of the clip or resizing it?
Tyler.Durden wrote on 10/22/2002, 7:16 AM
Hi Tim,

A couple of other Qs:

NTSC DV?

Are the images shown from the timeline, trimmer, preview or Vegas capture window?

If from the TL, is "quantize to frames" ON?

Can you recapture the segment a few times and consistantly get the same result?

Does the artifact repeat throughout the footage?

What was the framerate of the film at time of transfer?

Was the transfer Telecine (flying spot scanner), or film-chain... direct to DV or to other tape, dubbed to DV?

MPH

TimTyler wrote on 10/22/2002, 11:41 AM
This is NTSC DV. The images were "copied" from the preview window in VV.

I just recaptured from the DV tape and got the exact same result. The artifact appears throughout the footage on fast moving elements in the frame.

The telecine was done to Digibeta, which was dumped via component into a Mac. The Dv was edited in FCP and then digitally output to DVCAM. A Mini-DV dub was made digitally from the DVCAM. I've seen this "distortion" on plain DV footage that I've shot and captured though, so the pre-DV tape info shouldn't matter.

Here's something interesting; I just recaptured the DV from tape. Same artifact shows up in VV and in AVI file via WMP. When I Print to Tape in VV, the new DV tape does NOT show the distortion.

I also just recaptured from the "original" DV tape using Michael Carr's DVIO app and got the same bad result. The app is only a 32k .exe, so it must be using a codec on my XP.
kkolbo wrote on 10/22/2002, 11:51 AM
Well, if it shows up on your monitor, but plays correctly when shown on a TV, from the pictures that you posted, that is just interlacing and will show up that badly in a high motion clip. That is normal. It is the way television is projected within the TV tube. Interlaced video seen on a computer which does not interlace will look like that. Vegas can improve it some when you render to 320x240 size and by selcting progressive, but at the speed you were going I doubt it will go away for computer monitor play.

K
TimTyler wrote on 10/22/2002, 12:12 PM
I tried previewing on an external monitor, and the frames that are "distorted" in VV vibrate (a lot) on my NTSC monitor. The whole frame doesn't vibrate, just the area with the distortion (the moving car).

If I frame-advance through the original DV tape on the NTSC monitor, there is no vibration or distortion of any kind.

I get the feeling that VV does not capture every frame exactly as it is on tape, and then somehow compensates when it renders to reverse that difference.
SonyEPM wrote on 10/22/2002, 12:54 PM
does the video capture tool say that you dropped frames when capturing this problem clip (in the Video Capture app's clip database)?

If it indicates frames WERE dropped, you'll need to recapture the clip (and probably tweak your system in general- you shouldn't be dropping any frames during capture).
TimTyler wrote on 10/22/2002, 1:04 PM
No frames are dropped.

I've captured up to 60 minutes of tape in the past without any dropped frames.
SonyDennis wrote on 10/22/2002, 2:18 PM
That is 2:3 pulldown applied during telecine, used when converting 24p to 60i. You get 2 flickering frames out of every 5.

The interlaced frames are most definitely on the DV master, I'd put money on this. You just think they are not because the device you are using to step through the video is only showing you one field. Most consumer VCRs and camcorders do this all the time when frame stepping.

There is no problem with Vegas here.

///d@

P.S. For what it's worth, some versions of DirectX under some versions of Windows don't flicker when displaying non-updating video (such as during non-playback in Vegas). When I upgraded my machine from 98SE to XP, it went from not flickering to flickering. Some people prefer one over the other, but there's no way to change it <g>.