Slow motion problem

ScorpioProd wrote on 1/31/2008, 12:11 AM
A friend of mine moved to Vegas 7 this summer, he's a wedding videographer, shooting exclusively DVCAM. His weddings always have slow motion parts in the highlight recap. He did about 3 weddings in Vegas 7 and the slow motion always looked great.

Then Vegas Pro 8 came out, he waited for 8.0a before installing it.

The first project he tried in it was a wedding started in Vegas 7. In Vegas Pro 8.0a, any of his slow motion parts, whether newly added or in the existing veg didn't render and play smoothly. It was like there was no interpolation between frames. And the temporary render, either to RAM or to a temp file rendered faster than it should have. For instance, if a new project was started and the same clip was put in at the same slow motion speed, the temporary render would take longer since interpolation was happening, and the quality looked smooth in the final output.

Output in all the cases described here was on a standard NTSC monitor fed from the DV preview in Vegas through a Canopus DV to analog converter. And after the temporary renders, the frame rate while playing in the preview window was always 29.97fps. And the quality of the preview monitor was set at Best (full) for the temp renders and playback.

I thought it was maybe something to do with it starting as a Vegas 7 veg, so he scrapped that project and did a fresh one in Vegas Pro 8 and didn't have a problem.

But now he's in a middle of editing another wedding, and it's happening again, even though this veg was a Vegas Pro 8.0a one right from the start.

Any suggestions on a setting that could be wrong that would cause this?

The project is standard NTSC DV, interlaced. The slow motion is done with velocity envelopes on the clips, typically around 50% speed, but definitely between 40-60% speed.

The resampling for the clips is set to "smart resampling" by default, but we tried "force resampling" as well, and that didn't improve it. We also tried "reduce interlace flicker", but it isn't an interlace flicker problem, so that didn't help.

Like I said, it looks like it actually isn't creating the inbetween frames in the slow motion.

Is this a bug in 8.0a? Would installing 8.0b fix it?

Thanks for any suggestions.

Comments

Jøran Toresen wrote on 1/31/2008, 1:13 AM
Make sure the Project Properties are appropriate for the quality you want. I usually specify these settings:

Full-resolution rendering quality: Best
Motion blur type: Gaussian
Deinterlace method: Blend fields or Interpolate fields

Jøran Toresen
johnmeyer wrote on 1/31/2008, 10:07 AM
Right-click on one of the slo-mo events and select "force resample." Try rendering that one section and see if it looks any better. The effect you describe sounds like, for some reason, the video is not being resampled (which is where Vegas interpolates the intermediate frames when slowing down video).
Jim H wrote on 1/31/2008, 3:05 PM
Does vegas interpolate tween frames? I always thought vegas blended the two as I've never seen anything in those new frames but crap.. I thought "force" just did the same thing by force..... so are the resample and force resample different?
cspvideo wrote on 1/31/2008, 4:57 PM
Hi John...

I'm working with the same guy as "scorpio." He tried forcing the resample and also "reduce interlace flicker." Neither cures the issue.

He also isn't having it with all slo-mo, but most of it. I can't find any commonality to pin point a cause.

pc
johnmeyer wrote on 1/31/2008, 7:35 PM
Sorry about the use of the word "interpolate." I am not sure what words to use to differentiate from what Twixtor does (synthesizing intermediate frames using motion estimation) vs. what Vegas does, which you correctly point out is to just blend adjacent frames in varying strengths, by simply "cross-fading" one frame with the next.
ScorpioProd wrote on 1/31/2008, 11:20 PM
My friend is finding that in some of his vegs the slow motion is fine, while in others it isn't. Very odd.

Any other ideas?

Thanks.
ScorpioProd wrote on 1/31/2008, 11:22 PM
Oh, and yeah, we did check all of those project properties and they were set as per what Joran said.
Udi wrote on 2/1/2008, 1:03 PM
Try to clean the pre-renders.

Does the veg contain many stils? might be memory problem when many high-res stills are used.

Any other effects on the slo-mo events or tracks? try to remove them, including pan-crop or opacity.

If working in 32b - try to change to 8b.

Udi
ScorpioProd wrote on 2/3/2008, 1:08 AM
Good news! Well, we figured out the problem! Though we don't know why/how it happened.

Turns out that for some reason, clips were changing from the proper lower field first that they should be to progressive! So that was causing the slow motion problem.

Now the question is: What in the world would cause clips to change their fielding like that, on their own???

All the clips involved in these projects were cut from the same 3 hour long AVI captured from DVCAM. When you check the properties of the clip in Explorer in Vegas it says it's progressive. Which it obviously isn't.

But when you put it in the timeline, it was normally claiming to be lower field first, as it actually is. It's just when one started doing velocity envelope changes to it, it would revert to thinking it was progressive.

And as I explained earlier in the thread, loading different vegs, which had pieces of the same clip in them, rather randomly had the problem or didn't.

So although we've figured out what actually caused the slow motion problem, does anyone have any idea what would cause the fielding to switch on its own like that? Or why the full AVI reports itself as progressive in Explorer?

Thanks for all your help. :)