720p to 1080i without tweening?

corug7 wrote on 7/19/2007, 2:20 PM

I'm working on trying to get a Blu-Print compliant 1080i MPEG-2 out of Vegas from a 720p source. The issue I'm having is that Vegas keeps tweening the interlaced fields, rather than rendering two similar fields per frame.

My settings are as follows:

720p project with deinterlacing set to blend or none.

Clip is 1280x720 Quicktime Animation, with properties set to progressive, and resampling turned off.

I am rendering to a 1080i file instead of a 1080p file for compliance reasons. Anyone know what I'm missing? Thanks.

Corey

PS, also, if anyone else here is using DVDit Pro, are there any other settings that need to be checked to make the Blu-print output compliant?

Comments

farss wrote on 7/19/2007, 2:56 PM

You cannot have two identical fields in a sequence. It's too early in the morning to try to describe what a horrible mess that would create visually but it would be a mess of some sort. If nothing else you would loose half the vertical resolution.

Bob.

farss wrote on 7/19/2007, 3:29 PM

OK, had coffee.

What is the fps of your source and destination?

At a rough guess your source is 720p24 and you're trying to output 1080i60?

If so then Vegas is quite likely inserting pulldown and that's about the only way to make that conversion. In this case you will get some parts of the sequence where merged fields show interlace artifacts. For a better explaination Google "pulldown" although I think the Vegas manual explains this as well.

If your source is 720p30 and it's going to 1080i60 then no pulldown is needed. What you should get as the output is 30PsF 1080. In this scenario the two fields are not identical as each field contains half the lines of the original frame. If you merge the two fields you should get back the original frame. That's what you should see on the Vegas preview monitor at Full - Best.

Bob.

Chienworks wrote on 7/19/2007, 3:33 PM

Would disabling resampling force Vegas to not do the pulldown, whether it might be needed or not? If so, then that should prevent the tweening. The frame cadence would be off then, but that might be less objectionable than the tweening.

farss wrote on 7/20/2007, 1:25 AM

Assuming the source is 24p then is say 10 seconds there's 240 frames. To create the 10 seconds at 30fps we need 300 frames. If we keep the fps the same so we don't alter motion Vegas (I assume) will have to duplicate frames. This as you say might produce some really wierd cadence and judder.
I'd assume if this was such a wise thing to do then why is it the norm to add pulldown?

Or have we misunderstood the problem perhaps. Maybe Vegas hasn't been told to add pulldown and therefore is resampling and producing those tweened frames.

Bob.

Chienworks wrote on 7/20/2007, 4:05 AM

Ahhh, that's a very good point. The pulldown is there to fix the cadence problem without tweening ... assuming the pulldown is actually there in this case.

JJKizak wrote on 7/20/2007, 7:40 AM

"Tweening". Is this a new term I have to memorize?

JJK

farss wrote on 7/20/2007, 7:45 AM

YES.
Use in in conversation a lot, like "I did a lot of tweening today". This will earn you lots of respect, they'll be as clueless as you about what it means but if they don't know and they assume you do then obviously you're more knowledgable than them.

It's a term from animation. The animator creates only the significant frames and an underling draws the in between frames, i.e. does the tweening (betweening). Oftenly sent offshore where labour is cheap.

Bob.

Spot|DSE wrote on 7/20/2007, 8:03 AM

LOL "Tweening" as a buzzword. I'll have to remember that.
Hmm..."I'm not really angry, just kinda tweened."
Just tried an experiment that everyone can do.
For testing, we have a bunch of clips that are numbered, one per frame.
They are five seconds long, each, in Cineform format.
24p (generated source) 25p, etc.
You can roll your own. Render them, then use them for testing.
You'll be surprised at the result of the 24p to 60i (or other framerates) in Vegas.

corug7 wrote on 7/20/2007, 2:18 PM

Thanks for all the replies, fellas.

Guess I should have been more specific about framerates. 720p30 to 1080i60. Farss, you are correct in that I am looking for 30PsF. However, when playing back on a progressive monitor I am getting interlacing artifacts, and I'm not seeing that when using other encoding software (StreamZ w/Mainconcept plug-in). Since the codec is very nearly the same, I have to believe I am missing a tick-box or something along those lines. I believe I have resampling disabled, so there should be no reason for frame blending. Thanks.