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Using Progressive footage in comp that will be interlaced... how to interpret?

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Christian Glawe
Using Progressive footage in comp that will be interlaced... how to interpret?
on Oct 26, 2006 at 10:02:13 pm


Hey, gang...

I'm using some HD 1920 footage in a composite for standard def NTSC projection... the footage appears to be progressive scan (i.e., no fields that I can see)

My question is how do I interpret this footage? Separate it lower field? Leave it no field? Final render will be lower field first (DVCPro 50 codec)

Thanks!


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Straight A
Re: Using Progressive footage in comp that will be interlaced... how to interpret?
on Oct 26, 2006 at 11:39:20 pm

If it is progressive then you have no choice other than to leave the seperate fields option set to 'off' any other choice will simply reduce the vertical resolution by half.

This will have no bearing on your plan to output as 'lower field first (DVCPro 50 codec)' other than the section with the HD footage will be progressive and may not match your interlaced footage too well.

If the footage miss-match is obvious and a problem you could de-interlace your interlaced footage or ...(now this is where it gets compex for the faint hearted)... turn your progressive footage into interlaced footage by using the time warp plug-in to stretch it to 200% in length (half speed / twice as many frames) then interlace this footage back down to normal speed interlacing every two frames (effectively becoming fields) into one frame.

Got it ?


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Christian Glawe
Re: Using Progressive footage in comp that will be interlaced... how to interpret?
on Oct 27, 2006 at 1:39:10 am


Yikes....

Well, that's definitely an interesting thought... this video is a combination of progressive HD footage, and motion graphics, that will be projected in standard def (DVCPro deck). There's no standard def footage to match to.

Anyone else?


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mark harvey
Re: Using Progressive footage in comp that will be interlaced... how to interpret?
on Oct 27, 2006 at 1:44:50 am

Leave it progressive and introduce the fields in the render. Should be fine.

Mark


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Steve Roberts
Re: Using Progressive footage in comp that will be interlaced... how to interpret?
on Oct 27, 2006 at 1:50:25 am

Straight A is right:

- if the footage is progressive, you interpret "field separation off". No questions, no arguments.
- this is not affected by your choice of rendering with or without fields.

But I'd add: why interlace in the render? You don't have to. I only render interlaced if I absolutely have to, and that rarely happens. It's an aesthetic choice.

(The only choice you have to make is: if you render fields, you must pick the correct field order for the hardware that will be laying off to tape.)

But as I said, you don't have to render fields if there is no interlaced footage involved.


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Christian Glawe
Re: Using Progressive footage in comp that will be interlaced... how to interpret?
on Oct 27, 2006 at 1:55:05 am


That's interesting...

I guess I had always sort of assumed that if you have motion graphics, you wanted to render with fields... this particular piece features a lot of fast moving elements (shapes, text, etc.).. and the layoff to tape will be done on a Final Cut system with a Kona 3 card to, I think, a 1200A DVCPro deck.

I guess it would be worth a test to render with no fields.

This whole thing got prompted by me pulling in a "fielded" render back into After Effects, and I noticed it didn't look as sharp as my original comp... thought I may have been doing something wrong.


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Steve Roberts
Re: Using Progressive footage in comp that will be interlaced... how to interpret?
on Oct 27, 2006 at 2:48:19 am

Here's how it goes:

If you're creating motion graphics from scratch, it's your choice: render fields or no fields. Just make sure you pick the right field order if you render fields.

If you're creating motion graphics over field-rendered footage that you will not change in any way (or footage that you will neither blur, move, rotate nor distort the pixels), you should interpret the footage with field separation off (leave as is), then render with fields if you want the motion graphics to match the footage. And you usually do.

If you're doing the above with no graphics (say, just color-correcting), you should interpret with field separation off, and render with no fields. This just leaves everything as it was: a series of frames with comb-like images on them, only now coloured slightly differently. Actually, in this case, rendering with fields wouldn't change anything either, since there's no motion to render interlaced or field-separated footage to reassemble.

If you're creating motion graphics over progressive footage (whether you distort it or not), you interpret the footage field separation off, then render with no fields so the graphics match the footage.

If you're creating motion graphics over field-rendered footage that you expect to move/rotate/blur/distort pixels, you must interpret with fielld separation on, and the choice of field order is crucial: you must pick the correct order. Pick one, then alt-double-click on the footage, then step through the footage in the just-opened layer window with the PageDn key. If it jerks back and forth, you picked the wrong field order. If it only moves on every second keystroke (if you separated fields), the footage is progressive. Once you get the field separation right, you can choose to render with fields or without. Do a test.

You should get the discs by Chris and Trish Meyer called "Videosyncrasies".


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Christian Glawe
Re: Using Progressive footage in comp that will be interlaced... how to interpret?
on Oct 27, 2006 at 3:29:04 am


Cool! Thanks for the insights!

I have Chris and Trish's 3 AE books, but didn't know about "Videosyncracies"... thanks a lot for the info!


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Chris Smith
Re: Using Progressive footage in comp that will be interlaced... how to interpret?
on Oct 27, 2006 at 6:02:29 am

Unless you're going for the "hyper real" video look, then render progressive. Normally ppl hate the look of interlaced video because it's really 60 new movements a second where doing progressive is approx 30. Just like a film camera. It's progressive obviously because it exposes an entire frame. So unless you've ever been to a movie and thought "I really hate this look, I wish it was way more hyper real looking like a soap opera or news", then by all means render fields. But unless you're trying to go for a retro 80's switcher type of video movement, I would do progressive renders with motion blur turned on which will give you the most film like motion.



Chris Smith
http://www.sugarfilmproduction.com


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Straight A
Re: Using Progressive footage in comp that will be interlaced... how to interpret?
on Oct 27, 2006 at 2:53:22 am

Whoops!

I thought you were mixing fields and frames (interlaced and progressive).

If all your source material is HD (1080p) progressive then do not interpret to either upper or lower fields, leave it on 'off'

[although - just to throw a spanner into the works!! - by the time you reduce HD down to NTSC SD - you throw away so much information that your original progressive footage will look much the same whether it is set to 'off' - 'upper' - or 'lower']

I personally would not render the final project to fields either, I simply prefer the look of progressive frames, but that is simply an aesthetic and not technical choice, see what you prefer.


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