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Interlaced output from AE comp with progressive sources?

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Oliver Prothero
Interlaced output from AE comp with progressive sources?
on Apr 19, 2012 at 9:43:01 am

Hi, I’ve been doing a lot of reading on the forums, which are very helpful, but I still don’t think I quite have an answer to my problem.

The question I have is; Can I output 29.97 interlaced renders of my AE composition, where all the source footage is progressive? And if I can, does the progressive source footage and the composition itself need to have a framerate of 59.97?

Hoping someone can help verify if I’m on the right track, or point out where I’m going wrong!

Here are some more details:
I’m working in Adobe After Effects CS5, trying to create a video ad for broadcast on regional TV in the US, with an additional version for broadcast on web. My source footage is progressive (it can be either 29.97p or 59.94p at this stage) and I’m doing a lot of time remapping (speeding up, not slowing down), animated 3D camera moves between footage, scaling, chroma keying, and so on.

Ultimately I need to output three different versions:
A 1080 29.97i square pixel ratio version for HD tv broadcast
A 720x480 27.97i 0.91 pixel ratio version for SD tv broadcast
A 1080 29.97p square pixel version for web

Creating the last output from the list above should be simple as it’ll be progressive.
However, creating the first two is causing me some concern as they’ll need to be interlaced and, as I understand it, the field order will be different for both also, not to mention the different dimensions and pixel ratio between HD and SD. But at this stage, my main concern is the interlacing and necessary framerate.

I read a very helpful tutorial from Marco Solorio here on Creative Cow about interlacing progressive footage, but I think it addressed how to convert progressive footage for use in an interlaced project, which isn’t quite the same problem.
Here’s the link to that tutorial:

What I took from his tutorial though, was that, in order to render 29.97 interlaced output from a progressive source, the source needs to be 59.97p, not 29.97p.
Is this the case?

If anyone has any thoughts, they’d be most appreciated. Also happy to give more detail if required.

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Jon Bagge
Re: Interlaced output from AE comp with progressive sources?
on Apr 20, 2012 at 11:42:19 am

Someone else will have to comment on US issues of 29.97i versus 23.98p. I'm pretty sure there is no standard for 29.97p anywhere. (I could be wrong)

You have two overall choices regarding interlaced/progressive: The simplest is to create the whole project 1080p, and then make the other versions from this master. Some compression software can 're-interlace' which will add inbetween frames to add interlacing to progressive footage. But you may be ok with simply converting from progressive to interlaced, which will make the two fields from the same point in time.
(This may be different if you can master to 23.98p I think)

Your better quality but lots more work option is to render the three versions out of after effects in the correct format. To do this, set your comps up for 1080 29.97. Do all your animation/whatever.

You can now render progressive for the web straight out.

Turn on field render (upper) for the broadcast HD version. Render again.
This will cause AE to render an additional frame inbetween the normal frames and use this for the second field. If you have progressive footage the second field will be from the same point in time as the first. If you're using Time Remapping AE should properly render the interlaced frames as long as you use Pixel Motion interpolation.

Drop your master comp into a new comp with correct size for SD and scale it to fit. You can try to turn on collapse transformations for better overall quality, but depending on the kind of stuff you have in your master comp this may not work.
Turn on field render (lower) and render again.

Job done.

For upper/lower field you should be fine simply changing one to the other when you render provided your project contains progressive footage, animation created in AE, or footage of the correct field.

Rendering upper field in a project containing lower field footage or the other way around will look very bad and you will need some workarounds.

Hope this is of help. Someone else will have to help you with US specific issues.

Jon Bagge - Editor - London, UK
Avid - FCP - After Effects

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