AE genius needed...footage interpretation questions

[grahamdunn]

Hi all, please help! I've always interpreted interlaced footage in D-Beta as lower fields and just gone on with my life, but now I'm finding the files I render out look different.

Basically I'm getting interlaced SD footage as targa sequences and importing them into AE. I interpret the footage as lower fields (no pulldown necessary...this has been added in when the footage is transferred to D-Beta and our AVID only wants 29.97) and do my compositing, then render out. I do NOT set the footage to lower fields when I render out, I simply render back out as targas. When I open the same frame of the raw footage I received and the footage I rendered out after compositing, the original frame looks ripped like an interlaced file usually does (and like it does in AE before I interpret it as lower). The footage rendered out once I interpreted it, on the other hand, looks progressive (no ripping, like what the footage looks like after AE interpretation).

What does the interpretation do? It is not de-interlacing, though the overall look is the same, because there's no processing or anything that takes time...

Should I interpret as lower and then render back out as lower? We've tried in the past and had problems (it looks like it's taking lower fields and then setting it to lower fields yet again, causing a fielding problem when we reimport).

When I interpret and render, why does the file I render out look progressive? It looks absolutely identical when we reimport into the AVID at 29.97, but the targas before and after AE look different.

I thought the interpret fields setting was temporary just so that you don't have to deal with the interlaced frames ripping.

Thank you!

[milksac]

You're kinda all over the map there Graham.

I'm no expert but I'll try to help.
In the simplest terms, Interpret footage is a way of telling AE the needed information about the source footage. (This is 24p or this is 29.97 interlaced, etc.) From reading your post I'm not sure if you're sourcing from Digibeta or Targa files. Figure out what your source footage is and interpret it appropriately.

The second thing you need to do is find out the final destination for the footage. An Avid for online? The best way to find out is to talk to the editor.
If you're outputting for Avid you should output a quicktime with either Avid's Meridien codec or the Animation codec, again ask the editor how he/she wants the file. Once you know how they want the file set it up in the render que and start rendering.

If you really want to understand how AE handles the footage the you should get a hold of Trish and Chris Meyers Creating Motion Graphics book. It explains all this is great detail.

good luck.