1 person found this helpful
The new format constraints check in After Effects CS5 will correct export settings that do not match the constraints of the output format. For a good explanation of why this mechanism was added to After Effects, see this article on Todd Kopriva's blog.
Regarding the QuickTime DV50 NTSC codec, it only supports a frame rate of 29.97. So your comp frame rate of 23.976 is corrected to 29.97 before the frames are sent to be encoded. You can have 23.976 inside of DV50, of course, using pulldown. In the Render Queue, open the Render Settings for your comp, enable Field Render and 3:2 Pulldown. See here and here for more information about those settings.
That you could export 23.976 directly to DV50 in After Effects CS4 and earlier without all this hassle isn't because it was correct to do so. It's that QuickTime simply doesn't care so much about using the correct settings. For most codecs you can dump almost anything in terms of frame rate, pixel aspect ratio, and frame size into the QuickTime container and it will probably work. But things got more complicated for After Effects CS5 because there's no 64-bit version of QuickTime. Now After Effects does the encoding for many of the default codecs. Rather than trust that QuickTime would stay lazy in this regard forever, After Effects CS5 sticks closely to the specifications for the codecs. Thus only 29.97 is valid for the NTSC codecs, save for the DV25, 24p-specific codec, DV/NTSC 24P.
-=After Effects QE/Adobe Media Encoder QE
Thank you for the thorough and helpful reply. I understand now, and I agree with the move to stick closely with the specs. The one thing I don't understand is how we're able to shoot 24p in DVCPRO50 straight from the camera (Panasonic HPX500), if the codec doesn't support it? I'm new, obviously, so I'm sure there's a basic principle I'm overlooking, like where pulldown originates or something.
1 person found this helpful
There's the rub. The camera really does not shoot 24P. What happens is the camera introduces a pulldown scheme and interlaces the video at 29.97. When you bring the video back into an editing system, you just tell it that it's 24P and it will look for the pulldown scheme separate fields to turn the video into 24P. It is not a very good system and it completely falls apart when you edit the footage if you don't do everything just right, but that's the standard.
Oh. I see. Well, that leads me to wonder two things: 1) why are we bothering to shoot in 24p, and 2) if it's for the film look - why don't we use a codec that doesn't make us jump through all these hoops?
I feel like I might have arrived at this party a tad late..
We do have codecs now that support true progressive but the DV50 codec was designed to output to NTSC video. Anyone going out to film from 24P video camera would not be rendering back to the original DV format. They would be bring the footage into their post workflow, separating fields, removing pulldown, working at 24fps, then rendering to a lossless or nearly lossless format to send to a film printer. The only reason that I can think of to render to a highly compressed format (any DV or MPEG format) is to come up with a file that is downloadable or usable on the internet or mobile device. I'd never use AE because AE cannot do multi-pass compression.
You cannot get 24P into a NTSC device. It's always interlaced and always at 29.97 fps. At the time the DV50 (all DV codecs) were developed there was no such thing as a progressive format for broadcast and the number of devices that would accept a progressive video stream could be counted on one hand.
Yea, I'm not outputting to film. But the reason I'm trying to stay at 24p in DV50 is because we were upgraded to CS5 mid-project and I'm trying not to jam up our editor's timeline with new frame rates or new codecs on the fx shots. Or is that not really an issue?