Improve AE render speed when rendering transparent frames

[Rafael Dessotti]

Hello all,

Is there a possiblity to improve the speed of AE render when rendering transparent frames? I have a composition that is 1h longer, but it contais just 5% of actual content. The other 95% is just transparent frames.

Well, why not render just the 5%? Because this rendered video will be overlayed on top of a master video in a automated system. So this transparent "gap" is important to make the 5% of the video, that has important stuff, be alinged correctly on top of the master video. (I hope this make sense 🙂

AE takes the same time to render a transparent frame as it takes to render a frame with a image. Is there a configuration that would make AE render this kind of frames (transparent frames) faster?

Thank you,

Rafa

[Rick Gerard · Accepted solution]

Pick a codec that renders quickly like GoPro Cineform or choose to render an image sequence. Make sure you are not using an unnecessarily high frame rate. Depending on the motion in your frame you may be able to successfully cut the frame rate in half. Loony Toons, in fact, most hand-drawn cartoons are 12 frames per second with every frame repeated twice so they can be played back at 24. 

Unless the project is one continuous shot that is one hour long with no possibility of cutting it up you can break it up. I almost never string more than two shots together in one comp. Most of my comps are seven seconds or less because I work mostly on movies, corporate videos, commercials, and it's all live-action. The average time between shots in modern productions is around 4 seconds. 

If I had a project like this, I would make the comps as short as possible, and as soon as I had a few seconds successfully designed I would start rendering. If the render takes longer than a few seconds a frame I almost always render image sequences because you never have to re-render the whole thing to fix 20 frames the client doesn't like in the middle of the comp. 

If you are being paid for this work then invest in a background rendering option like RenderGarden. I have several and it is my favorite. On my main system render times drop by about 75%. A comp that takes 20 minutes to render using the Render Queue might take 30 minutes to render in the Media Encoder. That same sequence will render in five or six minutes with a good 3rd party background rendering option. Any comp I have that takes longer than a few seconds a frame to render is always sent to a background renderer. 

[Rafael Dessotti]

Thank you Rick, for your reply.

Unfortunately we are tied to a workflow that uses ProRes 4444 (I shoud have mentioned that, sorry). And we can't change that, at least for now.

About third party background renders, we have developed one. It is similar with RenderGarden, but with some improvements, considering our workflow. It works good, but I was wondering if AE has any render config that would make it faster when rendering blank frames (Y: 0, U: 0, V: 0, A: 255).

Thank you again.

[Rick Gerard]

If your comps take a long time to render I would consider rendering image sequences. They may be faster. It is very easy and quick for image sequences to be transcoded into ProRez. 

If your empty frames have any layers in them with opacity set to zero or they are moved out of the frame you might consider setting in and out points for those layers so that the render engine isn't looking for pixels. It might speed things up a bit.

[Warren Heaton]

Layers are hidden in the 0, 0, 0, 255 areas, correct?  Or you have gaps?  

• If you have Layers with the Opacity set to 0%, AE will still calculate the Layer properites.
• If the Layer is hidden or there's no Layer Time Span, AE will advance to the next frame.

ProRes 4444 is already pretty fast.  If the system that you're sending the rendered file to will accept Uncompressed/None Compressed with Alpha, you could remove compression from the render time.  There's also faster processors and faster storage media (unless, of course, you're arleady on high GHz i9s with lightning fast Flash Storage).

Did you see the news that dropped today about Multi-Frame Rendering now being available in the AE Beta?  
https://blog.adobe.com/en/publish/2021/03/10/multi-frame-rendering-now-in-after-effects-beta.html#gs...

That's probably going to give you the better speed boost.

[Rafael Dessotti]

Thanks Warren for the reply.

We have gaps on our sequence like you can see in the picture. I was expecting that AE would render faster those frames that are transparent. On my system I got a average of 30 frames render per second when rendering those gaps. My system is far from a high-end system but because it is blanks frames I was expecting AE to be more faster. (Just for comparison purpose ffmpeg has an average of 4k frames per second when rendering blanks frames)

Also thank you so much about the news. I was hoping that the multi frame render would speed the render of those gaps but not 😞 Ae renders just one frame at time. 

[Rafael Dessotti]

Just correcting:

(Just for comparison purpose ffmpeg has an average of 4k frames per second when rendering blanks frames)

By @Rafael Dessotti

This is not when ffmpeg is encoding. You get this speed when you use 'stream_loop' option. This makes ffmpeg copy a frame(s) over for a period of time, without re-enconding.

[Warren Heaton]

You could do the assembly in a Premiere Pro Sequence, filling the gaps between Comps with pre-rendered Apple ProRes4444 with Alpha.

ProRes takes advantage of Premiere Pro's Smart Rendering feature.  Sending a PR Sequence with A mix of Comps and ProRes clips to Media Encoder exporting to QuickTime ProRes should get though the transparent slug time spans faster than coming directly out of After Effects.

[Rafael Dessotti]

I didn't know about this Smart Rendering feature that Premiere has. I made a project on Premiere with spread pngs and with big gaps between them and the render was super fast. It rendered 1h video in less than 20 seconds. This is the behavior I was expecting on AE.

We have a constraint on using Premiere. It export ProRes 4444 with straight alpha instead of premultiplied alpha. And this is a issue for us. We sent this to Adobe some time ago but not sure if they change that, (or if they will do at all).

Something interesting: Sending a sequence with gaps from Premiere to AME render very fast. But if I import a AE comp with gaps to a sequence on Premiere then send it to AME, it renders slow. Also if I send the same comp from AE to AME it renders slow. This comp doesn't have anything special, just png and gaps. 

I sent a email with a sample project to Adobe. Let see if they can reproduce this issue.

[Rick Gerard]

For 99% of all footage with an alpha channel, Straight Alpha is preferred. Premultiplied Alpha tints the transparent edges the color of the background color you set in After Effects. No compositing or editing app is set to use Pre-multiplied with alpha as a default compositing method. The same thing goes for Premiere Pro. If you set a background color you will get tinted edges. If you leave it black, the antialiased edge will just be a little thinner.