Rotobrushing Advice

[Synthtony]

I am fairly new to using the roto brush tool and have a couple of issues I am hoping to get some advice on. 

The first is in regards to rendering speed. Like many I have read, the AI works good for 1-2 seconds of footage and then begins to bog down eventually coming to a crawl. I am trying to make sure I have cropped footage comp size to just the area I need to roto and I am trying to cut the footage down to small pieces and then string them together. Still, the propagation of the frames whether I am letting AI do or am manually adjusting just gets untenably. How can I speed this up?

The second issue is in the rendering of an adjusted frame. When I stop the AI to make a manual adjustment after I release the mouse the adjustment is rendered. I have to wait for that to finish in order to either further refine or move onto the next frame. All well and good when it is propagating fast, but when it is slowing down to take 5 to 15 seconds to render, I don't want to sit and wait on it to finish. But if I move to another screen or program to check or work on something, the propagation stops until I come back to AE, and then it starts over. In fact, whenever I leave the program in active Roto mode, each time I come back the project has to refresh. Is there a way to stop this from occurring?

If anyone has or wants to point to any good roto tip for speeding up the process, I would be appreciative.
Thanks.
Computer Spec:
Windows 10
Intel Xeon CPU E5-1620 v3 @ 3.50GHz

32.0 GB DDR Ram

NVIDIA RTX2080 Super Video Card
AE 18.2.1

[Mylenium]

Impossible to advise without any info on your footage and what specifically needs to be done. From employing a completely different workflow without RB to switching to basic mode and effectively turning off the AI that way or even going back to v1 this could be anything. Just because Adobe are advertising it as the end-all-be-all doesn't mean that RB is actually always the best tool for many given task. You know, a few years ago this didn't even exist and people still got sometimes amazing stuff done... So for what it's worth, provide a screenshot/ reference frame and tell us what you have in mind.

Mylenium

[Synthtony]

Here are the footage specs. I am working with four 6 second clips 1920x1080 at 59.94FPS. Clips are h264.MP4 encoded. I am simply trying to roto in an image to appear behind the subjects in the clip. I have attached a screenshot of the workspace. The logo image never exceeds below the bottom of the pink outline in the screenshot. So that is where I tried just framing a composition at 1920x560 to see if it would improve speed, but it did not.
As far as other workflows, I did try to work with a track mask but it just comes out too jerky for my taste no matter the algorithm I use. I personally do not want to take the time to manually keyframe a mask which is why I wanted to try and see how the rotoscope did. 
On a couple of clips, I was able to get a good final render as I think the background and roto selection were simpler and better defined. But on this clip and the others I have, it just chokes after a couple of seconds.
Thanks for any further advice.

[Mylenium]

As I figured... This is exactly one of those scenarios RB was not meant for. There's some notable depth of field and if the protagonists move across different depth planes, that would complicate matters even further. The lack of vertical structure in the roof also may work against you, as the algorithm would simply travel along the horizontal lines forever, never detecting a "stop" pattern. Same for the brightly colored shirts. The underlying vector field is likely looking smooth like a baby butt with not many discernible structures and the AI has to make up for it. With all that in mind I really think you need to face the facts and can't avoid some masking. Using AE's own mask tracking or mochaAE this shouldn't really be that dramatic. If the clips realyl are only 6 seconds long, that's about two hours and a cup of coffee for all of them, including manually tweaking some masks.

Mylenium

[ShiveringCactus]

After your post, I intend to estimate all my working duration in units of coffee. 😄

[Synthtony]

Mylenium, Thanks for the input. That is the kind of stuff I don't know and want to. I appreciate the input. I'll get the coffee pot going.