Rotobrush 2 - random selection

Question

I have a rotoscope project, a clip about 1:30 long. It's a person at a podum, I'm attempting to replace the background with a clean still frame because the live background has people looking silly.

I'm new to AE, and certainly Rotobrus 2. Following a few tutorial videos, I've created a mask that includes just the desired forground.

Problem 1: Rotobrush precision is random. I've tried varying the size, contrast setting, etc, but when I let AE propagate for about 1 second's worth of footage, and find an error in the mask, cleaning it up with the rotobrush is a study in repatitive futility. How it selects what it selects seems random, and unpredictable. Is there a way to trim the mask fully manually without using the AI rotobrush?

Problem 2: This has happend several times now. I'm working on the clip about 1 or 2 seconds at a time, propagating, then cleaning with key frames as needed. Sometimes it's every couple of frames, sometimes the whole 2 seconds works fine. But then "something happens", and AE goes off to propagate the entire clip! Thousands of frames, hours and hours of chunking along. Is there any way to stop propagation if you're really not ready to do the whole clip?

Problem 3: Saving the project (as a new copy), Quit AE. The next day, I relaunch AE, open the project, and the first thing AE wants to do is re-propagate everything. Again, hours of cruching along, during which I can do nothing on the project, and very little else ont he computer. Any way to save all of the propagation information and NOT have it re-do the whole mess every time the project gets closed and re-opened?

Last Q is about work flow. I can't work with the Rotobrush set to "best", it's just bogging everything down. Is it valid to work through the clip touching up the mask every so often, then when it's done, change to "Best" and go to bed while it works? And at what point do you "freeze" propagation?

Just a comment about Adobe support. The available documentation on the current AE is sketchy at best. I have to dig and dig for the most simple function. Yesterday I took the above questions to Adobe Support, got in the chat que...and gave up after 90 minutes of no help. Today I got back the que again, got someone on chat. Spent two hours with only about 10% of this agent's attention (mostly just waited for any response at all), during which I was directed to uninstall AE, reinstall it with a direct download link provided, which installed the 2019 version, not current, so my project wouldn't open at all. When I called this to attention, the agent provided another link to a less-old, but still not current version. Nothing else was accomplished. Wasted two hours.

So the last question is: what's the best way to get support for CC aps? Clearly chat ain't it!

Thanks in advance.

Rick Gerard · Answer

Not all shots are suitable for Rotobrush. Rotobrush looks for edge contrast. Anything that matches the pixel values of your subject in the background will cause the automated process to fail and require that you make manual adjustments. Without seeing the shot or at least a still frame of the shot we can not really give you any meaningful suggestions. Please embed a screenshot using the toolbar so we can see what you are dealing with.

If you are new the User Guide is a great place to start and this forum is pretty good at pointing you to solutions. Just make sure that you include screenshots with the modified properties of the problem layers showing. Select a layer, press 'uu' then take a screenshot of everything. Give us workflow and design goals.

One other note. If your final movie is going to include the entire minute and thirty shot and you must replace the background you'll be in for a lot of work. Only spend time editing frames that are going to be in the final project.

If you need the entire 1:30 clip repaired break it up into sections that are no more than about 20 seconds long by splitting the layers then run Rotobrush on each section separately. If you manage to get Rotobrush to successfully propagate on the entire clip it's going to take AE a long time to freeze the entire shot, and if you need to fix anything after it's all done you'll have to go through the entire process again. If you split up the shot into sections that are 20 seconds or less by splitting on the end of sentences or changes in position, and you need to fix something you will be dealing with only a few seconds of footage instead of the entire shot.

There also maybe some other options. I remove backgrounds all the time. Only a few of the shots I've worked on in the last two years required anything more than a few seconds of Rotobrush work. Most of my roto work is either done in mocha or on a Motion Stabilized clip, and most of my background replacement projects are a combination of track mattes, a procedural matte, and some other trickery. Show us the clip and we can give you some meaningful suggestions.

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