Roto Brush Freezing Taking Long And So Much Frames

appreciate the reply guys i am also trying to go back to version 18.0

4000 frames? That's a huge amount of time. You are risking running out of system resources and having a render or preview failure with that many frames. I would break up the shot into sections that were only five to seven seconds long.

You should also consider adding manual rotoscoping or generating a matte using color channels or color correction. We could give you better suggestions if we saw what kind of shot you were working with.

Rotobrush is not designed to be used on shots that are more than a few seconds. If you need more than 2 minutes of video, split the layer every five to seven seconds, pre-compose each trimmed layer, move all attributes and trim the new comp to the length of the layer. Rotobrush, the layer in the pre-comp, then go to Composition/Pre-render to render a high-quality production master with an alpha channel. When each section is rendered, delete the Comp you just rendered.

Rotobrush bloats the comp size, eats up resources, and can make AE unstable. If you do not render your Rotobrushed layers, you can get way too much data stored in the AEP file. Unless my shot is less than 5 seconds and very simple to roto, I always render and replace. When you use Rotobrush on a layer, that layer should be the only layer in the comp, and it should have no other effects applied to the layer.

I hope this ramble helps. 

Over 4000 frames is awfully long and if you haven't done a full analysis before it's quite normal that the freezing may take a moment, especially on a weaker system. This sounds perfectly normal. A more precise assessment of the situation would require specific info about your system and your project.

Mylenium

Try to post more information about your Device specs and your AE release number.