I made a test where I added this on a new video track with screen blending in one of my somewhat complex projects that is 2:28 minutes. In version 19.09 it took 6:09 to export. In version 19.10 it took only 4:22.
My project is not using Mask:From File. I made another test with that included on the clips in the video track I added. In version 19.09 it took 4:13. In version 19.10, it took 4:06. These times are shorter than previous tests because the clip Mask filter created less work for the track filters and blending.
I did not test with WebVfx cube because:
- I do not have it.
- It does not come with Shotcut.
- No code in WebVfx changed between these versions.
Like another performance regression report and my subsequent tests, I am not reproducing it, and it is probably due to a specific combination of things in your project. I decline to profile other peoples’ projects at this time. If the regression is where I suspected as mentioned in my first reply, I have not run into it with these tests, and the bug fix is very important to image integrity. General image-processing performance improvements are already on my road map.