The CPU load increases from 120 to 525 percent, the FPS decreases from 50 to 13. What is the reason for this, is the video data passed through the videoscope instead of being picked up?
Handling and calculating the data shown on the Videoscope is CPU intensive.
BUT the good news is, if you compare using the Videoscope on the Compositor as opposed to using the Videoscope plugin on the timeline, it is quite a bit better as there were some coding improvements incorporated. Here are fuzzy stats. YOUR MILEAGE may vary (and there is nothing scientific about my runs). Forgot to mention that I do not have Play Every Frame on.
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Big Buck Bunny 3840x2160 on a 16-cpu laptop with 32 GB memory:
Compositor Videoscope -- 470% cpu & 15 fps
Plugin Videoscope -- 800-900% cpu & 2.6 fps
No Videoscope -- 170% cpu & 60 fps
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Same file on Dec. 2019 Cinelerra-GG
Plugin Videoscope -- 830-900% cpu & 2.75-3.4 fps
No Videoscope -- 170-225% cpu & 60 fps
Okay, so the videoscope needs a lot of CPU. But that doesn't explain why the frame rate (fps) decreases. Your example shows that ~ 5 of the 16 cores are used. So there are still ~ 11 in idle and still the fps breaks down. As a layman I ask myself how that can be.
Because it is a serial process. First, it reads an image and then does the calculation so it has to wait to show the next image until that calculation finishes.
In my statistical report, it is very important to note that I had Video Driver set to X11 and NOT OpenGL. When driver is OpenGL with my graphics card, the FPS is significantly lower at only about 3.5 fps. Play Every Frame versus not, makes little difference.
Don't go into actionism right away. By the way, the link to the display of my posting is located right below the comments (this is due to the forum software).
