​crop and brightness calc?

[JJHP3]

Hello! I had what I thought was a simple idea: run a video clip through 12 crop actors thus dividing the clip into sections, 4 across and 3 down. I want to produce triggers from both medium and bright moments in each of the 12 sections. I used the CalcBrightness actor. On my 10 year old MBP = 300+% cpu and on my 2019 iMac = 75% cpu. Surprised to say the least. Testing shows me that it is not the crop, but the calc that's adding so much processing. Is there an easier way to determine the brightness of a section of a clip?

The movie I used was very dark with white dots... which is why the limit-range actors are set so low.

Thanks, John

cropncalc.izz

[DusX]

@jjhp3

The calculate brightness actor adds the values of all pixels together to determine the brightness of the target rect. With HD video this can be a lot of calculation.

Two methods I have used to reduce this load are:

• scale the video to 1/2 (or another fraction eg: 1/4) before input to the Calculate Brightness actor. Since the scaling is done on the GPU it doesn't add any work to the CPU, rather it reduces the number of pixels the cpu has to calculate for. Generally the scaled image should have nearly the same brightness as the original un-scaled image.
• limit the frame rate to the Calculate Brightness actor (using the Multi Block). This reduces the responsiveness somewhat but also directly reduces the CPU load, so it can be a useful tool.

[JJHP3]

@dusx Thank you for such a quick and helpful answer... at 1/4 size, reduced cpu from 77% to 13% on my iMac.   - John