WCAG 2.3.1: Keeping the Flash Area Small Enough (G176)

[nezihtopaloglu]

I have a question regarding the area requirement in flash detection. In G176: Keeping the flashing area small enough, the following expression is made:

Since the criterion is 25% of any 10 degree visual field, any single flashing event on a screen (there is no other flashing on screen) that is smaller than a contiguous area of 21,824 sq pixels (any shape), would pass the General and Red Flash Thresholds.
1024 x 768 was chosen because it represents the most common screen size. It also works with higher resolution screens since the tighter pixel density would result in a smaller and safer image size.
Users with lower resolution displays or that enlarge or view their screens closely would have a higher risk depending on the viewing distance. To address the needs of this group, G19: Ensuring that no component of the content flashes more than three times in any 1-second period should be used since it is independent of screen resolution or viewing distance.

I have three questions:

1. If I analyze a frame of a 1024x768 resolution video, should I scan any 341 x 256 pixels rectangular region on the frame, to find out whether there is a flash of 21824 pixels?
2. If my video resolution is lower than 1024x768 pixels, what should I do? If I am not doing any area checks, then even one-pixel flash violates the thresholds?
3. If my video resulution is higher than 1024x768 pixels, should I still check 21824 pixels in a 341x256 rectangle, or should I scale these thresholds accordingly?