Efficiently capturing distributed pixels from display output (TX2 NX)

Hi,

I have a setup with a TX2 NX module which is comparable to a dev-kit with L4T 4.6.1 and the related sample root filesystem on it. The board runs an application which outputs some kind of video stream with an overlay via HDMI (the application uses the SFML-library to do this).

To achieve a safety goal, I need to periodically (~25Hz) capture 256 defined pixels from the display’s output. These pixels are evenly distributed over the entire display frame (except of some excluded areas).

A quite easy solution to get those pixels is to capture the screen using the X-Server-API-call to XGetImage(…). Basically this is like taking a screenshot and afterwards extracting the required pixels from it. However, this is (obviously) very inefficient and consumes a lot of CPU-power (~15%).

Does anybody have an idea how to capture those pixels in a more efficient way?

Thanks in advance!

Maybe you can use a external capture card? We don’t have any existing tool for this.

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