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Joined: Thu Dec 07, 2017 11:48 am

Mnimizing latency raspicam C++

Fri Dec 08, 2017 11:28 am

I have read a couple of suggestions on these forums on how to minimize the latency (links below), but I still get a latency couple frames of latency using raspicam. More precisely.

Measuring condition: I use high-speed camera to see the delay between the change of brightness in a room and the time this change is seen on a CPU. I am capturing 1920x1440 grayscale images at 30fps via RaspberryPi3 and camera module, averaging the values of pixels and printing out this average Calculating the mean pixel value takes around a millisecond and the monitor, where I printout the value has refresh rate at 60Hz, which should not give me more than 10ms of "printing the mean value time".

Instead of seeing the change of average pixel value on screen after lighting up the room, it stays consistent for two or three more frames and only then changes. The delay varies from 110ms to 150ms, depending on the number of frames in-between the two changes. Even more strangely for me, this delay can be decreased by using lower framerate, since then there are less in-between frames - 20fps gives me ~90ms latency

Could someone explain why this happens and how to minimize this latency - I do not care for dropped frames or dropping fps below 10, my only request is to achieve minimum latency possible at this resolution.

Useful links:
viewtopic.php?t=186928 ... -operation

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