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Re: MJPG lag OpenCV
The docs seem to say that cv.QueryFrame returns "the just grabbed frame". If you have only 0.25 seconds of lag from an external camera through an embedded card to a PC and to a display, I would think you are fine. To measure the lag more accurately, consider something that the embedded board can control and a measurement made on the video capture. This will allow you to turn on an LED and determine how long afterwards it takes for the board to see the LED. In the past, I've done this using some clamps to hold everything in place and done the simplest code that measure the delay from a pixel's green value go from below a threshold to above the threshold.
If you have ten second lag, that seems like a significant issue. Running the LED test will help determine whether this is possibly caused by the transmission to the display or caused by the capture.
Greg McKaskle
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