I've been having a lot of trouble with webcam recording due to videos dropping from 25/30 fps to 10 fps, which speeds the video dramatically. After attempting so many different things, it turns out the culprit (on MS Windows 10/11) is simply to focus the window, when the window that displays the recordings with cv2 imshow() (the one with waitkey attached) is being focused, webcams take 0.01-0.03 seconds to get a new frame with cap.read(), however when the window is not focused the time goes to 0.07-0.11 seconds, and the fps drop to 10 You can see a video of this behaviour here: https://www.youtube.com/watch?v=lGSksrtMZfA The simplified code looked like this: while True: camlog.debug("camera loop start %d, %s" % (framecount, str(datetime.now()))) stream_ok, frame = webcam.read() if pipeargs.source2 is not None: stream_ok2, frame2 = webcam2.read() else: stream_ok2 = True camlog.debug("camera read %s, %s" % (stream_ok, str(datetime.now()))) if stream_ok and stream_ok2: framecount += 1 camlog.debug("image show %s" % str(datetime.now())) cv2.imshow(self.tablename, frame) video.write(frame) if cv2.waitKey(1) & 0xFF == 27: break So the question is: can I give the window a priority similar to being on focus on windows while it is minimized? EDIT: The problem is not exactly that the window is not on the front for higher priority, but rather that it loses priority when it is minimized, so a work around is to not have any window (no imshow, no waitkey), so the recording is at 30FPS I tried to show the image on a different thread that the camera comunicates with a FIFO pipe, but the problem repeats itself, windows lowers the priority of the just-camera thread when the other thread is minimized as well, perhaps because they share same class space, or the cv2 module, not sure yet Continue reading...
