imshow() with desired framerate with opencv
I don't believe there is such a function in opencv but maybe you could improve your method by adding a dynamic wait time using timers? timeit.default_timer()
calculate the time taken to process and subtract that from the expected framerate and maybe add a few ms buffer.
eg cv2.WaitKey((1000/50) - (time processing finished - time read started) - 10)
or you could have a more rigid timing eg script start time + frame# * 20ms - time processing finished
I haven't tried this personally so im not sure if it will actually work, also might be worth having a check so the number isnt below 1
Is there any workaround how to use cv2.imshow() with a specific framerate? Im capturing the video via VideoCapture and doing some easy postprocessing on them (both in a separeted thread, so it loads all frames in Queue and the main thread isn't slowed by the computation). I tryed to fix the framerate by calculating the time used for "reading" the image from the queue and then substract that value from number of miliseconds avalible for one frame:
if I have as input video with 50FPS and i want to playback it in real-time i do 1000/50 => 20ms per frame. 
And then wait that time using cv2.WaitKey()
But still I get some laggy output. Which is slower then the source video