opencv imshow with waitKey too slow on Mac OS X 10.10.2 (using c++)
I am using opencv c++ on Mac OS X 10.10.2 to process video frames and display them. The performance of imshow with waitKey to display the video is extremely slow.
I have the following code which displays HD (1920x1080) grayscale frames correctly, except that it runs about 10 times too slow (ie 2 to 3 frames per second instead of 30 frames per second).
cv::Mat framebuf[TEST_COUNT];
//--- Code here to allocate and fill the frame buffer with about 4 seconds of video. This part works correctly.
//--- This loop runs too slow by factor of approximately 10x
for (int f = 0; f < TEST_COUNT; f++)
{
cv::imshow(windowName, framebuf[f]);
cv::waitKey(33);
}
Can anyone suggest how to get real-time or near real-time performance from opencv imshow()? I have seen many posts that state that they are displaying video in real-time or even faster than real-time, so I am not sure what I am doing wrong. Any help would be greatly appreciated.
I could be wrong but for me the problem is not with your code, but with your os/configuration. I've written a small test:
import cv2
import numpy as np
from random import randrange
img = np.zeros((1920, 1080), dtype = np.uint8)
counter = 0
while counter < 1000:
cv2.line(img, (randrange(0, 1920), randrange(0, 1080)), (randrange(0, 1920), randrange(0, 1080)), (randrange(0, 255)))
cv2.imshow('test', img)
temp = cv2.waitKey(1)
counter += 1
print counter
On my machine (Core 2 duo 2,6Ghz x64, 8gb ram, ssd) it took about 30 seconds for this test to complete. Run it and if you will get significantly bigger time than definitelly something is wrong with your laptop/opencv configuration/etc. I've used OpenCV 2.4.x on Mac OS X (it was 10.9 i think) and it was running fine. Reinstalling OpenCV is the most obvious solution which comes to my mind. When you remove OpenCV, use brew to install it again - brew install opencv --with-tbb --with-python --with-ffpmeg (or something similar - check using brew options opencv ) should be fine. First options tells brew to build opencv with tbb(thread building block - library for multithreading, sometimes can significantly improve speed), second to install python wrappers, and the last one to install ffmpeg(handle codecs etc).
You would have to reduce the input to the function wait key. Try using a lower number in the range of 2-5. It also depends on the other processes you have running simultaneously, try shutting down other processes and see if it improves
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