Playing a movie in OpenCV - python-3.x

Question

I get the following error while trying to show a movie:
cv2.imshow("Video Output", frames)
TypeError: Expected Ptr<cv::UMat> for argument 'mat'
The commented-out lines are my attempts to fix the problem, but I still get the error.
What am i doing wrong?
import cv2
import numpy as np
vid = cv2.VideoCapture("resources/Plaza.mp4")
while True:
frames = vid.read()
# frames = cv2.cvtColor(frames, cv2.COLOR_RGB2BGR)
# frames_arr = np.array(frames)
cv2.imshow("Video Output", frames)
if cv2.waitKey(1) & 0xFF == ord('q'):
break

Answer 1

Better implementation would be:
Check if the video is opened using vid.isOpened()
vid = cv2.VideoCapture("resources/Plaza.mp4")
while vid.isOpened():
If the frame is returned successfully then display it.
ret, frames = vid.read()
if ret:
# frames = cv2.cvtColor(frames, cv2.COLOR_RGB2BGR)
# frames_arr = np.array(frames)
cv2.imshow("Video Output", frames)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
Make sure always close all the windows and release the VideoCapture object
cv2.destoyAllWindows()
vid.release()
Code:
import cv2
import numpy as np
vid = cv2.VideoCapture("resources/Plaza.mp4")
while vid.isOpened():
ret, frames = vid.read()
if ret:
# frames = cv2.cvtColor(frames, cv2.COLOR_RGB2BGR)
# frames_arr = np.array(frames)
cv2.imshow("Video Output", frames)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else
# continue with the next frame
continue
cv2.destoyAllWindows()
vid.release()

Answer 2

In your code, vid.read() returns two values. The first contains a boolean value, which, according to the documentation:
returns a bool (True/False). If frame is read correctly, it will be True. So you can check end of the video by checking this return value.
So your frames variable essentially is a tuple containing the boolean and the frames themselves. You need to index in to the second element (frames[1]) to play the video with imshow.
Always read the docs well!