How do I save a list of arrays (frames) to a video using OpenCV?

Question

I have tried to save a list of arrays to a video using the following code, but it isn't working.

out = cv2.VideoWriter("output.mp4", cv2.VideoWriter_fourcc(*'mp4v'), 30, (1280, 720))
for frame in frames:
    out.write(frame) # frame is a numpy.ndarray with shape (1280, 720, 3)
out.release()

It fails with no error message, but the output file (output.mp4) is around 200 bytes long and doesn't open in QuickTime or VLC. My assumption is that out.write is somehow failing silently. Is it possible to write arrays to a video in this way? If not, how could it be done?

Any and all help is very much appreciated.

Can you check your frame size? Most probably the creates the problem — Joy Mazumder
– Joy Mazumder, Commented May 24, 2020 at 4:26
I believe the frame size is correct, but I will double check. Thanks. — Robinson
– Robinson, Commented May 24, 2020 at 4:30
Try this out = cv2.VideoWriter("output.mp4", cv2.VideoWriter_fourcc(*'mp4v'), 30, (720, 1080)) — Joy Mazumder
– Joy Mazumder, Commented May 24, 2020 at 4:35
It would seem the x and y axis were switched in the numpy array. Thanks for your help. — Robinson
– Robinson, Commented May 24, 2020 at 4:39

Joy Mazumder · Accepted Answer · 2020-08-16 20:45:03Z

3

Numpy array is (row,column) but OpenCV defines images by (width,height). So, in your numpy array height=row=1080 and width=column=720. So, Change the frame size (1080,720) to (720,1080).

out = cv2.VideoWriter("output.mp4", cv2.VideoWriter_fourcc(*'mp4v'), 30, (720, 1080))
for frame in frames:
    out.write(frame) # frame is a numpy.ndarray with shape (1280, 720, 3)
out.release()

edited Aug 16, 2020 at 20:45

answered May 24, 2020 at 4:39

Joy Mazumder

9301 gold badge10 silver badges16 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

How do I save a list of arrays (frames) to a video using OpenCV?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related