python - cv2 Writing stream from array

Question

This code records video from a webcam:

import cv2
w,h = 640,480
cap = cv2.VideoCapture(0,cv2.CAP_DSHOW)
out = cv2.VideoWriter('test1.mp4', cv2.VideoWriter_fourcc(*'XVID'), 24.0, (w,h))
while True:
    key = cv2.waitKey(1) & 0xFF
    if key == ord('q'):
        break
    ret, frame = cap.read()
    cv2.imshow('frame', frame)
    out.write(frame)

out.release()
cap.release()
cv2.destroyAllWindows()

It works, but i want to make it write list of frames:

import cv2
w,h = 640,480
frames = []
cap = cv2.VideoCapture(0,cv2.CAP_DSHOW)
out = cv2.VideoWriter('test1.mp4', cv2.VideoWriter_fourcc(*'XVID'), 24.0, (w,h))
while True:
    key = cv2.waitKey(1) & 0xFF
    if key == ord('q'):
        break
    ret, frame = cap.read()
    cv2.imshow('frame', frame)
    frames.append(frame)

for frame in frames:
    out.write(frame)
out.release()
cap.release()
cv2.destroyAllWindows()

And this gives me a 4 kb file, that i can't open. What's wrong between cv2 and arrays?

question from:https://stackoverflow.com/questions/65902327/cv2-writing-stream-from-array

Answer 1

I think that you lost the argument for out.write().

for frame in frames:
    out.write(frame)
out.release()
cap.release()
cv2.destroyAllWindows()