Record a video in python

Question

I try to record a video in python. Running the code below create me a .mp4 file but is is 0KB and when i open i get the error that the data is corrupted and unable to open. I tried opening with VLC, Media Player and all other toold i got on Windows 11. Also tried everything available on the internet same problem every time

 import cv2
    
cap = cv2.VideoCapture(0)
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 1280)
cap.set(cv2.CAP_PROP_FRAME_WIDTH, 720)
fourcc = cv2.VideoWriter_fourcc(*'mp4v')
writer = cv2.VideoWriter('recording.mp4', fourcc, 30.0, (1280, 720))
recording = False

while True:
    ret, frame = cap.read()
    if ret:
        print('working')
        cv2.imshow("video", frame)
        if recording:
            writer.write(frame)
    
    key = cv2.waitKey(1)
    if key == ord('q'):
        break
    elif key == ord('r'):
        recording = not recording
        print(f'recording: {recording}')

# Release the video capture and writer objects
cap.release()
writer.release()
cv2.destroyAllWindows()

Answer 1

You are setting a size manually, but the camera might not work at that resolution.

To solve the problem, you can manually set the resolution to 1280x720 but then instead of hardcoding the capture resultion, retrieve it from the camera

This way if the camera works at the desired resolution good, if not it will work at the default one.

import cv2
    
cap = cv2.VideoCapture(0)
# set the camera to 1280x720
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 1280)
cap.set(cv2.CAP_PROP_FRAME_WIDTH, 720)

# but here get the actual resolution
width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH) + 0.5)
height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT) + 0.5)
size = (width, height)
fourcc = cv2.VideoWriter_fourcc(*'mp4v')

# then use here the actual resolution instead of the hardcoded one
writer = cv2.VideoWriter('recording.mp4', fourcc, 30.0,(width,height)) 

recording = False

while True:
    ret, frame = cap.read()
    if ret:
        print('working')
        cv2.imshow("video", frame)
        if recording:
            writer.write(frame)
    
    key = cv2.waitKey(1)
    if key == ord('q'):
        break
    elif key == ord('r'):
        recording = not recording
        print(f'recording: {recording}')

# Release the video capture and writer objects
cap.release()
writer.release()
cv2.destroyAllWindows()