CODEWITHSUNDEEP
pythonopencvvideo-capture
THE_GREAT_MARKER
THE_GREAT_MARKER

Reputation: 544

How to use OpenCV VideoWriter properly?

I would like to crop a region of a video, and save it. I used the following code to do it.

import cv2

cap = cv2.VideoCapture('input.avi')
fourcc = cv2.VideoWriter_fourcc(*'MJPG')
out = cv2.VideoWriter('output.avi', fourcc, 25, (1280, 720))

while True:
    ret, image_np = cap.read()
    if not ret:
        break;

    roi = image_np[300:1020, 0:1280]
    out.write(roi)

cap.release()
out.release()

Video file is created, and I can watch in a media player, but if a want to read this file in python, I get an error message.

import cv2

cap = cv2.VideoCapture('output.avi')
_, image_np = cap.read()

Process finished with exit code -1073741819 (0xC0000005)

I think the problem is with the video I made, but I am not sure.

Upvotes: 1

Views: 5049

Answers (1)

mibrahimy
mibrahimy

Reputation: 732

cv2.VideoWriter expects the size of the frame to be same as the frame you write. roi shape is not (1280, 720). 

import cv2

cap = cv2.VideoCapture('input.avi')
fourcc = cv2.VideoWriter_fourcc(*'MJPG')
out = cv2.VideoWriter('output.avi', fourcc, 25, (1280, 720))
writerInit = False
while True:
    ret, image_np = cap.read()
    if not ret:
        break;

    roi = image_np[300:1020, 0:1280]
    if(not writerInit):
        h,w,_ = roi.shape
        out = cv2.VideoWriter('output.avi', fourcc, 25, (w, h))
        writerInit = True

    out.write(roi)

cap.release()
out.release()

Upvotes: 2

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