OpenCV Python VideoWriter saves corrupted video

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I am trying to get a very simple example of copying a video before I start modifying frames in the video. However, the output.avi video is a 5kb corrupted file compared to the 2.8 mb barriers.avi video. I am using OpenCV version 4.2.0 and Python version 3.7.7.

Here is the code:

import cv2

input = cv2.VideoCapture("../video/barriers.avi")
height = int(input.get(cv2.CAP_PROP_FRAME_HEIGHT))
width = int(input.get(cv2.CAP_PROP_FRAME_WIDTH))

fourcc = cv2.VideoWriter_fourcc(*'DIVX')
out = cv2.VideoWriter('../video/output5.avi', fourcc, 30, (height, width), isColor=True)

while input.isOpened():
    # get validity boolean and current frame
    ret, frame = input.read()

    # if valid tag is false, loop back to start
    if not ret:
        break
    else:
        out.write(frame)

input.release()
out.release()

If I printed the frame shape, I get:

(480, 640, 3)

Note: None of the other stack overflow solutions have helped.

Edit: All frames display fine if cv2.imshow() is used.

video-processing opencv save python
1 Answers

I would like to address two issues in your code:

Issue#1:: You want to create a .avi video file. Therefore you need to initialize your fourcc as MJPG:

fourcc = cv2.VideoWriter_fourcc(*'MJPG')

There are certain combinations for creating a video file. For instance, if you want to create a .mp4 you initialize your fourcc as *'mp4v'.

Issue#2: Make sure the size of the output video is the same as the input frame. For instance: you declared your Videowriter object size (height, width). Then your frame must be the same size:

frame = cv2.resize(frame, (height, width))

Code:

import cv2

cap = cv2.VideoCapture("output.mp4")
height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))
width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))

fourcc = cv2.VideoWriter_fourcc(*'MJPG')
out = cv2.VideoWriter('output5.avi', fourcc, 30, (width, height), isColor=True)

while cap.isOpened():
    # get validity boolean and current frame
    ret, frame = cap.read()

    # if valid tag is false, loop back to start
    if not ret:
        break
    else:
        frame = cv2.resize(frame, (width, height))
        out.write(frame)

cap.release()
out.release()
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