Python cv2 VideoWriter File getting corrupted

Question

I was following this tutorial and I tried to save the video to an avi file, but every time I tried the file was corrupted. I was able to save the frames individually using cv2.imwrite(), but stitching together the individual frames was a lot of work, and would lag the entire program. Here is my code:

from imutils.video import VideoStream
import imutils
import time
import cv2

MINIMUM_AREA = 500

# For Video Recording Purposes
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('vibralert_test001.avi', fourcc, 20, (640, 480))

vs = VideoStream(src=0).start()

print("Setting up feed.")
time.sleep(2)
print("Live")

firstFrame = None

while True:
    frame = vs.read()
    text = "No Movement Detected"

    frame = imutils.resize(frame, width=500)
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    gray = cv2.GaussianBlur(gray, (21, 21), 0)

    if firstFrame is None:
        firstFrame = gray
        continue

    delta = cv2.absdiff(firstFrame, gray)
    thresh = cv2.threshold(delta, 25, 255, cv2.THRESH_BINARY)[1]

    thresh = cv2.dilate(thresh, None, iterations=2)
    cnts = cv2.findContours(thresh.copy(), cv2.RETR_EXTERNAL,
                            cv2.CHAIN_APPROX_SIMPLE)
    cnts = imutils.grab_contours(cnts)

    for c in cnts:
        if cv2.contourArea(c) < MINIMUM_AREA:
            continue

        (x, y, w, h) = cv2.boundingRect(c)
        cv2.rectangle(frame, (x, y), (x + w, y + h), (0, 255, 0), 2)
        text = "Movement Detected"

    cv2.putText(frame, "Room Status: {}".format(text), (10, 20),
                cv2.FONT_HERSHEY_SIMPLEX, 0.5, (0, 0, 255), 2)

    cv2.imshow("VibrAlert v0.1", frame)
    out.write(frame)

    key = cv2.waitKey(1) & 0xFF

    if key == 27:
        break

vs.stop()
out.release()
cv2.destroyAllWindows()

print('End Feed')

Answer 1

The size of the frame images need to be the same as the frameSize given to the VideoWriter, (640,480). The frame is being resized to have a width of 500, while the videoWriter is expecting a width of 640.

However, changing the resize to frame = imutils.resize(frame, width=640) probably won't work either. imutils.resize will return images with the same aspect ratio as the original image, so the height won't necessarily be 480. I would suggest replacing that line with the opencv.resize:

frame = cv2.resize(frame, (640,480))