使用OpenCV在Python中保存视频时出现问题

Question

我正在尝试将处理后的视频另存为MPEG4文件。原始视频是一个文件。它加载正常，我也可以将其另存为MPEG4。因此，我认为cv2.VideoWriter参数很好。但是，当我尝试进行背景减法，然后进行腐蚀和膨胀时，即使修改后的视频可以正确显示在屏幕上，我也无法保存。代码如下所示：

import cv2

#declare I/O
video_capture = cv2.VideoCapture('C:\\Users\\good.avi')
 out = cv2.VideoWriter('output.mp4',cv2.VideoWriter_fourcc(*'MP4V'), 30.0, (800,600))

#background subtraction configruation
subtractor = cv2.createBackgroundSubtractorMOG2(history=10, varThreshold=25)

while True:
    # Capture frame-by-frame
    ret, frame = video_capture.read()

    if ret != True:
        break

    #video processing
    mask = subtractor.apply(frame)
    img_erosion = cv2.erode(mask, None, iterations=3)
    img_dilate = cv2.dilate(img_erosion, None, iterations=3)

    #show Videos
    cv2.imshow("Original", frame)
    cv2.imshow("Subtractor", mask)
    cv2.imshow("erosion", img_dilate)

    #write video DOES NOT WORK.  It can saves "frame" but not img_dilate
    out.write(img_dilate)

    if cv2.waitKey(300) & 0xFF == ord('q'):
        break 
    #When everything is done, release the capture
    video_capture.release()
    cv2.destroyAllWindows()
    out.release