無法使用 python 和 opencv 保存視頻

Question

我正在嘗試將視頻更改為灰度並保存它，但視頻僅在完成運行后在運行過程中顯示我單擊保存的文件但我只收到無法渲染文件消息

import cv2
import numpy as np
import matplotlib.pyplot as plt


import numpy as np
import cv2



    cap = cv2.VideoCapture ('DJI_0055.mov')

    ret, frame = cap.read()
    print('ret =', ret, 'W =', frame.shape[1], 'H =', frame.shape[0], 
    'channel =', frame.shape[2])


     FPS= 60.0
     FrameSize=(frame.shape[1], frame.shape[0])
     fourcc = cv2.VideoWriter_fourcc(*'MJPG')
     out = cv2.VideoWriter('Video_output3.mov', fourcc, FPS, FrameSize, 
      0)

     while(cap.isOpened()):
     ret, frame = cap.read()

     gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
     frame = gray

     # Save the video
     out.write(frame)

     cv2.imshow('frame',frame)
     if cv2.waitKey(1) & 0xFF == ord('q'):
     break

     cap.release()
     out.release()
     cv2.destroyAllWindows()

除了無法呈現文件消息之外，我還在視頻在 IDLE 上完成運行后收到此消息

     Traceback (most recent call last):
     File "C:\Users\fido\Desktop\Practice\E-1-00pm-12m-1mps- 
     8wp\BlackAndWhite.py", line 25, in <module>
     gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
     cv2.error: OpenCV(4.1.1) C:\projects\opencv- 
     python\opencv\modules\imgproc\src\color.cpp:182: error: 
    (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'

Answer 1

在最后一幀之后，ret ---> False 和 Frame ---> []，這就是你會得到的。 這就是 cvtColor 顯示此錯誤的原因。

所以，如果你添加

if not ret:
    break

它將正確退出循環，您的視頻將被保存。

像這樣編輯您的代碼：

while(cap.isOpened()):
     ret, frame = cap.read()

     if not ret:
         break

     gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
     frame = gray

     # Save the video
     out.write(frame)

     cv2.imshow('frame',frame)
     if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
out.release()
cv2.destroyAllWindows()