Converting video into frames by openCV

while converting video into frames , it does converted but it show this error

4     while success:
     35         success, frame = cap.read()
---> 36         grayFrame = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
     37         if(success==False and frame==None):
     38             pass

error: OpenCV(3.4.2) c:\miniconda3\conda-bld\opencv suite_1534379934306\work\modules\imgproc\src\color.hpp:253: error: (-215:Assertion failed) VScn::contains(scn) && VDcn::contains(dcn) && VDepth::contains(depth) in function 'cv::CvtHelper<struct cv::Set<3,4,-1>,struct cv::Set<1,-1,-1>,struct cv::Set<0,2,5>,2>::CvtHelper'

Instead of using success variable twice, check whether the camera or video is opened:

while cap.isOpened():

Then get the read outputs.

ret, frame = cap.read()

If the frame is returned successfully, write it to the folder:

if ret:
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    cv2.imwrite("output_frames/gray.png", gray)

Since you'll have multiple frames, you can use a counter to save each frame.

count = 0

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

    if ret:
        gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
        cv2.imwrite("output_frames/gray_{}.png".format(count), gray)
        count += 1

Full code:

import cv2

cap = cv2.VideoCapture("video.mp4")

count = 0

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

    if ret:
        gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
        cv2.imwrite("output_frames/gray_{}.png".format(count), gray)
        cv2.imshow("output", gray)
        count += 1

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


cv2.destroyAllWindows()
cap.release()