播放.avi时发生OpenCV Python断言失败错误

Question

I am just beginning to learn OpenCV and am working through the tutorials here: https://opencv24-python-tutorials.readthedocs.io/en/stable/py_tutorials/py_gui/py_video_display/py_video_display.html

This is the code I've written to play the sample video.

import numpy as np
import cv2

cap = cv2.VideoCapture('samples/vtest.avi')

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

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

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

cap.release()
cv2.destroyAllWindows()

This is the error message I get:

OpenCV Error: Assertion failed (scn == 3 || scn == 4) in cvtColor, file /tmp/opencv-20161020-7399-1yrk4nm/opencv-2.4.13.1/modules/imgproc/src/color.cpp, line 3739
Traceback (most recent call last):
  File "vidFile_tutorial.py", line 14, in <module>
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
cv2.error: /tmp/opencv-20161020-7399-1yrk4nm/opencv-2.4.13.1/modules/imgproc/src/color.cpp:3739: error: (-215) scn == 3 || scn == 4 in function cvtColor

I'm unsure that the problem is an assertion fail error since I've chosen the file as specified by the tutorial. Moreover, when I attempt to play vtest.avi manually I encounter a codec error with QuickTime. Therefore, I suspect it's video codec issues with OpenCV. But I'm unsure if the diagnosis is correct and how I would go about fixing it.

Thanks in advance.

Answer 1

Okay, So I've managed to resolve the issue by using OpenCV 3.1.0 rather than 2.4.13.1.

With OpenCV 3.1.0 everything works fine.