No video file created by OpenCV 2.3.1 with Python on Raspberry Pi

问题

I'm trying to capture video from a webcam(Logitech c210) and create a video file from it.

This is on Raspbian Wheezy 2013-05-25.

The light on the camera comes on for about 30 seconds but no file is created. I've had the webcam displaying in an OpenCV window.

I'm wondering if this is a codec problem as the script works on windows with the -1 parameter?

If so are there any recommended codecs for Raspberry Pi?

If I buy the mpeg2 codec would that work?

I've listed the codecs that I've tried though none work.

The script is as follows:

import cv2
import time

def InitialiseCamera():
    camera = cv2.VideoCapture(0)
    if camera is None:
        print('Warning: unable to access camera')
    else:
        print('initialized camera')
    return camera

def InitialiseWriter():
    fps = 5
    size = (640, 480)
    destinationFile = 'video.avi'

    # These are the codecs I've tried so far
    codec = cv2.cv.CV_FOURCC('I','4','2','0')
    #codec = cv2.cv.CV_FOURCC('A','V','C','1')
    #codec = cv2.cv.CV_FOURCC('Y','U','V','1')
    #codec = cv2.cv.CV_FOURCC('P','I','M','1')
    #codec = cv2.cv.CV_FOURCC('M','J','P','G')
    #codec = cv2.cv.CV_FOURCC('M','P','4','2')
    #codec = cv2.cv.CV_FOURCC('D','I','V','3')
    #codec = cv2.cv.CV_FOURCC('D','I','V','X')
    #codec = cv2.cv.CV_FOURCC('U','2','6','3')
    #codec = cv2.cv.CV_FOURCC('I','2','6','3')
    #codec = cv2.cv.CV_FOURCC('F','L','V','1')
    #codec = cv2.cv.CV_FOURCC('H','2','6','4')
    #codec = cv2.cv.CV_FOURCC('A','Y','U','V')
    #codec = cv2.cv.CV_FOURCC('I','U','Y','V')
    #codec = -1

    video  = cv2.VideoWriter(destinationFile, codec, fps, size, True);
    if video is None:
        print('Warning: unable to create video writer')
    else:
    print('initialized writer')
    return video

def CaptureVideo(c,w):
i = 0
    while i<150:
        i+=1
        f,img = c.read()
        try:
            w.write(img)
        except:
            print "Unexpected error: ", sys.exec_info()[0]
    print('complete')
    c.release()

if __name__ == '__main__':    
    cam = InitialiseCamera()
    writer = InitialiseWriter()
    CaptureVideo(cam,writer)

回答1:

I eventually went through and tried all of the fourcc codecs and none worked.

Same with the mpeg2 codec.

I ended up using avconv to create and capture the video with this line:

import os
os.system("avconv -f video4linux2 -input_format mjpeg -i /dev/video0 output.avi")

os.system() is used to run a terminal command.

OpenCV can still be used to process the video files at a later time.

Hope this helps someone.

回答2:

If this answer isn't too late, try

CV_FOURCC('M','P','E','G')

works for me on Raspbian. Although, an fps of 5 is probably not supported.

回答3:

check the tutorial on using OpenCV with Pi.

http://thinkrpi.wordpress.com/2013/05/22/opencv-and-camera-board-csi/

来源：https://stackoverflow.com/questions/17102564/no-video-file-created-by-opencv-2-3-1-with-python-on-raspberry-pi