python opencv: no image

Question

I am trying to capture from a Sony Handicam DCR-HC38, running the code below, and passing [-1 .. 3] to the CaptureFromCAM function. The code runs, but I get no image. Do I need to "wrap" the camera somehow? Skype recognizes the camera, but python/opencv won't. I'm running Windows Vista if that helps any.

import cv

cv.NamedWindow("camera", 1)

capture = cv.CaptureFromCAM(-1)

while True:
    img = cv.QueryFrame(capture)
    cv.ShowImage("camera", img)
    if cv.WaitKey(10) == 27:
        break

img = cv.QueryFrame(capture) needs to be tested for if img actually has a value or is None. — Photodeus
– Photodeus, Commented May 7, 2011 at 18:34

Owen · Accepted Answer · 2010-12-06 11:29:21Z

3

try increasing the delay on the cv.WaitKey

answered Dec 6, 2010 at 11:29

Owen

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digiphd · Accepted Answer · 2011-04-24 06:57:43Z

not sure if you fixed it or not. But the solution I figured out is by checking which driver OpenCv is trying to access... I have both v4l1 and v4l2, however I can only access device /dev/video0 by using gstreamer codec and the v4l2 driver on my lenovo x200 (internal webcam) using ubuntu 10.10. So I had to recompile Opencv from source, by firstly applying the patch found at:

Opencv-2.0.0.link.v4l2.patch

extract the patch to your opencv root directory: then open terminal and cd to the opencv root directory, and do the following:

patch -p0 <OpenCV-2.0.0-link-v4l2.patch

then:

make
make install

Now your opencv libraries should access the v4l2 driver instead, hope this helps someone

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