cvCreateCameraCapture returns null

Question

I've got a webcam which is working perfectly in vlc, and is available as /dev/video0. However, whenever I use cvCreateCameraCapture, it returns null. I've used 0,1,-1 as indexes. What could be causing the problem? I'm on Ubuntu 9.10 BTW, using openCV 2.1.0.1 ppa.

What is the make/model of webcam you are using? I have had this problem with a few cheap web cams and one creative labs one, if you let me know what you're using I may be able to help. However the built in camera on my netbook and a PS3 Eye cam work fine. — Diziet
I'm using 2 webcams, one is a Sirius USB webcam. The other one is the inbuilt webcam that came with my laptop (Lenovo Y330). — Karan
Could you do the following and let me know. I'm a bit knew to stackoverflow so bare with me! Firstly afaik opencv only supports V4L for USB devices under linux so you need to check they are doing that. I think if you check in /var/log/udev with: grep video /var/log/udev and grep -i v4l /var/log/udev|grep DEVLINKS and copy back the lines for your camera. Also here's an really basic camera test, I'm sure i'm preaching to the converted but what does it do on your system? Press escape to quit. pastebin.com/9n3BJKVa Also does the camera work in 'Cheese'? — Diziet
@Karan maybe it's time for you to review some questions and accept the answers that solved them. Has this question been answered? — karlphillip

karlphillip karlphillip · Accepted Answer · 2010-10-25T19:40:41

I'm using OpenCV 2.1 on Ubuntu 9.04 and this works fine:

CvCapture* capture = NULL;
if ((capture = cvCaptureFromCAM(-1)) == NULL)
{
    std::cerr << "!!! ERROR: cvCaptureFromCAM No camera found\n";
    return -1;
}

Note that I'm using cvCaptureFromCAM() instead of cvCreateCameraCapture().

cvCreateCameraCapture returns null

2 Answers