Unable to query number of channels

asked 2018-04-02 06:09:09 -0500

updated 2018-04-02 06:16:51 -0500

berak gravatar image

when I am using opencv-3.0.0 function VideoCapture cap(0); It throws a error VIDEOIO ERROR: V4L: device /dev/video0: Unable to query number of channels

Here is my code :

#include "opencv2/opencv.hpp"

using namespace cv:
int main(int,char**)
{
    VideoCapture cap(0);
    if(!cap.isOpened())
        return -1;
    Mat edges;
    namedWindow("edges",1);
    for(;;)
    {
        Mat frame;
        cap >> frame;
        cvtColor(frame,edges,COLOR_BGR2GRAY);
        GaussianBlur(edges,edges,Size(7,7),1.5,1.5);
        Canny(edges,edges,0,30,3);
        imshow("edges",edges);
        if(waitKey(30)>=0)
        break;

    }
}

Can someone help me what might be the issue,btw I am using MIPI camera to Tinker Board

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Comments

"I am using MIPI camera to Tinker Board"

unfortunately, the problem is not in your code, but that v4l could not open the capture properly.

did you build with gstreamer support ? there seems to be hope, it works better with that, than V4l.

berak gravatar imageberak ( 2018-04-02 06:19:37 -0500 )edit
1

Hi berak, Yeah, I used Gstreamer with opencv-3.0.0 ,but I'm getting v4l2 issue

Errors facing: 1.VIDEOIO ERROR: V4L: device /dev/video0: Unable to query number of channels 2.cap_gstreamer.cpp:383: error: (-2) GStreamer: unable to start pipeline here, is my code for it :

cv::VideoCapture cap(" v4l2src device=/dev/video0 num-buffers=50 ! video/x-raw,format=NV12,width=640,height=480,framerate=20/1 ! videoconvert ! ximagesink ! appsink");

chetan1729 gravatar imagechetan1729 ( 2018-04-02 08:13:29 -0500 )edit