accessing cameras- abort() call

edit

@pklab with the same logic (without even a single change) it worked precised but now it gives an error :/... Anyhow according to your suggestion I've altered the code, surprisingly the error is removed :) but ... only frame of device 0 is captured, nothing is taken from Device 1 :/ :(

and what is the logic of using AND around the empty(), why not OR? what difference does it make ?

Is device1 currently working ? did you try to use just device 1. Finally try to give a bit of time between grabs with a sleep(5) or simply grab and show from 0 than grab and show from 1. About the logic it's very basic please try it yourself

@pklab the error is somewhere else... its still not working ... for a test, i just tried to run another fine and working code while only laptop builtin camera was working, this code (written below) worked. The moment i plugged in my 1st webcam (now 1 webcam and builtin cam is connected) this code also give a call to abort() .. the same error for previous code.. closing VS13 running code again , makes everything correct again...so its not the code, the error is some where else?? am i right ? 2nd Code:

int main(int, char**)

{ VideoCa1pture cap(0); if (!cap.isOpened()) { std::cerr << "ERROR: Could not open camera" << std::endl; } namedWindow("video", 1); for (;;) { Mat frame; cap >> frame; if (waitKey(30) >= 0) break; }

Correct logic is needed to prevent errors with NULL device and NULL frames. In addiction because device opening done by VideoCapture obj declaration you don't have to open them again... Change this line too if (!cap.isOpened() || !cap2.isOpened()). Finally when you connect a second camera device enumerations would change causing troubles.

@pklab: its still not done :( this is what I've made in accordance with your suggestion, the problem is still the same, either of the 2 cams captures the frame. I want to take picture from both the webcams simultaneously :(

#include "opencv2/opencv.hpp"
using namespace cv;

int main(int argc, char** argv)
{

    VideoCapture cap(2);

    if (!cap.isOpened())
    {
        std::cout << " --(!) Error reading image from Device 2 " << std::endl;
        return -1;
    }
    Mat frame;
    cap >> frame;

    if (!frame.empty())
    imshow("Frame of Device 1", frame);

    VideoCapture cap2(0);

    if (!cap2.isOpened())
    {
        std::cout << " --(!) Error reading image from Device 0 " << std::endl;
        return -1;
    }
    Mat frame2;
    cap2 >> frame2;

    if (!frame2.empty())
        imshow("Frame of Device 0", frame2)

    waitKey();
    return;
}

i'm new to OpenCV one thing i just don't understand, one code worked fine one day and the very next day the same code for same cameras gives such errors lol how is that possible.

You can grab the frames consecutively but you will always have a little timeshift because of grabbing time and the cams aren't synchronized. Anyway try the code in my answer it should work.

I think your issues is coming from usb cam device enumeration. As stated when you connect a second camera device enumerations would change (by DirectShow on Windows) causing troubles if not right managed.

@pklab: so how would i add the time delay in between? sleep() method isn't recognized by the editor.

Again... try the code in my answer, it should work. If Ok acept the answer. In case of errors, do some test and/or modification and give us detailed info about. Help us to help you, remeber that this is not a chat.