ColinS747's profile - activity

I should also point out that this program previously worked as expected on a desktop PC running debian based linux. I have only had these problems when trying to run the program on a macbook running OSX.

I only have code to access the camera in a one of the two threads. These two programs are never ran at the same time.

I'm not sure what you mean, could you elaborate?

This doesn't solve my problem though. As I said my code was working fine when it was all included in a single thread but fails to open the camera when it is applied in a multi-threaded implementation. I'm looking to know why it fails in this case and how to fix it.

The code you provided works fine. I only had to add std:: to the cerr and endl.

I have an OpenCV program that is supposed to use a webcam (in this case the built in laptop camera). The program compiles fine without error but when I run it the program seems to hang on the line:

img_scene = cvCaptureFromCAM(0);

I have a different program that access the camera in the same fashion so I don't understand as to why this program seems to be having trouble.

Full capture code from non-working program:

Mat captureThread() {
  if(captureOpen == false){
    img_scene = cvCaptureFromCAM(0);
    cvSetCaptureProperty(img_scene, CV_CAP_PROP_FRAME_WIDTH, 640);
    cvSetCaptureProperty(img_scene, CV_CAP_PROP_FRAME_HEIGHT, 480);
  }
  while(1) {
    image = cvQueryFrame(img_scene);
    if(image.empty()) {
      continue;
    }
    cvtColor(image, gray, CV_BGR2GRAY);
    return gray;
  }
}

This is the code that is being used in a different program that is working as expected:

  img_scene = cvCaptureFromCAM(0);
  cvSetCaptureProperty(img_scene, CV_CAP_PROP_FRAME_WIDTH, 640);
  cvSetCaptureProperty(img_scene, CV_CAP_PROP_FRAME_HEIGHT, 480);
  while(1) {
    imageFrame = cvQueryFrame(img_scene);
    if(imageFrame.empty()) {
      continue;
      cout << "image frame is empty" << endl;
    }
    cvtColor(imageFrame, gray, CV_BGR2GRAY);

What is causing the non-working program to have trouble access the camera? I have also tried plugging in a USB camera and setting cvCaptureFromCam(-1) but it does not work either.

EDIT: The non-working program uses multiple threads whereas the working program does not.

I should also point out that this program previously worked as expected on a desktop PC running debian based linux. I have only had these problems when trying to run the program on a macbook running OSX.