OpenCV Multithreaded Camera Reads - c++

Question

I am attempting to use OpenCV to capture images from multiple cameras via separate thread workers.
Eventually, CaptureWorker will feed frames to a worker queue for processing, but currently I'd like to save the image. The following code runs, but the saved 'frames' are damaged and unable to be opened, but are not empty.
Originally, I was constructing and storing the VideoCapture in CaptureWorker::startCapture(); however, the program crashed while opening the stream. Constructing and opening the VideoCapture in main() turns on the camera and allows the thread to run.
What is causing the frame writing to break? No errors are reported.
main.cpp
int main(int argc, char * argv[]) {
if(argc <= 1) {
cout << "No camera arguments have been specified. Exiting." << endl;
return -1;
}
int numberOfCameras = argc - 1;
int cameraNumbers[argc-1];
for(int i=0; i<numberOfCameras; i++) {
cameraNumbers[i] = atoi(argv[i+1]);
}
VideoCapture cameras[10];
pthread_t cameraThreads[numberOfCameras];
for(int i=0; i<numberOfCameras; i++) {
cout << "Creating camera thread: " << i << endl;
cameras[i] = VideoCapture(i);
CaptureWorker capWorker(cameras[i], i);
pthread_create(&cameraThreads[i], NULL, &CaptureWorker::startCaptureWrap, &capWorker);
}
cout << "Closing Main" << endl;
pthread_exit(NULL);
}
CaptureWorker.cpp
class CaptureWorker {
private:
int cameraNumber;
string cameraName;
VideoCapture camera;
public:
CaptureWorker(VideoCapture camera, int cameraNumber) {
this->cameraNumber = cameraNumber;
this->camera = camera;
this->cameraName = "Camera_";
cameraName.append(to_string(cameraNumber));
cout << "CaptureWorker: Worker created" << endl;
}
void *startCapture(void) {
string imageSavePath = "Resources/images/" + this->cameraName;
mkdir(imageSavePath.c_str(), 0777);
cout << "CaptureWorker: Starting capture from camera" << endl;
int count = 0;
while(count <= 3) {
cout << "Capturing frame " << count;
Mat frame;
this->camera >> frame;
cout << " --- ";
string imageNameAndPath;
imageNameAndPath.append(imageSavePath);
imageNameAndPath.append("/img_");
imageNameAndPath.append(to_string(count).c_str());
imageNameAndPath.append(".jpg");
cout << "Saving to: " << imageNameAndPath.c_str() << endl;
imwrite(imageNameAndPath.c_str(), frame);
int c = cvWaitKey(1000);
if((char)c==27 ) {
break;
}
count++;
}
return 0;
}
static void *startCaptureWrap(void *arg) {
return ((CaptureWorker *) arg)->startCapture();
}
};
On OSX using cross g++ compiler in eclipse. Disclaimer: New to C++, OpenCV, multithreading, hopefully I've avoided a silly error.