Add USB and OpenCV processed dual stream example.

examples/usbcvstream/usbcvstream.cpp

@@ -0,0 +1,27 @@
+#include "cameraserver.h"
+#include "opencv2/core/core.hpp"
+
+#include <iostream>
+#include <stdio.h>
+
+int main() {
+  cs::USBCamera camera{"usbcam", 0};
+  camera.SetVideoMode(cs::VideoMode::kMJPEG, 320, 240, 30);
+  cs::MJPEGServer mjpegServer{"httpserver", 8080};
+  mjpegServer.SetSource(camera);
+  cs::CvSink cvsink{"cvsink"};
+  cvsink.SetSource(camera);
+  cs::CvSource cvsource{"cvsource", cs::VideoMode::kMJPEG, 320, 240, 30};
+  cs::MJPEGServer cvMjpegServer{"cvhttpserver", 8081};
+  cvMjpegServer.SetSource(cvsource);
+
+  cv::Mat test;
+  cv::Mat flip;
+  for (;;) {
+    uint64_t time = cvsink.GrabFrame(test);
+    std::cout << "got frame at time " << time << " size " << test.size() << std::endl;
+    if (time == 0) continue;
+    cv::flip(test, flip, 0);
+    cvsource.PutFrame(flip);
+  }
+}