WebRTC播放本地攝像頭內容

WebRTC裏面有peerconnection_client & server，需要仔細研究。研究後你就知道如何編寫一個製作本地播放攝像頭的代碼。

現在就寫下關鍵代碼：

1. 打開攝像頭

rtc::scoped_refptr<webrtc::PeerConnectionFactoryInterface> peer_connection_factory_111;
// 打開本地攝像頭
cricket::VideoCapturer* OpenVideoCaptureDevice() {
  rtc::scoped_ptr<cricket::DeviceManagerInterface> dev_manager(
    cricket::DeviceManagerFactory::Create());
  if (!dev_manager->Init()) {
    LOG(LS_ERROR) << "Can't create device manager";
    return NULL;
  }
  std::vector<cricket::Device> devs;
  if (!dev_manager->GetVideoCaptureDevices(&devs)) {
    LOG(LS_ERROR) << "Can't enumerate video devices";
    return NULL;
  }
  std::vector<cricket::Device>::iterator dev_it = devs.begin();
  cricket::VideoCapturer* capturer = NULL;
  for (; dev_it != devs.end(); ++dev_it) {
    capturer = dev_manager->CreateVideoCapturer(*dev_it);
    if (capturer != NULL)
      break;
  }
  return capturer;
}

2. 在HWND的OnPaint裏面繪製

void MainWnd::OnPaint() {
  PAINTSTRUCT ps;
  ::BeginPaint(handle(), &ps);

  RECT rc;
  ::GetClientRect(handle(), &rc);

  VideoRenderer* local_renderer = local_renderer_.get();
  if (local_renderer) {
    const BITMAPINFO& bmi = local_renderer->bmi();
    int height = abs(bmi.bmiHeader.biHeight);
    int width = bmi.bmiHeader.biWidth;

    const uint8* image = local_renderer->image();
    if (image != NULL) {
      HDC dc_mem = ::CreateCompatibleDC(ps.hdc);
      ::SetStretchBltMode(dc_mem, HALFTONE);

      // Set the map mode so that the ratio will be maintained for us.
      HDC all_dc[] = { ps.hdc, dc_mem };
      for (int i = 0; i < ARRAY_SIZE(all_dc); ++i) {
        SetMapMode(all_dc[i], MM_ISOTROPIC);
        SetWindowExtEx(all_dc[i], width, height, NULL);
        SetViewportExtEx(all_dc[i], rc.right, rc.bottom, NULL);
      }

      HBITMAP bmp_mem = ::CreateCompatibleBitmap(ps.hdc, rc.right, rc.bottom);
      HGDIOBJ bmp_old = ::SelectObject(dc_mem, bmp_mem);

      POINT logical_area = { rc.right, rc.bottom };
      DPtoLP(ps.hdc, &logical_area, 1);

      HBRUSH brush = ::CreateSolidBrush(RGB(0, 0, 0));
      RECT logical_rect = {0, 0, logical_area.x, logical_area.y };
      ::FillRect(dc_mem, &logical_rect, brush);
      ::DeleteObject(brush);

      int x = (logical_area.x / 2) - (width / 2);
      int y = (logical_area.y / 2) - (height / 2);

      StretchDIBits(dc_mem, x, y, width, height,
                    0, 0, width, height, image, &bmi, DIB_RGB_COLORS, SRCCOPY);

      BitBlt(ps.hdc, 0, 0, logical_area.x, logical_area.y,
             dc_mem, 0, 0, SRCCOPY);

      // Cleanup.
      ::SelectObject(dc_mem, bmp_old);
      ::DeleteObject(bmp_mem);
      ::DeleteDC(dc_mem);
    }

}

這樣就可以繪製了。效果如下：