From Raymon de Vries, "I've made a small change to DirectShowTexture.cpp: in the options for the directshow plugin it is possible to specify the capture device by number. For instance:

options->setPluginStringData("captureVideoDevice", "0");

Lines added in getDevice() are:
      int deviceId = atoi(name.c_str());
      if(deviceId >= 0 && deviceId < (int)_listDevice.size())
        return _listDevice[deviceId];

This makes it easy to use a capture device without knowing it's name. Attached is the whole file against rev 11044"

src/osgPlugins/directshow/DirectShowTexture.cpp

@@ -843,6 +843,11 @@ struct ListDeviceAvailable
                 return _listDevice[i];
         //if (!_listDevice.empty())
         //    return _listDevice.front();
+
+        int deviceId = atoi(name.c_str());
+        if(deviceId >= 0 && deviceId < (int)_listDevice.size())
+          return _listDevice[deviceId];
+
         return DeviceEntry();
     }