add config to enable MJPG encoded stream

Author: machinekoder

cfg/VideoStream.cfg

@@ -34,5 +34,6 @@ gen.add("reopen_on_read_failure", bool_t, LEVEL.RUNNING, "Re-open camera device
 gen.add("output_encoding", str_t, LEVEL.NORMAL, "Output encoding", "bgr8")
 gen.add("start_frame", int_t, LEVEL.RUNNING, "Start frame of the video ", 0, 0)
 gen.add("stop_frame", int_t, LEVEL.RUNNING, "Stop frame of the video", -1, -1)
+gen.add("enable_mjpg", bool_t, LEVEL.NORMAL, "Try to use MJPG capture stream", False)
 
 exit(gen.generate(PKG, PKG, "VideoStream"))

src/video_stream.cpp

@@ -269,6 +269,10 @@ virtual void subscribe() {
   }
   NODELET_INFO_STREAM("Video stream provider type detected: " << video_stream_provider_type);
 
+  if (latest_config.enable_mjpg) {
+    cap->set(cv::CAP_PROP_FOURCC, cv::VideoWriter::fourcc('M', 'J', 'P', 'G'));
+  }
+
   double reported_camera_fps;
   // OpenCV 2.4 returns -1 (instead of a 0 as the spec says) and prompts an error
   // HIGHGUI ERROR: V4L2: Unable to get property <unknown property string>(5) - Invalid argument
@@ -391,6 +395,10 @@ virtual void configCallback(VideoStreamConfig& new_config, uint32_t level) {
     NODELET_INFO_STREAM("Forced image width is: " << new_config.width);
     NODELET_INFO_STREAM("Forced image height is: " << new_config.height);
   }
+  if (new_config.enable_mjpg)
+  {
+    NODELET_INFO_STREAM("Trying to use MJPG camera stream.");
+  }
 
   NODELET_DEBUG_STREAM("subscriber_num: " << subscriber_num << " and level: " << level);
   if (subscriber_num > 0 && (level & 0x1))