add config to enable MJPG encoded stream

README.md

@@ -56,7 +56,7 @@ You can use any input that OpenCV on your system accepts, e.g.:
 
 Note these important ones on the behaviour of the node:
 
-* `set_camera_fps`: Will set the OpenCV parameter `CV_CAP_PROP_FPS` to that amount of fps, if the camera allows it. 
+* `set_camera_fps`: Will set the OpenCV parameter `CV_CAP_PROP_FPS` to that amount of fps, if the camera allows it.
 Does nothing on video streams or video files.
 
 * `buffer_queue_size`: Will set the size of the buffer of images read from the capturing device. We read
@@ -70,9 +70,9 @@ So if you want the very latest image published from a camera, set `buffer_queue_
 
 If you want to publish all images (don't drop any and you don't mind some possible delay from real time), set `buffer_queue_size` big enough for your case (1000?),
  `set_camera_fps` and `fps` to whatever FPS it has.
- 
+
  The rest of the parameters explained, even though they are pretty self explanatory:
- 
+
  * `camera_name`: node name and ros graph name. All topics will hang from this e.g.: /camera_name/<TOPICS>.
  * `video_stream_provider`: A number for the /dev/videoX device, e.g.: 0 for /dev/video0. A string for a path for a video file, e.g.: /home/user/Videos/myvideo.avi
  or a url of a video stream e.g.: rtsp://wowzaec2demo.streamlock.net/vod/mp4:BigBuckBunny_115k.mov and http://10.68.0.6/mjpg/video.mjpg.
@@ -84,6 +84,7 @@ If you want to publish all images (don't drop any and you don't mind some possib
  * `width` and `height`: force a width and height to the capturing device (if it allows), 0 means no forcing.
  * `start_frame`: if the provider is a video file, set the start frame of video.
  * `stop_frame`: if the provider is a video file, set the stop frame of video. `-1` means the end of the video. Also setting `stop_frame = start_frame + 1`  can publish a single frame with a certain rate.
+ * `enable_mjpg`: try to force MJPG capture stream on camera devices
 
 # Extras
 
@@ -100,4 +101,3 @@ And you'll see an output like:
     Correctly opened resource, starting to show feed.
 
 With an OpenCV image show window showing the stream (which should close when pressing ESC, or Control+C the shell).
-

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))