Further Optimization suggestion for wireless openni streaming

Question

Let me first describe the system that I've came up with..

I have two Odroid-U3 with Asus Xtion Pro Live and Wifi. Both of them run the

 roslaunch openni2_launch openni2.launch

with the video resolution changed from VGA to QVGA...

The base station system (my computer) decompresses

 /cameraX/depth_registered/image_raw (compressedDepth)
 /cameraX/rgb/image_color_rect (compressed)

and synchronizes

/cameraX/rgb/image_rect_color_unsync (decompressed)
/cameraX/depth_registered/image_raw_unsync (decompressed)
/cameraX/rgb/camera_info 

and advertises

/cameraX/rgb/image_rect_color_sync
/cameraX/depth_registered/image_raw_sync
/cameraX/rgb/camera_info_sync

which the rgbdslam node subscribes to; where X may be 1 or 2.

They are both connected to a wireless N-lite router which bandwidth may reach upto 150 Mbps.

Using Wifi Analyzer Android App, it detected no other wifi signal in the same channel as the current wifi network.

Result: It is somewhat smooth but there are times when it drop frames. Running only one openni2 streaming do not really drop frames.. I therefore concluded that it was due to wifi bandwidth.

The further optimization that I can think of are..

1.) Instead of transmitting colored images, transmit only grayscale images.

2.) Rethrottle frame rate around 15fps only.

Questions..

1.) What are other optimization suggestions I can do?

2.) running openni2_launch openni2.launch does not advertise grayscale image. What ros parameter should I include in the openni2.launch in order to generate /camera/rgb/image_rect_mono?? Because running imgproc node DO generate image_rect_mono

3.) Using dynamic reconfigure, the openni camera can only be rethrottled to 30 fps.. I tried 25 fps but it did not work. How do I rethrottle it to 15fps?

EDIT: I tried running the dynamic reconfigure and set to data skip to 1. I assume this means it will publish 1 in every 1 frame. It should mean no difference. However, it seems after setting data skip to 1, the frame rate starts to decline and wants to approach zero.

When data skip is set to 0

When data skip is set to 1

(/upfiles/14062739298942344.png)

as of 15:39, the frame rate is 16.559 and still keeps on decreasing.

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Originally posted by Xegara on ROS Answers with karma: 52 on 2014-07-24

Post score: 0

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Original comments

Comment by yincanben on 2014-11-19:
I was trying to run rgbdslam over multiple machines, but the speed of mapping is very slow ,Have you solve this problem?Can you advertise some advice?Thanks in advance.

Answer 1

The original openni_camera node has a data_skip parameter which can instruct the driver to only publish 1 in every N frames. openni2_camera is not nearly as well documented, but perhaps it has a similar parameter?

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Originally posted by ahendrix with karma: 47576 on 2014-07-25

This answer was ACCEPTED on the original site

Post score: 1

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Original comments

Comment by Xegara on 2014-07-25:
Initially, data_skip is set to 0. I tried to set it to 1. If the driver now will only publish 1 in every 1 frame, there should be no difference right? I have attached a screenshot above. As time progresses, the frame rate seems to decline and wants to approach zero. Why is that?

Comment by ahendrix on 2014-07-25:
I think setting data_skip to 1 will drop every other frame; it's probably approaching 15, not 0. Try setting the window parameter in rostopic hz to something that isn't infinite, to get better readings:

rostopic hz -w 120