How to decrease (openni_)kinect cpu usage in turtlebot pkg

asked 2011-08-23 01:34:10 -0600

Marco
75 ●9 ●10 ●17

Hi!

I've been experimenting with the turtlebot-pkg on a fitpc2 with icreate and kinect but am running into the limits of the cpu now. I noticed that the openni_camera nodelet combined with the throttler uses quite a lot of cpu power. My guess is that this is caused by the fact that the driver publishes data at 30hz, and only after the throttler i get the advantage of the lower framerate (i only need about 5hz). The combination of driver/throttler thus still uses quite some cpu power as it works with the full 30hz datastream.

Is it possible to lower the framerate in the driver itself, as the cpu-power it uses to publish pointclouds at 30hz is wasted..?

answered 2011-08-23 02:11:02 -0600

Nick Armstrong-Crews
481 ●12 ●16 ●19

I believe dynamic_reconfigure can adjust kinect driver parameters (or at least downsamples pre-publication, avoiding CPU overhead).

Use the GUI: rosrun dynamic_reconfigure reconfigure_gui
Change params in a launch script: e.g., <node pkg="dynamic_reconfigure" type="dynparam" name="resetter" args="set /openni_node image_mode 8" />

Note that you can't re-set params for openni_node if it has an subscriber...

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Setting the image_mode to qvga(5) or qqvga(8) indeed decreases cpu usage, and also disabling the rgb depth registration here lowers cpu usage. However, I am looking for a way to reduce framerate (Hz) instead of resolution to lower cpu usage.. any ideas?

Marco ( 2011-08-23 18:52:16 -0600 )edit

In the reconfigure_gui, I recall that each image mode specifies a framerate and a resolution; however, I don't recall the lowest framerate...maybe 15 Hz? Your best bet may be to modify the openni_camera node source code and downsample frames in memory, before publishing on a ROS topic.

Nick Armstrong-Crews ( 2011-08-24 00:50:15 -0600 )edit

Yes it indeed specifies both, however for the depth image only 30Hz modes are available. One 15Hz mode is possible for the cam, but not for depth mode. I might take a look at openni_camera.. or maybe someone already did something like this some time?

Marco ( 2011-08-24 22:21:42 -0600 )edit

Looks like there's a similar question with a better answer: http://answers.ros.org/question/686/openni_node-internal-throttle-to-limit-cpu-usage

Nick Armstrong-Crews ( 2011-08-25 03:02:50 -0600 )edit

I saw that indead and am already using the nodelet implementation. My problem is the same as stated in the comments there: the nodelet still computes the 30Hz pointcloud before the throttler throttles it to 5Hz. This is still quite a waste of cpu power.

Marco ( 2011-08-29 22:46:26 -0600 )edit

Feel free to file a feature request for the driver, especially with a patch. That feature does not exist at the moment.

tfoote ( 2011-12-08 05:19:20 -0600 )edit

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