subscribe to image topic over WiFi

asked 2012-06-19 08:25:28 -0600

yan
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updated 2012-06-20 11:55:07 -0600

Eric Perko

8406 ●73 ●90 ●144 http://ericperko.com/

Hi guys,

I have an Asctec Pelican here with a Ueye camera attached to it. We're trying to set it up such that we can subscribe to the topic from a remote PC, and view the video feed in real time.

We set up a local WiFi network, and experienced tons of latency and very low framerate. We verified that the images are published at the desired rate on the Asctec itself, so it seems like it's either Asctec or WiFi bandwidth that's causing the issue.

Has any of you tried this type of things before?

Thanks,

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answered 2012-06-21 22:37:13 -0600

Thomas

4478 ●39 ●58 ●84 http://thomas.moulard.net/

You should try the following:

rosrun image_view image_view image:=/camera/image _image_transport:=theora

...with /camera/image the image topic you want to display. Using image transport decreases a lot the bandwith required by the streaming, but it requires CPU power to compress the data on your robot.

The only other option is to stream different data: lower resolution, black and white only, etc.

PS: yes, wifi router usually behaves very badly when they reach theirs limits. Freeze, bad performances, reboot, etc. So what you experience is probably an access point performance issue.

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answered 2012-06-20 03:27:47 -0600

DimitriProsser

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You can check how much bandwidth your image topic is using by calling:

rostopic bw /your_image_topic

In the past, I've noticed quite a bit of latency when using images over distributed ROS networks. One thing that you could try would be to compress the image using image_transport. This might help a bit.