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Is there anyway to measure the published bandwidth?

asked 2013-02-27 07:07:52 -0500

AdrianPeng gravatar image

I am using Gumstix Overo to stream video to my laptop through ad-hoc wireless network.

However, the streaming video has about 4 sec delay and the frame rate is really bad. I thought the published message bandwidth may be larger than the bandwidth of ad-hoc wireless network. So I want to measure the published bandwidth.

I know "rostopic bw" measures the received bandwidth, so if rostopic cannot keep up with the publisher, the reported number may be lower than the actual bandwidth.

My first question: Is there anyway to measure the published bandwidth?

My second question: If the published bandwidth is bigger than the ad-hoc network bandwidth, is there anyway to compress ROS messages to reduce the bandwidth?

Thanks in advance!

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answered 2013-02-27 08:04:29 -0500

updated 2013-02-27 11:06:29 -0500

Indeed, rostopic bw will only see the received bandwidth. My first thought is to run rostopic bw on the same machine that your publisher is on. In this case, you will only be limited by CPU and whatever restrictions there are on the loopback interface (I don't know what, if any, there are).

If this doesn't to it for you, you could basically reimplement rostopic bw within your node. All you would have to do is serialize the message (in python you can do this with msg.serialize(buffer)), and keep an average of the buffer size over some sampling period.

EDIT: another tip

Another way to figure out of you're having connection issues is to use a tool like wireshark and look at the network traffic. Things like lots of DUP ACKs can indicate that packets are being lost, which could happen if your connection is saturated.

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Asked: 2013-02-27 07:07:52 -0500

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Last updated: Feb 27 '13