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FRC1076 / drivercam

Installation and debugging notes, performance evaluation, installation scripts, and user interface
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Figure out how much bandwidth gets used by drivercam for a variety of configurations #6

Open mcolinj opened 5 years ago

mcolinj commented 5 years ago

One way to do this is to do some experiments with different resolutions and framerates.

Maybe setup the drivercam so that it streams to a file instead of the driverstation. We can use the size of that file to measure the bandwidth.

Other options would be to see if there are some stats in the mjpg_streamer that we can get at to tell use what bandwidth is being used.

Or, even on the receiving end, maybe we can use some existing tool to measure the bandwidth used.

We have a hard limit of 10 mega bits per second, so we need to be careful to stay under it.

Be sure to measure the bandwidth for real driving action rather than just static images. Otherwise video compression might skew the data and make usage look very small.

mcolinj commented 5 years ago

I installed iftop on my machine and made some measurements of the bandwidth use for a few settings. 640x480 is not possible at all under the bandwidth cap. Here are the bandwidth use for a few resolutions and frame rates. (Note: the bandwidth limit to the driverstation is 4 megabits per second.)

B/W in MB/s Video Resolution (pixels) Framerate (fps)

5.0 320 x 240 (grey) 20 4.0 320 x 240 (grey) 15 9.0 240 x 180 (grey) 60 3.0 240 x 180 (grey) 20

mcolinj commented 5 years ago

Conclusion is that we should be able to do well if we use 240 x 180 at 20 fps. That tops out at 3 MB/s and should work and look fine.