libfreenect2 - OpenNI2 depth always runs at 15fps

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Lorne Covington

Aug 27, 2017, 8:05:25 PM8/27/17

I am using the libfreenect2 0.2.0 x64 libusbk binaries under Win7 x64.
The depth stream in my OpenNI2 app always runs at exactly 15fps. This
is odd, because in reading the source it appears the libfreenect2 OpenNI
driver always sets it to 30fps no matter what is passed in to the OpenNI

The fact that it is exactly 15fps, and happens on a laptop as well as a
high-end gaming system makes me doubt it is any kind of throughput
issue, but rather a setting somewhere. I am only opening the depth
stream, not the IR or RGB (at least via the OpenNI2 calls, no idea if
they are getting opened by libfreenect2 anyway).

Even more odd, two Kinect2s on the same USB3 adapter will run fine, but
both at 15fps. I have tried unplugging all USB3 devices from the PC
except the one K2.

And this same program can happily set Primesense/Xtion cameras to 30 or
60fps, so that code is not the problem. And I tested it on a third
system with the same 15fps result.

Any ideas? Thanks!

- Lorne


Lorne Covington

Aug 28, 2017, 8:19:01 PM8/28/17

Again answering my own question (partially):

It turns out the RGB frame rate can throttle down from 30fps to 15 in
low lighting.

I pointed the K2 at a light, and sure enough, the depth frame rate shot
up to 30fps.

Now, the question is:

Why is the RGB frame rate controlling the depth frame rate? Particularly
since I am only opening the OpenNI2 depth stream, and never the RGB stream.

Is this a K2 "feature", or something in the way libfreenect2 works?

Is the RGB stream always enabled with the OpenNI2 driver, no matter what?

Thanks folks!

- Lorne
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