Hi Christian,

Well, I don't know how the OSG-DirectShow plugin works regarding threading and 
latency.


When I did a similar setup I used OpenCV and wrote a plugin that spawn a thread 
for image acquisition. Here is my code:

https://github.com/bjornblissing/osgopencv


Hopefully the new Oculus SDK has cut the latency a bit, BUT this does not 
matter much if the main part of the latency comes originates from the image

acquisition.


Best regards

Björn

________________________________
Från: osg-users <[email protected]> för Christian 
Buchner <[email protected]>
Skickat: den 1 september 2015 14:57
Till: OpenSceneGraph Users
Ämne: Re: [osg-users] Oculus+OSG


In this case I am using a slightly modified DirectShow OSG plug-in, running the 
osgviewer in single threaded mode. The plug-in provides an osg::ImageStream and 
updates a texture that is displayed in the OSG scene. The camera is an USB 3.0 
model, and I would expect it to be one of the fastest "web cams" out there.

I am hoping that OpenGL applications also benefit from the low level driver 
support created for the Oculus and similar VR devices.

Christian


2015-09-01 12:48 GMT+02:00 Björn Blissing 
<[email protected]<mailto:[email protected]>>:

cbuchner1 wrote:
> Can you make any statements regarding latency improvements upgrading from the 
> 0.6 SDK to 0.7 for osgoculusviewer based applications?


Hi Christian,

I have not had time to do any measurements regarding latency differences 
between 0.6 and 0.7 yet. Sorry.



cbuchner1 wrote:
> Our current use case is currently, attaching an Intel RealSense camera to the 
> front of the Oculus DK2 and streaming a live image into the viewer's eyes. 
> Our latency is currently in the area of about 3-4 video frames @75 Hz, 
> amounting to 40-50 ms. This is a bit too high and causes some motion sickness 
> and slow reactions in our unfortunate test persons. ;)


Are you talking about pure rendering latency (motion to photon) or the camera 
to HMD latency (photon to photon)?

If you are talking about the latter 40-50 is quite good I would say. And as Jan 
says, the camera is probably the limiting factor in that case. Another problem 
can be if you run the camera capture in the same thread as the rest of the 
rendering. Moving the camera capture to an own thread gave me a great 
performance boost, but results in the cameras running asynchronous with the 
rendering. This in turn can gives a larger variance in latency.

Best regards
Björn

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