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Issue with mirroring

November 16, 2018 - 5:40am #1

Hi community,

I have an AR experience involving a model target.

I haven’t been able to mirror the HoloLens AR experience on the Windows 10 HoloLens app:

- Either I enable the recording before loading the library which contains the model target, in which case the target doesn’t lock

- Or I load the library, in which case the HoloLens goes offline / disconnects from the app

I tested with a ThingMark-based AR experience and it worked fine.

Is it a known bug, due to the use of the model target?

Thanks for your help!

Issue with mirroring

November 20, 2018 - 3:43pm #2

Hello,

Based upon experiments with HoloLens while running Vuforia, here is what we know about the Mixed Reality Capture (MRC) feature:

  1. You can record videos of Vuforia apps running on HoloLens. Note that for this to work, the app running Vuforia must be started *before* you started to record with HL’s MRC. If you start recording first, the video will abruptly stop once Vuforia gets access to the HL camera.
  2. You *cannot* do MRC Live preview while a Vuforia app is running in any case. If you try to start Live preview while a Vuforia-based app is running on HL, you will get an error in MRC. If you try to start a Vuforia-based app while Live preview is running, the app will not start.

The limitations above are related to real-time camera access for apps running on the HoloLens. In order to guarantee optimal detection and tracking performance, Vuforia is granted sole access to the live camera feed. This is similar to other platforms that we support, such as Android and iOS. You can see that it also works the other way around for apps that do not run Vuforia. The Live preview app requires real-time camera access, so while it is running Vuforia is blocked from accessing the camera.

The instructions below are for HoloLens device running RS4:

  1. You can record videos of Vuforia apps running on HoloLens. Note that for this to work, the Vuforia performance mode must be set to MODE_OPTIMIZE_SPEED, which sets the camera capture resolution to be 720p, e.g. 1280x720.
  2. The app running Vuforia must be started *before* you started to record with HL’s MRC. If you start recording first, the video will abruptly stop once Vuforia gets access to the HL camera.
  3. The MRC capture resolution must be set to the same as the Vuforia performance mode (720p)
  4. You *cannot* do MRC Live preview while a Vuforia app is running in any case. If you try to start Live preview while a Vuforia-based app is running on HL, you will get an error in MRC. If you try to start a Vuforia-based app while Live preview is running, the app will not start.

We've had mixed success with these steps in RS4, with results in that it works every time to it works once in a while.

Thanks,

Vuforia Engine Support

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