Initializing MediaCapture fails when SpectatorView has been used before

[aleneum]

I try to use WebRTC together with SpectatorView. Together as in "as part of the same Unity app", not at the same time. It seems that when one service has initialized the MediaCapture, the other one cannot do it afterwards unless I restart the app. SpectatorView needs temporary access to the camera to track ArUco markers. The camera is released after synchronization and the handle is disposed. However, when PeerConnection tries to initialize the device after SpectatorView released the media capture, exceptions are thrown. When I use WebRTC first, SpectatorView cannot initialize marker tracking. Even when all GameObjects related to WebRTC have been destroyed. Both services work fine in conjunction with Vuforia though. I can switch back and forth without any issues.

System

• Unity: 2019.2.19f1
• WebRTC: 73b69d7
• SpectatorView: microsoft/MixedReality-SpectatorView@8f7d76c
• HoloLens: 17763.973.x86fre.rs5_release_svc_prod1.200103-1310

I also filed that issue in the SpectatorView project (microsoft/MixedReality-SpectatorView#322) with a detailled debug log.

[aleneum]

I updated the above mentioned issue with a recent 'minimal' example which reproduces the error.

[djee-ms]

Thanks @aleneum. Yes I am aware that at the moment the MediaCapture is locked by the local video track. I will have to talk with @chrisfromwork about this to understand the details and how we can share the MediaCapture between the two projects.

[djee-ms]

Discussed with @chrisfromwork, initial thoughts are that SpectatorView is not initializing MediaCapture from the UI thread, which might cause the issue.

[fibann]

Closing as this is not an issue with MR-WebRTC (see microsoft/MixedReality-SpectatorView#322).