Branches

The release/2.0 branch contains the latest stable version of the API, from which the NuGet and UPM packages are published.

The master branch contains the latest developments. Care has been taken to keep this branch in a fairly clean state (branch can build, tests pass). However the master branch contains API breaking changes compared to the latest release, and therefore is not compatible with NuGet/UPM packages and should be built from sources instead (see Building from sources documentation).

Documentation

The official documentation is hosted at https://microsoft.github.io/MixedReality-WebRTC/.

User Manual

The User Manual contains a general overview of the various libraries of the project and some tutorials on how to use them.

• The Hello, Unity world! tutorial introduces the Unity integration by building a simple audio and video chat client.
• The C# tutorials introduce the .NET Standard 2.0 C# API, which can be used outside Unity.
  • Hello, C# world! (Desktop) shows how to build a simple console app in .NET Core 3.0, which runs as a Windows Desktop (Win32) app.
  • Hello, C# world! (UWP) shows how to build a GUI app with a UI based on WPF (XAML), including how to render the local and remote video.

API reference

An API reference is available for the C# library and the Unity integration.

• C# library API reference
• Unity integration reference

Overview

The overall architecture is as follow:

MixedReality-WebRTC is currently available for Windows 10 Desktop and UWP, with or without Unity, and Android (Unity only).

Note - In the following and elsewhere in this repository the term "Win32" is used as a synonym for "Windows Desktop", the historical Windows API for Desktop application development, and in opposition to the "Windows UWP" API. However Microsoft Windows versions older than Windows 10 with Windows SDK 17134 (April 2018 Update, 1803) are not officially supported for this project. In particular, older versions of Windows (Windows 7, Windows 8, etc.) are explicitly not supported.

Sources

This repository follows the Pitchfork Layout in an attempt to standardize its hierarchy:

bin/               # Binary outputs (generated)
build/             # Intermediate build artifacts (generated)
docs/              # Documentation sources
+ manual/          # User manual sources
examples/          # Examples of use and sample apps
external/          # Third-party external dependencies (git submodules)
libs/              # Source code for the individual libraries
tests/             # Source code for feature tests
tools/             # Utility scripts
+ build/           # Build scripts for the various platforms
  + android/       # Android Studio project to build libmrwebrtc.so
  + libwebrtc/     # Android build scripts for Google's WebRTC library
  + mrwebrtc/      # Windows build tools to build mrwebrtc.dll
+ ci/              # CI Azure pipelines

The Microsoft.MixedReality.WebRTC.sln Visual Studio 2019 solution located at the root of the repository contains several projects:

• The native C/C++ library mrwebrtc, which can be compiled:
  • for Windows Desktop with the mrwebrtc-win32 project
  • for UWP with the mrwebrtc-uwp project
• A C/C++ library unit tests project mrwebrtc-win32-tests
• The C# library project Microsoft.MixedReality.WebRTC
• A C# unit tests project Microsoft.MixedReality.WebRTC.Tests
• A UWP C# sample app project Microsoft.MixedReality.WebRTC.TestAppUWP based on WPF and XAML which demonstrates audio / video / data communication by mean of a simple video chat app.

Note - Currently due to CI limitations some projects are downgraded to VS 2017, as the Google M71 milestone the master and release/1.0 branches are building upon does not support VS 2019, and Azure DevOps CI agents do not support multiple Visual Studio versions on the same agent. This will be reverted to VS 2019 eventually (see #14).

Building MixedReality-WebRTC

See the user manual section on Building from sources.

Special considerations for HoloLens 2

• Mixed Reality Capture (MRC) has some inherent limitations:
  • MRC only works up to 1080p (see the Mixed reality capture for developers documentation), but the default resolution of the webcam on HoloLens 2 is 2272 x 1278 (see the Locatable Camera documentation). In order to access different resolutions, one need to use a different video profile, like the VideoRecording or VideoConferencing ones. This is handled automatically in the Unity integration layer (see here) if WebcamSrouce.FormatMode = Automatic (default), but must be handled manually if using the C# library directly.
  • MRC requires special permission to record the content of the screen:
    • For shared apps (2D slates), this corresponds to the screenDuplication restricted capability, which cannot be obtained by third-party applications. In short, MRC is not available for shared apps. This is an OS limitation.
    • For exclusive-mode apps (fullscreen), there is no particular UWP capability, but the recorded content is limited to the application's own content.
• Be sure to use PreferredVideoCodec = "H264" to make use of the hardware encoder present on the device; software encoding with e.g. VP8 or VP9 codecs is very CPU intensive and strongly discouraged.

Known Issues

The current version is a public preview which contains known issues:

• By default, the WebRTC UWP implementation accesses video capture devices on the system in exclusive mode. This will cause an error when enabling video capture if another application is using the device.
• ARM64 build: Not supported by WebRTC m71/WebRTC UWP SDK.
• H.265: Not supported by WebRTC m71/WebRTC UWP SDK.
• HoloLens 2 exhibits some small performance penalty due to the missing support (#157) for SIMD-accelerated YUV conversion in WebRTC UWP SDK on ARM.
• H.264 hardware video encoding (UWP only) exhibits some quality degrading (blockiness). See #74 and #153 for details.
• H.264 is not currently available on Desktop at all (even in software). Only VP8 and VP9 are available instead (software encoding/decoding).
• The NuGet packages (v1.x) for the former C++ library Microsoft.MixedReality.WebRTC.Native include s