MixedReality-WebRTC

MixedReality-WebRTC is a collection of libraries to help mixed reality app developers to integrate peer-to-peer real-time audio and video communication into their application and improve their collaborative experience.

• Enables multi-track real-time audio / video / data communication with a remote peer
• Provides an abstracted signaling interface to easily switch implementation
• Exposes an API for C++ and C# to integrate into existing apps
• Provides a set of Unity3D components for rapid prototyping and integration
• Includes support for Microsoft HoloLens (x86) and Microsoft HoloLens 2 (ARM)
• Allows easy use of Mixed Reality Capture (MRC) to stream the view point of the user for multi-device experiences

MixedReality-WebRTC is part of the collection of repositories developed and maintained by the Mixed Reality Sharing team.

Download

NuGet (C++, C#) and UPM (Unity) packages are available for stable releases (release/* branches). See the Release page on GitHub or the Download documentation page for details.

Note: The master branch contains the code for the next release, and therefore sometimes contains breaking API changes from the latest stable release. It is therefore not guaranteed to work with NuGet packages, which are only available for stable releases. In particular, the Unity library scripts are only guaranteed to be compatible with NuGet packages if copied from a release/* branch, though it is strongly recommended to use the UPM packages instead.

Build Status

Branch	WebRTC	API	C library (mrwebrtc)	C# Library	Docs
release/1.0	M71	Stable
master	M71	Unstable

The release/1.0 branch contains the latest stable version of the API, from which the NuGet packages are published. When using the NuGet packages, the Unity integration scripts from this branch must be used to ensure API compatibility.

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

Both branches are based off the M71 milestone of the Google WebRTC library, which provides the underlying WebRTC native implementation.

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

Getting Started

MixedReality-WebRTC is a set of individual building blocks in the form of C and C# libraries building upon each other to deliver a consistent API to C/C++ and C# developers across its supported platforms, and a set of handful drop-in Unity3D components for easy integration. The pure C library allows easy integration as a shared module (DLL) into C/C++ projects while avoiding issues with compiler and CRT variants.

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 library mrwebrtc, which can be compiled:
  • for Windows Desktop with the mrwebrtc-win32 project
  • for UWP with the mrwebrtc-uwp project
• A 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 avail 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 under active development, which contains known issues being addressed:

• 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 some WebRTC headers from the Google repository, which are not shipped with any of the NuGet packages themselves, but instead require cloning this repository and its dependencies (see #123).

In addition, the Debug config of WebRTC core implementation is known to exhibit some performance issues on most devices, including some higher-end PCs. Using the Release config of the core WebRTC implementation usually prevents this, and is strongly recommended when not debugging.

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.

When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.

Reporting security issues and bugs

MixedReality-WebRTC builds upon the WebRTC implementation provided by Google. Security issues and bugs related to this implementation should be reported to Google.

Security issues and bugs related to MixedReality-WebRTC itself or to WebRTC UWP SDK should be reported privately, via email, to the Microsoft Security Response Center (MSRC) secure@microsoft.com. You should receive a response within 24 hours. If for some reason you do not, please follow up via email to ensure we received your original message. Further information, including the MSRC PGP key, can be found in the Security TechCenter.