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Requirements and considerations for application-hosted media bots

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An application-hosted media bot requires the Microsoft.Graph.Communications.Calls.Media .NET library to access the audio and video media streams. The bot must be deployed on a Windows Server on-premises machine or a Windows Server guest Operating System (OS) in Azure.

Note

  • The guidance for developing messaging and Interactive Voice Response (IVR) bots doesn't completely apply to building application-hosted media bots.
  • As the Microsoft Real-time Media Platform for bots is in developer preview, the guidance in this document is subject to change.

C# or .NET and Windows Server for development

An application-hosted media bot has the following requirements:

  • The bot must be developed using C# and the standard .NET Framework, and deployed on Microsoft Azure. You can't use C++ or Node.js APIs to access real-time media. However, .NET Core is supported for an application-hosted media bot, and the SDK provides support for .NET 6.0.

  • The bot can be hosted within one of the following Azure service environments:

    • Cloud Service.
    • Service Fabric with Virtual Machine Scale Sets (VMSS).
    • Infrastructure as a Service (IaaS) Virtual Machine (VM).
    • Azure Kubernetes Service (AKS).

  • The bot can't be deployed as an Azure web app.

  • The bot must be running on a recent version of the Microsoft.Graph.Communications.Calls.Media .NET library. The bot must use either the newest available version of the NuGet package, or a version that isn't more than three months old. Older versions of the library are deprecated and don't work after a few months. Keeping the Microsoft.Graph.Communications.Calls.Media library up-to-date ensures the best interoperability between the bot and Microsoft Teams.

The next section provides details on where real-time media calls are located.

Real-time media calls stay where they're created

Real-time media calls stay on the computer where they were created. A real-time media call is pinned to the virtual machine (VM) instance that accepted or started the call. Media from a Teams call or meeting flows to that VM instance, and media the bot sends back to Teams must also originate from that VM. If there are any real-time media calls in progress when the VM is stopped, those calls are abruptly terminated. If the bot has prior knowledge of the pending VM shutdown, it can end the calls.

The next section provides details on accessibility of application-hosted media bots.

Application-hosted media bots accessible on the internet

Application-hosted media bots must be directly accessible on the internet. These bots must include the following features:

  • Each VM instance hosting an application-hosted media bot in Azure must be directly accessible from the internet using an instance-level public IP address (ILPIP).
  • The service hosting an application-hosted media bot must also configure each VM instance with a public-facing port, which maps to the specific instance.
  • Bot Framework Emulator doesn't support application-hosted media bots.

The next section provides details on scalability and performance considerations of application-hosted media bots.

Scalability and performance considerations

The application-hosted media bots require the following scalability and performance considerations:

  • Application-hosted media bots require more compute and network (bandwidth) capacity than messaging bots and may incur higher operational costs. A real-time media bot developer must carefully measure the bot's scalability, and ensure the bot doesn't accept more simultaneous calls than it can manage. A video-enabled bot may be able to sustain only one or two concurrent media sessions per CPU core (if using the "raw" RGB24 or NV12 video formats).
  • The Real-time Media Platform doesn't take advantage of any Graphics Processing Units (GPU) available on the VM to off-load H.264 video encoding/decoding. Instead, video encode and decode are done in software on the CPU. If a GPU is available, the bot may take advantage of it for its own graphics rendering, for example, if the bot is using a 3D graphics engine.
  • The VM instance hosting the real-time media bot must have at least two CPU cores. For Azure, a Dv2-series virtual machine is recommended. For other Azure VM types, a system with four virtual CPUs (vCPU) is the minimum size required. Detailed information about Azure VM types is available in the Azure documentation.

Supported media formats for bots

Bots on Microsoft Teams support only the following media formats for audio and video content:

Format More information
Vorbis http://www.vorbis.com/
PCM_U8, PCM_S16LE, PCM_S32LE, PCM_F32LE, PCM_S16BE, PCM_S24BE, PCM_MULAW https://wiki.multimedia.cx/?title=PCM
Ogg http://www.vorbis.com/
Matroska https://matroska.org/
WAV https://en.wikipedia.org/wiki/WAV
AAC https://en.wikipedia.org/wiki/Advanced_Audio_Coding
H264 https://en.wikipedia.org/wiki/H.264/MPEG-4_AVC
MP3 https://en.wikipedia.org/wiki/MP3
Opus http://opus-codec.org/
MP4 https://en.wikipedia.org/wiki/MPEG-4

Code sample

Application-hosted media bots samples are as follows:

Sample name Description Graph
Local media sample Sample that illustrates different local media scenarios. View
Remote media sample Sample that illustrates different remote media scenarios. View

See also