Calling SDK overview

The Calling SDK enables end-user devices to drive voice and video communication experiences. This page provides detailed descriptions of Calling features, including platform and browser support information. To get started right away, check out Calling quickstarts or Calling hero sample.

Once you've started development, check out the known issues page to find bugs we're working on.

Key features of the Calling SDK:

  • Addressing - Azure Communication Services provides generic identities that are used to address communication endpoints. Clients use these identities to authenticate to the service and communicate with each other. These identities are used in Calling APIs that provide clients visibility into who is connected to a call (the roster).
  • Encryption - The Calling SDK encrypts traffic and prevents tampering on the wire.
  • Device Management and Media - The Calling SDK provides facilities for binding to audio and video devices, encodes content for efficient transmission over the communications dataplane, and renders content to output devices and views that you specify. APIs are also provided for screen and application sharing.
  • PSTN - The Calling SDK can initiate voice calls with the traditional publicly switched telephone network, using phone numbers you acquire in the Azure portal or programmatically.
  • Teams Meetings - The Calling SDK can join Teams meetings and interact with the Teams voice and video dataplane.
  • Notifications - The Calling SDK provides APIs allowing clients to be notified of an incoming call. In situations where your app isn't running in the foreground, patterns are available to fire pop-up notifications ("toasts") to inform end-users of an incoming call.
  • User Facing Diagnostics (UFD) - The Calling SDK provides events that are designed to provide insights into underlying issues that could affect call quality. Developers can subscribe to triggers such as weak network signals or muted microphones, ensuring that they're always aware of any factors impacting the calls.
  • Media Stats - The Calling SDK provides comprehensive insights into the metrics of your VoIP and video calls. With this information, developers have a clearer understanding of call quality and can make informed decisions to further enhance their communication experience.
  • Video Constraints - The Calling SDK provides APIs that gain the ability to regulate video quality among other parameters during video calls by adjusting parameters such as resolution and frame rate supporting different call situations for different levels of video quality

Detailed capabilities

The following list presents the set of features that are currently available in the Azure Communication Services Calling SDKs.

Group of features Capability JS Windows Java (Android) Objective-C (iOS)
Core Capabilities Place a one-to-one call between two users ✔️ ✔️ ✔️ ✔️
Place a group call with more than two users (up to 100 users) ✔️ ✔️ ✔️ ✔️
Promote a one-to-one call with two users into a group call with more than two users ✔️ ✔️ ✔️ ✔️
Join a group call after it has started ✔️ ✔️ ✔️ ✔️
Invite another VoIP participant to join an ongoing group call ✔️ ✔️ ✔️ ✔️
Mid call control Turn your video on/off ✔️ ✔️ ✔️ ✔️
Mute/Unmute mic ✔️ ✔️ ✔️ ✔️
Switch between cameras ✔️ ✔️ ✔️ ✔️
Local hold/un-hold ✔️ ✔️ ✔️ ✔️
Active speaker ✔️ ✔️ ✔️ ✔️
Choose speaker for calls ✔️ ✔️ ✔️ ✔️
Choose microphone for calls ✔️ ✔️ ✔️ ✔️
Show state of a participant
Idle, Early media, Connecting, Connected, On hold, In Lobby, Disconnected
✔️ ✔️ ✔️ ✔️
Show state of a call
Early Media, Incoming, Connecting, Ringing, Connected, Hold, Disconnecting, Disconnected
✔️ ✔️ ✔️ ✔️
Show if a participant is muted ✔️ ✔️ ✔️ ✔️
Show the reason why a participant left a call ✔️ ✔️ ✔️ ✔️
Screen sharing Share the entire screen from within the application ✔️ ✔️1 ✔️1 ✔️1
Share a specific application (from the list of running applications) ✔️ ✔️1
Share a web browser tab from the list of open tabs ✔️
Share system audio during screen sharing
Participant can view remote screen share ✔️ ✔️ ✔️ ✔️
Roster List participants ✔️ ✔️ ✔️ ✔️
Remove a participant ✔️ ✔️ ✔️ ✔️
PSTN Place a one-to-one call with a PSTN participant ✔️ ✔️ ✔️ ✔️
Place a group call with PSTN participants ✔️ ✔️ ✔️ ✔️
Promote a one-to-one call with a PSTN participant into a group call ✔️ ✔️ ✔️ ✔️
Dial-out from a group call as a PSTN participant ✔️ ✔️ ✔️ ✔️
Support for early media ✔️ ✔️ ✔️ ✔️
General Test your mic, speaker, and camera with an audio testing service (available by calling 8:echo123) ✔️ ✔️ ✔️ ✔️
Device Management Ask for permission to use audio and/or video ✔️ ✔️ ✔️ ✔️
Get camera list ✔️ ✔️ ✔️ ✔️
Set camera ✔️ ✔️ ✔️ ✔️
Get selected camera ✔️ ✔️ ✔️ ✔️
Get microphone list ✔️ ✔️ 2 2
Set microphone ✔️ ✔️ 2 2
Get selected microphone ✔️ ✔️ 2 2
Get speakers list ✔️ ✔️ 2 2
Set speaker ✔️ ✔️ 2 2
Get selected speaker ✔️ ✔️ 2 2
Video Rendering Render single video in many places (local camera or remote stream) ✔️ ✔️ ✔️ ✔️
Set / update scaling mode ✔️ ✔️ ✔️ ✔️
Render remote video stream ✔️ ✔️ ✔️ ✔️
Video Effects Background Blur ✔️ ✔️ ✔️ ✔️
Custom background image ✔️
  1. The Share screen capability can be achieved using Raw Media, if you want to learn, how to add Raw Media, visit the quickstart guide.
  2. The Calling SDK doesn't have an explicit API, you need to use the OS (android & iOS) API to achieve it.

UI Library

UI Library makes it easy for you to build modern communications user experiences using Azure Communication Services. It provides a library of production-ready UI components to drop into your application.

With this set of prebuilt controls, you can create beautiful designs using the fluent UI SDK components and audio/video communication experiences. If you want to learn more about the UI Library, you can visit the overview site, where you find details about web and mobile platforms.

Calling SDK streaming support

The Azure Communication Services Calling SDK supports the following streaming configurations:

Limit Web Windows/Android/iOS
Maximum # of outgoing local streams that can be sent simultaneously 1 video and 1 screen sharing 1 video + 1 screen sharing
Maximum # of incoming remote streams that can be rendered simultaneously 9 videos + 1 screen sharing on desktop browsers*, 4 videos + 1 screen sharing on web mobile browsers 9 videos + 1 screen sharing

* Starting from ACS Web Calling SDK version 1.16.3 While the Calling SDK don't enforce these limits, your users may experience performance degradation if they're exceeded. Use the API of Optimal Video Count to determine how many current incoming video streams your web environment can support.

Calling SDK timeouts

The following timeouts apply to the Communication Services Calling SDKs:

Action Timeout in seconds
Reconnect/removal participant 60
Add or remove new modality from a call (Start/stop video or screen sharing) 40
Call Transfer operation timeout 60
1:1 call establishment timeout 85
Group call establishment timeout 85
PSTN call establishment timeout 115
Promote 1:1 call to a group call timeout 115

Maximum call duration

The maximum call duration is 30 hours, participants that reach the maximum call duration lifetime of 30 hours will be disconnected from the call.

JavaScript Calling SDK support by OS and browser

The following table represents the set of supported browsers, which are currently available. We support the most recent three major versions of the browser (most recent three minor versions for Safari) unless otherwise indicated.

Platform Chrome Safari Edge Firefox Webview
Android ✔️ ✔️ ✔️ *
iOS ✔️ ✔️ ✔️
macOS ✔️ ✔️ ✔️ ✔️
Windows ✔️ ✔️ ✔️
Ubuntu/Linux ✔️
  • Outgoing Screen Sharing isn't supported on iOS or Android mobile browsers.
  • Firefox support is in public preview.
  • Currently, the calling SDK only supports Android System WebView on Android, iOS WebView(WKWebView) in public preview. Other types of embedded browsers or WebView on other OS platforms aren't officially supported, for example, GeckoView, Chromium Embedded Framework (CEF), Microsoft Edge WebView2. Running JavaScript Calling SDK on these platforms isn't actively tested, it may or may not work.
  • An iOS app on Safari can't enumerate/select mic and speaker devices (for example, Bluetooth); this issue is a limitation of the OS, and there's always only one device, OS controls default device selection.

Android Calling SDK support

  • Support for Android API Level 21 or Higher
  • Support for Java 7 or higher
  • Support for Android Studio 2.0

iOS Calling SDK support

  • Support for iOS 10.0+ at build time, and iOS 12.0+ at run time
  • Xcode 12.0+

Calling client - browser security model

User WebRTC over HTTPS

WebRTC APIs like getUserMedia require that the app that calls these APIs is served over HTTPS.

For local development, you can use http://localhost.

Embed the Communication Services Calling SDK in an iframe

A new permissions policy (also called a feature policy) is available in various browsers. This policy affects calling scenarios by controlling how applications can access a device's camera and microphone through a cross-origin iframe element.

If you want to use an iframe to host part of the app from a different domain, you must add the allow attribute with the correct value to your iframe.

For example, this iframe allows both camera and microphone access:

<iframe allow="camera *; microphone *">

Known issues

Once you've started development, check out the known issues page to find bugs we're working on.

Next steps

For more information, see the following articles: