Voice and video concepts
The Plan B Session Description Protocol (SDP) API is being deprecated. Update your Communication Services Calling SDKs to v1.1.0 (or newer) by July 31, 2021 to prevent this deprecation from impacting your users. See the calling library release notes for more information.
Call types in Azure Communication Services
There are multiple types of calls you can make in Azure Communication Services. The type of calls that you make determine your signaling schema, media traffic flows, and pricing model.
Voice Over IP (VoIP)
When a user of your application calls another user of your application over an internet or data connection, the call is made over Voice Over IP (VoIP). In this case, both signaling and media flow over the internet.
Public switched telephone network (PSTN)
Any time your users interact with a traditional telephone number, calls are facilitated by PSTN (Public Switched Telephone Network) voice calling. To make and receive PSTN calls, you need to add telephony capabilities to your Azure Communication Services resource. In this case, signaling and media use a combination of IP-based and PSTN-based technologies to connect your users.
A one-to-one call on Azure Communication Services happens when one of your users connects to another user using one of our SDKs. The call can be either VoIP or PSTN.
A group call on Azure Communication Services happens when three or more participants connect to one another. Any combination of VoIP and PSTN-connected users can be present on a group call. A one-to-one call can be converted into a group call by adding more participants to the call. One of those participants can be a bot.
Supported video standards
We support H.264 (MPEG-4).
We support up to Full HD 1080p on the native (iOS, Android) SDKs. For Web (JS) SDK we support Standard HD 720p. The quality depends on the available bandwidth.
For more information, see the following articles: