Using the Amazon Chime SDK

An ephemeral resource identified by a unique MeetingId. The MeetingId is placed onto a group of media services that host the active meeting.

The group of media services that hosts an active meeting.

A set of regionalized URLs that represents a media service group. Attendees connect to the media service group with their clients to send and receive real-time audio and video, and share their screens.

A meeting participant that is identified by a unique AttendeeId. Attendees may freely join and leave meetings using a client application built with an Amazon Chime SDK client library.

A unique token assigned to each attendee. Attendees use the join token to authenticate with the media service group.

When the server application creates an Amazon Chime SDK meeting, the meeting is assigned to a region-specific media service. The hosts in the service are responsible for securely transferring real-time media between attendee clients. Each created attendee is assigned a unique join token, an opaque secret key that your server application must securely transfer to the client authorized to join the meeting on behalf of an attendee. Each client uses a join token to authenticate with the media service group. Clients use a combination of secure WebSockets and Datagram Transport Layer Security (DTLS) to securely signal the media service group, and to send and receive media to and from other attendees through the media service group.

The media service mixes audio together from each attendee and sends the mix to each recipient, after subtracting their own audio from the mix. The Amazon Chime SDKs sample audio at the highest rate supported by the device and browser, up to a maximum of 48kHz. We use the Opus codec to encode audio, with a default bitrate of 32kbps, which can be increased to up to 128kbps stereo and 64kbps mono.

The media service acts as a Selective Forwarding Unit (SFU) using a publish and subscribe model. Each attendee can publish one video source, up to a total of 25 simultaneous videos per meeting. The Amazon Chime SDK client library for JavaScript supports video resolutions up to 1280x720 at 30 frames per second without simulcast, and 15 frames per second with simulcast. The Amazon Chime SDK client libraries for iOS, Android, and Windows support video resolutions up to 1280x720 and 30 frames per second, however the actual framerate and resolution is automatically managed by the Amazon Chime SDK.

When active, video simulcast sends each video stream in two different resolutions and bitrates. Clients with bandwidth constraints automatically subscribe to the lower bitrate stream. Video encoding and decoding uses hardware acceleration where available to improve performance.

In addition to audio and video content, meeting attendees can send each other real-time data messages of up to 2 KB each. You can use messages to implement custom meeting features such as whiteboarding, chat, real-time emoji reactions, and application-specific floor control signaling.

The client application can share audio and video content, such as screen captures or media files. Content sharing supports pre-recorded content video up to 1280x720 at 15 frames per second, and audio up to 48kHz at 64kbps. Screen capture for content sharing is supported up to 15 frames per second, but may be limited by the capabilities of the device and browser.