Conference Capacity

The Communications APIs conferencing infrastructure supports large conferences while maintaining high audio and video quality. The conferencing infrastructure also offers a mechanism that prevents overloading conferences.

Supported conference capacity

This article describes a conference capacity in relation to participants. There are two types of participants: users who join conferences using the join method and listeners who join conferences using the listen method. Users can send and receive streams whereas listeners can only receive streams. The ratio of users to listeners determines how many total participants can join a conference without degrading audio and video quality.

Note: In order to achieve the maximum number of audio only users (250) and listeners (5000), the audioOnly parameter must be set to true when the conference is created, otherwise the video capacity limits are applied.

Maximum number of users

The supported number of users depends on the conference type and the audio codec used. The list of the supported codecs for each SDK is available in the Dolby Voice document. The following table presents the supported number of users in different scenarios:

Conference typeCodecShared mediaMaximum number of users
Dolby VoiceDVCAudio250
Dolby VoiceDVCAudio and video50
Dolby VoiceOpusAudio50
Dolby VoiceOpusAudio and video50
Non-Dolby VoiceOpusAudio50
Non-Dolby VoiceOpusAudio and video50

Participants can only receive up to 25 video streams. In conferences where more than 25 users join a conference with an enabled camera, each conference participant receives video streams from only 25 users who actively talk. Mobile devices can receive only up to 4 video streams. Applications can choose which streams to receive using the Video Forwarding API.

Maximum number of listeners

The maximum number of listeners who may join a conference depends on the number of users that are in the same conference. In a conference where only one user shares audio and video, the platform can support up to 3000 listeners. If more users join a conference, the maximum number of listeners decreases. For example, if five users join an audio and video conference, the maximum number of listeners is 600. In an audio-only conference, the platform can handle up to 5000 listeners, with up to 50 users. The following table presents the supported number of listeners in different scenarios:

Number of usersShared mediaMaximum number of listeners
1 - 250Audio *5000
1 - 50Audio5000
1 - 10Audio and video3000/Number of users
11 - 50Audio and video120

* With the audioOnly flag set to true and using only the DVC codec.

To handle large webinars, we disabled the participantAdded and participantUpdated events for listeners. Listeners only receive events about users; they do not receive events for other listeners. In SDK 3.2 and prior releases, users receive events about users and the first 1000 listeners. However, in SDK 3.3 and next releases, users receive events about other users and do not receive any events about listeners. To notify all application users about the number of participants who are present at a conference, SDK 3.3 introduces the activeParticipants events. If you want to continue to use participantAdded and participantUpdated for listener events, please contact the Support team to enable the events through backend configuration.

Overload prevention

Overloading conferences may trigger a decreased audio and video quality and result in a poor experience for end-users. To avoid such behavior, the Communications APIs platform offers a capacity limit mechanism that impacts streams distributed by the platform. If a conference capacity reaches the limit, the mechanism does not allow additional participants to join the conference. Participants who can exceed the limit are not able to join a conference and receive ConferenceAtMaxCapacityError in the case of the Web SDK, capacityLimit error in the case of iOS SDK, and ConferenceAtMaxCapacityError in the case of Android SDK. The Dolby Communications APIs platform does not allow creating conferences that may exceed the capacity limit.

Conference streaming conferences can be streamed to up to 60,000 viewers using the sub-second latency technology provided by Real-time Streaming (formerly Millicast WebRTC streaming services) and the Real-time Streaming REST APIs.