About the OpenTok scalable video feature
Scalable video can greatly improve the quality of video in multi-party sessions. Using this feature, a client automatically publishes a multi-quality video stream, composed of multiple video resolutions and frame rates. This allows simultaneous subscribing endpoints to consume different video resolutions and frame rates.
The scalable video feature is only available in routed sessions (sessions that use the OpenTok Media Router). See The OpenTok Media Router and media modes.
The OpenTok Media Router dynamically switches between different video resolutions and frame rates for a subscriber's stream, as network conditions on the subscribing endpoint change.
You do not need to add any code to use the scalable video feature. The OpenTok Media Router handles the switching of subscriber stream resolutions and frame rates automatically. The OpenTok Media Router turns on this feature when it determines the session will benefit from it based on the topology of clients connected to the session.
Scalable video is only available in streams published by clients that use:
The OpenTok iOS SDK (on certain devices)
The OpenTok Android SDK (on certain devices)
The OpenTok Windows SDK
The OpenTok Linux SDK
OpenTok.js in Chrome and Safari (with beta support in desktop versions of Opera and Chromium-based versions of Edge)
It is only supported for VP8 streams. It is not supported for H.264 streams.
For screen-sharing streams, you need to enable scalable video for the published stream:
In OpenTok.js, for streams that have the video source set to "screen", set the
scalableScreenshare option for the
In the OpenTok Android SDK, for streams that have the video type set to
PublisherKitVideoTypeScreen, use the
In the OpenTok iOS SDK, for streams that have the
OTStreamVideoType set to
OTStreamVideoTypeScreen, use the
In Windows SDK, for streams that have the
VideoSourceType set to
Screen, use the
In the Linux SDK, for streams that have the video type set to
OTC_PUBLISHER_VIDEO_TYPE_SCREEN, use the
By default, scalable video is disabled for screen-sharing streams.
All OpenTok clients can subscribe to scalable video streams. The client SDKs include methods or properties for setting the preferred frame rate and resolution for the stream a subscribing client receives from the OpenTok Media Router:
For more information, see this article.