Adaptive Bitrate (Simulcast)

Simulcast enables Adaptive Bitrate (ABR) in video conferencing scenarios. This means 100ms SDKs can upgrade or downgrade video quality for remote tracks based on user preferences or network conditions.

Minimum Requirements

• SDK version 0.5.1 or higher
• Simulcast enabled in room template

100ms SDK Simulcast APIs

You interact with the simulcast feature by setting HMSRemoteVideoTrack's layer property. Let's look at the track interface:

class HMSRemoteVideoTrack {
    open var layerDefinitions: [HMSSimulcastLayerDefinition]?
    open var layer: HMSSimulcastLayer
}

class HMSSimulcastLayerDefinition : NSObject {
    open var layer: HMSSimulcastLayer
    open var resolution: CGSize
}

enum HMSSimulcastLayer {
    case high
    case mid
    case low
}

Here layerDefinitions property holds an array of currently available layers for the track and layer property is the currently selected layer. Within HMSSimulcastLayerDefinition you get its resolution and the layer name such as high/mid/low.

Auto Layer Selection

HMSVideoView has an automatic simulcast layer selection capability which is enabled by default. It will select a layer that best matches the current view frame size and reacts to frame updates. In case manual layer selection is preferred set disableAutoSimulcastLayerSelect property to true. By default, the track layer is set to high.