Channel and Track - STMLink Docs

Channel

Channel represents an established channel session and is the core entry point for publishing, subscribing, messaging, and user state.

Properties

Property	Type	Description
`delegates`	`MulticastDelegate<ChannelDelegate>`	Registers channel event callbacks
`connectState`	`ConnectionState`	Current connection state
`channelInfo`	`ChannelInfo?`	Current channel info
`me`	`User?`	The current user
`streamVendor`	`StreamVendor`	The current media streaming engine vendor

`getUsers()`

Gets info for all users currently in the channel.

let users = channel.getUsers()

Returns: [String: UserInfo]

`getUser(_:)`

Gets a user object by uid.

let user = channel.getUser("alice")

Returns: User?

`publishLocalTrack(_:)`

Publishes a local audio or video track.

try await channel.publishLocalTrack(micTrack)
try await channel.publishLocalTrack(cameraTrack)

Supported overloads:

publishLocalTrack(_ track: LocalAudioTrack, options: AudioPublishOptions? = nil)
publishLocalTrack(_ track: LocalVideoTrack, options: VideoPublishOptions? = nil)

Note:

Audio tracks go through the internal mixed sending model
If a LocalScreenTrack carries screen audio, its audio part is published automatically along with it

`unpublishLocalTrack(_:)`

Unpublishes a local audio or video track.

try await channel.unpublishLocalTrack(micTrack)
try await channel.unpublishLocalTrack(cameraTrack)

We recommend calling stopCapture() after unpublishing to release capture resources.

`subscribeRemoteAudioTrack(uid:trackId:)`

Subscribes to a remote audio track.

try await channel.subscribeRemoteAudioTrack(uid: uid, trackId: trackId)

`subscribeRemoteVideoTrack(uid:trackId:)`

Subscribes to a remote video track.

try await channel.subscribeRemoteVideoTrack(uid: uid, trackId: trackId)

`unsubscribeRemoteTrack(_:debounceMs:)`

Unsubscribes from a remote track.

try await channel.unsubscribeRemoteTrack(track)

Parameter	Type	Required	Description
`track`	`Track`	Yes	The remote track object
`debounceMs`	`Int`	No	Default `2000`; debounces frequent subscribe/unsubscribe toggling

`getRemoteTrack(uid:trackId:)`

Gets a remote track object by user and track ID.

let track = channel.getRemoteTrack(uid: uid, trackId: trackId)

Returns: Track?

`getRemoteTrackByDesc(uid:desc:)`

Gets a remote track by desc.

let screenTrack = channel.getRemoteTrackByDesc(uid: uid, desc: "screen")

Track base class

All tracks inherit from Track and share the following core properties:

Property	Type	Description
`id`	`String`	Track ID
`kind`	`TrackKind`	`audio` or `video`
`desc`	`String`	Track description, such as `mic`, `screen`, or `camera_big`
`info`	`TrackInfo`	Snapshot of the current track info
`uid`	`String?`	UID of the user the track belongs to
`delegates`	`MulticastDelegate<TrackDelegate>`	Track-level event callbacks

Common methods:

getInfo()

LocalMicTrack

Capture control

startCapture(options:)
stopCapture()
restartCapture()

User control

mute()
unmute()
changeDeviceId(_:)

Typical usage:

let micTrack = srtc.createLocalMicTrack(preset: .music)
try await micTrack.startCapture()
try await channel.publishLocalTrack(micTrack)
micTrack.mute()
micTrack.unmute()

LocalCameraTrack

Capture control

startCapture(options:)
stopCapture()
restartCapture()

User control

mute()
unmute()
changeDeviceId(_:)
switchCamera()

Rendering

addRenderer(_:)
removeRenderer(_:)
removeAllRenderers()

LocalScreenTrack

Capture control

startCapture(options:)
stopCapture()
restartCapture()

User control

mute()
unmute()

Screen audio

audioTrack
setAudioTrack(_:)
getAudioTrack()

Capture mode and state (iOS)

Member	Type	Description
`captureMode`	`ScreenCaptureMode`	Capture mode, decided at creation by `createLocalScreenTrack(mode:)`; ignored on macOS
`isCapturing`	`Bool`	Whether capture has started. With full-screen capture it means “listening is ready”, not that there’s video
`isBroadcastActive`	`Bool`	With full-screen capture, whether the extension is sending video, i.e. whether the remote side can see video; check this to display a “sharing” state

LocalAudioTrack

For custom audio input:

mute()
unmute()
pushAudioBuffer(_:)

This kind of track usually doesn’t need startCapture(); instead, your app keeps injecting PCM data.

LocalVideoTrack

For custom video input:

addRenderer(_:)
removeRenderer(_:)
removeAllRenderers()
pushFrame(_:rotation:timestampNs:)

If you have an external rendering pipeline, a canvas, a screen encoder, or an AI processing pipeline, this entry point is the better fit.

RemoteAudioTrack

Playback control

startPlay()
stopPlay()
isPlaying

PCM data callback

add(audioRenderer:)
remove(audioRenderer:)

The AudioRenderer callback receives AVAudioPCMBuffer values, suitable for speech transcription, recording, or further analysis.

RemoteVideoTrack

Rendering control

addRenderer(_:)
removeRenderer(_:)
removeAllRenderers()

Remote video is usually displayed after a successful subscription, through SRTCVideoView(track:) or SRTCVideoRenderer.

Receive status

isReceiveTimedOut: Bool

Whether this video has currently been judged to have timed out on receiving. The value matches the timedOut last reported by channel(_:didChangeReceiveStreamStatus:), and is suited for filling in the current state once when a render view initializes or when the app returns from the background to the foreground, so the UI doesn’t fall out of sync with reality by relying on events alone. For the everyday “loading” indicator, we still recommend driving it with events—see Events for details.

Rendering components

`SRTCVideoView`

Preferred for SwiftUI:

SRTCVideoView(track: track)
    .frame(width: 320, height: 180)

`VideoView`

For UIKit / AppKit, use bind(track:) / unbind() to manage binding.

`SRTCVideoRenderer`

A lower-level rendering view, bound by the track explicitly calling addRenderer(_:).

​Channel

​Properties

​getUsers()

​getUser(_:)

​publishLocalTrack(_:)

​unpublishLocalTrack(_:)

​subscribeRemoteAudioTrack(uid:trackId:)

​subscribeRemoteVideoTrack(uid:trackId:)

​unsubscribeRemoteTrack(_:debounceMs:)

​getRemoteTrack(uid:trackId:)

​getRemoteTrackByDesc(uid:desc:)

​Track base class

​LocalMicTrack

​Capture control

​User control

​LocalCameraTrack

​Capture control

​User control

​Rendering

​LocalScreenTrack

​Capture control

​User control

​Screen audio

​Capture mode and state (iOS)

​LocalAudioTrack

​LocalVideoTrack

​RemoteAudioTrack

​Playback control

​PCM data callback

​RemoteVideoTrack

​Rendering control

​Receive status

​Rendering components

​SRTCVideoView

​VideoView

​SRTCVideoRenderer

Channel

Properties

`getUsers()`

`getUser(_:)`

`publishLocalTrack(_:)`

`unpublishLocalTrack(_:)`

`subscribeRemoteAudioTrack(uid:trackId:)`

`subscribeRemoteVideoTrack(uid:trackId:)`

`unsubscribeRemoteTrack(_:debounceMs:)`

`getRemoteTrack(uid:trackId:)`

`getRemoteTrackByDesc(uid:desc:)`

Track base class

LocalMicTrack

Capture control

User control

LocalCameraTrack

Capture control

User control

Rendering

LocalScreenTrack

Capture control

User control

Screen audio

Capture mode and state (iOS)

LocalAudioTrack

LocalVideoTrack

RemoteAudioTrack

Playback control

PCM data callback

RemoteVideoTrack

Rendering control

Receive status

Rendering components

`SRTCVideoView`

`VideoView`

`SRTCVideoRenderer`