SRTCEngine

SRTCEngine is the main entry point of the Swift SDK. It’s responsible for joining channels, leaving channels, creating local tracks, and configuring logging and audio processors.

Initialization

`init()`

Creates an SDK instance and completes the underlying WebRTC initialization.

let srtc = SRTCEngine()

Properties

`logLevel`

Sets the SDK log level.

Parameter	Type	Required	Description
`logLevel`	`LogLevel`	No	Possible values include `debug`, `info`, `warning`, and `error`

Example:

srtc.logLevel = .debug

`audioCaptureProcessor`

Audio processor applied after microphone capture, usable for voice changing, noise suppression, and similar processing.

`audioRenderProcessor`

Processor applied to remote audio before playback, usable for playback-side audio enhancement.

`channels`

The list of channels that have been joined and are still live ([Channel]), ordered by join time. An empty array means you’re not in any channel.

`defaultChannel`

The default channel (Channel?): the earliest-joined one that’s still live; once you leave it, the next one takes its place. The no-argument leaveChannel() applies to it. See Multi-channel for details.

Methods

`joinChannel(token:options:)`

Joins a channel and returns a Channel instance. You can call it multiple times to join several channels at once; each channel’s publishing, subscriptions, users, and events are independent of each other. It throws alreadyJoined only when the same channel name has already been joined (or a join is in progress).

let channel = try await srtc.joinChannel(
    token: token,
    options: JoinOptions(autoSubscribeAudio: true)
)

Parameter	Type	Required	Description
`token`	`String`	Yes	Base64-encoded channel token
`options`	`JoinOptions`	No	Join options; default `JoinOptions()`

Returns: Channel Throws:

SRTCError.alreadyJoined
SRTCError.tokenExpired
SRTCError.tokenInvalid
Other network, signaling, and media streaming connection errors

`leaveChannel()`

Leaves the default channel (the earliest-joined one that’s still live).

await srtc.leaveChannel()

If no channel is currently joined, the call is safely ignored.

`leaveChannel(_:)`

Leaves the specified channel, equivalent to channel.leave(); other channels aren’t affected. With multiple channels we recommend this version, to avoid ambiguity from “the default channel moving to the next one”.

await srtc.leaveChannel(groupChannel)

Parameter	Type	Required	Description
`channel`	`Channel`	Yes	The channel to leave

`createLocalMicTrack(preset:)`

Creates a local microphone track.

let micTrack = srtc.createLocalMicTrack(preset: .music)

Parameter	Type	Required	Description
`preset`	`MicPreset`	No	Default `.music`

Returns: LocalMicTrack

`createLocalCameraTrack(preset:)`

Creates a local camera track.

let cameraTrack = srtc.createLocalCameraTrack(preset: .h720p)

Parameter	Type	Required	Description
`preset`	`CameraPreset`	No	Default `.h720p`

Returns: LocalCameraTrack

`createLocalScreenTrack(preset:audioPreset:mode:)`

Creates a local screen-sharing track.

let screenTrack = srtc.createLocalScreenTrack(
    preset: .h1080p,
    audioPreset: .default
)

// iOS full-screen capture (requires integrating a Broadcast Upload Extension first)
let fullScreen = srtc.createLocalScreenTrack(
    preset: .h720p,
    mode: .broadcast(appGroup: "group.your.app.group")
)

Parameter	Type	Required	Description
`preset`	`ScreenPreset`	No	Screen-sharing video preset; default `.h1080p`
`audioPreset`	`ScreenAudioPreset?`	No	On macOS, can be used to enable screen audio
`mode`	`ScreenCaptureMode`	No	iOS only; default `.inApp` (in-app capture); `.broadcast(appGroup:)` is full-screen capture—see Screen sharing

Returns: LocalScreenTrack

With iOS full-screen capture, a successful startCapture() only means the SDK has started listening; video is transmitted only after the user starts the broadcast from the system UI. The actual start / end is notified through TrackDelegate.screenBroadcastDidStart / screenBroadcastDidFinish(_:reason:).

`createLocalScreenTrack(source:preset:audioPreset:excludedWindowIds:excludesCurrentApplication:)`

Overload for macOS 12.3+ only, used to specify a display or window source.

let track = srtc.createLocalScreenTrack(
    source: selectedSource,
    preset: .h1080p,
    audioPreset: .default
)

// Share the full display while cutting out your own windows that render this shared content
let previewWindowIds = NSApplication.shared.windows
    .filter { $0.isVisible && $0.identifier?.rawValue == "meeting-room" }
    .map { UInt32($0.windowNumber) }
let shared = srtc.createLocalScreenTrack(
    source: display,
    excludedWindowIds: previewWindowIds
)

Parameter	Type	Required	Description
`source`	`ScreenCaptureSource?`	No	`DisplaySource` or `WindowSource`; defaults to the main display when empty
`preset`	`ScreenPreset`	No	Default `.h1080p`
`audioPreset`	`ScreenAudioPreset?`	No	Whether to capture system audio
`excludedWindowIds`	`[UInt32]`	No	Your own windows to cut out when sharing a full display, as `UInt32(NSWindow.windowNumber)`; meaningless when capturing a single window. Default `[]`
`excludesCurrentApplication`	`Bool`	No	Set to `true` to go back to the old behavior of excluding the entire app from the capture; `excludedWindowIds` is then ignored. Default `false`

Returns: LocalScreenTrack

Since 1.4.2, full-display sharing includes your own app’s windows by default. Put every window that renders this shared content into excludedWindowIds; otherwise you get an infinite mirror. The window list is snapshotted once at startCapture(), and windows opened afterward all appear in the capture.

`createLocalCustomVideoTrack(desc:)`

Creates a custom video track, for scenarios where frames are pushed from outside.

let customVideoTrack = srtc.createLocalCustomVideoTrack(desc: "canvas")

Parameter	Type	Required	Description
`desc`	`String`	No	Track description; default `"custom"`

Returns: LocalVideoTrack After calling it, you can inject CVPixelBuffer values through pushFrame(...).

`createLocalCustomAudioTrack(desc:)`

Creates a custom audio track, for scenarios with external PCM input.

let customAudioTrack = srtc.createLocalCustomAudioTrack(desc: "bgm")

Parameter	Type	Required	Description
`desc`	`String`	No	Track description; default `"custom"`

Returns: LocalAudioTrack After calling it, you can inject AVAudioPCMBuffer values through pushAudioBuffer(...).

Video preprocessing

`defaultVideoProcessors`

The default video processor pipeline. Configure it once here, and every camera track created afterward picks it up automatically.

srtc.defaultVideoProcessors = [myProcessor]

Parameter	Type	Required	Description
`defaultVideoProcessors`	`[VideoProcessor]`	No	Empty by default

A camera track is created anew every time the camera is turned on (turning the camera off destroys it), so if you set processors only on the track, the effect is gone the next time the camera is turned on—this property exists for exactly that reason. It affects only tracks created afterward and doesn’t apply retroactively to existing tracks; custom video tracks aren’t affected (frames on that path are pushed by you via pushFrame, so you decide whether they go through processors).

Virtual background

The following methods forward to SRTCVirtualBackground.shared, with a single process-wide state. Once enabled, it automatically applies to all camera tracks, and you don’t need to add anything to videoProcessors. For usage and tuning, see Virtual background.

Member	Signature	Description
Install	`installVirtualBackground(modelPath: String? = nil) throws`	Loads the model + creates the inference session, taking hundreds of milliseconds; don’t call it on the main thread / capture thread; `nil` uses the built-in model
Uninstall	`uninstallVirtualBackground()`	Releases the inference session and buffers; doesn’t clear effect parameters
Master switch	`enableVirtualBackground(_ enabled: Bool) throws`	When off, it’s a zero-overhead pass-through with no inference
Switch state	`isVirtualBackgroundEnabled: Bool`	Read-only
Background blur	`setVirtualBackgroundBlur(level: Int)`	`level` ranges 1–10, default 5; out-of-range values are clamped to the bounds
Background replacement	`setVirtualBackgroundImage(_ image: SRTCNativeImage?)`	Scaled to cover (cropped, not stretched); `nil` falls back to blur. There’s also a `CGImage` overload
Inference interval	`setVirtualBackgroundInferenceInterval(_ interval: Int)`	Segmentation runs once every N frames (compositing still runs every frame); default 1
Mask sync	`setVirtualBackgroundMaskSync(_ enabled: Bool)`	Default `false`; makes no difference when `interval` is 1
Instance	`virtualBackground: SRTCVirtualBackground`	For diagnostics: `droppedFrameCount`, `isInstalled`, `effect`, `inferenceIntervalMs`, and more

Throws: SRTCError.virtualBackgroundAlreadyInstalled, .virtualBackgroundNotInstalled, .virtualBackgroundModelNotFound(String), .virtualBackgroundSessionFailed(String) Background blur and background replacement are mutually exclusive, and the later call wins; both are also remembered if called before installing, and take effect automatically once installation completes.

Overview

Web SDK

Android SDK

Swift SDK (iOS/macOS)

C SDK (server/embedded)

Python SDK (server-side AI)

Server API

Initialization

`init()`

Properties

`logLevel`

`audioCaptureProcessor`

`audioRenderProcessor`

`channels`

`defaultChannel`

Methods

`joinChannel(token:options:)`

`leaveChannel()`

`leaveChannel(_:)`

`createLocalMicTrack(preset:)`

`createLocalCameraTrack(preset:)`

`createLocalScreenTrack(preset:audioPreset:mode:)`

`createLocalScreenTrack(source:preset:audioPreset:excludedWindowIds:excludesCurrentApplication:)`

`createLocalCustomVideoTrack(desc:)`

`createLocalCustomAudioTrack(desc:)`

Video preprocessing

`defaultVideoProcessors`

Virtual background

​Initialization

​init()

​Properties

​logLevel

​audioCaptureProcessor

​audioRenderProcessor

​channels

​defaultChannel

​Methods

​joinChannel(token:options:)

​leaveChannel()

​leaveChannel(_:)

​createLocalMicTrack(preset:)

​createLocalCameraTrack(preset:)

​createLocalScreenTrack(preset:audioPreset:mode:)

​createLocalScreenTrack(source:preset:audioPreset:excludedWindowIds:excludesCurrentApplication:)

​createLocalCustomVideoTrack(desc:)

​createLocalCustomAudioTrack(desc:)

​Video preprocessing

​defaultVideoProcessors

​Virtual background

​Related pages

Initialization

`init()`

Properties

`logLevel`

`audioCaptureProcessor`

`audioRenderProcessor`

`channels`

`defaultChannel`

Methods

`joinChannel(token:options:)`

`leaveChannel()`

`leaveChannel(_:)`

`createLocalMicTrack(preset:)`

`createLocalCameraTrack(preset:)`

`createLocalScreenTrack(preset:audioPreset:mode:)`

`createLocalScreenTrack(source:preset:audioPreset:excludedWindowIds:excludesCurrentApplication:)`

`createLocalCustomVideoTrack(desc:)`

`createLocalCustomAudioTrack(desc:)`

Video preprocessing

`defaultVideoProcessors`

Virtual background

Related pages