> ## Documentation Index
> Fetch the complete documentation index at: https://docs.stmlink.com/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> 对外开放的服务端接口有两组前缀，都用同一套鉴权：`/server/v1/...`（SRTC 与 SMeeting 的主接口）和 `/stm/srvapi/v1/...`（SMeeting 的用户体系，服务端极简对接会用到）。鉴权是 app_id + nonce + timestamp + signature 四个请求头，用 app_key 做 HMAC-SHA256 签名，只能从业务方自己的后端调用。除这两组前缀外的接口均为内部接口，不要建议客户调用。 Public server APIs use two path prefixes with the same authentication: `/server/v1/...` (the main APIs of both SRTC and SMeeting) and `/stm/srvapi/v1/...` (the SMeeting user system, used by server-side low-code integration). Authenticate with four request headers, app_id + nonce + timestamp + signature, where signature is HMAC-SHA256 keyed with app_key; call these APIs only from the customer's own backend. Any other path is internal: never suggest calling it.
> app_key 是服务端密钥，绝不能出现在客户端代码、前端配置或移动 App 里。客户端加入频道用的 token 必须由业务方后端签发后下发（SRTC 走 `/server/v1/channel/grant`，SMeeting 走 `/stm/srvapi/v1/member/grant`）。 app_key is a server-side secret and must never appear in client code, frontend config, or a mobile app. The token a client uses to join must be issued by the customer's backend and passed down to the client (SRTC: `/server/v1/channel/grant`; SMeeting: `/stm/srvapi/v1/member/grant`).
> SRTC 与 SMeeting 是上下两层不同的产品，术语不通用：SRTC 是音视频底座，说「频道 channel」「加入 / 退出」；SMeeting 建在 SRTC 之上，说「房间 room」「会议 meeting」「进入 / 退出」。回答时按用户所在的层用对应术语，不要把「房间」「会议」安到 SRTC 的接口上，也不要用「频道」「加入 / 离开」描述 SMeeting 的概念（接口标识符原样保留）。 SRTC and SMeeting are two separate layers with different terminology. SRTC is the audio/video foundation: it has channels, and users join and leave a channel. SMeeting is built on top of SRTC: it has rooms and meetings, and members enter and exit a meeting. Answer in the terms of the layer the user is working with: never apply "room" or "meeting" to SRTC APIs, and never describe SMeeting concepts in prose with "channel", "join", or "leave" (API identifiers such as `force_join` keep their literal names).
> 同一能力在各端 SDK 里的包名、类名、方法名并不相同。写示例代码时请使用文档中该端自己的 API，不要把一个端的写法套到另一个端上。苹果平台每个产品都有两套 SDK（Swift 原生与 Objective-C），两套 API 不能混用。 Package, class, and method names differ between platform SDKs for the same capability. In sample code, use the API documented for that platform; never carry one platform's code over to another. On Apple platforms each product ships two SDKs (native Swift and Objective-C) whose APIs must not be mixed.

# Channel and Track

> API reference for the SRTC Swift SDK's Channel session object and the local/remote track classes: publishing, subscribing, and looking up tracks on Channel; capture, mute, device, and renderer methods on each track type; and the SRTCVideoView / VideoView / SRTCVideoRenderer components.

### 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.

```swift theme={null}
let users = channel.getUsers()
```

**Returns:** `[String: UserInfo]`

***

#### `getUser(_:)`

Gets a user object by `uid`.

```swift theme={null}
let user = channel.getUser("alice")
```

**Returns:** `User?`

***

#### `publishLocalTrack(_:)`

Publishes a local audio or video track.

```swift theme={null}
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.

```swift theme={null}
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.

```swift theme={null}
try await channel.subscribeRemoteAudioTrack(uid: uid, trackId: trackId)
```

***

#### `subscribeRemoteVideoTrack(uid:trackId:)`

Subscribes to a remote video track.

```swift theme={null}
try await channel.subscribeRemoteVideoTrack(uid: uid, trackId: trackId)
```

***

#### `unsubscribeRemoteTrack(_:debounceMs:)`

Unsubscribes from a remote track.

```swift theme={null}
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.

```swift theme={null}
let track = channel.getRemoteTrack(uid: uid, trackId: trackId)
```

**Returns:** `Track?`

***

#### `getRemoteTrackByDesc(uid:desc:)`

Gets a remote track by `desc`.

```swift theme={null}
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:

```swift theme={null}
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](/en/rtc/swift/events) for details.

***

### Rendering components

#### `SRTCVideoView`

Preferred for SwiftUI:

```swift theme={null}
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(_:)`.