> ## 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.

# Quickstart

> A minimal SwiftUI example for the SRTC Swift SDK: create SRTCEngine, join a channel, capture and publish local microphone and camera tracks, subscribe to remote video in ChannelDelegate, and leave. Also explains why joinChannel returns a Channel and why create, capture, and publish are separate.

### Prerequisites

* You have completed [SDK integration](/en/rtc/swift/integration)
* Your server can issue tokens for joining a channel
* Your app has requested camera and microphone permissions

The token must be issued by your backend; the client isn't involved in signing. For how to issue it, see [Token and authentication](/en/rtc/token).

***

### Minimal runnable example

The example below covers the core path: initialize the SDK, join a channel, turn on the microphone and camera, subscribe to remote video, and leave the channel.

```swift theme={null}
import SRTC
import SwiftUI

@MainActor
final class RoomViewModel: ObservableObject, ChannelDelegate {
    @Published var localTrack: LocalCameraTrack?
    @Published var remoteTrack: Track?

    private let srtc = SRTCEngine()
    private var channel: Channel?
    private var micTrack: LocalMicTrack?

    func join(with token: String) async throws {
        srtc.logLevel = .debug

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

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

        let cameraTrack = srtc.createLocalCameraTrack(preset: .h720p)
        try await cameraTrack.startCapture()
        try await channel.publishLocalTrack(cameraTrack)
        self.localTrack = cameraTrack
    }

    func leave() async {
        // The SDK stops capture and unpublishes internally; your code only needs to clear references
        await srtc.leaveChannel()
        channel = nil
        micTrack = nil
        localTrack = nil
        remoteTrack = nil
    }

    func channel(_ channel: Channel, user: UserInfo, didAddTrack track: TrackInfo) {
        guard track.kind == .video else { return }

        Task {
            try? await channel.subscribeRemoteVideoTrack(uid: user.uid, trackId: track.id)
            let subscribedTrack = channel.getRemoteTrack(uid: user.uid, trackId: track.id)
            await MainActor.run {
                self.remoteTrack = subscribedTrack
            }
        }
    }
}

struct RoomView: View {
    @StateObject private var vm = RoomViewModel()
    let token: String

    var body: some View {
        VStack(spacing: 12) {
            if let localTrack = vm.localTrack {
                SRTCVideoView(track: localTrack)
                    .frame(height: 220)
            }

            if let remoteTrack = vm.remoteTrack {
                SRTCVideoView(track: remoteTrack)
                    .frame(height: 220)
            }

            HStack {
                Button("Join channel") {
                    Task { try? await vm.join(with: token) }
                }

                Button("Leave channel") {
                    Task { await vm.leave() }
                }
            }
        }
        .padding()
    }
}
```

***

### How the flow works

#### 1. Initialize `SRTCEngine`

`SRTCEngine` is the main entry point of the SDK. It is responsible for:

* Creating local tracks
* Parsing the token and joining the channel
* Managing the lifecycle of the current `Channel`
* Configuring the log level and audio processors

#### 2. Call `joinChannel`

```swift theme={null}
let channel = try await srtc.joinChannel(
    token: token,
    options: JoinOptions(autoSubscribeAudio: true)
)
```

The key idea: the core object in real-time audio and video isn't a UI page but the connected channel state. That's why `joinChannel(...)` returns a `Channel` object rather than a Boolean, and publishing, subscribing, messaging, and the user list all revolve around it.

#### 3. Create and publish local tracks

Audio and video follow the same path:

* `create...Track(...)` only creates the track object
* `startCapture()` is what actually starts hardware capture
* `publishLocalTrack(...)` is what sends the data to the channel

With these three steps separated, you get finer control over "when to acquire hardware resources" and "when to actually publish".

#### 4. Subscribe to remote video in the callback

When a remote user publishes, you're notified through the `didAddTrack` callback of `ChannelDelegate`. Once you have the `TrackInfo`:

* Call `subscribeRemoteVideoTrack(uid:trackId:)` to subscribe
* Then get the track object with `getRemoteTrack(uid:trackId:)`
* Pass the track to `SRTCVideoView`, `VideoView`, or `SRTCVideoRenderer`

***

### Next steps

* [Key concepts](/en/rtc/swift/key-concepts)
* [Mute vs. unpublish](/zh/rtc/swift/advanced/mute-vs-unpublish) (Chinese)
* [Device management](/zh/rtc/swift/advanced/device-management) (Chinese)
* [Screen sharing](/zh/rtc/swift/advanced/screen-sharing) (Chinese)
* [Custom tracks](/zh/rtc/swift/advanced/custom-track) (Chinese)
* [API reference - SRTCEngine](/zh/rtc/swift/api-reference/SRTCEngine) (Chinese)
* [API reference - Channel and Track](/zh/rtc/swift/api-reference/media-tracks) (Chinese)