> ## 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.

# Mute vs. unpublish

> The difference between mute / unmute and unpublish / stopCapture in the SRTC Swift SDK: which layer each controls, how microphone, camera, and screen tracks behave on mute, and which to use for microphone, camera, and screen-sharing buttons.

### Overview

A common misconception in the Swift SDK is treating "mute" and "unpublish" as the same thing.

From first principles, they control two different layers of state:

* `mute / unmute` controls "whether this track is outputting media data right now"
* `unpublishLocalTrack` controls "whether this track is still one of the published tracks in the channel"

So the two differ in their result, their cost to restore, and their effect on remote users.

***

### How the two operations differ

| Operation | Layer controlled | Keeps the Track object | Requires publishing again | Use cases |
| - | - | - | - | - |
| `mute()` / `unmute()` | Track output layer | Yes | No | Temporarily mute, temporarily turn off video |
| `unpublishLocalTrack(...)` | Channel publishing layer | Usually no | Yes | Stop publishing entirely, leave the stage |

In the Swift SDK, however, `mute()` has a further difference in meaning depending on the track type.

***

### Microphone track: `mute()` is a lightweight operation

`mute()` on a `LocalMicTrack` doesn't destroy the track object and doesn't require you to publish again.

Typical flow:

```swift theme={null}
let micTrack = srtc.createLocalMicTrack(preset: .music)
try await micTrack.startCapture()
try await channel.publishLocalTrack(micTrack)

// Temporarily mute
micTrack.mute()

// Restore
micTrack.unmute()
```

This approach suits:

* A "mute / unmute" button in a meeting app
* A host briefly muting their microphone
* Scenarios that need fast toggling without interrupting the audio session as much as possible

The reason is that local audio in the current Swift SDK goes through an internal mixing model. Muting a `LocalMicTrack` essentially silences the microphone input in the mixed output, rather than tearing down the whole publishing pipeline.

***

### Camera and screen sharing: `mute()` keeps the track published but stops capture

`mute()` / `unmute()` on `LocalCameraTrack` and `LocalScreenTrack` are `async`, which is an important signal: they aren't a pure in-memory flag, but involve the capture lifecycle.

```swift theme={null}
let cameraTrack = srtc.createLocalCameraTrack(preset: .h720p)
try await cameraTrack.startCapture()
try await channel.publishLocalTrack(cameraTrack)

// Temporarily turn off video
try await cameraTrack.mute()

// Restore video
try await cameraTrack.unmute()
```

The key points here:

* The track object still exists
* You don't need to call `publishLocalTrack(...)` again
* But capture stops, and it restarts when you restore

So it suits:

* The user temporarily turns off the camera, but the UI still keeps "this video track"
* Screen sharing is paused temporarily and then resumes sharing the same content

***

### `unpublishLocalTrack(...)` removes the track at the publishing layer

If you want remote users to no longer see this track from the channel's point of view, unpublish it:

```swift theme={null}
try await channel.unpublishLocalTrack(cameraTrack)
try await cameraTrack.stopCapture()
```

To restore it, we usually recommend creating the track again or restarting capture, then publishing:

```swift theme={null}
let newCameraTrack = srtc.createLocalCameraTrack(preset: .h720p)
try await newCameraTrack.startCapture()
try await channel.publishLocalTrack(newCameraTrack)
```

This suits:

* The user actually leaves the speaker slot / video slot
* Stopping screen sharing and releasing that track
* Your business logic needs the track info removed from remote users' user lists

***

### Recommendations

#### Microphone button

* Regular mute button: prefer `mute()` / `unmute()`
* Cleanup before the user leaves the channel: call `srtc.leaveChannel()` directly; the SDK stops capture and unpublishes internally

#### Camera button

* Temporarily turn off video and restore it later: use `mute()` / `unmute()`
* Fully turn off the camera and have remote users remove the track: use `unpublishLocalTrack(...)` + `stopCapture()`

#### Screen-sharing button

* Stop sharing briefly and then continue the current session: you can use `mute()` / `unmute()`
* End sharing and clean up resources: use `unpublishLocalTrack(...)` + `stopCapture()`

***

### A practical rule of thumb

If you don't want to go through the full publishing flow again when the user turns it back on, prefer `mute()`.

If your goal is "make this stream disappear from the channel entirely", prefer `unpublishLocalTrack(...)`.