> ## 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.

# RTCEngineDelegate

> API reference for RTCEngineDelegate, the process-level engine event protocol in the Objective-C SRTC SDK on iOS: audio route changes, network speed test results, and app performance, independent of any channel. Look here for events not tied to a channel.

This protocol carries only events for shared capabilities scoped to the [RTCEngineKit](/en/rtc/ios/api-reference/RTCEngineKit) singleton, independent of any specific channel.

For in-channel connection, user, message, stream, audio, and screen sharing events, implement [RTCEngineChannelDelegate](/en/rtc/ios/api-reference/RTCEngineChannelDelegate).

<Warning>
  Starting with `3.0.0`, all in-channel callbacks in this protocol have moved to `RTCEngineChannelDelegate`, and their method signatures now all take the channel instance the event comes from as the first parameter. If you keep implementing only `RTCEngineDelegate`, you won't receive any in-channel events; update your code as described in [RTCEngineChannelDelegate](/en/rtc/ios/api-reference/RTCEngineChannelDelegate).
</Warning>

## Audio callbacks

### onAudioRouteChange:previousRoute:()

`- (void)onAudioRouteChange:(RTCAudioRoute)route previousRoute:(RTCAudioRoute)previousRoute`

Called when the audio route changes.

The audio route is process-level shared device state, and a change applies to all channels at once.

Starting with `2.5.8`, when neither the speaker nor the earpiece has been explicitly selected and an external device is available, the SDK restores the external device first; once it's restored, the speaker or earpiece routes that briefly appear while the audio session is being reconfigured aren't reported, so what you receive is the final actual route.

**Parameters**

| route | Audio route; see [RTCAudioRoute](/en/rtc/ios/types#rtcaudioroute) |
| - | - |
| previousRoute | Audio route before the change |

## Network speed test callbacks

### onSpeedTestBegined()

`- (void)onSpeedTestBegined`

Called when a network speed test starts.

You receive this callback after calling `startSpeedTest:()` in `RTCEngineKit` to start a network speed test.

### onSpeedTestUploadResult:downResult:connectResult:()

`- (void)onSpeedTestUploadResult:(nullable RTCSpeedTestResult *)uploadResult downResult:(nullable RTCSpeedTestResult *)downResult connectResult:(nullable RTCSpeedTestConnectResult *)connectResult`

Called with the network speed test results.

After you call `startSpeedTest:()` in `RTCEngineKit` to start a network speed test, you receive this callback once the underlying measurement completes.

**Parameters**

| uploadResult | Uplink speed test result; see [RTCSpeedTestResult](/en/rtc/ios/types#rtcspeedtestresult) |
| - | - |
| downResult | Downlink speed test result; see [RTCSpeedTestResult](/en/rtc/ios/types#rtcspeedtestresult) |
| connectResult | Connectivity test result; see [RTCSpeedTestConnectResult](/en/rtc/ios/types#rtcspeedtestconnectresult) |

## Other callbacks

### onApplicationPerformance:cpuUsage:()

`- (void)onApplicationPerformance:(CGFloat)memory cpuUsage:(CGFloat)cpuUsage`

Called with app performance data.

Statistics are for the current app process and aren't broken down by channel.

**Parameters**

| memory | Memory usage |
| - | - |
| cpuUsage | CPU usage |