> ## 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.

# Custom tracks

> Publish any MediaStreamTrack with the Web SDK: wrap synthesized audio with createLocalCustomAudioTrack, Canvas video with createLocalCustomVideoTrack, mix several audio tracks with createMixedAudioMediaStreamTrack, and stop custom tracks. Read when built-in mic and camera capture isn't enough.

### Overview

When the built-in microphone and camera capture don't meet your needs, you can use any `MediaStreamTrack` as an audio or video source. Common scenarios:

* Draw content with Canvas and publish it as a video track (avatars, game footage)
* Synthesize audio with the Web Audio API and publish it
* Mix several audio tracks and publish the result

***

### Custom audio track

Wrap a `MediaStreamTrack` with `srtc.createLocalCustomAudioTrack(msTrack)` to publish it as a local audio track:

```typescript theme={null}
import { SRTC } from '@seastart/srtc-web-sdk';

const srtc = new SRTC();

// Example: synthesize an audio MediaStreamTrack with the Web Audio API
const audioContext = new AudioContext();
const oscillator = audioContext.createOscillator();
const destination = audioContext.createMediaStreamDestination();
oscillator.connect(destination);
oscillator.start();

const msAudioTrack = destination.stream.getAudioTracks()[0];

// Wrap it as an SDK track and publish
const customAudioTrack = srtc.createLocalCustomAudioTrack(msAudioTrack);
await srtc.publishLocalTrack(customAudioTrack, { desc: 'synthesized audio' });
```

***

### Custom video track

Wrap it with `srtc.createLocalCustomVideoTrack(msTrack)`, which suits Canvas drawing scenarios:

```typescript theme={null}
import { SRTC } from '@seastart/srtc-web-sdk';

const srtc = new SRTC();

// Example: publish Canvas content as a video track
const canvas = document.querySelector<HTMLCanvasElement>('#my-canvas')!;
const ctx = canvas.getContext('2d')!;

// Draw content (an animated rectangle here as an example)
function draw() {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  ctx.fillStyle = `hsl(${Date.now() / 10 % 360}, 70%, 50%)`;
  ctx.fillRect(50, 50, 200, 200);
  requestAnimationFrame(draw);
}
draw();

// Capture the Canvas as a MediaStream (the parameter is the frame rate)
const canvasStream = canvas.captureStream(15);
const msVideoTrack = canvasStream.getVideoTracks()[0];

// Wrap it as an SDK track
const customVideoTrack = srtc.createLocalCustomVideoTrack(msVideoTrack);

// Local preview
customVideoTrack.addPlayView(document.querySelector<HTMLElement>('#preview')!);

// Publish
await srtc.publishLocalTrack(customVideoTrack, { desc: 'canvas video' });
```

***

### Publishing mixed audio (createMixedAudioMediaStreamTrack)

When you need to merge several `MediaStreamTrack`s into one audio track for publishing, use the `createMixedAudioMediaStreamTrack` utility function:

```typescript theme={null}
import { SRTC, createMixedAudioMediaStreamTrack } from '@seastart/srtc-web-sdk';

const srtc = new SRTC();

// Assume you already have two MediaStreamTracks: a microphone track + a system audio track
const micMsTrack: MediaStreamTrack = /* ... */;
const systemAudioMsTrack: MediaStreamTrack = /* ... */;

// Merge into a single mixed audio track
const mixedMsTrack = createMixedAudioMediaStreamTrack([micMsTrack, systemAudioMsTrack]);

// Wrap it as an SDK track and publish
const mixedAudioTrack = srtc.createLocalCustomAudioTrack(mixedMsTrack);
await srtc.publishLocalTrack(mixedAudioTrack, { desc: 'mixed audio' });
```

> **When to use:** when you talk while sharing a video and need to merge microphone audio and system audio into one track for publishing.

***

### Stop a custom track

Custom tracks also support the standard unpublish flow:

```typescript theme={null}
// Unpublish
await srtc.unpublishLocalTrack(customVideoTrack);

// Stop the underlying MediaStreamTrack
msVideoTrack.stop();
```