基于 Web SDK 实现视频通话场景 | 声网 SDK 教程

声网视频 SDK 被广泛应用于多种实时互动场景中，例如视频会议、视频通话、音视频社交、在线教育等。为了让刚刚接触声网 SDK 的开发者，可以更顺畅地实现基础的视频通话功能，我们基于声网 Web SDK 4.x 版本梳理了本篇教程。

在本文末，会提供相应 Demo 、文档地址供大家参考使用。同时，欢迎点击此处注册声网账号体验。声网每个月会为开发者提供 10000 分钟的免费额度。

本文为「声网 SDK 教程」系列内容

01 Demo 体验

我们在 GitHub 上提供一个开源的基础视频通话示例项目，在开始开发之前你可以通过该示例项目体验音视频通话效果。Demo 与线上体验地址，可在文末获取。

02 动手实践

实践任务

从 Web 前端页面引入声网 SDK，发起视频通话。

开发环境

声网 SDK 的兼容性良好，对硬件设备和软件系统的要求不高，开发环境和测试环境满足以下条件即可：

Chrome
Firefox
Safari
Edge

以下是本文的开发环境和测试环境：

开发环境

MacBook Pro (13-inch, M1, 2020)
Visual Studio Code (1.67.1)

测试环境

Chrome (101.0.4951.64)

如果你此前还未接触过声网 SDK，那么你还需要做以下准备工作：

注册一个声网账号，进入后台创建 AppID、获取 Token；
下载声网官方最新的视频 SDK。

项目设置

文件组织结构

实现视频通话之前，参考如下步骤设置你的项目：

如需创建新项目，可以在 Visual Studio Code 里 File > New Window，创建 Web 项目。完整的目录结构如下，根据个人经验会有所变化。

.
├── index.css # 用于设计 Web 应用的用户界面样式
├── index.html # 用于设计 Web 应用的用户界面
├── index.js # 通过 AgoraRTCClient 实现具体应用逻辑的代码。
└── vendor # 第三方前端插件，辅助页面布局和交互，本教程中是下载到本地使用，你也可以使用 CDN 的方式
    ├── bootstrap.bundle.min.js
    ├── bootstrap.min.css
    └── jquery-3.4.1.min.js

集成声网 SDK

可以下载到本地使用，也可以直接使用声网的 CDN 引入，本文推荐使用 CDN 方式集成声网 SDK。

在 index.html 中添加以下代码

<!DOCTYPE html>
...
  <link rel="stylesheet" href="./vendor/bootstrap.min.css">
  <link rel="stylesheet" href="./index.css">
...
  <script src="./vendor/jquery-3.4.1.min.js"></script>
  <script src="./vendor/bootstrap.bundle.min.js"></script>
  <script src="https://download.agora.io/sdk/release/AgoraRTC_N.js"></script>
  <script src="./index.js"></script>
...

最终完整代码为

可以直接复制运行。

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Basic Video Call -- Agora</title>
  <link rel="stylesheet" href="./vendor/bootstrap.min.css">
  <link rel="stylesheet" href="./index.css">
</head>
<body>
  <div class="container-fluid banner">
    <p class="banner-text">Basic Video Call</p>
    <a style="color: rgb(255, 255, 255);fill: rgb(255, 255, 255);fill-rule: evenodd; position: absolute; right: 10px; top: 4px;"
      class="Header-link " href="https://github.com/AgoraIO-Community/AgoraWebSDK-NG/tree/master/Demo">
      <svg class="octicon octicon-mark-github v-align-middle" height="32" viewBox="0 0 16 16" version="1.1" width="32" aria-hidden="true"><path fill-rule="evenodd" d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82-.01-1.49-2.01.37-2.53-.49-2.69-.94-.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52-.01-.53.63-.01 1.08.58 1.23.82.72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12 0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27.68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.013 8.013 0 0016 8c0-4.42-3.58-8-8-8z"></path></svg>
    </a>
  </div>
 
 
  <div id="success-alert" class="alert alert-success alert-dismissible fade show" role="alert">
    <strong>Congratulations!</strong><span> You can invite others join this channel by click </span><a href="" target="_blank">here</a>
    <button type="button" class="close" data-dismiss="alert" aria-label="Close">
      <span aria-hidden="true">&times;</span>
    </button>
  </div>
  <div id="success-alert-with-token" class="alert alert-success alert-dismissible fade show" role="alert">
    <strong>Congratulations!</strong><span> Joined room successfully. </span>
    <button type="button" class="close" data-dismiss="alert" aria-label="Close">
      <span aria-hidden="true">&times;</span>
    </button>
  </div>
  <div id="success-alert-with-token" class="alert alert-success alert-dismissible fade show" role="alert">
    <strong>Congratulations!</strong><span> Joined room successfully. </span>
    <button type="button" class="close" data-dismiss="alert" aria-label="Close">
      <span aria-hidden="true">&times;</span>
    </button>
  </div>
   
  <div class="container">
    <form id="join-form">
      <div class="row join-info-group">
          <div class="col-sm">
            <p class="join-info-text">AppID</p>
            <input id="appid" type="text" placeholder="enter appid" required>
            <p class="tips">If you don`t know what is your appid, checkout <a href="https://docs.agora.io/en/Agora%20Platform/terms?platform=All%20Platforms#a-nameappidaapp-id">this</a></p>
          </div>
          <div class="col-sm">
            <p class="join-info-text">Token(optional)</p>
            <input id="token" type="text" placeholder="enter token">
            <p class="tips">If you don`t know what is your token, checkout <a href="https://docs.agora.io/en/Agora%20Platform/terms?platform=All%20Platforms#a-namekeyadynamic-key">this</a></p>
          </div>
          <div class="col-sm">
            <p class="join-info-text">Channel</p>
            <input id="channel" type="text" placeholder="enter channel name" required>
            <p class="tips">If you don`t know what is your channel, checkout <a href="https://docs.agora.io/en/Agora%20Platform/terms?platform=All%20Platforms#channel">this</a></p>
          </div>
      </div>
 
      <div class="button-group">
        <button id="join" type="submit" class="btn btn-primary btn-sm">Join</button>
        <button id="leave" type="button" class="btn btn-primary btn-sm" disabled>Leave</button>
      </div>
    </form>
 
    <div class="row video-group">
      <div class="col">
        <p id="local-player-name" class="player-name"></p>
        <div id="local-player" class="player"></div>
      </div>
      <div class="w-100"></div>
      <div class="col">
        <div id="remote-playerlist"></div>
      </div>
    </div>
  </div>
 
  <script src="./vendor/jquery-3.4.1.min.js"></script>
  <script src="./vendor/bootstrap.bundle.min.js"></script>
  <script src="https://download.agora.io/sdk/release/AgoraRTC_N.js"></script>
  <script src="./index.js"></script>
</body>
</html>

视频通话逻辑

实现视频通话逻辑

下图展示视频通话的 API 调用时序,注意图中的方法是对不同的对象调用的。

参考以下步骤实现音视频通话的逻辑：

1.调用 createClient 方法创建 AgoraRTCClient 对象。

2.调用 join 方法加入一个 RTC 频道，你需要在该方法中传入 App ID 、用户 ID、Token、频道名称。

3.先调用 createMicrophoneAudioTrack 通过麦克风采集的音频创建本地音频轨道对象，调用 createCameraVideoTrack 通过摄像头采集的视频创建本地视频轨道对象；然后调用 publish 方法，将这些本地音视频轨道对象当作参数即可将音视频发布到频道中。

4.当一个远端用户加入频道并发布音视频轨道时：

a.监听 client.on("user-published") 事件。当 SDK 触发该事件时，在这个事件回调函数的参数中你可以获取远端用户 AgoraRTCRemoteUser 对象。

b.调用 subscribe 方法订阅远端用户 AgoraRTCRemoteUser 对象，获取远端用户的远端音频轨道 RemoteAudioTrack 和远端视频轨道 RemoteVideoTrack 对象。

c.调用 play 方法播放远端音视频轨道。

注：以下代码都将在 index.js 中添加**

初始化client

var client = AgoraRTC.createClient({ mode: "rtc", codec: "vp8" });

加入RTC 频道并创建本地音频轨道

// Join a channel and create local tracks. Best practice is to use Promise.all and run them concurrently.
[ options.uid, localTracks.audioTrack, localTracks.videoTrack ] = await Promise.all([
  // Join the channel.
  client.join(options.appid, options.channel, options.token || null, options.uid || null),
  // Create tracks to the local microphone and camera.
  AgoraRTC.createMicrophoneAudioTrack(),
  AgoraRTC.createCameraVideoTrack()
]);

播放本地视频

// Play the local video track to the local browser and update the UI with the user ID.
localTracks.videoTrack.play("local-player");

发布本地音视频到频道中

// Publish the local video and audio tracks to the channel.
await client.publish(Object.values(localTracks));

监听远端用户音视频

// Add an event listener to play remote tracks when remote user publishes.
client.on("user-published", handleUserPublished);
client.on("user-unpublished", handleUserUnpublished);
 
function handleUserPublished(user, mediaType) {
  const id = user.uid;
  remoteUsers[id] = user;
  subscribe(user, mediaType);
}
 
function handleUserUnpublished(user, mediaType) {
  if (mediaType === 'video') {
    const id = user.uid;
    delete remoteUsers[id];
    $(`#player-wrapper-${id}`).remove();
  }
}
 
 
async function subscribe(user, mediaType) {
  const uid = user.uid;
  // subscribe to a remote user
  await client.subscribe(user, mediaType);
  console.log("subscribe success");
  if (mediaType === 'video') {
    const player = $(`
      <div id="player-wrapper-${uid}">
        <p class="player-name">remoteUser(${uid})</p>
        <div id="player-${uid}" class="player"></div>
      </div>
    `);
    $("#remote-playerlist").append(player);
    user.videoTrack.play(`player-${uid}`);
  }
 
  if (mediaType === 'audio') {
    user.audioTrack.play();
  }
}

离开频道

async function leave() {
  for (trackName in localTracks) {
    var track = localTracks[trackName];
    if(track) {
      track.stop();
      track.close();
      localTracks[trackName] = undefined;
    }
  }
 
  // Remove remote users and player views.
  remoteUsers = {};
  $("#remote-playerlist").html("");
 
  // leave the channel
  await client.leave();
 
}

最终完整的代码

// create Agora client
var client = AgoraRTC.createClient({ mode: "rtc", codec: "vp8" });
 
 
var localTracks = {
  videoTrack: null,
  audioTrack: null
};
var remoteUsers = {};
// Agora client options
var options = {
  appid: null,
  channel: null,
  uid: null,
  token: null
};
 
// the demo can auto join channel with params in url
$(() => {
  var urlParams = new URL(location.href).searchParams;
  options.appid = urlParams.get("appid");
  options.channel = urlParams.get("channel");
  options.token = urlParams.get("token");
  if (options.appid && options.channel) {
    $("#appid").val(options.appid);
    $("#token").val(options.token);
    $("#channel").val(options.channel);
    $("#join-form").submit();
  }
})
 
$("#join-form").submit(async function (e) {
  e.preventDefault();
  $("#join").attr("disabled", true);
  try {
    options.appid = $("#appid").val();
    options.token = $("#token").val();
    options.channel = $("#channel").val();
    await join();
    if(options.token) {
      $("#success-alert-with-token").css("display", "block");
    } else {
      $("#success-alert a").attr("href", `index.html?appid=${options.appid}&channel=${options.channel}&token=${options.token}`);
      $("#success-alert").css("display", "block");
    }
  } catch (error) {
    console.error(error);
  } finally {
    $("#leave").attr("disabled", false);
  }
})
 
$("#leave").click(function (e) {
  leave();
})
 
async function join() {
 
  // add event listener to play remote tracks when remote user publishs.
  client.on("user-published", handleUserPublished);
  client.on("user-unpublished", handleUserUnpublished);
 
  // join a channel and create local tracks, we can use Promise.all to run them concurrently
  [ options.uid, localTracks.audioTrack, localTracks.videoTrack ] = await Promise.all([
    // join the channel
    client.join(options.appid, options.channel, options.token || null),
    // create local tracks, using microphone and camera
    AgoraRTC.createMicrophoneAudioTrack(),
    AgoraRTC.createCameraVideoTrack()
  ]);
   
  // play local video track
  localTracks.videoTrack.play("local-player");
  $("#local-player-name").text(`localVideo(${options.uid})`);
 
  // publish local tracks to channel
  await client.publish(Object.values(localTracks));
  console.log("publish success");
}
 
async function leave() {
  for (trackName in localTracks) {
    var track = localTracks[trackName];
    if(track) {
      track.stop();
      track.close();
      localTracks[trackName] = undefined;
    }
  }
 
  // remove remote users and player views
  remoteUsers = {};
  $("#remote-playerlist").html("");
 
  // leave the channel
  await client.leave();
 
  $("#local-player-name").text("");
  $("#join").attr("disabled", false);
  $("#leave").attr("disabled", true);
  console.log("client leaves channel success");
}
 
async function subscribe(user, mediaType) {
  const uid = user.uid;
  // subscribe to a remote user
  await client.subscribe(user, mediaType);
  console.log("subscribe success");
  if (mediaType === 'video') {
    const player = $(`
      <div id="player-wrapper-${uid}">
        <p class="player-name">remoteUser(${uid})</p>
        <div id="player-${uid}" class="player"></div>
      </div>
    `);
    $("#remote-playerlist").append(player);
    user.videoTrack.play(`player-${uid}`);
  }
  if (mediaType === 'audio') {
    user.audioTrack.play();
  }
}
 
function handleUserPublished(user, mediaType) {
  const id = user.uid;
  remoteUsers[id] = user;
  subscribe(user, mediaType);
}
 
function handleUserUnpublished(user) {
  const id = user.uid;
  delete remoteUsers[id];
  $(`#player-wrapper-${id}`).remove();
}