h5播放WebRTC，WebRTC（Web Real-Time Communication）是一种基于网页浏览器的开源项目，提供了实时音视频传输、数据共享等功能，现在各大浏览器已经逐渐加大对WebRTC技术的支持，实现WebRTC的视频推流，播放WebRTC流。
一、初始化连接
1、初始化WebRTC连接。主要涉及到获取本地媒体流、设置ICE服务器配置、创建PeerConnection对象等
this.pc = new RTCPeerConnection(null);this.pc.ontrack = (event) => { this._mediaElement['srcObject'] = event.streams[0];};this.pc.addTransceiver('audio', {direction: 'recvonly'});this.pc.addTransceiver('video', {direction: 'recvonly'});this.sendChannel = this.pc.createDataChannel('keepalive');this.sendChannel.onclose = this.onChannelClose.bind(this);this.sendChannel.onopen = this.onChannelOpen.bind(this);this.sendChannel.onmessage = this.onChannelMessage.bind(this);this.pc.createOffer({ offerToReceiveVideo: !0, offerToReceiveAudio: !0}).then((offer) => { return this.pc.setLocalDescription(offer).then(() => { return offer; });}).then((offer) => { return new Promise((resolve, reject) => { this.HttpPost(url, window.btoa(offer.sdp)).then((res) => { resolve(res); }, function (rej) { reject(rej); }); });}).then((answerSdp) => { return this.pc.setRemoteDescription(new RTCSessionDescription({ type: 'answer', sdp: window.atob(answerSdp) }));}).then(() => { this._isLoad = true;}).catch((reason) => { throw reason;});2、ontrack回调中将媒体播放地址，绑定到video上。
3、createOffer方法,这个方法返回本地会话描述。
4、setLocalDescription方法。
5、需要先与服务端建立一个连接。HttpPost()，发送：offer.sdp 到推流端，服务端收到offer.sdp，再返回回来。
HttpPost(url, data) { return new Promise((resolve, reject) => { var xhr = new XMLHttpRequest(); xhr.onreadystatechange = () => { if (xhr.readyState === 4 && (xhr.status >= 200 && xhr.status < 300)) { var respone = xhr.responseText; xhr.onreadystatechange = new Function; xhr = null; resolve(respone); } }; xhr.open('POST', url.replace('webrtc', 'http'), true); xhr.send(data); });}6、收到应答返回的offer.sdp， 设置为你的远端连接。
this.pc.setRemoteDescription(new RTCSessionDescription({ type: 'answer', sdp: window.atob(answerSdp)}));7、监听 sendChannel.onopen 连接是否建立成功。
8、前端播放的过程中需要与服务器通信保持连接，可以 sendChannel.send(msg)来保持持续拉流 。
9、服务器推流，前端开始播放。
二、完整代码
import PlayerEvents from '../FlvPlayer/flv.js/player/player-events';import EventEmitter from 'events';import * as common from '../common/common';export default class WebRtcPlayer { constructor(url, options) { this.TAG = 'WebRtcPlayer'; this._type = 'WebRtcPlayer'; this._emitter = new EventEmitter(); // this.options = options || {}; this.pc = null; this._mediaElement = null; this.url = url; this.autoplay = !!options.autoplay || false; this.typeCallback = options.typeCallback; this.statusCallback = options.statusCallback; if (!url.match(/^webrtc?:\/\/||^webrtcs?:\/\//)) { throw ('JSWebrtc just work with webrtc'); } this.timer = null; this.sendChannel = null; this._mediaInfo = null; this._statisticsInfo = null; this.isPlaying = false; this._isLoad = false; this._isDestroy = false; this.e = { onvLoadedMetadata: this._onvLoadedMetadata.bind(this), onvSeeking: this._onvSeeking.bind(this), onvCanPlay: this._onvCanPlay.bind(this), onvPlay: this._onvPlay.bind(this), onvStalled: this._onvStalled.bind(this), onvProgress: this._onvProgress.bind(this), onvWaiting: this._onvWaiting.bind(this), onvPlaying: this._onvPlaying.bind(this) }; this.attachMediaElement(options.mediaElement, url); } on(event, listener) { if (event === PlayerEvents.MEDIA_INFO) { if (this._mediaInfo != null) { Promise.resolve().then(() => { this._emitter.emit(PlayerEvents.MEDIA_INFO, this.mediaInfo); }); } } else if (event === PlayerEvents.STATISTICS_INFO) { if (this._statisticsInfo != null) { Promise.resolve().then(() => { this._emitter.emit(PlayerEvents.STATISTICS_INFO, this.statisticsInfo); }); } } this._emitter.addListener(event, listener); } off(event, listener) { this._emitter.removeListener(event, listener); } attachMediaElement(mediaElement, url) { this._mediaElement = mediaElement; this._mediaElement = mediaElement; mediaElement.addEventListener('loadedmetadata', this.e.onvLoadedMetadata); mediaElement.addEventListener('seeking', this.e.onvSeeking); mediaElement.addEventListener('canplay', this.e.onvCanPlay); mediaElement.addEventListener('play', this.e.onvPlay); mediaElement.addEventListener('stalled', this.e.onvStalled); mediaElement.addEventListener('progress', this.e.onvProgress); mediaElement.addEventListener('waiting', this.e.onvWaiting); mediaElement.addEventListener('playing', this.e.onvPlaying); this.typeCallback(!false); this.load(url); } load(url) { this.statusCallback(0); if (this.pc) { this.pc.close(); } this.pc = new RTCPeerConnection(null); this.pc.ontrack = (event) => { this._mediaElement['srcObject'] = event.streams[0]; }; this.pc.addTransceiver('audio', {direction: 'recvonly'}); this.pc.addTransceiver('video', {direction: 'recvonly'}); this.sendChannel = this.pc.createDataChannel('keepalive'); this.sendChannel.onclose = this.onChannelClose.bind(this); this.sendChannel.onopen = this.onChannelOpen.bind(this); this.sendChannel.onmessage = this.onChannelMessage.bind(this); this.pc.createOffer({ offerToReceiveVideo: !0, offerToReceiveAudio: !0 }).then((offer) => { return this.pc.setLocalDescription(offer).then(() => { return offer; }); }).then((offer) => { return new Promise((resolve, reject) => { this.HttpPost(url, window.btoa(offer.sdp)).then((res) => { resolve(res); }, function (rej) { reject(rej); }); }); }).then((answerSdp) => { return this.pc.setRemoteDescription(new RTCSessionDescription({ type: 'answer', sdp: window.atob(answerSdp) })); }).then(() => { this._isLoad = true; }).catch((reason) => { throw reason; }); } onChannelClose() { clearInterval(this.timer); if (!this._isDestroy) { common.sleep(3000).then(() => { this.load(this.url); }); } } onChannelOpen() { this.timer = setInterval((() => { if (this.sendChannel) { this.sendChannel.send('ping'); } }), 3000); } onChannelMessage() { // console.log('onmessage'); } HttpPost(url, data) { return new Promise((resolve, reject) => { var xhr = new XMLHttpRequest(); xhr.onreadystatechange = () => { if (xhr.readyState === 4 && (xhr.status >= 200 && xhr.status < 300)) { var respone = xhr.responseText; xhr.onreadystatechange = new Function; xhr = null; resolve(respone); } }; xhr.open('POST', url.replace('webrtc', 'http'), true); xhr.send(data); }); } _onvLoadedMetadata() { } _onvSeeking() { } _onvCanPlay() { if (this.autoplay) { this._mediaElement.play(); } } _onvPlay() { this.isPlaying = true; this.statusCallback(100); } _onvStalled() { } _onvProgress() { } _onvWaiting() { } _onvPlaying() { } unload() { } play() { if (!this.isPlaying) { this._mediaElement.play(); this.isPlaying = true; } } pause() { if (this.isPlaying) { this._mediaElement.pause(); this.isPlaying = false; } } resume() { } openAudio() { } closeAudio() { } seek() { } stop() { this.destroy(); } destroy() { this._isDestroy = true; if (this.pc) { this.pc.close(); this.pc = null; } if (this._mediaElement) { this._mediaElement = null; } if (this.sendChannel) { this.sendChannel = null; } this.autoplay = null; this.typeCallback = null; this.statusCallback = null; this.isPlaying = false; this._isLoad = false; clearInterval(this.timer); } get isLoad() { return this._isLoad; }}player-events.js
const PlayerEvents = { ERROR: 'error', LOADING_COMPLETE: 'loading_complete', RECOVERED_EARLY_EOF: 'recovered_early_eof', MEDIA_INFO: 'media_info', METADATA_ARRIVED: 'metadata_arrived', SCRIPTDATA_ARRIVED: 'scriptdata_arrived', STATISTICS_INFO: 'statistics_info'};export default PlayerEvents;common.js
export function sleep(ms) { return new Promise(resolve => setTimeout(resolve, ms));}
