如何使用 HTML5 WebRTC 录制和保存视频

Question

First run code snippet then read the description ... It will give you the structure

I want to record, play and save video in the 2nd video element . The problem I am facing is: stream is running in the 1st video-element but unable to record and save video

 .video { border: 1px solid gray; box-shadow: 3px 4px lightgray; }

 <link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet"/> <div style="text-align:center"> <h1>Welcome to WebRTC</h1> <video class="video" #video autoplay controls></video> <video class="video" style="width:360;" autoplay controls #recordedVideo></video> <br> <button class="btn btn-warning" (click)="startRecording()">Start</button> <button class="btn btn-warning" (click)="stopRecording()">Stop</button> <button class="btn btn-warning" (click)="playRecording()">Play</button> </div>

------------------------ Modified and Resolved the issue

What I did here, in Luis Estevez code, I declared the event there in startRecording method because when I tried to push stream-chunk in blob-array, it responded an error: push method does not exist, even I created an object-array after I declared an array.

startRecording(stream) {
    let options = { mimeType: 'video/webm' }
    this.recordedBlobs = []
    console.log(this.recordedBlobs)
    try {
      this.mediaRecorder = new MediaRecorder(stream, options)
    } catch (e0) {
      console.log('Try different mimeType')
    }

    console.log('Created MediaRecorder', this.mediaRecorder, 'with options', options)
    // this.mediaRecorder.onstop = this.handleStop
    this.mediaRecorder.onstop = (event) => {
      console.log('Recorder stopped: ', event)
      const videoBuffer = new Blob(this.recordedBlobs, { type: 'video/webm' })
      this.downloadUrl = window.URL.createObjectURL(videoBuffer) // you can download with <a> tag

      this.recordVideoElement = this.recordVideoElementRef.nativeElement
      this.recordVideoElement.src = this.downloadUrl
    }
    // this.mediaRecorder.ondataavailable = this.handleDataAvailable
    this.mediaRecorder.ondataavailable = (event) => {
      if (event.data && event.data.size > 0) {
        this.recordedBlobs.push(event.data)
      }
    }
    this.mediaRecorder.start(100) // collect 100ms of data
    console.log('MediaRecorder started', this.mediaRecorder)
  }

Thanks Luis Estevez :)

Answer 1

You didn't 'really' record the stream, you just copied the stream object, not the event data coming from the stream.

Use MediaRecorder and pass the stream as constructor argument. Grab the video blob from the event handler ondataavailable. Join the recorded array of blobs to a new Blob. From there you can get url using createObbjectURL(blob);

The follow snippet is pseudo code:

** typescript doesn't recognize 'MediaRecorder' so you'll have to find a way to add type any to MediaRecorder

---

mediaRecorder: any;
recordedBlobs: Blob[];
downloadUrl: string;

handleDataAvailable(event) {
    if (event.data && event.data.size > 0) {
      this.recordedBlobs.push(event.data);
    }
}

handleStop(event) {
    console.log('Recorder stopped: ', event);
    const videoBuffer = new Blob(this.recordedBlobs, {type: 'video/webm'});
    this.downloadUrl = window.URL.createObjectURL(videoBuffer); // you can download with <a> tag
    this.recordVideoElement.src = this.downloadUrl;
}

startRecording(stream) {
    let options = {mimeType: 'video/webm'};
    this.recordedBlobs = [];
    try {
        this.mediaRecorder = new MediaRecorder(stream, options);
    } catch (e0) {
        console.log('Try different mimeType');
    }
    console.log('Created MediaRecorder', this.mediaRecorder, 'with options', options);
    this.mediaRecorder.onstop = this.handleStop;
    this.mediaRecorder.ondataavailable = this.handleDataAvailable;
    this.mediaRecorder.start(100); // collect 100ms of data
    console.log('MediaRecorder started', this.mediaRecorder);
}

stopRecording() {
  this.mediaRecorder.stop();
  console.log('Recorded Blobs: ', this.recordedBlobs);
  this.recordVideoElement.controls = true;
}

playRecording() {
  if (!this.recordedBlobs.length) {
      console.log('cannot play.');
      return;
  }
  this.recordVideoElement.play();
}

async ngOnInit() {
  navigator.mediaDevices.getUserMedia({ video: { width: 360 } }).then(stream => {
    this.videoElement.srcObject = stream
    this.startRecording(stream);
  })
}

Answer 2

Complete working code to record Video in Angular 6

RecordComponent.ts

  @ViewChild('recordedVideo') recordVideoElementRef: ElementRef
  @ViewChild('video') videoElementRef: ElementRef

  videoElement: HTMLVideoElement
  recordVideoElement: HTMLVideoElement
  mediaRecorder: MediaRecorder
  recordedBlobs: Blob[]
  isRecording: boolean = false
  downloadUrl: string
  stream: MediaStream

  constructor() {
  }

  async ngOnInit() {
    this.videoElement = this.videoElementRef.nativeElement
    this.recordVideoElement = this.recordVideoElementRef.nativeElement

    navigator.mediaDevices.getUserMedia({
      video: {
        width: 360
      }
    }).then(stream => {
      this.stream = stream
      this.videoElement.srcObject = this.stream
    })
  }

  startRecording() {
    this.recordedBlobs = []
    let options: MediaRecorderOptions = { mimeType: 'video/webm' }

    try {
      this.mediaRecorder = new MediaRecorder(this.stream, options)
    } catch (err) {
      console.log(err)
    }

    this.mediaRecorder.start() // collect 100ms of data
    this.isRecording = !this.isRecording
    this.onDataAvailableEvent()
    this.onStopRecordingEvent()
  }

  stopRecording() {
    this.mediaRecorder.stop()
    this.isRecording = !this.isRecording
    console.log('Recorded Blobs: ', this.recordedBlobs)
  }

  playRecording() {
    if (!this.recordedBlobs || !this.recordedBlobs.length) {
      console.log('cannot play.')
      return
    }
    this.recordVideoElement.play()
  }

  onDataAvailableEvent() {
    try {
      this.mediaRecorder.ondataavailable = (event: BlobEvent) => {
        if (event.data && event.data.size > 0) {
          this.recordedBlobs.push(event.data)
        }
      }
    } catch (error) {
      console.log(error)
    }
  }

  onStopRecordingEvent() {
    try {
      this.mediaRecorder.onstop = (event: Event) => {
        const videoBuffer = new Blob(this.recordedBlobs, { type: 'video/webm' })
        this.downloadUrl = window.URL.createObjectURL(videoBuffer) // you can download with <a> tag
        this.recordVideoElement.src = this.downloadUrl
      }
    } catch (error) {
      console.log(error)
    }
  }

}

RecordComponent.html

<div style="text-align:center">
    <h1>Welcome to WebRTC</h1>
    <video class="video" #video autoplay controls></video>
    <span class="m-1"></span>
    <video class="video" style="width:360 !important;" controls #recordedVideo></video>
    <br>
    <button class="btn btn-primary btn-lg" *ngIf="!isRecording" (click)="startRecording()">Start Recording</button>
    <button class="btn btn-warning btn-lg" *ngIf="isRecording" (click)="stopRecording()">Stop Recording</button>
  </div>

Note: if you get an error that MediaRecorder is not found etc then do

npm i @types/dom-mediacapture-record

Be sure to update your Chrome browser too.

Have a Good day