Solution 1:

You can decide if the file is type of video/image and then forward it to suitable html controls

<img [src]="url" *ngIf="format==='image' && url" height="200"> <br/>
<video [src]="url" *ngIf="format==='video' && url" height="200" controls></video> <br/>
<input type='file' (change)="onSelectFile($event)" />
onSelectFile(event) {
  const file = event.target.files && event.target.files[0];
  if (file) {
    var reader = new FileReader();
    reader.readAsDataURL(file);
    if(file.type.indexOf('image')> -1){
      this.format = 'image';
    } else if(file.type.indexOf('video')> -1){
      this.format = 'video';
    }
    reader.onload = (event) => {
      this.url = (<FileReader>event.target).result;
    }
  }
}

Updated Stackblitz: https://stackblitz.com/edit/angular-video-or-image-upload-preview-fjsukm