How to stream a video from API using Angular

I am able to play the video after it downloads completely using the below code. I am not sure how to buffer a video while the download is in progress.

Service:

getTestVideo() {
    return this.http.post(this.getATestVideoURL, null, {
      observe: 'response', reportProgress: true, responseType: 'blob'
    }).pipe(
      catchError(this.errorHandler.handleError)
    );
  }

Component:

ngAfterViewInit(): void {
    this.userService.getTestVideo().pipe(takeUntil(this.ngUnsubscribe)).subscribe(
      result => {
        this.videoElement.nativeElement.src = URL.createObjectURL(result.body);
        this.videoElement.nativeElement.load();
      }
    );
}