Ios video'sounds in iframe is too small

my Page web.html has a iframe like this :

` and my ts is: `import { Component } from '@angular/core';

import { NavController, NavParams } from ‘ionic-angular’;
import { DomSanitizer } from ‘@angular/platform-browser’;
selector: ‘page-web’,
templateUrl: ‘web.html’
export class WebPage {
title: string;
srcUrl: any;
constructor(public navCtrl: NavController,public navParams: NavParams, private sanitizer: DomSanitizer) {

this.title = this.navParams.get(‘title’);
this.srcUrl = this.sanitizer.bypassSecurityTrustResourceUrl(this.navParams.get(‘url’));
console.log(‘url=’ + this.srcUrl);
console.log(‘title=’ + this.title);


srcUrl is passed from previous page like:
this.srcUrl = ’’;

And then ,the video like this is no sounds or too small sounds on iphone.
However,Android is fine.
Please help me ,Thanks.