shaka-player
Version:
DASH/EME video player library
910 lines (832 loc) • 27.1 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.util.Platform');
goog.require('shaka.drm.DrmUtils');
goog.require('shaka.log');
goog.require('shaka.util.Timer');
/**
* A wrapper for platform-specific functions.
*
* @final
*/
shaka.util.Platform = class {
/**
* Check if the current platform supports media source. We assume that if
* the current platform supports media source, then we can use media source
* as per its design.
*
* @return {boolean}
*/
static supportsMediaSource() {
const mediaSource = window.ManagedMediaSource || window.MediaSource;
// Browsers that lack a media source implementation will have no reference
// to |window.MediaSource|. Platforms that we see having problematic media
// source implementations will have this reference removed via a polyfill.
if (!mediaSource) {
return false;
}
// Some very old MediaSource implementations didn't have isTypeSupported.
if (!mediaSource.isTypeSupported) {
return false;
}
return true;
}
/**
* Returns true if the media type is supported natively by the platform.
*
* @param {string} mimeType
* @return {boolean}
*/
static supportsMediaType(mimeType) {
const video = shaka.util.Platform.anyMediaElement();
return video.canPlayType(mimeType) != '';
}
/**
* Check if the current platform is MS Edge.
*
* @return {boolean}
*/
static isEdge() {
// Legacy Edge contains "Edge/version".
// Chromium-based Edge contains "Edg/version" (no "e").
if (navigator.userAgent.match(/Edge?\//)) {
return true;
}
return false;
}
/**
* Check if the current platform is Legacy Edge.
*
* @return {boolean}
*/
static isLegacyEdge() {
// Legacy Edge contains "Edge/version".
// Chromium-based Edge contains "Edg/version" (no "e").
if (navigator.userAgent.match(/Edge\//)) {
return true;
}
return false;
}
/**
* Check if the current platform is MS IE.
*
* @return {boolean}
*/
static isIE() {
return shaka.util.Platform.userAgentContains_('Trident/');
}
/**
* Check if the current platform is an Xbox One.
*
* @return {boolean}
*/
static isXboxOne() {
return shaka.util.Platform.userAgentContains_('Xbox One');
}
/**
* Check if the current platform is a Tizen TV.
*
* @return {boolean}
*/
static isTizen() {
return shaka.util.Platform.userAgentContains_('Tizen');
}
/**
* Check if the current platform is a Tizen 6 TV.
*
* @return {boolean}
*/
static isTizen6() {
return shaka.util.Platform.userAgentContains_('Tizen 6');
}
/**
* Check if the current platform is a Tizen 5.0 TV.
*
* @return {boolean}
*/
static isTizen5_0() {
return shaka.util.Platform.userAgentContains_('Tizen 5.0');
}
/**
* Check if the current platform is a Tizen 5 TV.
*
* @return {boolean}
*/
static isTizen5() {
return shaka.util.Platform.userAgentContains_('Tizen 5');
}
/**
* Check if the current platform is a Tizen 4 TV.
*
* @return {boolean}
*/
static isTizen4() {
return shaka.util.Platform.userAgentContains_('Tizen 4');
}
/**
* Check if the current platform is a Tizen 3 TV.
*
* @return {boolean}
*/
static isTizen3() {
return shaka.util.Platform.userAgentContains_('Tizen 3');
}
/**
* Check if the current platform is a Tizen 2 TV.
*
* @return {boolean}
*/
static isTizen2() {
return shaka.util.Platform.userAgentContains_('Tizen 2');
}
/**
* Check if the current platform is a WebOS.
*
* @return {boolean}
*/
static isWebOS() {
return shaka.util.Platform.userAgentContains_('Web0S');
}
/**
* Check if the current platform is a WebOS 3.
*
* @return {boolean}
*/
static isWebOS3() {
// See: https://webostv.developer.lge.com/develop/specifications/web-api-and-web-engine#useragent-string
return shaka.util.Platform.isWebOS() &&
shaka.util.Platform.chromeVersion() === 38;
}
/**
* Check if the current platform is a WebOS 4.
*
* @return {boolean}
*/
static isWebOS4() {
// See: https://webostv.developer.lge.com/develop/specifications/web-api-and-web-engine#useragent-string
return shaka.util.Platform.isWebOS() &&
shaka.util.Platform.chromeVersion() === 53;
}
/**
* Check if the current platform is a WebOS 5.
*
* @return {boolean}
*/
static isWebOS5() {
// See: https://webostv.developer.lge.com/develop/specifications/web-api-and-web-engine#useragent-string
return shaka.util.Platform.isWebOS() &&
shaka.util.Platform.chromeVersion() === 68;
}
/**
* Check if the current platform is a WebOS 6.
*
* @return {boolean}
*/
static isWebOS6() {
// See: https://webostv.developer.lge.com/develop/specifications/web-api-and-web-engine#useragent-string
return shaka.util.Platform.isWebOS() &&
shaka.util.Platform.chromeVersion() === 79;
}
/**
* Check if the current platform is a Google Chromecast.
*
* @return {boolean}
*/
static isChromecast() {
const Platform = shaka.util.Platform;
return Platform.userAgentContains_('CrKey') && !Platform.isVizio();
}
/**
* Check if the current platform is a Google Chromecast without
* Android or Fuchsia.
*
* @return {boolean}
*/
static isOlderChromecast() {
const Platform = shaka.util.Platform;
return Platform.isChromecast() &&
!Platform.isAndroid() && !Platform.isFuchsia();
}
/**
* Check if the current platform is a Google Chromecast with Android
* (i.e. Chromecast with GoogleTV).
*
* @return {boolean}
*/
static isAndroidCastDevice() {
const Platform = shaka.util.Platform;
return Platform.isChromecast() && Platform.isAndroid();
}
/**
* Check if the current platform is a Google Chromecast with Fuchsia
* (i.e. Google Nest Hub).
*
* @return {boolean}
*/
static isFuchsiaCastDevice() {
const Platform = shaka.util.Platform;
return Platform.isChromecast() && Platform.isFuchsia();
}
/**
* Returns a major version number for Chrome, or Chromium-based browsers.
*
* For example:
* - Chrome 106.0.5249.61 returns 106.
* - Edge 106.0.1370.34 returns 106 (since this is based on Chromium).
* - Safari returns null (since this is independent of Chromium).
*
* @return {?number} A major version number or null if not Chromium-based.
*/
static chromeVersion() {
if (!shaka.util.Platform.isChrome()) {
return null;
}
// Looking for something like "Chrome/106.0.0.0".
const match = navigator.userAgent.match(/Chrome\/(\d+)/);
if (match) {
return parseInt(match[1], /* base= */ 10);
}
return null;
}
/**
* Check if the current platform is Google Chrome.
*
* @return {boolean}
*/
static isChrome() {
// The Edge Legacy user agent will also contain the "Chrome" keyword, so we
// need to make sure this is not Edge Legacy.
return shaka.util.Platform.userAgentContains_('Chrome') &&
!shaka.util.Platform.isLegacyEdge();
}
/**
* Check if the current platform is Firefox.
*
* @return {boolean}
*/
static isFirefox() {
return shaka.util.Platform.userAgentContains_('Firefox');
}
/**
* Check if the current platform is from Apple.
*
* Returns true on all iOS browsers and on desktop Safari.
*
* Returns false for non-Safari browsers on macOS, which are independent of
* Apple.
*
* @return {boolean}
*/
static isApple() {
return shaka.util.Platform.isAppleVendor_() &&
(shaka.util.Platform.isMac() || shaka.util.Platform.isIOS());
}
/**
* Check if the current platform is Playstation 5.
*
* Returns true on Playstation 5 browsers.
*
* Returns false for Playstation 5 browsers
*
* @return {boolean}
*/
static isPS5() {
return shaka.util.Platform.userAgentContains_('PlayStation 5');
}
/**
* Check if the current platform is Playstation 4.
* @return {boolean}
*/
static isPS4() {
return shaka.util.Platform.userAgentContains_('PlayStation 4');
}
/**
* Check if the current platform is Hisense.
* @return {boolean}
*/
static isHisense() {
return shaka.util.Platform.userAgentContains_('Hisense') ||
shaka.util.Platform.userAgentContains_('VIDAA');
}
/**
* Check if the current platform is Vizio TV.
* @return {boolean}
*/
static isVizio() {
return shaka.util.Platform.userAgentContains_('VIZIO SmartCast');
}
/**
* Check if the current platform is Orange.
* @return {boolean}
*/
static isOrange() {
return shaka.util.Platform.userAgentContains_('SOPOpenBrowser');
}
/**
* Check if the current platform is SkyQ STB.
* @return {boolean}
*/
static isSkyQ() {
return shaka.util.Platform.userAgentContains_('Sky_STB');
}
/**
* Check if the current platform is Deutsche Telecom Zenterio STB.
* @return {boolean}
*/
static isZenterio() {
return shaka.util.Platform.userAgentContains_('DT_STB_BCM');
}
/**
* Returns a major version number for Safari, or Webkit-based STBs,
* or Safari-based iOS browsers.
*
* For example:
* - Safari 13.0.4 on macOS returns 13.
* - Safari on iOS 13.3.1 returns 13.
* - Chrome on iOS 13.3.1 returns 13 (since this is based on Safari/WebKit).
* - Chrome on macOS returns null (since this is independent of Apple).
*
* Returns null on Firefox on iOS, where this version information is not
* available.
*
* @return {?number} A major version number or null if not iOS.
*/
static safariVersion() {
// All iOS browsers and desktop Safari will return true for isApple().
if (!shaka.util.Platform.isApple() && !shaka.util.Platform.isWebkitSTB()) {
return null;
}
// This works for iOS Safari and desktop Safari, which contain something
// like "Version/13.0" indicating the major Safari or iOS version.
let match = navigator.userAgent.match(/Version\/(\d+)/);
if (match) {
return parseInt(match[1], /* base= */ 10);
}
// This works for all other browsers on iOS, which contain something like
// "OS 13_3" indicating the major & minor iOS version.
match = navigator.userAgent.match(/OS (\d+)(?:_\d+)?/);
if (match) {
return parseInt(match[1], /* base= */ 10);
}
return null;
}
/**
* Guesses if the platform is an Apple mobile one (iOS, iPad, iPod).
* @return {boolean}
*/
static isIOS() {
if (/(?:iPhone|iPad|iPod)/.test(navigator.userAgent)) {
// This is Android, iOS, or iPad < 13.
return true;
}
// Starting with iOS 13 on iPad, the user agent string no longer has the
// word "iPad" in it. It looks very similar to desktop Safari. This seems
// to be intentional on Apple's part.
// See: https://forums.developer.apple.com/thread/119186
//
// So if it's an Apple device with multi-touch support, assume it's a mobile
// device. If some future iOS version starts masking their user agent on
// both iPhone & iPad, this clause should still work. If a future
// multi-touch desktop Mac is released, this will need some adjustment.
//
// As of January 2020, this is mainly used to adjust the default UI config
// for mobile devices, so it's low risk if something changes to break this
// detection.
return shaka.util.Platform.isAppleVendor_() && navigator.maxTouchPoints > 1;
}
/**
* Guesses if the platform is a mobile one.
* @return {boolean}
*/
static isMobile() {
if (navigator.userAgentData) {
return navigator.userAgentData.mobile;
}
return shaka.util.Platform.isIOS() || shaka.util.Platform.isAndroid();
}
/**
* Return true if the platform is a Mac, regardless of the browser.
*
* @return {boolean}
*/
static isMac() {
// Try the newer standard first.
if (navigator.userAgentData && navigator.userAgentData.platform) {
return navigator.userAgentData.platform.toLowerCase() == 'macos';
}
// Fall back to the old API, with less strict matching.
if (!navigator.platform) {
return false;
}
return navigator.platform.toLowerCase().includes('mac');
}
/**
* Return true if the platform is a VisionOS.
*
* @return {boolean}
*/
static isVisionOS() {
if (!shaka.util.Platform.isMac()) {
return false;
}
if (!('xr' in navigator)) {
return false;
}
return true;
}
/**
* Checks is non-Apple STB based on Webkit.
* @return {boolean}
*/
static isWebkitSTB() {
return shaka.util.Platform.isAppleVendor_() &&
!shaka.util.Platform.isApple();
}
/**
* Return true if the platform is a Windows, regardless of the browser.
*
* @return {boolean}
*/
static isWindows() {
// Try the newer standard first.
if (navigator.userAgentData && navigator.userAgentData.platform) {
return navigator.userAgentData.platform.toLowerCase() == 'windows';
}
// Fall back to the old API, with less strict matching.
if (!navigator.platform) {
return false;
}
return navigator.platform.toLowerCase().includes('win32');
}
/**
* Return true if the platform is a Android, regardless of the browser.
*
* @return {boolean}
*/
static isAndroid() {
if (navigator.userAgentData && navigator.userAgentData.platform) {
return navigator.userAgentData.platform.toLowerCase() == 'android';
}
return shaka.util.Platform.userAgentContains_('Android');
}
/**
* Return true if the platform is a Fuchsia, regardless of the browser.
*
* @return {boolean}
*/
static isFuchsia() {
if (navigator.userAgentData && navigator.userAgentData.platform) {
return navigator.userAgentData.platform.toLowerCase() == 'fuchsia';
}
return shaka.util.Platform.userAgentContains_('Fuchsia');
}
/**
* Return true if the platform is controlled by a remote control.
*
* @return {boolean}
*/
static isSmartTV() {
const Platform = shaka.util.Platform;
if (Platform.isTizen() || Platform.isWebOS() ||
Platform.isXboxOne() || Platform.isPS4() ||
Platform.isPS5() || Platform.isChromecast() ||
Platform.isHisense() || Platform.isVizio() ||
Platform.isWebkitSTB()) {
return true;
}
return false;
}
/**
* Check if the user agent contains a key. This is the best way we know of
* right now to detect platforms. If there is a better way, please send a
* PR.
*
* @param {string} key
* @return {boolean}
* @private
*/
static userAgentContains_(key) {
const userAgent = navigator.userAgent || '';
return userAgent.includes(key);
}
/**
* @return {boolean}
* @private
*/
static isAppleVendor_() {
return (navigator.vendor || '').includes('Apple');
}
/**
* For canPlayType queries, we just need any instance.
*
* First, use a cached element from a previous query.
* Second, search the page for one.
* Third, create a temporary one.
*
* Cached elements expire in one second so that they can be GC'd or removed.
*
* @return {!HTMLMediaElement}
*/
static anyMediaElement() {
const Platform = shaka.util.Platform;
if (Platform.cachedMediaElement_) {
return Platform.cachedMediaElement_;
}
if (!Platform.cacheExpirationTimer_) {
Platform.cacheExpirationTimer_ = new shaka.util.Timer(() => {
Platform.cachedMediaElement_ = null;
});
}
Platform.cachedMediaElement_ = /** @type {HTMLMediaElement} */(
document.getElementsByTagName('video')[0] ||
document.getElementsByTagName('audio')[0]);
if (!Platform.cachedMediaElement_) {
Platform.cachedMediaElement_ = /** @type {!HTMLMediaElement} */(
document.createElement('video'));
}
Platform.cacheExpirationTimer_.tickAfter(/* seconds= */ 1);
return Platform.cachedMediaElement_;
}
/**
* Returns true if the platform requires encryption information in all init
* segments. For such platforms, MediaSourceEngine will attempt to work
* around a lack of such info by inserting fake encryption information into
* initialization segments.
*
* @param {?string} keySystem
* @param {string} contentType
* @return {boolean}
* @see https://github.com/shaka-project/shaka-player/issues/2759
*/
static requiresEncryptionInfoInAllInitSegments(keySystem, contentType) {
const Platform = shaka.util.Platform;
const isPlayReady = shaka.drm.DrmUtils.isPlayReadyKeySystem(keySystem);
return (Platform.isApple() && contentType === 'audio') ||
Platform.isTizen() || Platform.isXboxOne() || Platform.isOrange() ||
(Platform.isEdge() && Platform.isWindows() && isPlayReady);
}
/**
* @param {string} contentType
* @return {boolean}
*/
static requiresTfhdFix(contentType) {
return shaka.util.Platform.isApple() && contentType === 'audio';
}
/**
* Returns true if the platform requires AC-3 signalling in init
* segments to be replaced with EC-3 signalling.
* For such platforms, MediaSourceEngine will attempt to work
* around it by inserting fake EC-3 signalling into
* initialization segments.
*
* @return {boolean}
*/
static requiresEC3InitSegments() {
return shaka.util.Platform.isTizen3();
}
/**
* Returns true if the platform supports SourceBuffer "sequence mode".
*
* @return {boolean}
*/
static supportsSequenceMode() {
const Platform = shaka.util.Platform;
if (Platform.isTizen3() || Platform.isTizen2() ||
Platform.isWebOS3() || Platform.isPS4() || Platform.isPS5()) {
return false;
}
// See: https://bugs.webkit.org/show_bug.cgi?id=210341
const safariVersion = Platform.safariVersion();
if (Platform.isWebkitSTB() && safariVersion != null && safariVersion < 15) {
return false;
}
return true;
}
/**
* Returns if codec switching SMOOTH is known reliable device support.
*
* Some devices are known not to support <code>SourceBuffer.changeType</code>
* well. These devices should use the reload strategy. If a device
* reports that it supports <code<changeType</code> but supports it unreliably
* it should be disallowed in this method.
*
* @return {boolean}
*/
static supportsSmoothCodecSwitching() {
const Platform = shaka.util.Platform;
// All Tizen versions (up to Tizen 8) do not support SMOOTH so far.
// webOS seems to support SMOOTH from webOS 22.
if (Platform.isTizen() || Platform.isPS4() || Platform.isPS5() ||
Platform.isWebOS6()) {
return false;
}
// Older chromecasts without GoogleTV seem to not support SMOOTH properly.
if (Platform.isOlderChromecast()) {
return false;
}
// See: https://chromium-review.googlesource.com/c/chromium/src/+/4577759
if (Platform.isWindows() && Platform.isEdge()) {
return false;
}
return true;
}
/**
* On some platforms, such as v1 Chromecasts, the act of seeking can take a
* significant amount of time.
*
* @return {boolean}
*/
static isSeekingSlow() {
const Platform = shaka.util.Platform;
if (Platform.isChromecast()) {
if (Platform.isAndroidCastDevice()) {
// Android-based Chromecasts are new enough to not be a problem.
return false;
} else {
return true;
}
}
return false;
}
/**
* Detect the maximum resolution that the platform's hardware can handle.
*
* @return {!Promise<shaka.extern.Resolution>}
*/
static async detectMaxHardwareResolution() {
const Platform = shaka.util.Platform;
/** @type {shaka.extern.Resolution} */
const maxResolution = {
width: Infinity,
height: Infinity,
};
if (Platform.isChromecast()) {
// In our tests, the original Chromecast seems to have trouble decoding
// above 1080p. It would be a waste to select a higher res anyway, given
// that the device only outputs 1080p to begin with.
// Chromecast has an extension to query the device/display's resolution.
const hasCanDisplayType = window.cast && cast.__platform__ &&
cast.__platform__.canDisplayType;
// Some hub devices can only do 720p. Default to that.
maxResolution.width = 1280;
maxResolution.height = 720;
try {
if (hasCanDisplayType && await cast.__platform__.canDisplayType(
'video/mp4; codecs="avc1.640028"; width=3840; height=2160')) {
// The device and display can both do 4k. Assume a 4k limit.
maxResolution.width = 3840;
maxResolution.height = 2160;
} else if (hasCanDisplayType && await cast.__platform__.canDisplayType(
'video/mp4; codecs="avc1.640028"; width=1920; height=1080')) {
// Most Chromecasts can do 1080p.
maxResolution.width = 1920;
maxResolution.height = 1080;
}
} catch (error) {
// This shouldn't generally happen. Log the error.
shaka.log.alwaysError('Failed to check canDisplayType:', error);
// Now ignore the error and let the 720p default stand.
}
} else if (Platform.isTizen()) {
const devicePixelRatio = window.devicePixelRatio;
maxResolution.width = window.screen.width * devicePixelRatio > 1920 ?
3840 : 1920;
maxResolution.height = window.screen.height * devicePixelRatio > 1080 ?
2160 : 1080;
try {
if (webapis.systeminfo && webapis.systeminfo.getMaxVideoResolution) {
const maxVideoResolution =
webapis.systeminfo.getMaxVideoResolution();
maxResolution.width = maxVideoResolution.width;
maxResolution.height = maxVideoResolution.height;
} else {
if (webapis.productinfo.is8KPanelSupported &&
webapis.productinfo.is8KPanelSupported()) {
maxResolution.width = 7680;
maxResolution.height = 4320;
} else if (webapis.productinfo.isUdPanelSupported &&
webapis.productinfo.isUdPanelSupported()) {
maxResolution.width = 3840;
maxResolution.height = 2160;
}
}
} catch (e) {
shaka.log.alwaysWarn('Tizen: Error detecting screen size, default ' +
'screen size 1920x1080.');
}
} else if (Platform.isWebOS()) {
try {
const deviceInfo =
/** @type {{screenWidth: number, screenHeight: number}} */(
JSON.parse(window.PalmSystem.deviceInfo));
// WebOS has always been able to do 1080p. Assume a 1080p limit.
maxResolution.width = Math.max(1920, deviceInfo['screenWidth']);
maxResolution.height = Math.max(1080, deviceInfo['screenHeight']);
} catch (e) {
shaka.log.alwaysWarn('WebOS: Error detecting screen size, default ' +
'screen size 1920x1080.');
maxResolution.width = 1920;
maxResolution.height = 1080;
}
} else if (Platform.isHisense()) {
let supports4k = null;
if (window.Hisense_Get4KSupportState) {
try {
// eslint-disable-next-line new-cap
supports4k = window.Hisense_Get4KSupportState();
} catch (e) {
shaka.log.debug('Hisense: Failed to get 4K support state', e);
}
}
if (supports4k == null) {
// If API is not there or not working for whatever reason, fallback to
// user agent check, as it contains UHD or FHD info.
supports4k = Platform.userAgentContains_('UHD');
}
if (supports4k) {
maxResolution.width = 3840;
maxResolution.height = 2160;
} else {
maxResolution.width = 1920;
maxResolution.height = 1080;
}
} else if (Platform.isPS4() || Platform.isPS5()) {
let supports4K = false;
try {
const result = await window.msdk.device.getDisplayInfo();
supports4K = result.resolution === '4K';
} catch (e) {
try {
const result = await window.msdk.device.getDisplayInfoImmediate();
supports4K = result.resolution === '4K';
} catch (e) {
shaka.log.alwaysWarn(
'PlayStation: Failed to get the display info:', e);
}
}
if (supports4K) {
maxResolution.width = 3840;
maxResolution.height = 2160;
} else {
maxResolution.width = 1920;
maxResolution.height = 1080;
}
} else {
// For Xbox and UWP apps.
let winRT = undefined;
try {
// Try to access to WinRT for WebView, if it's not defined,
// try to access to WinRT for WebView2, if it's not defined either,
// let it throw.
if (typeof Windows !== 'undefined') {
winRT = Windows;
} else {
winRT = chrome.webview.hostObjects.sync.Windows;
}
} catch (e) {}
if (winRT) {
maxResolution.width = 1920;
maxResolution.height = 1080;
try {
const protectionCapabilities =
new winRT.Media.Protection.ProtectionCapabilities();
const protectionResult =
winRT.Media.Protection.ProtectionCapabilityResult;
// isTypeSupported may return "maybe", which means the operation
// is not completed. This means we need to retry
// https://learn.microsoft.com/en-us/uwp/api/windows.media.protection.protectioncapabilityresult?view=winrt-22621
let result = null;
const type =
'video/mp4;codecs="hvc1,mp4a";features="decode-res-x=3840,' +
'decode-res-y=2160,decode-bitrate=20000,decode-fps=30,' +
'decode-bpc=10,display-res-x=3840,display-res-y=2160,' +
'display-bpc=8"';
const keySystem = 'com.microsoft.playready.recommendation';
do {
result = protectionCapabilities.isTypeSupported(type, keySystem);
} while (result === protectionResult.maybe);
if (result === protectionResult.probably) {
maxResolution.width = 3840;
maxResolution.height = 2160;
}
} catch (e) {
shaka.log.alwaysWarn('Xbox: Error detecting screen size, default ' +
'screen size 1920x1080.');
}
} else if (Platform.isXboxOne()) {
maxResolution.width = 1920;
maxResolution.height = 1080;
shaka.log.alwaysWarn('Xbox: Error detecting screen size, default ' +
'screen size 1920x1080.');
}
}
return maxResolution;
}
};
/** @private {shaka.util.Timer} */
shaka.util.Platform.cacheExpirationTimer_ = null;
/** @private {HTMLMediaElement} */
shaka.util.Platform.cachedMediaElement_ = null;