/**
* @license
* Copyright 2016 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
goog.provide('shaka.polyfill.MediaSource');
goog.require('shaka.log');
goog.require('shaka.polyfill.register');
/**
* @namespace shaka.polyfill.MediaSource
*
* @summary A polyfill to patch MSE bugs.
*/
/**
* Install the polyfill if needed.
*/
shaka.polyfill.MediaSource.install = function() {
shaka.log.debug('MediaSource.install');
// MediaSource bugs are difficult to detect without checking for the affected
// platform. SourceBuffer is not always exposed on window, for example, and
// instances are only accessible after setting up MediaSource on a video
// element. Because of this, we use UA detection and other platform detection
// tricks to decide which patches to install.
if (!window.MediaSource) {
shaka.log.info('No MSE implementation available.');
} else if (window.cast && cast.__platform__ &&
cast.__platform__.canDisplayType) {
shaka.log.info('Patching Chromecast MSE bugs.');
// Chromecast cannot make accurate determinations via isTypeSupported.
shaka.polyfill.MediaSource.patchCastIsTypeSupported_();
} else if (navigator.vendor && navigator.vendor.indexOf('Apple') >= 0) {
var version = navigator.appVersion;
// TS content is broken in Safari in general.
// See https://github.com/google/shaka-player/issues/743
// and https://bugs.webkit.org/show_bug.cgi?id=165342
shaka.polyfill.MediaSource.rejectTsContent_();
if (version.indexOf('Version/8') >= 0) {
// Safari 8 does not implement appendWindowEnd. If we ignore the
// incomplete MSE implementation, some content (especially multi-period)
// will fail to play correctly. The best we can do is blacklist Safari 8.
shaka.log.info('Blacklisting Safari 8 MSE.');
shaka.polyfill.MediaSource.blacklist_();
} else if (version.indexOf('Version/9') >= 0) {
shaka.log.info('Patching Safari 9 MSE bugs.');
// Safari 9 does not correctly implement abort() on SourceBuffer.
// Calling abort() causes a decoder failure, rather than resetting the
// decode timestamp as called for by the spec.
// Bug filed: http://goo.gl/UZ2rPp
shaka.polyfill.MediaSource.stubAbort_();
} else if (version.indexOf('Version/10') >= 0) {
shaka.log.info('Patching Safari 10 MSE bugs.');
// Safari 10 does not correctly implement abort() on SourceBuffer.
// Calling abort() before appending a segment causes that segment to be
// incomplete in buffer.
// Bug filed: https://goo.gl/rC3CLj
shaka.polyfill.MediaSource.stubAbort_();
// Safari 10 fires spurious 'updateend' events after endOfStream().
// Bug filed: https://goo.gl/qCeTZr
shaka.polyfill.MediaSource.patchEndOfStreamEvents_();
} else if (version.indexOf('Version/11') >= 0) {
shaka.log.info('Patching Safari 11 MSE bugs.');
// Safari 11 does not correctly implement abort() on SourceBuffer.
// Calling abort() before appending a segment causes that segment to be
// incomplete in buffer.
// Bug filed: https://goo.gl/rC3CLj
shaka.polyfill.MediaSource.stubAbort_();
// If you remove up to a keyframe, Safari 11 incorrectly will also remove
// that keyframe and the content up to the next.
// Offsetting the end of the removal range seems to help.
// Bug filed: https://goo.gl/h2yDPN
shaka.polyfill.MediaSource.patchRemovalRange_();
}
} else {
shaka.log.info('Using native MSE as-is.');
}
};
/**
* Blacklist the current browser by making MediaSourceEngine.isBrowserSupported
* fail later.
*
* @private
*/
shaka.polyfill.MediaSource.blacklist_ = function() {
window['MediaSource'] = null;
};
/**
* Stub out abort(). On some buggy MSE implementations, calling abort() causes
* various problems.
*
* @private
*/
shaka.polyfill.MediaSource.stubAbort_ = function() {
var addSourceBuffer = MediaSource.prototype.addSourceBuffer;
MediaSource.prototype.addSourceBuffer = function() {
var sourceBuffer = addSourceBuffer.apply(this, arguments);
sourceBuffer.abort = function() {}; // Stub out for buggy implementations.
return sourceBuffer;
};
};
/**
* Patch remove(). On Safari 11, if you call remove() to remove the content up
* to a keyframe, Safari will also remove the keyframe and all of the data up to
* the next one. For example, if the keyframes are at 0s, 5s, and 10s, and you
* tried to remove 0s-5s, it would instead remove 0s-10s.
*
* Offsetting the end of the range seems to be a usable workaround.
*
* @private
*/
shaka.polyfill.MediaSource.patchRemovalRange_ = function() {
var originalRemove = SourceBuffer.prototype.remove;
SourceBuffer.prototype.remove = function(startTime, endTime) {
return originalRemove.call(this, startTime, endTime - 0.001);
};
};
/**
* Patch endOfStream() to get rid of 'updateend' events that should not fire.
* These extra events confuse MediaSourceEngine, which relies on correct events
* to manage SourceBuffer state.
*
* @private
*/
shaka.polyfill.MediaSource.patchEndOfStreamEvents_ = function() {
var endOfStream = MediaSource.prototype.endOfStream;
MediaSource.prototype.endOfStream = function() {
// This bug manifests only when endOfStream() results in the truncation
// of the MediaSource's duration. So first we must calculate what the
// new duration will be.
var newDuration = 0;
for (var i = 0; i < this.sourceBuffers.length; ++i) {
var buffer = this.sourceBuffers[i];
var bufferEnd = buffer.buffered.end(buffer.buffered.length - 1);
newDuration = Math.max(newDuration, bufferEnd);
}
// If the duration is going to be reduced, suppress the next 'updateend'
// event on each SourceBuffer.
if (!isNaN(this.duration) &&
newDuration < this.duration) {
this.ignoreUpdateEnd_ = true;
for (var i = 0; i < this.sourceBuffers.length; ++i) {
var buffer = this.sourceBuffers[i];
buffer.eventSuppressed_ = false;
}
}
return endOfStream.apply(this, arguments);
};
var cleanUpHandlerInstalled = false;
var addSourceBuffer = MediaSource.prototype.addSourceBuffer;
MediaSource.prototype.addSourceBuffer = function() {
// After adding a new source buffer, add an event listener to allow us to
// suppress events.
var sourceBuffer = addSourceBuffer.apply(this, arguments);
sourceBuffer['mediaSource_'] = this;
sourceBuffer.addEventListener('updateend',
shaka.polyfill.MediaSource.ignoreUpdateEnd_, false);
if (!cleanUpHandlerInstalled) {
// If we haven't already, install an event listener to allow us to clean
// up listeners when MediaSource is torn down.
this.addEventListener('sourceclose',
shaka.polyfill.MediaSource.cleanUpListeners_, false);
cleanUpHandlerInstalled = true;
}
return sourceBuffer;
};
};
/**
* An event listener for 'updateend' which selectively suppresses the events.
*
* @see shaka.polyfill.MediaSource.patchEndOfStreamEvents_
*
* @param {Event} event
* @private
*/
shaka.polyfill.MediaSource.ignoreUpdateEnd_ = function(event) {
var sourceBuffer = event.target;
var mediaSource = sourceBuffer['mediaSource_'];
if (mediaSource.ignoreUpdateEnd_) {
event.preventDefault();
event.stopPropagation();
event.stopImmediatePropagation();
sourceBuffer.eventSuppressed_ = true;
for (var i = 0; i < mediaSource.sourceBuffers.length; ++i) {
var buffer = mediaSource.sourceBuffers[i];
if (buffer.eventSuppressed_ == false) {
// More events need to be suppressed.
return;
}
}
// All events have been suppressed, all buffers are out of 'updating'
// mode. Stop suppressing events.
mediaSource.ignoreUpdateEnd_ = false;
}
};
/**
* An event listener for 'sourceclose' which cleans up listeners for 'updateend'
* to avoid memory leaks.
*
* @see shaka.polyfill.MediaSource.patchEndOfStreamEvents_
* @see shaka.polyfill.MediaSource.ignoreUpdateEnd_
*
* @param {Event} event
* @private
*/
shaka.polyfill.MediaSource.cleanUpListeners_ = function(event) {
var mediaSource = /** @type {!MediaSource} */ (event.target);
for (var i = 0; i < mediaSource.sourceBuffers.length; ++i) {
var buffer = mediaSource.sourceBuffers[i];
buffer.removeEventListener('updateend',
shaka.polyfill.MediaSource.ignoreUpdateEnd_, false);
}
mediaSource.removeEventListener('sourceclose',
shaka.polyfill.MediaSource.cleanUpListeners_, false);
};
/**
* Patch isTypeSupported() to reject TS content. Used to avoid TS-related MSE
* bugs on Safari.
*
* @private
*/
shaka.polyfill.MediaSource.rejectTsContent_ = function() {
var originalIsTypeSupported = MediaSource.isTypeSupported;
MediaSource.isTypeSupported = function(mimeType) {
// Parse the basic MIME type from its parameters.
var pieces = mimeType.split(/ *; */);
var basicMimeType = pieces[0];
var container = basicMimeType.split('/')[1];
if (container == 'mp2t') {
return false;
}
return originalIsTypeSupported(mimeType);
};
};
/**
* Patch isTypeSupported() to parse for HDR-related clues and chain to a private
* API on the Chromecast which can query for support.
*
* @private
*/
shaka.polyfill.MediaSource.patchCastIsTypeSupported_ = function() {
var originalIsTypeSupported = MediaSource.isTypeSupported;
// Docs from Dolby detailing profile names: https://goo.gl/LVVXrS
var dolbyVisionRegex = /^dv(?:he|av)\./;
MediaSource.isTypeSupported = function(mimeType) {
// Parse the basic MIME type from its parameters.
var pieces = mimeType.split(/ *; */);
var basicMimeType = pieces[0];
// Parse the parameters into key-value pairs.
/** @type {Object.<string, string>} */
var parameters = {};
for (var i = 1; i < pieces.length; ++i) {
var kv = pieces[i].split('=');
var k = kv[0];
var v = kv[1].replace(/"(.*)"/, '$1');
parameters[k] = v;
}
var codecs = parameters['codecs'];
if (!codecs) {
return originalIsTypeSupported(mimeType);
}
var isHDR = false;
var isDolbyVision = false;
var codecList = codecs.split(',').filter(function(codec) {
// Remove Dolby Vision codec strings. These are not understood on
// Chromecast, even though the content can still be played.
if (dolbyVisionRegex.test(codec)) {
isDolbyVision = true;
// Return false to remove this string from the list.
return false;
}
// We take this string as a signal for HDR, but don't remove it.
if (/^(hev|hvc)1\.2/.test(codec)) {
isHDR = true;
}
// Keep all other strings in the list.
return true;
});
// If the content uses Dolby Vision, we take this as a sign that the content
// is not HDR after all.
if (isDolbyVision) isHDR = false;
// Reconstruct the "codecs" parameter from the results of the filter.
parameters['codecs'] = codecList.join(',');
// If the content is HDR, we add this additional parameter so that the Cast
// platform will check for HDR support.
if (isHDR) {
parameters['eotf'] = 'smpte2084';
}
// Reconstruct the MIME type, possibly with additional parameters.
var extendedMimeType = basicMimeType;
for (var k in parameters) {
var v = parameters[k];
extendedMimeType += '; ' + k + '="' + v + '"';
}
return cast.__platform__.canDisplayType(extendedMimeType);
};
};
shaka.polyfill.register(shaka.polyfill.MediaSource.install);