remoting/webapp/media_source_renderer.js

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 'use strict';
   6
   7 /** @suppress {duplicate} */
   8 var remoting = remoting || {};
   9
  10 /**
  11  * @param {HTMLMediaElement} videoTag <video> tag to render to.
  12  * @constructor
  13  */
  14 remoting.MediaSourceRenderer = function(videoTag) {
  15   /** @type {HTMLMediaElement} */
  16   this.video_ = videoTag;
  17
  18   /** @type {MediaSource} */
  19   this.mediaSource_ = null;
  20
  21   /** @type {SourceBuffer} */
  22   this.sourceBuffer_ = null;
  23
  24   /** @type {!Array.<ArrayBuffer>} Queue of pending buffers that haven't been
  25    * processed. A null element indicates that the SourceBuffer can be reset
  26    * because the following buffer contains a keyframe. */
  27   this.buffers_ = [];
  28
  29   this.lastKeyFramePos_ = 0;
  30 }
  31
  32 /**
  33  * @param {string} format Format of the stream.
  34  */
  35 remoting.MediaSourceRenderer.prototype.reset = function(format) {
  36   // Reset the queue.
  37   this.buffers_ = [];
  38
  39   // Create a new MediaSource instance.
  40   this.sourceBuffer_ = null;
  41   this.mediaSource_ = new MediaSource();
  42   this.mediaSource_.addEventListener('sourceopen',
  43                                      this.onSourceOpen_.bind(this, format));
  44   this.mediaSource_.addEventListener('sourceclose', function(e) {
  45     console.error("MediaSource closed unexpectedly.");
  46   });
  47   this.mediaSource_.addEventListener('sourceended', function(e) {
  48     console.error("MediaSource ended unexpectedly.");
  49   });
  50
  51   // Start playback from new MediaSource.
  52   this.video_.src =
  53       /** @type {string} */(
  54           window.URL.createObjectURL(/** @type {!Blob} */(this.mediaSource_)));
  55   this.video_.play();
  56 }
  57
  58 /**
  59  * @param {string} format
  60  * @private
  61  */
  62 remoting.MediaSourceRenderer.prototype.onSourceOpen_ = function(format) {
  63   this.sourceBuffer_ =
  64       this.mediaSource_.addSourceBuffer(format);
  65
  66   this.sourceBuffer_.addEventListener(
  67       'updateend', this.processPendingData_.bind(this));
  68   this.processPendingData_();
  69 }
  70
  71 /**
  72  * @private
  73  */
  74 remoting.MediaSourceRenderer.prototype.processPendingData_ = function() {
  75   if (this.sourceBuffer_) {
  76     while (this.buffers_.length > 0 && !this.sourceBuffer_.updating) {
  77       var buffer = /** @type {ArrayBuffer} */ this.buffers_.shift();
  78       if (buffer == null) {
  79         // Remove data from the SourceBuffer from the beginning to the previous
  80         // key frame. By default Chrome buffers up to 150MB of data. We never
  81         // need to seek the stream, so it doesn't make sense to keep any of that
  82         // data.
  83         if (this.sourceBuffer_.buffered.length > 0) {
  84           // TODO(sergeyu): Check currentTime to make sure that the current
  85           // playback position is not being removed. crbug.com/398290 .
  86           if (this.lastKeyFramePos_ > this.sourceBuffer_.buffered.start(0)) {
  87             this.sourceBuffer_.remove(this.sourceBuffer_.buffered.start(0),
  88                                       this.lastKeyFramePos_);
  89           }
  90
  91           this.lastKeyFramePos_ = this.sourceBuffer_.buffered.end(
  92               this.sourceBuffer_.buffered.length - 1);
  93         }
  94       } else {
  95         // TODO(sergeyu): Figure out the way to determine when a frame is
  96         // rendered and use it to report performance statistics.
  97         this.sourceBuffer_.appendBuffer(buffer);
  98       }
  99     }
 100   }
 101 }
 102
 103 /**
 104  * @param {ArrayBuffer} data
 105  * @param {boolean} keyframe
 106  */
 107 remoting.MediaSourceRenderer.prototype.onIncomingData =
 108     function(data, keyframe) {
 109   if (keyframe) {
 110     // Queue SourceBuffer reset request.
 111     this.buffers_.push(null);
 112   }
 113   this.buffers_.push(data);
 114   this.processPendingData_();
 115 }
 116