Add several features about playback rate.

* Move trick play logic from Player to Playhead.
* Add a method on Player to get the playback rate.
* Use native playback rate when possible.
* Support changes to video.playbackRate while trick play.
* Support setting video.playbackRate to negative values.

Closes #344

Change-Id: I984cc735a27d700cee84984ed295a7e8118b808f

lib/media/playhead.js

@@ -80,7 +80,10 @@ shaka.media.Playhead = function(
   this.buffering_ = false;
 
   /** @private {number} */
-  this.lastPlaybackRate_ = 0;
+  this.playbackRate_ = 1;
+
+  /** @private {?number} */
+  this.trickPlayIntervalId_ = null;
 
   // Check if the video has already loaded some metadata.
   if (video.readyState > 0) {
@@ -89,6 +92,8 @@ shaka.media.Playhead = function(
     this.eventManager_.listen(
         video, 'loadedmetadata', this.onLoadedMetadata_.bind(this));
   }
+
+  this.eventManager_.listen(video, 'ratechange', this.onRateChange_.bind(this));
 };
 
 
@@ -97,6 +102,11 @@ shaka.media.Playhead.prototype.destroy = function() {
   var p = this.eventManager_.destroy();
   this.eventManager_ = null;
 
+  if (this.trickPlayIntervalId_ != null) {
+    window.clearInterval(this.trickPlayIntervalId_);
+    this.trickPlayIntervalId_ = null;
+  }
+
   this.video_ = null;
   this.timeline_ = null;
   this.onBuffering_ = null;
@@ -164,21 +174,62 @@ shaka.media.Playhead.prototype.getStartTime_ = function() {
  *   continue.
  */
 shaka.media.Playhead.prototype.setBuffering = function(buffering) {
-  if (buffering && !this.buffering_) {
-    this.lastPlaybackRate_ = this.video_.playbackRate;
-    this.video_.playbackRate = 0;
-    this.buffering_ = true;
-    this.onBuffering_(true);
-  } else if (!buffering && this.buffering_) {
-    if (this.video_.playbackRate == 0) {
-      // The app hasn't set a new playback rate, so restore the old one.
-      this.video_.playbackRate = this.lastPlaybackRate_;
-    } else {
-      // There's nothing we could have done to stop the app from setting a new
-      // rate, so we don't need to do anything here.
-    }
-    this.buffering_ = false;
-    this.onBuffering_(false);
+  if (buffering != this.buffering_) {
+    this.buffering_ = buffering;
+    this.setPlaybackRate(this.playbackRate_);
+    this.onBuffering_(buffering);
+  }
+};
+
+
+/**
+ * Gets the current effective playback rate.  This may be negative even if the
+ * browser does not directly support rewinding.
+ * @return {number}
+ */
+shaka.media.Playhead.prototype.getPlaybackRate = function() {
+  return this.playbackRate_;
+};
+
+
+/**
+ * Sets the playback rate.
+ * @param {number} rate
+ */
+shaka.media.Playhead.prototype.setPlaybackRate = function(rate) {
+  if (this.trickPlayIntervalId_ != null) {
+    window.clearInterval(this.trickPlayIntervalId_);
+    this.trickPlayIntervalId_ = null;
+  }
+
+  this.playbackRate_ = rate;
+  // All major browsers support playback rates above zero.  Only need fake
+  // trick play for negative rates.
+  this.video_.playbackRate = (this.buffering_ || rate < 0) ? 0 : rate;
+
+  if (!this.buffering_ && rate < 0) {
+    // Defer creating the timer until we stop buffering.  This function will be
+    // called again from setBuffering().
+    this.trickPlayIntervalId_ = window.setInterval(function() {
+      this.video_.currentTime += rate / 4;
+    }.bind(this), 250);
+  }
+};
+
+
+/**
+ * Handles a 'ratechange' event.
+ *
+ * @private
+ */
+shaka.media.Playhead.prototype.onRateChange_ = function() {
+  // NOTE: This will not allow explicitly setting the playback rate to 0 while
+  // the playback rate is negative.  Pause will still work.
+  var expectedRate =
+      this.buffering_ || this.playbackRate_ < 0 ? 0 : this.playbackRate_;
+  if (this.video_.playbackRate != expectedRate) {
+    shaka.log.debug('Video playback rate changed to', this.video_.playbackRate);
+    this.setPlaybackRate(this.video_.playbackRate);
   }
 };
 

lib/player.js

@@ -117,9 +117,6 @@ shaka.Player = function(video) {
   /** @private {?shakaExtern.PlayerConfiguration} */
   this.config_ = this.defaultConfig_();
 
-  /** @private {?number} */
-  this.trickPlayIntervalId_ = null;
-
   /** @private {!Array.<shakaExtern.StreamChoice>} */
   this.switchHistory_ = [];
 
@@ -682,6 +679,18 @@ shaka.Player.prototype.unload = function() {
 };
 
 
+/**
+ * Gets the current effective playback rate.  If using trick play, it will
+ * return the current trick play rate; otherwise, it will return the video
+ * playback rate.
+ * @return {number}
+ * @export
+ */
+shaka.Player.prototype.getPlaybackRate = function() {
+  return this.playhead_ ? this.playhead_.getPlaybackRate() : 0;
+};
+
+
 /**
  * Skip through the content without playing.  Simulated using repeated seeks.
  *
@@ -694,15 +703,8 @@ shaka.Player.prototype.unload = function() {
  * @export
  */
 shaka.Player.prototype.trickPlay = function(rate) {
-  this.cancelTrickPlay();
-  if (rate == 1) {
-    return;
-  }
-
-  this.video_.playbackRate = 0;
-  this.trickPlayIntervalId_ = window.setInterval(function() {
-    this.video_.currentTime += rate / 4;
-  }.bind(this), 250);
+  if (this.playhead_)
+    this.playhead_.setPlaybackRate(rate);
 };
 
 
@@ -711,11 +713,8 @@ shaka.Player.prototype.trickPlay = function(rate) {
  * @export
  */
 shaka.Player.prototype.cancelTrickPlay = function() {
-  this.video_.playbackRate = 1;
-  if (this.trickPlayIntervalId_ != null) {
-    window.clearInterval(this.trickPlayIntervalId_);
-  }
-  this.trickPlayIntervalId_ = null;
+  if (this.playhead_)
+    this.playhead_.setPlaybackRate(1);
 };
 
 

test/playhead_unit.js

@@ -26,6 +26,9 @@ describe('Playhead', function() {
   // Callback to Playhead to simulate 'seeking' event from |video|.
   var videoOnSeeking;
 
+  // Callback to Playhead to simulate 'ratechange' event from |video|.
+  var videoOnRateChange;
+
   // Callback to us from Playhead when the buffering state changes.
   var onBuffering;
 
@@ -47,6 +50,8 @@ describe('Playhead', function() {
         videoOnLoadedMetadata = f;
       } else if (eventName == 'seeking') {
         videoOnSeeking = f;
+      } else if (eventName == 'ratechange') {
+        videoOnRateChange = f;
       } else {
         throw new Error('Unexpected event:' + eventName);
       }
@@ -77,7 +82,7 @@ describe('Playhead', function() {
 
       expect(video.addEventListener).toHaveBeenCalledWith(
           'loadedmetadata', videoOnLoadedMetadata, false);
-      expect(video.addEventListener.calls.count()).toBe(1);
+      expect(video.addEventListener.calls.count()).toBe(2);
 
       expect(playhead.getTime()).toBe(5);
       expect(video.currentTime).toBe(0);
@@ -87,7 +92,7 @@ describe('Playhead', function() {
 
       expect(video.addEventListener).toHaveBeenCalledWith(
           'seeking', videoOnSeeking, false);
-      expect(video.addEventListener.calls.count()).toBe(2);
+      expect(video.addEventListener.calls.count()).toBe(3);
 
       expect(playhead.getTime()).toBe(5);
       expect(video.currentTime).toBe(5);
@@ -132,6 +137,7 @@ describe('Playhead', function() {
 
     // Set to 2 to ensure Playhead restores the correct rate.
     video.playbackRate = 2;
+    videoOnRateChange();
 
     playhead.setBuffering(false);
     expect(onBuffering).not.toHaveBeenCalled();