Add bFrameAdjustment configuration option to address PTS/DTS bug

externs/shaka/player.js

@@ -468,9 +468,58 @@ shakaExtern.HlsManifestConfiguration;
 shakaExtern.ManifestConfiguration;
 
 
+/**
+ * @typedef {{
+ *   adjustOffset: boolean,
+ *   adjustWindowEnd: boolean,
+ *   bFrameCount: number
+ * }}
+ *
+ * @description
+ * This configuration block can be used to account for a bug in chrome that
+ * uses the DTS instead of the PTS for timestamp comparisons in the MSE.
+ * https://bugs.chromium.org/p/chromium/issues/detail?id=398130
+ *
+ * There are two problems that arise from this bug:
+ *
+ * 1. The presentationTimeOffset (PTO) will be set too far in the future since
+ *    the DTS falls before the PTS. This will lead to a negative starting value
+ *    for the presentation time, which, in Chrome throws error 3014. This
+ *    will only happen if the base_media_decode_time in your tftd is set
+ *    (correctly) to the DTS. ffmpeg, for example, will set it to the PTS by
+ *    default, which would mask the aforementioned bug.
+ * 2. Periods will get incorrect durations, leading to gaps in the timeline.
+ *    This happens because the Chrome MSE expects appendWindowEnd to be in DTS
+ *    time, and thus it filters frames after the last DTS, which will always
+ *    be count(bframes) before the last PTS.
+ *
+ * The bframe count is typically an encoder configuration option, and can be
+ * held constant within fragments. Given the number of bframes, and the
+ * framerate, shaka can adjust the windowEnd, and the timestampOffset to
+ * account for Chrome's bug. To address (1) above, set adjustOffset to true,
+ * and to address (2), set adjustWindowEnd to true. You must provide an accurate
+ * bFrameCount for this to work correctly.
+ *
+ * Shaka will use the frameRate provided by the manifest to calculate frame
+ * durations.
+ *
+ * @property {boolean} adjustOffset
+ *   If true, adjust the timestampOffset on the MSE to account for bframes.
+ *   Use this if your base_media_decode time is set to the DTS.
+ * @property {boolean} adjustWindowEnd
+ *   If true, adjust the windowEnd on the MSE to accounbt for bframes.
+ *   Use this to correct your period durations.
+ * @property {number} bFrameCount
+ *   The number of bframes in each segment.
+ * @exportDoc
+ */
+shakaExtern.BFrameAdjustment;
+
+
 /**
  * @typedef {{
  *   retryParameters: shakaExtern.RetryParameters,
+ *   bFrameAdjustment: shakaExtern.BFrameAdjustment,
  *   rebufferingGoal: number,
  *   bufferingGoal: number,
  *   bufferBehind: number,
@@ -483,6 +532,8 @@ shakaExtern.ManifestConfiguration;
  * @description
  * The StreamingEngine's configuration options.
  *
+ * @property {shakaExtern.BFrameAdjustment} bFrameAdjustment
+ *   Configuration to address Chrome PTS/DTS bug
  * @property {shakaExtern.RetryParameters} retryParameters
  *   Retry parameters for segment requests.
  * @property {number} rebufferingGoal

lib/media/media_source_engine.js

@@ -41,12 +41,15 @@ goog.require('shaka.util.PublicPromise');
  * @param {MediaSource} mediaSource The MediaSource, which must be in the
  *   'open' state.
  * @param {TextTrack} textTrack The TextTrack to use for subtitles/captions.
+ * @param {shakaExtern.BFrameAdjustment} bFrameAdjustment Configuration options
+ *   for adjusting the timestampOffset and windowEnd to account for bframes.
  *
  * @struct
  * @constructor
  * @implements {shaka.util.IDestroyable}
  */
-shaka.media.MediaSourceEngine = function(video, mediaSource, textTrack) {
+shaka.media.MediaSourceEngine =
+    function(video, mediaSource, textTrack, bFrameAdjustment) {
   goog.asserts.assert(mediaSource.readyState == 'open',
                       'The MediaSource should be in the \'open\' state.');
 
@@ -59,10 +62,16 @@ shaka.media.MediaSourceEngine = function(video, mediaSource, textTrack) {
   /** @private {TextTrack} */
   this.textTrack_ = textTrack;
 
+  /** @private {shakaExtern.BFrameAdjustment} */
+  this.bFrameAdjustment_ = bFrameAdjustment;
+
   /** @private {!Object.<shaka.util.ManifestParserUtils.ContentType,
                          SourceBuffer>} */
   this.sourceBuffers_ = {};
 
+  /** @private {?number} */
+  this.videoFrameRate_ = null;
+
   /** @private {shaka.media.TextEngine} */
   this.textEngine_ = null;
 
@@ -457,10 +466,11 @@ shaka.media.MediaSourceEngine.prototype.flush = function(contentType) {
  *   value does not affect segments which have already been inserted.
  * @param {?number} appendWindowEnd The timestamp to set the append window end
  *   to. Media beyond this value will be truncated.
+ * @param {?number} frameRate The framerate; only provided by video tracks
  * @return {!Promise}
  */
 shaka.media.MediaSourceEngine.prototype.setStreamProperties = function(
-    contentType, timestampOffset, appendWindowEnd) {
+    contentType, timestampOffset, appendWindowEnd, frameRate) {
   var ContentType = shaka.util.ManifestParserUtils.ContentType;
   if (contentType == ContentType.TEXT) {
     this.textEngine_.setTimestampOffset(timestampOffset);
@@ -469,6 +479,10 @@ shaka.media.MediaSourceEngine.prototype.setStreamProperties = function(
     return Promise.resolve();
   }
 
+  if (contentType == ContentType.VIDEO) {
+    this.videoFrameRate_ = frameRate;
+  }
+
   if (appendWindowEnd == null)
     appendWindowEnd = Infinity;
 
@@ -634,7 +648,17 @@ shaka.media.MediaSourceEngine.prototype.flush_ = function(contentType) {
  */
 shaka.media.MediaSourceEngine.prototype.setTimestampOffset_ =
     function(contentType, timestampOffset) {
-  this.sourceBuffers_[contentType].timestampOffset = timestampOffset;
+  var ContentType = shaka.util.ManifestParserUtils.ContentType;
+  var fudge = 0;
+
+  if (contentType == ContentType.VIDEO &&
+        this.bFrameAdjustment_.adjustOffset) {
+    goog.asserts.assert(this.videoFrameRate_,
+        'Must provide frameRate for offset bframe adjustment');
+    fudge = this.bFrameAdjustment_.bFrameCount / this.videoFrameRate_;
+  }
+
+  this.sourceBuffers_[contentType].timestampOffset = timestampOffset + fudge;
 
   // Fake 'updateend' event to resolve the operation.
   this.onUpdateEnd_(contentType);
@@ -649,7 +673,16 @@ shaka.media.MediaSourceEngine.prototype.setTimestampOffset_ =
  */
 shaka.media.MediaSourceEngine.prototype.setAppendWindowEnd_ =
     function(contentType, appendWindowEnd) {
-  var fudge = 1 / 25;  // one frame, assuming a low framerate
+  var ContentType = shaka.util.ManifestParserUtils.ContentType;
+  var fudge = 1 / 25; // one frame, assuming a low framerate
+  if (contentType == ContentType.VIDEO &&
+        this.bFrameAdjustment_.adjustWindowEnd) {
+    goog.asserts.assert(this.videoFrameRate_,
+        'Must provide frameRate for windowEnd bframe adjustment');
+    // windowEnd is exclusive, so we need one extra frame on the end
+    fudge = (this.bFrameAdjustment_.bFrameCount + 1) / this.videoFrameRate_;
+  }
+
   this.sourceBuffers_[contentType].appendWindowEnd = appendWindowEnd + fudge;
 
   // Fake 'updateend' event to resolve the operation.

lib/media/streaming_engine.js

@@ -1385,7 +1385,8 @@ shaka.media.StreamingEngine.prototype.initSourceBuffer_ = function(
   shaka.log.v1(logPrefix, 'setting append window end to ' + appendWindowEnd);
   var setStreamProperties =
       this.playerInterface_.mediaSourceEngine.setStreamProperties(
-          mediaState.type, timestampOffset, appendWindowEnd);
+        mediaState.type, timestampOffset, appendWindowEnd,
+        mediaState.stream.frameRate || null);
 
   if (!mediaState.stream.initSegmentReference) {
     // The Stream is self initializing.

lib/player.js

@@ -698,7 +698,8 @@ shaka.Player.prototype.createMediaSource = function() {
  */
 shaka.Player.prototype.createMediaSourceEngine = function() {
   return new shaka.media.MediaSourceEngine(
-      this.video_, this.mediaSource_, this.textTrack_);
+      this.video_, this.mediaSource_, this.textTrack_,
+      this.config_.streaming.bFrameAdjustment);
 };
 
 
@@ -1725,7 +1726,13 @@ shaka.Player.prototype.defaultConfig_ = function() {
       bufferingGoal: 10,
       bufferBehind: 30,
       ignoreTextStreamFailures: false,
+      useRelativeCueTimestamps: false,
       startAtSegmentBoundary: false,
+      bFrameAdjustment: {
+        adjustOffset: true,
+        adjustWindowEnd: true,
+        bFrameCount: 2
+      },
       smallGapLimit: 0.5,
       jumpLargeGaps: false
     },