MSE: Warn when keyframe after track_buffer is significantly in future

media/filters/source_buffer_stream.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // SourceBufferStream is a data structure that stores media Buffers in ranges.
 // Buffers can be appended out of presentation order. Buffers are retrieved by
 // seeking to the desired start point and calling GetNextBuffer(). Buffers are
 // returned in sequential presentation order.
 
 #ifndef MEDIA_FILTERS_SOURCE_BUFFER_STREAM_H_
@@ skipping 301 matching lines @@
   // See GetNextBuffer() for additional details.  This method handles preroll
   // frame processing.
   Status HandleNextBufferWithPreroll(
       scoped_refptr<StreamParserBuffer>* out_buffer);
 
   // See GetNextBuffer() for additional details.  The internal method hands out
   // single buffers from the |track_buffer_| and |selected_range_| without
   // additional processing for splice frame or preroll buffers.
   Status GetNextBufferInternal(scoped_refptr<StreamParserBuffer>* out_buffer);
 
+  // If the next buffer's timestamp is significantly beyond the last output
+  // buffer, and if we just exhausted |track_buffer_| on the previous read, this
+  // method logs a warning to |media_log_| that there could be perceivable
+  // delay. Apps can avoid this behavior by not overlap-appending buffers near
+  // current playback position.
+  void WarnIfTrackBufferExhaustionSkipsForward(
+      const scoped_refptr<StreamParserBuffer>& next_buffer);
+
   // Called by PrepareRangesForNextAppend() before pruning overlapped buffers to
   // generate a splice frame with a small portion of the overlapped buffers.  If
   // a splice frame is generated, the first buffer in |new_buffers| will have
   // its timestamps, duration, and fade out preroll updated.
   void GenerateSpliceFrame(const BufferQueue& new_buffers);
 
   // If |out_buffer| has splice buffers or preroll, sets |pending_buffer_|
   // appropriately and returns true.  Otherwise returns false.
   bool SetPendingBuffer(scoped_refptr<StreamParserBuffer>* out_buffer);
 
@@ skipping 35 matching lines @@
 
   // Pointer to the seeked-to Range. This is the range from which
   // GetNextBuffer() calls are fulfilled after the |track_buffer_| has been
   // emptied.
   SourceBufferRange* selected_range_;
 
   // Queue of the next buffers to be returned from calls to GetNextBuffer(). If
   // |track_buffer_| is empty, return buffers from |selected_range_|.
   BufferQueue track_buffer_;
 
+  // If there has been no intervening Seek, this will be true if the last
+  // emitted buffer emptied |track_buffer_|.
+  bool just_exhausted_track_buffer_;
+
   // The start time of the current media segment being appended.
   DecodeTimestamp media_segment_start_time_;
 
   // Points to the range containing the current media segment being appended.
   RangeList::iterator range_for_next_append_;
 
   // True when the next call to Append() begins a new media segment.
   bool new_media_segment_;
 
   // The timestamp of the last buffer appended to the media segment, set to
@@ skipping 26 matching lines @@
   // Indicates which of the splice buffers in |splice_buffer_| should be
   // handled out next.
   size_t splice_buffers_index_;
 
   // Indicates that all buffers before |pending_buffer_| have been handed out.
   bool pending_buffers_complete_;
 
   // Indicates that splice frame generation is enabled.
   const bool splice_frames_enabled_;
 
-  // To prevent log spam, count the number of splice generation warnings and
-  // successes logged.
+  // To prevent log spam, count the number of warnings and successes logged.
   int num_splice_generation_warning_logs_;
   int num_splice_generation_success_logs_;
+  int num_track_buffer_gap_warning_logs_;
 
   DISALLOW_COPY_AND_ASSIGN(SourceBufferStream);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_SOURCE_BUFFER_STREAM_H_