MSE: Reduce spurious discontinuities caused by partial append window start overlaps

media/filters/frame_processor.cc

 // Copyright 2014 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.
 
 #include "media/filters/frame_processor.h"
 
 #include "base/stl_util.h"
 #include "media/base/buffers.h"
 #include "media/base/stream_parser_buffer.h"
 
@@ skipping 243 matching lines @@
     frame->SetDecodeTimestamp(decode_timestamp);
     if (track_buffer->stream()->supports_partial_append_window_trimming() &&
         HandlePartialAppendWindowTrimming(append_window_start,
                                           append_window_end,
                                           frame)) {
       // If |frame| was shortened a discontinuity may exist, so treat the next
       // frames appended as if they were the beginning of a new media segment.
       if (frame->timestamp() != presentation_timestamp && !sequence_mode_)
         *new_media_segment = true;
 
-      // |frame| has been partially trimmed or had preroll added.
+      // |frame| has been partially trimmed or had preroll added.  Though
+      // |frame|'s duration may have changed, do not update |frame_duration|
+      // here, so |track_buffer|'s last frame duration update uses original
+      // frame duration and reduces spurious discontinuity detection.
       decode_timestamp = frame->GetDecodeTimestamp();
       presentation_timestamp = frame->timestamp();
-      frame_duration = frame->duration();
 
       // The end timestamp of the frame should be unchanged.
-      DCHECK(frame_end_timestamp == presentation_timestamp + frame_duration);
+      DCHECK(frame_end_timestamp == presentation_timestamp + frame->duration());
     }
 
     if (presentation_timestamp < append_window_start ||
         frame_end_timestamp > append_window_end) {
       track_buffer->set_needs_random_access_point(true);
       DVLOG(3) << "Dropping frame that is outside append window.";
 
       if (!sequence_mode_) {
         // This also triggers a discontinuity so we need to treat the next
         // frames appended within the append window as if they were the
@@ skipping 81 matching lines @@
     DCHECK(group_end_timestamp_ >= base::TimeDelta());
 
     return true;
   }
 
   NOTREACHED();
   return false;
 }
 
 }  // namespace media