Read directly from 'senc' box when 'senc' box is present

media/formats/mp4/box_definitions.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/formats/mp4/box_definitions.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/command_line.h"
@@ skipping 1193 matching lines @@
 FourCC TrackFragment::BoxType() const { return FOURCC_TRAF; }
 
 bool TrackFragment::Parse(BoxReader* reader) {
   RCHECK(reader->ScanChildren() &&
          reader->ReadChild(&header) &&
          // Media Source specific: 'tfdt' required
          reader->ReadChild(&decode_time) &&
          reader->MaybeReadChildren(&runs) &&
          reader->MaybeReadChild(&auxiliary_offset) &&
          reader->MaybeReadChild(&auxiliary_size) &&
-         reader->MaybeReadChild(&sdtp));
+         reader->MaybeReadChild(&sdtp) &&
+         reader->MaybeReadChild(&sample_encryption));

[kqyang, 2016/09/15 22:06:32]

This line loads 'senc' box if it is present. 

It is in the packager cl but somehow got lost when the change was integrated to
Chromium.

With this change, we will load sample encryption information from 'senc' box if
it is available; this avoids loading 'saiz' and 'saio' boxes and caching buffer
data for reading sample encryption information later.

 
   // There could be multiple SampleGroupDescription and SampleToGroup boxes with
   // different grouping types. For common encryption, the relevant grouping type
   // is 'seig'. Continue reading until 'seig' is found, or until running out of
   // child boxes.
   while (reader->HasChild(&sample_group_description)) {
     RCHECK(reader->ReadChild(&sample_group_description));
     if (sample_group_description.grouping_type == FOURCC_SEIG)
       break;
     sample_group_description.entries.clear();
@@ skipping 49 matching lines @@
 SampleDependsOn IndependentAndDisposableSamples::sample_depends_on(
     size_t i) const {
   if (i >= sample_depends_on_.size())
     return kSampleDependsOnUnknown;
 
   return sample_depends_on_[i];
 }
 
 }  // namespace mp4
 }  // namespace media