Add a runtime flag to use dts in timeline for mp4

This flag is needed to workaround the Chromium bug
https://crbug.com/398130, which uses decoding timestamp
in buffered range.

Closes #113

Change-Id: Ib8f18be7165dd968bdc36c18ce29f694235c0c26

packager/app/packager_util.cc

@@ -25,6 +25,12 @@
 #include "packager/media/file/file.h"
 #include "packager/mpd/base/mpd_builder.h"
 
+DEFINE_bool(mp4_use_decoding_timestamp_in_timeline,
+            false,
+            "If set, decoding timestamp instead of presentation timestamp will "
+            "be used when generating media timeline, e.g. timestamps in sidx "
+            "and mpd. This is to workaround a Chromium bug that decoding "
+            "timestamp is used in buffered range, https://crbug.com/398130.");
 DEFINE_bool(dump_stream_info, false, "Dump demuxed stream info.");
 
 namespace shaka {
@@ -148,6 +154,16 @@ bool GetMuxerOptions(MuxerOptions* muxer_options) {
   muxer_options->segment_sap_aligned = FLAGS_segment_sap_aligned;
   muxer_options->fragment_sap_aligned = FLAGS_fragment_sap_aligned;
   muxer_options->num_subsegments_per_sidx = FLAGS_num_subsegments_per_sidx;
+
+  if (FLAGS_mp4_use_decoding_timestamp_in_timeline) {
+    LOG(WARNING) << "Flag --mp4_use_decoding_timestamp_in_timeline is set. "
+                    "Note that it is a temporary hack to workaround Chromium "
+                    "bug https://crbug.com/398130. The flag may be removed "
+                    "when the Chromium bug is fixed.";
+  }
+  muxer_options->mp4_use_decoding_timestamp_in_timeline =
+      FLAGS_mp4_use_decoding_timestamp_in_timeline;
+
   muxer_options->temp_dir = FLAGS_temp_dir;
   return true;
 }

packager/media/base/muxer_options.cc

@@ -16,6 +16,7 @@ MuxerOptions::MuxerOptions()
       segment_sap_aligned(false),
       fragment_sap_aligned(false),
       num_subsegments_per_sidx(0),
+      mp4_use_decoding_timestamp_in_timeline(false),
       bandwidth(0) {}
 MuxerOptions::~MuxerOptions() {}
 

packager/media/base/muxer_options.h

@@ -49,6 +49,13 @@ struct MuxerOptions {
   /// segment_duration/N/fragment_duration fragments per subsegment.
   int num_subsegments_per_sidx;
 
+  /// For ISO BMFF only.
+  /// Set the flag use_decoding_timestamp_in_timeline, which if set to true, use
+  /// decoding timestamp instead of presentation timestamp in media timeline,
+  /// which is needed to workaround a Chromium bug that decoding timestamp is
+  /// used in buffered range, https://crbug.com/398130.
+  bool mp4_use_decoding_timestamp_in_timeline;
+
   /// Output file name. If segment_template is not specified, the Muxer
   /// generates this single output file with all segments concatenated;
   /// Otherwise, it specifies the init segment name.

packager/media/file/file.cc

@@ -6,9 +6,9 @@
 
 #include "packager/media/file/file.h"
 
+#include <gflags/gflags.h>
 #include <algorithm>
 
-#include <gflags/gflags.h>
 #include "packager/base/logging.h"
 #include "packager/base/memory/scoped_ptr.h"
 #include "packager/media/file/local_file.h"

packager/media/formats/mp4/fragmenter.cc

@@ -21,7 +21,8 @@ namespace {
 const int64_t kInvalidTime = std::numeric_limits<int64_t>::max();
 
 uint64_t GetSeekPreroll(const StreamInfo& stream_info) {
-  if (stream_info.stream_type() != kStreamAudio) return 0;
+  if (stream_info.stream_type() != kStreamAudio)
+    return 0;
   const AudioStreamInfo& audio_stream_info =
       static_cast<const AudioStreamInfo&>(stream_info);
   return audio_stream_info.seek_preroll_ns();
@@ -29,7 +30,8 @@ uint64_t GetSeekPreroll(const StreamInfo& stream_info) {
 }  // namespace
 
 Fragmenter::Fragmenter(scoped_refptr<StreamInfo> info, TrackFragment* traf)
-    : traf_(traf),
+    : use_decoding_timestamp_in_timeline_(false),
+      traf_(traf),
       seek_preroll_(GetSeekPreroll(*info)),
       fragment_initialized_(false),
       fragment_finalized_(false),
@@ -64,15 +66,17 @@ Status Fragmenter::AddSample(scoped_refptr<MediaSample> sample) {
   data_->AppendArray(sample->data(), sample->data_size());
   fragment_duration_ += sample->duration();
 
-  int64_t pts = sample->pts();
+  const int64_t pts = sample->pts();
+  const int64_t dts = sample->dts();
 
-  // Set |earliest_presentation_time_| to |pts| if |pts| is smaller or if it is
-  // not yet initialized (kInvalidTime > pts is always true).
-  if (earliest_presentation_time_ > pts)
-    earliest_presentation_time_ = pts;
+  const int64_t timestamp = use_decoding_timestamp_in_timeline_ ? dts : pts;
+  // Set |earliest_presentation_time_| to |timestamp| if |timestamp| is smaller
+  // or if it is not yet initialized (kInvalidTime > timestamp is always true).
+  if (earliest_presentation_time_ > timestamp)
+    earliest_presentation_time_ = timestamp;
 
-  traf_->runs[0].sample_composition_time_offsets.push_back(pts - sample->dts());
-  if (pts != sample->dts())
+  traf_->runs[0].sample_composition_time_offsets.push_back(pts - dts);
+  if (pts != dts)
     traf_->runs[0].flags |= TrackFragmentRun::kSampleCompTimeOffsetsPresentMask;
 
   if (sample->is_key_frame()) {
@@ -141,7 +145,8 @@ void Fragmenter::FinalizeFragment() {
     sample_to_group_entry.group_description_index =
         SampleToGroupEntry::kTrackGroupDescriptionIndexBase + 1;
   }
-  for (const auto& sample_group_description : traf_->sample_group_descriptions) {
+  for (const auto& sample_group_description :
+       traf_->sample_group_descriptions) {
     traf_->sample_to_groups.resize(traf_->sample_to_groups.size() + 1);
     SampleToGroup& sample_to_group = traf_->sample_to_groups.back();
     sample_to_group.grouping_type = sample_group_description.grouping_type;

packager/media/formats/mp4/fragmenter.h

@@ -62,6 +62,15 @@ class Fragmenter {
   bool fragment_finalized() const { return fragment_finalized_; }
   BufferWriter* data() { return data_.get(); }
 
+  /// Set the flag use_decoding_timestamp_in_timeline, which if set to true, use
+  /// decoding timestamp instead of presentation timestamp in media timeline,
+  /// which is needed to workaround a Chromium bug that decoding timestamp is
+  /// used in buffered range, https://crbug.com/398130.
+  void set_use_decoding_timestamp_in_timeline(
+      bool use_decoding_timestamp_in_timeline) {
+    use_decoding_timestamp_in_timeline_ = use_decoding_timestamp_in_timeline;
+  }
+
  protected:
   TrackFragment* traf() { return traf_; }
 
@@ -75,6 +84,7 @@ class Fragmenter {
   // Check if the current fragment starts with SAP.
   bool StartsWithSAP();
 
+  bool use_decoding_timestamp_in_timeline_;
   TrackFragment* traf_;
   uint64_t seek_preroll_;
   bool fragment_initialized_;

packager/media/formats/mp4/segmenter.cc

@@ -264,6 +264,11 @@ Status Segmenter::Initialize(const std::vector<MediaStream*>& streams,
         muxer_listener_);
   }
 
+  if (options_.mp4_use_decoding_timestamp_in_timeline) {
+    for (uint32_t i = 0; i < streams.size(); ++i)
+      fragmenters_[i]->set_use_decoding_timestamp_in_timeline(true);
+  }
+
   // Choose the first stream if there is no VIDEO.
   if (sidx_->reference_id == 0)
     sidx_->reference_id = 1;