Add logic to correctly set subSegmentAlignment for VOD

- subSegmentAlignment logic assumed that all Representations were
  added before calling Representations::AddNewSegment() on any
  Representation in an AdaptationSet. It is not a valid assumption
  for VOD and is removed.

Change-Id: Ifb7e34ee103ee30027e45a804427baf281f3137c

packager/mpd/base/mpd_builder.cc

@@ -10,6 +10,7 @@
 #include <libxml/xmlstring.h>
 
 #include <cmath>
+#include <iterator>
 #include <list>
 #include <string>
 
@@ -732,6 +733,11 @@ xml::ScopedXmlPtr<xmlNode>::type AdaptationSet::GetXml() {
                                       video_frame_rates_.rbegin()->second);
   }
 
+  // Note: must be checked before checking segments_aligned_ (below).
+  if (mpd_type_ == MpdBuilder::kStatic) {
+    CheckVodSegmentAlignment();
+  }
+
   if (segments_aligned_ == kSegmentAlignmentTrue) {
     adaptation_set.SetStringAttribute(mpd_type_ == MpdBuilder::kStatic
                                           ? "subSegmentAlignment"
@@ -767,11 +773,24 @@ int AdaptationSet::Group() const {
   return group_;
 }
 
+// Check segmentAlignment for Live here. Storing all start_time and duration
+// will out-of-memory because there's no way of knowing when it will end.
+// VOD subSegmentAlignment check is *not* done here because it is possible
+// that some Representations might not have been added yet (e.g. a thread is
+// assigned per muxer so one might run faster than others).
+// To be clear, for Live, all Representations should be added before a
+// segment is added.
 void AdaptationSet::OnNewSegmentForRepresentation(uint32_t representation_id,
                                                   uint64_t start_time,
                                                   uint64_t duration) {
   base::AutoLock scoped_lock(lock_);
-  CheckSegmentAlignment(representation_id, start_time, duration);
+
+  if (mpd_type_ == MpdBuilder::kDynamic) {
+    CheckLiveSegmentAlignment(representation_id, start_time, duration);
+  } else {
+    representation_segment_start_times_[representation_id].push_back(
+        start_time);
+  }
 }
 
 void AdaptationSet::OnSetFrameRateForRepresentation(
@@ -827,12 +846,9 @@ bool AdaptationSet::GetEarliestTimestamp(double* timestamp_seconds) {
 // They are not aligned but this will be marked as aligned.
 // But since this is unlikely to happen in the packager (and to save
 // computation), this isn't handled at the moment.
-// TODO(rkuroiwa): For VOD, not all Representations get added to an
-// AdaptationSet before this is called. Add a similar but separate method that
-// keeps the timestamps around. It shouldn't out-of-memory for VOD.
-void AdaptationSet::CheckSegmentAlignment(uint32_t representation_id,
-                                          uint64_t start_time,
-                                          uint64_t /* duration */) {
+void AdaptationSet::CheckLiveSegmentAlignment(uint32_t representation_id,
+                                              uint64_t start_time,
+                                              uint64_t /* duration */) {
   if (segments_aligned_ == kSegmentAlignmentFalse ||
       force_set_segment_alignment_) {
     return;
@@ -874,6 +890,66 @@ void AdaptationSet::CheckSegmentAlignment(uint32_t representation_id,
   }
 }
 
+// Make sure all segements start times match for all Representations.
+// This assumes that the segments are contiguous.
+void AdaptationSet::CheckVodSegmentAlignment() {
+  if (segments_aligned_ == kSegmentAlignmentFalse ||
+      force_set_segment_alignment_) {
+    return;
+  }
+  if (representation_segment_start_times_.empty())
+    return;
+  if (representation_segment_start_times_.size() == 1) {
+    segments_aligned_ = kSegmentAlignmentTrue;
+    return;
+  }
+
+  // This is not the most efficient implementation to compare the values
+  // because expected_time_line is compared against all other time lines, but
+  // probably the most readable.
+  const std::list<uint64_t>& expected_time_line =
+      representation_segment_start_times_.begin()->second;
+
+  bool all_segment_time_line_same_length = true;
+  // Note that the first entry is skipped because it is expected_time_line.
+  RepresentationTimeline::const_iterator it =
+      representation_segment_start_times_.begin();
+  for (++it; it != representation_segment_start_times_.end(); ++it) {
+    const std::list<uint64_t>& other_time_line = it->second;
+    if (expected_time_line.size() != other_time_line.size()) {
+      all_segment_time_line_same_length = false;
+    }
+
+    const std::list<uint64_t>* longer_list = &other_time_line;
+    const std::list<uint64_t>* shorter_list = &expected_time_line;
+    if (expected_time_line.size() > other_time_line.size()) {
+      shorter_list = &other_time_line;
+      longer_list = &expected_time_line;
+    }
+
+    if (!std::equal(shorter_list->begin(), shorter_list->end(),
+                    longer_list->begin())) {
+      // Some segments are definitely unaligned.
+      segments_aligned_ = kSegmentAlignmentFalse;
+      representation_segment_start_times_.clear();
+      return;
+    }
+  }
+
+  // TODO(rkuroiwa): The right way to do this is to also check the durations.
+  // For example:
+  // (a)  3 4 5
+  // (b)  3 4 5 6
+  // could be true or false depending on the length of the third segment of (a).
+  // i.e. if length of the third segment is 2, then this is not aligned.
+  if (!all_segment_time_line_same_length) {
+    segments_aligned_ = kSegmentAlignmentUnknown;
+    return;
+  }
+
+  segments_aligned_ = kSegmentAlignmentTrue;
+}
+
 // Since all AdaptationSet cares about is the maxFrameRate, representation_id
 // is not passed to this method.
 void AdaptationSet::RecordFrameRate(uint32_t frame_duration,

packager/mpd/base/mpd_builder.h

@@ -312,13 +312,18 @@ class AdaptationSet {
 
   /// Called from OnNewSegmentForRepresentation(). Checks whether the segments
   /// are aligned. Sets segments_aligned_.
+  /// This is only for Live. For VOD, CheckVodSegmentAlignment() should be used.
   /// @param representation_id is the id of the Representation with a new
   ///        segment.
   /// @param start_time is the start time of the new segment.
   /// @param duration is the duration of the new segment.
-  void CheckSegmentAlignment(uint32_t representation_id,
-                             uint64_t start_time,
-                             uint64_t duration);
+  void CheckLiveSegmentAlignment(uint32_t representation_id,
+                                 uint64_t start_time,
+                                 uint64_t duration);
+
+  // Checks representation_segment_start_times_ and sets segments_aligned_.
+  // Use this for VOD, do not use for Live.
+  void CheckVodSegmentAlignment();
 
   // Records the framerate of a Representation.
   void RecordFrameRate(uint32_t frame_duration, uint32_t timescale);
@@ -377,6 +382,12 @@ class AdaptationSet {
   bool force_set_segment_alignment_;
 
   // Keeps track of segment start times of Representations.
+  // For VOD, this will not be cleared, all the segment start times are
+  // stored in this. This should not out-of-memory for a reasonable length
+  // video and reasonable subsegment length.
+  // For Live, the entries are deleted (see CheckLiveSegmentAlignment()
+  // implementation comment) because storing the entire timeline is not
+  // reasonable and may cause an out-of-memory problem.
   RepresentationTimeline representation_segment_start_times_;
 
   DISALLOW_COPY_AND_ASSIGN(AdaptationSet);

packager/mpd/base/mpd_builder_unittest.cc

@@ -947,6 +947,8 @@ TEST_F(CommonMpdBuilderTest,
 
 // Verify that subSegmentAlignment is set to true if all the Representations'
 // segments are aligned and the MPD type is static.
+// Also checking that not all Representations have to be added before calling
+// AddNewSegment() on a Representation.
 TEST_F(StaticMpdBuilderTest, SubSegmentAlignment) {
   base::AtomicSequenceNumber sequence_counter;
   const char k480pMediaInfo[] =
@@ -971,37 +973,36 @@ TEST_F(StaticMpdBuilderTest, SubSegmentAlignment) {
       "  pixel_height: 1\n"
       "}\n"
       "container_type: 1\n";
+
+  // First use same start time and duration, and verify that subSegmentAlignment
+  // is set to true.
+  const uint64_t kStartTime = 0u;
+  const uint64_t kDuration = 10u;
+  const uint64_t kAnySize = 19834u;
+
   AdaptationSet adaptation_set(kAnyAdaptationSetId, "", MpdOptions(),
                                MpdBuilder::kStatic, &sequence_counter);
   Representation* representation_480p =
       adaptation_set.AddRepresentation(ConvertToMediaInfo(k480pMediaInfo));
+  // Add a subsegment immediately before adding the 360p Representation.
+  // This should still work for VOD.
+  representation_480p->AddNewSegment(kStartTime, kDuration, kAnySize);
+
   Representation* representation_360p =
       adaptation_set.AddRepresentation(ConvertToMediaInfo(k360pMediaInfo));
-
-  // First use same start time and duration, and verify that that
-  // segmentAlignment is set.
-  const uint64_t kStartTime = 0u;
-  const uint64_t kDuration = 10u;
-  const uint64_t kAnySize = 19834u;
-  representation_480p->AddNewSegment(kStartTime, kDuration, kAnySize);
   representation_360p->AddNewSegment(kStartTime, kDuration, kAnySize);
+
   xml::ScopedXmlPtr<xmlNode>::type aligned(adaptation_set.GetXml());
   EXPECT_NO_FATAL_FAILURE(
       ExpectAttributeEqString("subSegmentAlignment", "true", aligned.get()));
-  EXPECT_EQ(2u, adaptation_set.representation_segment_start_times_.size());
 
-  // Also check that the start times are removed from the vector.
-  EXPECT_EQ(0u,
-            adaptation_set
-                .representation_segment_start_times_[representation_480p->id()]
-                .size());
-  EXPECT_EQ(0u,
-            adaptation_set
-                .representation_segment_start_times_[representation_360p->id()]
-                .size());
+  // Unknown because 480p has an extra subsegments.
+  representation_480p->AddNewSegment(11, 20, kAnySize);
+  xml::ScopedXmlPtr<xmlNode>::type alignment_unknown(adaptation_set.GetXml());
+  EXPECT_NO_FATAL_FAILURE(
+      ExpectAttributeNotSet("subSegmentAlignment", alignment_unknown.get()));
 
   // Add segments that make them not aligned.
-  representation_480p->AddNewSegment(11, 20, kAnySize);
   representation_360p->AddNewSegment(10, 1, kAnySize);
   representation_360p->AddNewSegment(11, 19, kAnySize);