Respect MPD@timeShiftBufferDepth

- Only Segments with end time in range [NOW - timeShiftBufferDepth, NOW] get
  listed as S elements under TemplateTimeline element. Any old segments
  do not get listed.
- Also adding tests

Change-Id: I52df9acaec107610757d809ac6c9cb13592d6f37

mpd/base/mpd_builder.cc

@@ -6,6 +6,7 @@
 
 #include "mpd/base/mpd_builder.h"
 
+#include <list>
 #include <string>
 
 #include "base/logging.h"
@@ -109,6 +110,50 @@ void SetIfPositive(const char* attr_name, double value, XmlNode* mpd) {
   }
 }
 
+uint32 GetTimeScale(const MediaInfo& media_info) {
+  if (media_info.has_reference_time_scale()) {
+    return media_info.reference_time_scale();
+  }
+
+  if (media_info.video_info_size() > 0) {
+    return media_info.video_info(0).time_scale();
+  }
+
+  if (media_info.audio_info_size() > 0) {
+    return media_info.audio_info(0).time_scale();
+  }
+
+  LOG(WARNING) << "No timescale specified, using 1 as timescale.";
+  return 1;
+}
+
+uint64 LastSegmentStartTime(const SegmentInfo& segment_info) {
+  return segment_info.start_time + segment_info.duration * segment_info.repeat;
+}
+
+// This is equal to |segment_info| end time
+uint64 LastSegmentEndTime(const SegmentInfo& segment_info) {
+  return segment_info.start_time +
+         segment_info.duration * (segment_info.repeat + 1);
+}
+
+uint64 LatestSegmentStartTime(const std::list<SegmentInfo>& segments) {
+  DCHECK(!segments.empty());
+  const SegmentInfo& latest_segment = segments.back();
+  return LastSegmentStartTime(latest_segment);
+}
+
+// Given |timeshift_limit|, finds out the number of segments that are no longer
+// valid and should be removed from |segment_info|.
+int SearchTimedOutRepeatIndex(uint64 timeshift_limit,
+                              const SegmentInfo& segment_info) {
+  DCHECK_LE(timeshift_limit, LastSegmentEndTime(segment_info));
+  if (timeshift_limit < segment_info.start_time)
+    return 0;
+
+  return (timeshift_limit - segment_info.start_time) / segment_info.duration;
+}
+
 }  // namespace
 
 MpdOptions::MpdOptions()
@@ -124,7 +169,7 @@ MpdOptions::~MpdOptions() {}
 
 MpdBuilder::MpdBuilder(MpdType type, const MpdOptions& mpd_options)
     : type_(type),
-      options_(mpd_options),
+      mpd_options_(mpd_options),
       adaptation_sets_deleter_(&adaptation_sets_) {}
 
 MpdBuilder::~MpdBuilder() {}
@@ -137,7 +182,7 @@ void MpdBuilder::AddBaseUrl(const std::string& base_url) {
 AdaptationSet* MpdBuilder::AddAdaptationSet() {
   base::AutoLock scoped_lock(lock_);
   scoped_ptr<AdaptationSet> adaptation_set(new AdaptationSet(
-      adaptation_set_counter_.GetNext(), &representation_counter_));
+      adaptation_set_counter_.GetNext(), mpd_options_, &representation_counter_));
 
   DCHECK(adaptation_set);
   adaptation_sets_.push_back(adaptation_set.get());
@@ -285,31 +330,32 @@ float MpdBuilder::GetStaticMpdDuration(XmlNode* mpd_node) {
 
 void MpdBuilder::SetMpdOptionsValues(XmlNode* mpd) {
   if (type_ == kStatic) {
-    if (!options_.availability_start_time.empty()) {
+    if (!mpd_options_.availability_start_time.empty()) {
       mpd->SetStringAttribute("availabilityStartTime",
-                              options_.availability_start_time);
+                              mpd_options_.availability_start_time);
     }
-    LOG_IF(WARNING, Positive(options_.minimum_update_period))
+    LOG_IF(WARNING, Positive(mpd_options_.minimum_update_period))
         << "minimumUpdatePeriod should not be present in 'static' profile. "
            "Ignoring.";
-    LOG_IF(WARNING, Positive(options_.time_shift_buffer_depth))
+    LOG_IF(WARNING, Positive(mpd_options_.time_shift_buffer_depth))
         << "timeShiftBufferDepth will not be used for 'static' profile. "
            "Ignoring.";
-    LOG_IF(WARNING, Positive(options_.suggested_presentation_delay))
+    LOG_IF(WARNING, Positive(mpd_options_.suggested_presentation_delay))
         << "suggestedPresentationDelay will not be used for 'static' profile. "
            "Ignoring.";
   } else if (type_ == kDynamic) {
     // 'availabilityStartTime' is required for dynamic profile, so use current
     // time if not specified.
-    const std::string avail_start = !options_.availability_start_time.empty()
+    const std::string avail_start =
-                                        ? options_.availability_start_time
+        !mpd_options_.availability_start_time.empty()
-                                        : XmlDateTimeNow();
+            ? mpd_options_.availability_start_time
+            : XmlDateTimeNow();
     mpd->SetStringAttribute("availabilityStartTime", avail_start);
 
-    if (Positive(options_.minimum_update_period)) {
+    if (Positive(mpd_options_.minimum_update_period)) {
       mpd->SetStringAttribute(
           "minimumUpdatePeriod",
-          SecondsToXmlDuration(options_.minimum_update_period));
+          SecondsToXmlDuration(mpd_options_.minimum_update_period));
     } else {
       // TODO(rkuroiwa): Set minimumUpdatePeriod to some default value.
       LOG(WARNING) << "The profile is dynamic but no minimumUpdatePeriod "
@@ -317,33 +363,36 @@ void MpdBuilder::SetMpdOptionsValues(XmlNode* mpd) {
     }
 
     SetIfPositive(
-        "timeShiftBufferDepth", options_.time_shift_buffer_depth, mpd);
+        "timeShiftBufferDepth", mpd_options_.time_shift_buffer_depth, mpd);
     SetIfPositive("suggestedPresentationDelay",
-                  options_.suggested_presentation_delay,
+                  mpd_options_.suggested_presentation_delay,
                   mpd);
   }
 
   const double kDefaultMinBufferTime = 2.0;
-  const double min_buffer_time = Positive(options_.min_buffer_time)
+  const double min_buffer_time = Positive(mpd_options_.min_buffer_time)
-                                     ? options_.min_buffer_time
+                                     ? mpd_options_.min_buffer_time
                                      : kDefaultMinBufferTime;
   mpd->SetStringAttribute("minBufferTime",
                           SecondsToXmlDuration(min_buffer_time));
 
-  if (!options_.availability_end_time.empty()) {
+  if (!mpd_options_.availability_end_time.empty()) {
     mpd->SetStringAttribute("availabilityEndTime",
-                            options_.availability_end_time);
+                            mpd_options_.availability_end_time);
   }
 
-  SetIfPositive("maxSegmentDuration", options_.max_segment_duration, mpd);
+  SetIfPositive("maxSegmentDuration", mpd_options_.max_segment_duration, mpd);
-  SetIfPositive("maxSubsegmentDuration", options_.max_subsegment_duration, mpd);
+  SetIfPositive(
+      "maxSubsegmentDuration", mpd_options_.max_subsegment_duration, mpd);
 }
 
 AdaptationSet::AdaptationSet(uint32 adaptation_set_id,
+                             const MpdOptions& mpd_options,
                              base::AtomicSequenceNumber* counter)
     : representations_deleter_(&representations_),
       representation_counter_(counter),
-      id_(adaptation_set_id) {
+      id_(adaptation_set_id),
+      mpd_options_(mpd_options) {
   DCHECK(counter);
 }
 
@@ -351,8 +400,8 @@ AdaptationSet::~AdaptationSet() {}
 
 Representation* AdaptationSet::AddRepresentation(const MediaInfo& media_info) {
   base::AutoLock scoped_lock(lock_);
-  scoped_ptr<Representation> representation(
+  scoped_ptr<Representation> representation(new Representation(
-      new Representation(media_info, representation_counter_->GetNext()));
+      media_info, mpd_options_, representation_counter_->GetNext()));
 
   if (!representation->Init())
     return NULL;
@@ -392,10 +441,14 @@ xml::ScopedXmlPtr<xmlNode>::type AdaptationSet::GetXml() {
   return adaptation_set.PassScopedPtr();
 }
 
-Representation::Representation(const MediaInfo& media_info, uint32 id)
+Representation::Representation(const MediaInfo& media_info,
+                               const MpdOptions& mpd_options,
+                               uint32 id)
     : media_info_(media_info),
       id_(id),
-      bandwidth_estimator_(BandwidthEstimator::kUseAllBlocks) {}
+      bandwidth_estimator_(BandwidthEstimator::kUseAllBlocks),
+      mpd_options_(mpd_options),
+      start_number_(1) {}
 
 Representation::~Representation() {}
 
@@ -458,6 +511,9 @@ void Representation::AddNewSegment(uint64 start_time,
 
   bandwidth_estimator_.AddBlock(
       size, static_cast<double>(duration) / media_info_.reference_time_scale());
+
+  SlideWindow();
+  DCHECK_GE(segment_infos_.size(), 1u);
 }
 
 // Uses info in |media_info_| and |content_protection_elements_| to create a
@@ -516,7 +572,8 @@ xml::ScopedXmlPtr<xmlNode>::type Representation::GetXml() {
   }
 
   if (HasLiveOnlyFields(media_info_) &&
-      !representation.AddLiveOnlyInfo(media_info_, segment_infos_)) {
+      !representation.AddLiveOnlyInfo(
+          media_info_, segment_infos_, start_number_)) {
     LOG(ERROR) << "Failed to add Live info.";
     return xml::ScopedXmlPtr<xmlNode>::type();
   }
@@ -599,6 +656,57 @@ bool Representation::IsContiguous(uint64 start_time,
   return false;
 }
 
+void Representation::SlideWindow() {
+  DCHECK(!segment_infos_.empty());
+  if (mpd_options_.time_shift_buffer_depth <= 0.0)
+    return;
+
+  const uint32 time_scale = GetTimeScale(media_info_);
+  DCHECK_GT(time_scale, 0u);
+
+  uint64 time_shift_buffer_depth =
+      static_cast<uint64>(mpd_options_.time_shift_buffer_depth * time_scale);
+
+  // The start time of the latest segment is considered the current_play_time,
+  // and this should guarantee that the latest segment will stay in the list.
+  const uint64 current_play_time = LatestSegmentStartTime(segment_infos_);
+  if (current_play_time <= time_shift_buffer_depth)
+    return;
+
+  const uint64 timeshift_limit = current_play_time - time_shift_buffer_depth;
+
+  // First remove all the SegmentInfos that are completely out of range, by
+  // looking at the very last segment's end time.
+  std::list<SegmentInfo>::iterator first = segment_infos_.begin();
+  std::list<SegmentInfo>::iterator last = first;
+  size_t num_segments_removed = 0;
+  for (; last != segment_infos_.end(); ++last) {
+    const uint64 last_segment_end_time = LastSegmentEndTime(*last);
+    if (timeshift_limit < last_segment_end_time)
+      break;
+    num_segments_removed += last->repeat + 1;
+  }
+  segment_infos_.erase(first, last);
+  start_number_ += num_segments_removed;
+
+  // Now some segment in the first SegmentInfo should be left in the list.
+  SegmentInfo* first_segment_info = &segment_infos_.front();
+  DCHECK_LE(timeshift_limit, LastSegmentEndTime(*first_segment_info));
+
+  // Identify which segments should still be in the SegmentInfo.
+  const int repeat_index =
+      SearchTimedOutRepeatIndex(timeshift_limit, *first_segment_info);
+  CHECK_GE(repeat_index, 0);
+  if (repeat_index == 0)
+    return;
+
+  first_segment_info->start_time = first_segment_info->start_time +
+                                   first_segment_info->duration * repeat_index;
+
+  first_segment_info->repeat = first_segment_info->repeat - repeat_index;
+  start_number_ += repeat_index;
+}
+
 std::string Representation::GetVideoMimeType() const {
   return GetMimeType("video", media_info_.container_type());
 }

mpd/base/mpd_builder.h

@@ -15,10 +15,11 @@
 
 #include "base/atomic_sequence_num.h"
 #include "base/basictypes.h"
+#include "base/gtest_prod_util.h"
 #include "base/stl_util.h"
 #include "base/synchronization/lock.h"
-#include "mpd/base/content_protection_element.h"
 #include "mpd/base/bandwidth_estimator.h"
+#include "mpd/base/content_protection_element.h"
 #include "mpd/base/media_info.pb.h"
 #include "mpd/base/mpd_utils.h"
 #include "mpd/base/segment_info.h"
@@ -105,13 +106,13 @@ class MpdBuilder {
 
   float GetStaticMpdDuration(xml::XmlNode* mpd_node);
 
-  // Use |options_| to set attributes for MPD. Only values that are set will be
+  // Use |mpd_options_| to set attributes for MPD. Only values that are set will be
   // used, i.e. if a string field is not empty and numeric field is not 0.
   // Required fields will be set with some reasonable values.
   void SetMpdOptionsValues(xml::XmlNode* mpd_node);
 
   MpdType type_;
-  MpdOptions options_;
+  MpdOptions mpd_options_;
   std::list<AdaptationSet*> adaptation_sets_;
   ::STLElementDeleter<std::list<AdaptationSet*> > adaptation_sets_deleter_;
 
@@ -128,11 +129,6 @@ class MpdBuilder {
 /// <ContentProtection> elements to the AdaptationSet element.
 class AdaptationSet {
  public:
-  /// @param adaptation_set_id is an ID number for this AdaptationSet.
-  /// @param representation_counter is a Counter for assigning ID numbers to
-  ///                               Representation. It can not be NULL.
-  AdaptationSet(uint32 adaptation_set_id,
-                base::AtomicSequenceNumber* representation_counter);
   ~AdaptationSet();
 
   /// Create a Representation instance using @a media_info.
@@ -161,6 +157,16 @@ class AdaptationSet {
   }
 
  private:
+  friend class MpdBuilder;
+  FRIEND_TEST_ALL_PREFIXES(StaticMpdBuilderTest, CheckAdaptationSetId);
+
+  /// @param adaptation_set_id is an ID number for this AdaptationSet.
+  /// @param representation_counter is a Counter for assigning ID numbers to
+  ///        Representation. It can not be NULL.
+  AdaptationSet(uint32 adaptation_set_id,
+                const MpdOptions& mpd_options_,
+                base::AtomicSequenceNumber* representation_counter);
+
   std::list<ContentProtectionElement> content_protection_elements_;
   std::list<Representation*> representations_;
   ::STLElementDeleter<std::list<Representation*> > representations_deleter_;
@@ -170,6 +176,7 @@ class AdaptationSet {
   base::AtomicSequenceNumber* const representation_counter_;
 
   const uint32 id_;
+  const MpdOptions& mpd_options_;
 
   DISALLOW_COPY_AND_ASSIGN(AdaptationSet);
 };
@@ -178,14 +185,6 @@ class AdaptationSet {
 /// well as optional ContentProtection elements for that stream.
 class Representation {
  public:
-  // TODO(rkuroiwa): Get the value from MpdOptions for constructing
-  // BandwidthEstimator.
-  /// @param media_info is a MediaInfo containing information on the media.
-  ///        @a media_info.bandwidth is required for 'static' profile. If @a
-  ///        media_info.bandwidth is not present in 'dynamic' profile, this
-  ///        tries to estimate it using the info passed to AddNewSegment().
-  /// @param representation_id is the numeric ID for the <Representation>.
-  Representation(const MediaInfo& media_info, uint32 representation_id);
   ~Representation();
 
   /// Tries to initialize the instance. If this does not succeed, the instance
@@ -217,6 +216,18 @@ class Representation {
   }
 
  private:
+  friend class AdaptationSet;
+  FRIEND_TEST_ALL_PREFIXES(StaticMpdBuilderTest, CheckRepresentationId);
+
+  /// @param media_info is a MediaInfo containing information on the media.
+  ///        @a media_info.bandwidth is required for 'static' profile. If @a
+  ///        media_info.bandwidth is not present in 'dynamic' profile, this
+  ///        tries to estimate it using the info passed to AddNewSegment().
+  /// @param representation_id is the numeric ID for the <Representation>.
+  Representation(const MediaInfo& media_info,
+                 const MpdOptions& mpd_options,
+                 uint32 representation_id);
+
   bool AddLiveInfo(xml::RepresentationXmlNode* representation);
 
   // Returns true if |media_info_| has required fields to generate a valid
@@ -227,6 +238,11 @@ class Representation {
   // segment is contiguous.
   bool IsContiguous(uint64 start_time, uint64 duration, uint64 size) const;
 
+  // Remove elements from |segment_infos_| if
+  // mpd_options_.time_shift_buffer_depth is specified. Increments
+  // |start_number_| by the number of segments removed.
+  void SlideWindow();
+
   // Note: Because 'mimeType' is a required field for a valid MPD, these return
   // strings.
   std::string GetVideoMimeType() const;
@@ -242,6 +258,11 @@ class Representation {
   std::string mime_type_;
   std::string codecs_;
   BandwidthEstimator bandwidth_estimator_;
+  const MpdOptions& mpd_options_;;
+
+  // startNumber attribute for SegmentTemplate.
+  // Starts from 1.
+  uint32 start_number_;
 
   DISALLOW_COPY_AND_ASSIGN(Representation);
 };

mpd/base/mpd_builder_unittest.cc

@@ -7,6 +7,7 @@
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "mpd/base/mpd_builder.h"
 #include "mpd/base/mpd_utils.h"
@@ -18,6 +19,10 @@
 namespace dash_packager {
 
 namespace {
+const char kSElementTemplate[] = "<S t=\"%lu\" d=\"%lu\" r=\"%lu\"/>\n";
+const char kSElementTemplateWithoutR[] = "<S t=\"%lu\" d=\"%lu\"/>\n";
+const int kDefaultStartNumber = 1;
+
 // Get 'id' attribute from |node|, convert it to std::string and convert it to a
 // number.
 void ExpectXmlElementIdEqual(xmlNodePtr node, uint32 id) {
@@ -90,9 +95,11 @@ class DynamicMpdBuilderTest : public MpdBuilderTest<MpdBuilder::kDynamic> {
   // Anchors availabilityStartTime so that the test result doesn't depend on the
   // current time.
   virtual void SetUp() {
-    mpd_.options_.availability_start_time = "2011-12-25T12:30:00";
+    mpd_.mpd_options_.availability_start_time = "2011-12-25T12:30:00";
   }
 
+  MpdOptions* mutable_mpd_options() { return &mpd_.mpd_options_; }
+
   std::string GetDefaultMediaInfo() {
     const char kMediaInfo[] =
         "video_info {\n"
@@ -109,7 +116,8 @@ class DynamicMpdBuilderTest : public MpdBuilderTest<MpdBuilder::kDynamic> {
     return base::StringPrintf(kMediaInfo, DefaultTimeScale());
   }
 
-  uint64 DefaultTimeScale() const { return 1000; };
+  // TODO(rkuroiwa): Make this a global constant in anonymous namespace.
+  uint64 DefaultTimeScale() const {  return 1000; };
 };
 
 class SegmentTemplateTest : public DynamicMpdBuilderTest {
@@ -128,8 +136,6 @@ class SegmentTemplateTest : public DynamicMpdBuilderTest {
                    uint64 size,
                    uint64 repeat) {
     DCHECK(representation_);
-    const char kSElementTemplate[] = "<S t=\"%lu\" d=\"%lu\" r=\"%lu\"/>\n";
-    const char kSElementTemplateWithoutR[] = "<S t=\"%lu\" d=\"%lu\"/>\n";
 
     SegmentInfo s = {start_time, duration, repeat};
     segment_infos_for_expected_out_.push_back(s);
@@ -155,8 +161,8 @@ class SegmentTemplateTest : public DynamicMpdBuilderTest {
         AddRepresentation(ConvertToMediaInfo(GetDefaultMediaInfo())));
   }
 
-  std::string TemplateOutputInsertSElementsAndBandwidth(
+  std::string TemplateOutputInsertValues(const std::string& s_elements_string,
-      const std::string& s_elements_string, uint64 bandwidth) {
+                                         uint64 bandwidth) {
     const char kOutputTemplate[] =
         "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
         "<MPD xmlns=\"urn:mpeg:DASH:schema:MPD:2011\" "
@@ -180,8 +186,9 @@ class SegmentTemplateTest : public DynamicMpdBuilderTest {
         "  </Period>\n"
         "</MPD>\n";
 
-    return base::StringPrintf(
+    return base::StringPrintf(kOutputTemplate,
-        kOutputTemplate, bandwidth, s_elements_string.data());
+                              bandwidth,
+                              s_elements_string.c_str());
   }
 
   void CheckMpdAgainstExpectedResult() {
@@ -189,22 +196,98 @@ class SegmentTemplateTest : public DynamicMpdBuilderTest {
     ASSERT_TRUE(mpd_.ToString(&mpd_doc));
     ASSERT_TRUE(ValidateMpdSchema(mpd_doc));
     const std::string& expected_output =
-        TemplateOutputInsertSElementsAndBandwidth(
+        TemplateOutputInsertValues(expected_s_elements_,
-            expected_s_elements_, bandwidth_estimator_.Estimate());
+                                   bandwidth_estimator_.Estimate());
-    ASSERT_TRUE(XmlEqual(expected_output, mpd_doc));
+    ASSERT_TRUE(XmlEqual(expected_output, mpd_doc))
+        << "Expected " << expected_output << std::endl << "Actual: " << mpd_doc;
   }
 
- private:
   std::list<SegmentInfo> segment_infos_for_expected_out_;
   std::string expected_s_elements_;
   BandwidthEstimator bandwidth_estimator_;
 };
 
+class TimeShiftBufferDepthTest : public SegmentTemplateTest {
+ public:
+  TimeShiftBufferDepthTest() {}
+  virtual ~TimeShiftBufferDepthTest() {}
+
+  // This function is tricky. It does not call SegmentTemplateTest::Setup() so
+  // that it does not automatically add a representation, that has $Time$
+  // template.
+  virtual void SetUp() {
+    DynamicMpdBuilderTest::SetUp();
+
+    // The only diff with current GetDefaultMediaInfo() is that this uses
+    // $Number$ for segment template.
+    const char kMediaInfo[] =
+        "video_info {\n"
+        "  codec: \"avc1.010101\"\n"
+        "  width: 720\n"
+        "  height: 480\n"
+        "  time_scale: 10\n"
+        "}\n"
+        "reference_time_scale: %lu\n"
+        "container_type: 1\n"
+        "init_segment_name: \"init.mp4\"\n"
+        "segment_template: \"$Number$.mp4\"\n";
+
+    const std::string& number_template_media_info =
+        base::StringPrintf(kMediaInfo, DefaultTimeScale());
+    ASSERT_NO_FATAL_FAILURE(
+        AddRepresentation(ConvertToMediaInfo(number_template_media_info)));
+  }
+
+  void CheckTimeShiftBufferDepthResult(const std::string& expected_s_element,
+                                       int expected_time_shift_buffer_depth,
+                                       int expected_start_number) {
+    const char kOutputTemplate[] =
+        "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
+        "<MPD xmlns=\"urn:mpeg:DASH:schema:MPD:2011\" "
+        "xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" "
+        "xmlns:xlink=\"http://www.w3.org/1999/xlink\" "
+        "xsi:schemaLocation=\"urn:mpeg:DASH:schema:MPD:2011 DASH-MPD.xsd\" "
+        "availabilityStartTime=\"2011-12-25T12:30:00\" minBufferTime=\"PT2S\" "
+        "type=\"dynamic\" profiles=\"urn:mpeg:dash:profile:isoff-live:2011\" "
+        "timeShiftBufferDepth=\"PT%dS\">\n"
+        "  <Period start=\"PT0S\">\n"
+        "    <AdaptationSet id=\"0\">\n"
+        "      <Representation id=\"0\" bandwidth=\"%lu\" "
+        "codecs=\"avc1.010101\" mimeType=\"video/mp4\" width=\"720\" "
+        "height=\"480\">\n"
+        "        <SegmentTemplate timescale=\"1000\" "
+        "initialization=\"init.mp4\" media=\"$Number$.mp4\" "
+        "startNumber=\"%d\">\n"
+        "          <SegmentTimeline>\n"
+        "              %s\n"
+        "          </SegmentTimeline>\n"
+        "        </SegmentTemplate>\n"
+        "      </Representation>\n"
+        "    </AdaptationSet>\n"
+        "  </Period>\n"
+        "</MPD>\n";
+
+    std::string expected_out =
+        base::StringPrintf(kOutputTemplate,
+                           expected_time_shift_buffer_depth,
+                           bandwidth_estimator_.Estimate(),
+                           expected_start_number,
+                           expected_s_element.c_str());
+
+    std::string mpd_doc;
+    ASSERT_TRUE(mpd_.ToString(&mpd_doc));
+    ASSERT_TRUE(ValidateMpdSchema(mpd_doc));
+    ASSERT_TRUE(XmlEqual(expected_out, mpd_doc))
+        << "Expected " << expected_out << std::endl << "Actual: " << mpd_doc;
+  }
+};
+
 TEST_F(StaticMpdBuilderTest, CheckAdaptationSetId) {
   base::AtomicSequenceNumber sequence_counter;
   const uint32 kAdaptationSetId = 42;
 
-  AdaptationSet adaptation_set(kAdaptationSetId, &sequence_counter);
+  AdaptationSet adaptation_set(
+      kAdaptationSetId, MpdOptions(), &sequence_counter);
   ASSERT_NO_FATAL_FAILURE(CheckIdEqual(kAdaptationSetId, &adaptation_set));
 }
 
@@ -212,7 +295,8 @@ TEST_F(StaticMpdBuilderTest, CheckRepresentationId) {
   const MediaInfo video_media_info = GetTestMediaInfo(kFileNameVideoMediaInfo1);
   const uint32 kRepresentationId = 1;
 
-  Representation representation(video_media_info, kRepresentationId);
+  Representation representation(
+      video_media_info, MpdOptions(), kRepresentationId);
   EXPECT_TRUE(representation.Init());
   ASSERT_NO_FATAL_FAILURE(CheckIdEqual(kRepresentationId, &representation));
 }
@@ -421,4 +505,286 @@ TEST_F(SegmentTemplateTest, OverlappingSegmentsWithinErrorRange) {
   ASSERT_NO_FATAL_FAILURE(CheckMpdAgainstExpectedResult());
 }
 
+// All segments have the same duration and size.
+TEST_F(TimeShiftBufferDepthTest, Normal) {
+  const int kTimeShiftBufferDepth = 10;  // 10 sec.
+  mutable_mpd_options()->time_shift_buffer_depth = kTimeShiftBufferDepth;
+
+  const uint64 kInitialStartTime = 0;
+  // Trick to make every segment 1 second long.
+  const uint64 kDuration = DefaultTimeScale();
+  const uint64 kSize = 10000;
+  const uint64 kRepeat = 1234;
+  const uint64 kLength = kRepeat;
+
+  CHECK_EQ(kDuration / DefaultTimeScale() * kRepeat, kLength);
+
+  AddSegments(kInitialStartTime, kDuration, kSize, kRepeat);
+
+  // There should only be the last 11 segments because timeshift is 10 sec and
+  // each segment is 1 sec and the latest segments start time is "current
+  // time" i.e., the latest segment does not count as part of timeshift buffer
+  // depth.
+  // Also note that S@r + 1 is the actual number of segments.
+  const int kExpectedRepeatsLeft = kTimeShiftBufferDepth;
+  const std::string expected_s_element =
+      base::StringPrintf(kSElementTemplate,
+                         kDuration * (kRepeat - kExpectedRepeatsLeft),
+                         kDuration,
+                         static_cast<uint64>(kExpectedRepeatsLeft));
+
+  const int kExpectedStartNumber = kRepeat - kExpectedRepeatsLeft + 1;
+  ASSERT_NO_FATAL_FAILURE(CheckTimeShiftBufferDepthResult(
+      expected_s_element, kTimeShiftBufferDepth, kExpectedStartNumber));
+}
+
+// TimeShiftBufferDepth is shorter than a segment. This should not discard the
+// segment that can play TimeShiftBufferDepth.
+// For example if TimeShiftBufferDepth = 1 min. and a 10 min segment was just
+// added. Before that 9 min segment was added. The 9 min segment should not be
+// removed from the MPD.
+TEST_F(TimeShiftBufferDepthTest, TimeShiftBufferDepthShorterThanSegmentLength) {
+  const int kTimeShiftBufferDepth = 10;  // 10 sec.
+  mutable_mpd_options()->time_shift_buffer_depth = kTimeShiftBufferDepth;
+
+  const uint64 kInitialStartTime = 0;
+  // Each duration is a second longer than timeShiftBufferDepth.
+  const uint64 kDuration = DefaultTimeScale() * (kTimeShiftBufferDepth + 1);
+  const uint64 kSize = 10000;
+  const uint64 kRepeat = 1;
+
+  AddSegments(kInitialStartTime, kDuration, kSize, kRepeat);
+
+  // The two segments should be both present.
+  const std::string expected_s_element = base::StringPrintf(
+      kSElementTemplate, kInitialStartTime, kDuration, kRepeat);
+
+  ASSERT_NO_FATAL_FAILURE(CheckTimeShiftBufferDepthResult(
+      expected_s_element, kTimeShiftBufferDepth, kDefaultStartNumber));
+}
+
+// More generic version the normal test.
+TEST_F(TimeShiftBufferDepthTest, Generic) {
+  const int kTimeShiftBufferDepth = 30;
+  mutable_mpd_options()->time_shift_buffer_depth = kTimeShiftBufferDepth;
+
+  const uint64 kInitialStartTime = 123;
+  const uint64 kDuration = DefaultTimeScale();
+  const uint64 kSize = 10000;
+  const uint64 kRepeat = 1000;
+
+  AddSegments(kInitialStartTime, kDuration, kSize, kRepeat);
+  const uint64 first_s_element_end_time =
+      kInitialStartTime + kDuration * (kRepeat + 1);
+
+  // Now add 2 kTimeShiftBufferDepth long segments.
+  const int kNumMoreSegments = 2;
+  const int kMoreSegmentsRepeat = kNumMoreSegments - 1;
+  const uint64 kTimeShiftBufferDepthDuration =
+      DefaultTimeScale() * kTimeShiftBufferDepth;
+  AddSegments(first_s_element_end_time,
+              kTimeShiftBufferDepthDuration,
+              kSize,
+              kMoreSegmentsRepeat);
+
+  // Expect only the latest S element with 2 segments.
+  const std::string expected_s_element =
+      base::StringPrintf(kSElementTemplate,
+                         first_s_element_end_time,
+                         kTimeShiftBufferDepthDuration,
+                         static_cast<uint64>(kMoreSegmentsRepeat));
+
+  const int kExpectedRemovedSegments = kRepeat + 1;
+  ASSERT_NO_FATAL_FAILURE(CheckTimeShiftBufferDepthResult(
+      expected_s_element,
+      kTimeShiftBufferDepth,
+      kDefaultStartNumber + kExpectedRemovedSegments));
+}
+
+// More than 1 S element in the result.
+// Adds 100 one-second segments. Then add 21 two-second segments.
+// This should have all of the two-second segments and 60 one-second
+// segments. Note that it expects 60 segments from the first S element because
+// the most recent segment added does not count
+TEST_F(TimeShiftBufferDepthTest, MoreThanOneS) {
+  const int kTimeShiftBufferDepth = 100;
+  mutable_mpd_options()->time_shift_buffer_depth = kTimeShiftBufferDepth;
+
+  const uint64 kInitialStartTime = 0;
+  const uint64 kSize = 20000;
+
+  const uint64 kOneSecondDuration = DefaultTimeScale();
+  const uint64 kOneSecondSegmentRepeat = 99;
+  AddSegments(
+      kInitialStartTime, kOneSecondDuration, kSize, kOneSecondSegmentRepeat);
+  const uint64 first_s_element_end_time =
+      kInitialStartTime + kOneSecondDuration * (kOneSecondSegmentRepeat + 1);
+
+  const uint64 kTwoSecondDuration = 2 * DefaultTimeScale();
+  const uint64 kTwoSecondSegmentRepeat = 20;
+  AddSegments(first_s_element_end_time,
+              kTwoSecondDuration,
+              kSize,
+              kTwoSecondSegmentRepeat);
+
+  const uint64 kExpectedRemovedSegments =
+      (kOneSecondSegmentRepeat + 1 + kTwoSecondSegmentRepeat * 2) -
+      kTimeShiftBufferDepth;
+
+  std::string expected_s_element =
+      base::StringPrintf(kSElementTemplate,
+                         kOneSecondDuration * kExpectedRemovedSegments,
+                         kOneSecondDuration,
+                         kOneSecondSegmentRepeat - kExpectedRemovedSegments);
+  expected_s_element += base::StringPrintf(kSElementTemplate,
+                                           first_s_element_end_time,
+                                           kTwoSecondDuration,
+                                           kTwoSecondSegmentRepeat);
+
+  ASSERT_NO_FATAL_FAILURE(CheckTimeShiftBufferDepthResult(
+      expected_s_element,
+      kTimeShiftBufferDepth,
+      kDefaultStartNumber + kExpectedRemovedSegments));
+}
+
+
+// Edge case where the last segment in S element should still be in the MPD.
+// Example:
+// Assuming timescale = 1 so that duration of 1 means 1 second.
+// TimeShiftBufferDepth is 9 sec and we currently have
+// <S t=0 d=1.5 r=1 />
+// <S t=3 d=2 r=3 />
+// and we add another contiguous 2 second segment.
+// Then the first S element's last segment should still be in the MPD.
+TEST_F(TimeShiftBufferDepthTest, UseLastSegmentInS) {
+  const int kTimeShiftBufferDepth = 9;
+  mutable_mpd_options()->time_shift_buffer_depth = kTimeShiftBufferDepth;
+
+  const uint64 kInitialStartTime = 1;
+  const uint64 kDuration1 =
+      static_cast<uint64>(DefaultTimeScale() * 1.5);
+  const uint64 kSize = 20000;
+  const uint64 kRepeat1 = 1;
+
+  AddSegments(kInitialStartTime, kDuration1, kSize, kRepeat1);
+
+  const uint64 first_s_element_end_time =
+      kInitialStartTime + kDuration1 * (kRepeat1 + 1);
+
+  const uint64 kTwoSecondDuration = 2 * DefaultTimeScale();
+  const uint64 kTwoSecondSegmentRepeat = 4;
+
+  AddSegments(first_s_element_end_time,
+              kTwoSecondDuration,
+              kSize,
+              kTwoSecondSegmentRepeat);
+
+  std::string expected_s_element = base::StringPrintf(
+      kSElementTemplateWithoutR,
+      kInitialStartTime + kDuration1,  // Expect one segment removed.
+      kDuration1);
+
+  expected_s_element += base::StringPrintf(kSElementTemplate,
+                                           first_s_element_end_time,
+                                           kTwoSecondDuration,
+                                           kTwoSecondSegmentRepeat);
+  ASSERT_NO_FATAL_FAILURE(CheckTimeShiftBufferDepthResult(
+      expected_s_element, kTimeShiftBufferDepth, 2));
+}
+
+// Gap between S elements but both should be included.
+TEST_F(TimeShiftBufferDepthTest, NormalGap) {
+  const int kTimeShiftBufferDepth = 10;
+  mutable_mpd_options()->time_shift_buffer_depth = kTimeShiftBufferDepth;
+
+  const uint64 kInitialStartTime = 0;
+  const uint64 kDuration = DefaultTimeScale();
+  const uint64 kSize = 20000;
+  const uint64 kRepeat = 6;
+  // CHECK here so that the when next S element is added with 1 segment, this S
+  // element doesn't go away.
+  CHECK_LT(kRepeat - 1u, static_cast<uint64>(kTimeShiftBufferDepth));
+  CHECK_EQ(kDuration, DefaultTimeScale());
+
+  AddSegments(kInitialStartTime, kDuration, kSize, kRepeat);
+
+  const uint64 first_s_element_end_time =
+      kInitialStartTime + kDuration * (kRepeat + 1);
+
+  const uint64 gap_s_element_start_time = first_s_element_end_time + 1;
+  AddSegments(gap_s_element_start_time, kDuration, kSize, /* no repeat */ 0);
+
+  std::string expected_s_element = base::StringPrintf(
+      kSElementTemplate, kInitialStartTime, kDuration, kRepeat);
+  expected_s_element += base::StringPrintf(
+      kSElementTemplateWithoutR, gap_s_element_start_time, kDuration);
+
+  ASSERT_NO_FATAL_FAILURE(CheckTimeShiftBufferDepthResult(
+      expected_s_element, kTimeShiftBufferDepth, kDefaultStartNumber));
+}
+
+// Case where there is a huge gap so the first S element is removed.
+TEST_F(TimeShiftBufferDepthTest, HugeGap) {
+  const int kTimeShiftBufferDepth = 10;
+  mutable_mpd_options()->time_shift_buffer_depth = kTimeShiftBufferDepth;
+
+  const uint64 kInitialStartTime = 0;
+  const uint64 kDuration = DefaultTimeScale();
+  const uint64 kSize = 20000;
+  const uint64 kRepeat = 6;
+  AddSegments(kInitialStartTime, kDuration, kSize, kRepeat);
+
+  const uint64 first_s_element_end_time =
+      kInitialStartTime + kDuration * (kRepeat + 1);
+
+  // Big enough gap so first S element should not be there.
+  const uint64 gap_s_element_start_time =
+      first_s_element_end_time +
+      (kTimeShiftBufferDepth + 1) * DefaultTimeScale();
+  const uint64 kSecondSElementRepeat = 9;
+  COMPILE_ASSERT(
+      kSecondSElementRepeat < static_cast<uint64>(kTimeShiftBufferDepth),
+      second_s_element_repeat_must_be_less_than_time_shift_buffer_depth);
+  AddSegments(gap_s_element_start_time, kDuration, kSize, kSecondSElementRepeat);
+
+  std::string expected_s_element = base::StringPrintf(kSElementTemplate,
+                                                      gap_s_element_start_time,
+                                                      kDuration,
+                                                      kSecondSElementRepeat);
+  const int kExpectedRemovedSegments = kRepeat + 1;
+  ASSERT_NO_FATAL_FAILURE(CheckTimeShiftBufferDepthResult(
+      expected_s_element,
+      kTimeShiftBufferDepth,
+      kDefaultStartNumber + kExpectedRemovedSegments));
+}
+
+// Check if startNumber is working correctly.
+TEST_F(TimeShiftBufferDepthTest, ManySegments) {
+  const int kTimeShiftBufferDepth = 1;
+  mutable_mpd_options()->time_shift_buffer_depth = kTimeShiftBufferDepth;
+
+  const uint64 kInitialStartTime = 0;
+  const uint64 kDuration = DefaultTimeScale();
+  const uint64 kSize = 20000;
+  const uint64 kRepeat = 10000;
+  const uint64 kTotalNumSegments = kRepeat + 1;
+  AddSegments(kInitialStartTime, kDuration, kSize, kRepeat);
+
+  const int kExpectedSegmentsLeft = kTimeShiftBufferDepth + 1;
+  const int kExpectedSegmentsRepeat = kExpectedSegmentsLeft - 1;
+  const int kExpectedRemovedSegments =
+      kTotalNumSegments - kExpectedSegmentsLeft;
+
+  std::string expected_s_element =
+      base::StringPrintf(kSElementTemplate,
+                         kExpectedRemovedSegments * kDuration,
+                         kDuration,
+                         static_cast<uint64>(kExpectedSegmentsRepeat));
+
+  ASSERT_NO_FATAL_FAILURE(CheckTimeShiftBufferDepthResult(
+      expected_s_element,
+      kTimeShiftBufferDepth,
+      kDefaultStartNumber + kExpectedRemovedSegments));
+}
+
 }  // namespace dash_packager

mpd/base/xml/xml_node.cc

@@ -412,7 +412,8 @@ bool RepresentationXmlNode::AddVODOnlyInfo(const MediaInfo& media_info) {
 
 bool RepresentationXmlNode::AddLiveOnlyInfo(
     const MediaInfo& media_info,
-    const std::list<SegmentInfo>& segment_infos) {
+    const std::list<SegmentInfo>& segment_infos,
+    uint32 start_number) {
   XmlNode segment_template("SegmentTemplate");
   if (media_info.has_reference_time_scale()) {
     segment_template.SetIntegerAttribute("timescale",
@@ -431,14 +432,21 @@ bool RepresentationXmlNode::AddLiveOnlyInfo(
                     "SegmentTemplate@initialization";
       return false;
     }
-
     segment_template.SetStringAttribute("initialization",
                                         media_info.init_segment_name());
   }
 
-  if (media_info.has_segment_template())
+  if (media_info.has_segment_template()) {
     segment_template.SetStringAttribute("media", media_info.segment_template());
 
+    // TODO(rkuroiwa): Need a better check. $$Number is legitimate but not a
+    // template.
+    if (media_info.segment_template().find("$Number") != std::string::npos) {
+      DCHECK_GE(start_number, 1u);
+      segment_template.SetIntegerAttribute("startNumber", start_number);
+    }
+  }
+
   // TODO(rkuroiwa): Find out when a live MPD doesn't require SegmentTimeline.
   XmlNode segment_timeline("SegmentTimeline");
 

mpd/base/xml/xml_node.h

@@ -152,8 +152,11 @@ class RepresentationXmlNode : public RepresentationBaseXmlNode {
   /// @return true on success, false otherwise.
   bool AddVODOnlyInfo(const MediaInfo& media_info);
 
+  /// @param segment_infos is a set of SegmentInfos. This method assumes that
+  ///        SegmentInfos are sorted by its start time.
   bool AddLiveOnlyInfo(const MediaInfo& media_info,
-                       const std::list<SegmentInfo>& segment_infos);
+                       const std::list<SegmentInfo>& segment_infos,
+                       uint32 start_number);
 
  private:
   // Add AudioChannelConfiguration elements. This will add multiple

mpd/base/xml/xml_node_unittest.cc

@@ -201,19 +201,22 @@ TEST_F(RepresentationTest, AddContentProtectionXml) {
 // Some template names cannot be used for init segment name.
 TEST_F(RepresentationTest, InvalidLiveInitSegmentName) {
   MediaInfo media_info;
+  const uint32 kDefaultStartNumber = 1;
 
-  // $NUMBER$ cannot be used for segment name.
+  // $Number$ cannot be used for segment name.
   media_info.set_init_segment_name("$Number$.mp4");
+  ASSERT_FALSE(representation_.AddLiveOnlyInfo(
+      media_info, segment_infos_, kDefaultStartNumber));
 
-  ASSERT_FALSE(representation_.AddLiveOnlyInfo(media_info, segment_infos_));
+  // $Time$ as well.
-
-  // $TIME$ as well.
   media_info.set_init_segment_name("$Time$.mp4");
-  ASSERT_FALSE(representation_.AddLiveOnlyInfo(media_info, segment_infos_));
+  ASSERT_FALSE(representation_.AddLiveOnlyInfo(
+      media_info, segment_infos_, kDefaultStartNumber));
 
   // This should be valid.
   media_info.set_init_segment_name("some_non_template_name.mp4");
-  ASSERT_TRUE(representation_.AddLiveOnlyInfo(media_info, segment_infos_));
+  ASSERT_TRUE(representation_.AddLiveOnlyInfo(
+      media_info, segment_infos_, kDefaultStartNumber));
 }
 
 }  // namespace xml