feat: Solution for adding startwithSAP/subsegmentstartswithSAP for audio tracks

packager/mpd/base/adaptation_set.cc

@@ -274,6 +274,14 @@ base::Optional<xml::XmlNode> AdaptationSet::GetXml() {
       return base::nullopt;
     }
   }
+  if (subsegment_start_with_sap_ == 1) {
+    if (!adaptation_set.SetIntegerAttribute("subsegmentStartsWithSAP", 1))
+      return base::nullopt;
+  }
+  else if (start_with_sap_ == 1) {
+    if (!adaptation_set.SetIntegerAttribute("startWithSAP", 1))
+      return base::nullopt;
+  }
 
   if (video_frame_rates_.size() == 1) {
     suppress_representation_frame_rate = true;
@@ -384,6 +392,14 @@ void AdaptationSet::AddAdaptationSetSwitching(
   switchable_adaptation_sets_.push_back(adaptation_set);
 }
 
+void AdaptationSet::ForceSubsegmentStartswithSAP(uint32_t sap_value) {
+  subsegment_start_with_sap_ = sap_value;
+}
+
+void AdaptationSet::ForceStartwithSAP(uint32_t sap_value) {
+  start_with_sap_ = sap_value;
+}
+
 // For dynamic MPD, storing all start_time and duration will out-of-memory
 // because there's no way of knowing when it will end. Static MPD
 // subsegmentAlignment check is *not* done here because it is possible that some

packager/mpd/base/adaptation_set.h

@@ -117,6 +117,17 @@ class AdaptationSet {
   ///        attribute.
   virtual void ForceSetSegmentAlignment(bool segment_alignment);
 
+  /// Forces the subsegmentStartswithSAP field to be set to @a sap_value.
+  /// Use this if you are certain with stream access point value of the
+  /// subsegment.
+  /// @param sap_value is the value used for subsegmentstartsWithSAP attribute.
+  virtual void ForceSubsegmentStartswithSAP(uint32_t sap_value);
+
+  /// Forces the StartswithSAP field to be set to @a sap_value.
+  /// Use this if you are certain with stream access point value of the segment.
+  /// @param sap_value is the value used for  startWithSAP attribute.
+  virtual void ForceStartwithSAP(uint32_t sap_value);
+
   /// Adds the adaptation set this adaptation set can switch to.
   /// @param adaptation_set points to the switchable adaptation set.
   virtual void AddAdaptationSetSwitching(const AdaptationSet* adaptation_set);
@@ -299,6 +310,12 @@ class AdaptationSet {
   SegmentAligmentStatus segments_aligned_;
   bool force_set_segment_alignment_;
 
+  // The stream access point for subsegment
+  uint8_t subsegment_start_with_sap_;
+
+  // The stream access point for segment
+  uint8_t start_with_sap_;
+
   // Keeps track of segment start times of Representations.
   // For static MPD, this will not be cleared, all the segment start times are
   // stored in this. This should not out-of-memory for a reasonable length

packager/mpd/base/period.cc

@@ -273,6 +273,26 @@ bool Period::SetNewAdaptationSetAttributes(
     // In practice it doesn't really make sense to adapt between text tracks.
     new_adaptation_set->ForceSetSegmentAlignment(true);
   }
+
+  if (mpd_options_.dash_profile == DashProfile::kLive) {
+    // According to Dolby Digital Plus and Dolby AC-4 specs, startWithSAP
+    // attribute shall be set to 1. Other audio codecs do not have
+    // requirement on this value, we assume them to be 1 as well.
+    if (GetBaseCodec(media_info) == "mp4a" ||
+        GetBaseCodec(media_info) == "ac-3" ||
+        GetBaseCodec(media_info) == "ec-3" ||
+        GetBaseCodec(media_info) == "ac-4") {
+      new_adaptation_set->ForceStartwithSAP(1);
+    }
+  }
+  else if (mpd_options_.dash_profile == DashProfile::kOnDemand) {
+    if (GetBaseCodec(media_info) == "mp4a" ||
+        GetBaseCodec(media_info) == "ac-3" ||
+        GetBaseCodec(media_info) == "ec-3" ||
+        GetBaseCodec(media_info) == "ac-4") {
+      new_adaptation_set->ForceSubsegmentStartswithSAP(1);
+    }
+  }
   return true;
 }