demux: adaptative: don't use first segment for live streams

segment could become unavailable before we could fully download it.

modules/demux/adaptative/SegmentTracker.cpp

@@ -50,6 +50,7 @@ SegmentTrackerEvent::SegmentTrackerEvent(const StreamFormat *fmt)
 
 SegmentTracker::SegmentTracker(AbstractAdaptationLogic *logic_, BaseAdaptationSet *adaptSet)
 {
+    first = true;
     count = 0;
     initializing = true;
     index_sent = false;
@@ -127,6 +128,11 @@ SegmentChunk * SegmentTracker::getNextChunk(bool switch_allowed, HTTPConnectionM
         /* Convert our segment number */
         count = rep->translateSegmentNumber(count, prevRep);
     }
+    else if(first && rep->getPlaylist()->isLive())
+    {
+        count = rep->getLiveStartSegmentNumber(count);
+        first = false;
+    }
 
     if(!rep->consistentSegmentNumber())
         curRepresentation->pruneBySegmentNumber(count);

modules/demux/adaptative/SegmentTracker.hpp

@@ -106,6 +106,7 @@ namespace adaptative
 
         private:
             void notify(const SegmentTrackerEvent &);
+            bool first;
             bool initializing;
             bool index_sent;
             bool init_sent;

modules/demux/adaptative/playlist/SegmentInformation.cpp

@@ -155,6 +155,49 @@ std::size_t SegmentInformation::getAllSegments(std::vector<ISegment *> &retSegme
     return retSegments.size();
 }
 
+uint64_t SegmentInformation::getLiveStartSegmentNumber(uint64_t def) const
+{
+    if( mediaSegmentTemplate )
+    {
+        SegmentTimeline *timeline = mediaSegmentTemplate->segmentTimeline.Get();
+        if(timeline)
+        {
+            const uint64_t start = timeline->minElementNumber();
+            const uint64_t end = timeline->maxElementNumber();
+            if(end > 2 && (end - start >= 2))
+                return end - 2;
+            else
+                return start;
+        }
+        return mediaSegmentTemplate->startNumber.Get();
+    }
+    else if ( segmentList && !segmentList->getSegments().empty() )
+    {
+        const std::vector<ISegment *> list = segmentList->getSegments();
+        if(list.size() > 3)
+            return list.at(list.size() - 3)->getSequenceNumber();
+        else if(!list.empty())
+            return list.front()->getSequenceNumber();
+        else
+            return segmentList->getStartIndex();
+    }
+    else if( segmentBase )
+    {
+        const std::vector<ISegment *> list = segmentBase->subSegments();
+        if(list.size() > 3)
+            return list.at(list.size() - 3)->getSequenceNumber();
+        else if(!list.empty())
+            return list.front()->getSequenceNumber();
+        else
+            return segmentBase->getSequenceNumber();
+    }
+
+    if(parent)
+        return parent->getLiveStartSegmentNumber(def);
+    else
+        return def;
+}
+
 /* Returns wanted segment, or next in sequence if not found */
 ISegment * SegmentInformation::getNextSegment(SegmentInfoType type, uint64_t i_pos,
                                               uint64_t *pi_newpos, bool *pb_gap) const

modules/demux/adaptative/playlist/SegmentInformation.hpp

@@ -82,6 +82,7 @@ namespace adaptative
                 ISegment * getNextSegment(SegmentInfoType, uint64_t, uint64_t *, bool *) const;
                 bool getSegmentNumberByTime(mtime_t, uint64_t *) const;
                 mtime_t getPlaybackTimeBySegmentNumber(uint64_t) const;
+                uint64_t getLiveStartSegmentNumber(uint64_t) const;
                 virtual void getDurationsRange(mtime_t *, mtime_t *) const;
                 virtual void mergeWith(SegmentInformation *, mtime_t);
                 virtual void mergeWithTimeline(SegmentTimeline *); /* ! don't use with global merge */