[FragmentedSampleReader] Rework method to find the sample index

Author: CastagnaIT

src/samplereader/FragmentedSampleReader.cpp

@@ -28,6 +28,8 @@
 
 #include <bento4/Ap4SencAtom.h>
 
+#include <limits>
+
 using namespace UTILS;
 
 namespace
@@ -838,22 +840,57 @@ AP4_Result CLinearReader::SeekSample(AP4_UI32 track_id,
 
   AP4_Result result;
 
-  if (!tracker->m_SampleTable && AP4_FAILED(result = Advance()))
-    return result;
+  if (!tracker->m_SampleTable)
+  {
+    LOG::LogF(LOGWARNING, "NO SAMPLETABLE Advance");
+    if (AP4_FAILED(result = Advance()))
+      return result;
+  }
+
+  //! @todo: remove our custom GetNearestSyncSampleIndex from Bento4
+  const AP4_Cardinal samplesCount = tracker->m_SampleTable->GetSampleCount();
+  constexpr AP4_Cardinal indexNoValue = std::numeric_limits<AP4_Cardinal>::max();
 
-  while (AP4_FAILED(result = tracker->m_SampleTable->GetSampleIndexForTimeStamp(ts, sample_index)))
+  AP4_UI64 bestSyncDiff = std::numeric_limits<AP4_UI64>::max();
+  AP4_Cardinal syncIndex{indexNoValue};
+  AP4_Cardinal sampleIndex{0};
+  // Try find a sample sync closer to the target ts
+  // or fallback to the closer sample without sync
+  for (AP4_Cardinal index{0}; index < samplesCount; ++index)
   {
-    if (result == AP4_ERROR_NOT_ENOUGH_DATA)
-    {
-      tracker->m_NextSampleIndex = tracker->m_SampleTable->GetSampleCount();
-      if (AP4_FAILED(result = Advance()))
-        return result;
+    AP4_Sample sample;
+    if (AP4_FAILED(tracker->m_SampleTable->GetSample(index, sample)))
       continue;
+
+    LOG::LogF(LOGWARNING, "sample CTS %llu -- ts %llu -- is sync: %i", sample.GetCts(), ts,
+              sample.IsSync());
+
+    const AP4_UI64 cts = sample.GetCts();
+    if (sample.IsSync())
+    {
+      const AP4_UI64 diff = (cts > ts) ? (cts - ts) : (ts - cts);
+      // choose the sample sync with the smallest difference to ts
+      // preferring if available a ts less than or equal to the target ts
+      if (diff < bestSyncDiff || (diff == bestSyncDiff && cts <= ts))
+      {
+        bestSyncDiff = diff;
+        syncIndex = index;
+      }
     }
-    return result;
+    // Find a sample (without sync) closer to the target ts
+    if (cts <= ts)
+      sampleIndex = index;
   }
 
-  sample_index = tracker->m_SampleTable->GetNearestSyncSampleIndex(sample_index, preceedingSync);
+  if (syncIndex == indexNoValue)
+  {
+    LOG::LogF(LOGWARNING, "Sync sample NOT FOUND, fallback to nearest ts");
+    sample_index = sampleIndex;
+  }
+  else
+    sample_index = syncIndex;
+  LOG::LogF(LOGWARNING, "sample_index %u", sample_index);
+
   //we have reached the end -> go for the first sample of the next segment
   if (sample_index == tracker->m_SampleTable->GetSampleCount())
   {
@@ -863,7 +900,7 @@ AP4_Result CLinearReader::SeekSample(AP4_UI32 track_id,
     // Temporarily set m_SampleTableIsOwned to false to prevent "Advance" method
     // from deleting the tracker sample table
     tracker->m_SampleTableIsOwned = false;
-
+    LOG::LogF(LOGWARNING, "sample_index END Advance");
     if (AP4_FAILED(result = Advance()))
     {
       tracker->m_SampleTableIsOwned = isOwned;