rdd9: set index segment byte counts equal if possible

RDD 9 2013, section B.6 states that the Index Byte Count of the last
Index Table Segment should equal the value of the other Index Table
Segments even when the Index Duration of the last Index Table Segment is
shorter.

include/bmx/rdd9_mxf/RDD9IndexTable.h

@@ -200,6 +200,7 @@ class RDD9IndexTable
     std::vector<RDD9IndexTableSegment*> mIndexSegments;
     int64_t mDuration;
     int64_t mStreamOffset;
+    int64_t mFirstIndexSegmentCount;
 
     std::vector<RDD9IndexTableSegment*> mWrittenIndexSegments;
 };

src/rdd9_mxf/RDD9IndexTable.cpp

@@ -237,6 +237,7 @@ RDD9IndexTable::RDD9IndexTable(uint32_t index_sid, uint32_t body_sid, Rational e
     mIndexEntrySize = 0;
     mDuration = 0;
     mStreamOffset = 0;
+    mFirstIndexSegmentCount = 0;
 }
 
 RDD9IndexTable::~RDD9IndexTable()
@@ -479,6 +480,8 @@ void RDD9IndexTable::WriteVBESegments(File *mxf_file, Partition *partition, vect
 {
     size_t i;
     for (i = 0; i < segments.size(); i++) {
+        int64_t segment_start_file_pos = mxf_file->tell();
+
         IndexTableSegment *segment = segments[i]->GetSegment();
         ByteArray *entries = segments[i]->GetEntries();
 
@@ -498,7 +501,20 @@ void RDD9IndexTable::WriteVBESegments(File *mxf_file, Partition *partition, vect
         segment->writeIndexEntryArrayHeader(mxf_file, mSliceCount, 0, (uint32_t)segment->getIndexDuration());
         mxf_file->write(entries->GetBytes(), entries->GetSize());
 
-        partition->fillToKag(mxf_file);
+        // The index byte count for all index segments should all be equal.
+        // The index durations for all index segments, except the last, should all be equal.
+        // The last index segment may have a shorter index duration and the code below should
+        // ensure that it has the same index byte count (as the first index segment).
+        if (mFirstIndexSegmentCount == 0) {
+            mFirstIndexSegmentCount = mxf_file->tell() - segment_start_file_pos;
+            partition->fillToKag(mxf_file);
+        } else {
+            int64_t current_count = mxf_file->tell() - segment_start_file_pos;
+            if (current_count < mFirstIndexSegmentCount)
+                partition->allocateSpaceToKag(mxf_file, mFirstIndexSegmentCount - current_count);
+            else
+                partition->fillToKag(mxf_file);
+        }
     }
 }