hls/m43953: signal geom_slice_id / attr_geom_slice_id

 - signal geom_slice_id / attr_geom_slice_id in geometry / attribute
   header.

 - attr_geom_slice_id set to current geom_slice_id to maintain
   relationship between attribute and geometry.

 - increment geom_slice_id after each round of encoding.

 - decoder checks that the attribute payload's attr_geom_slice_id
   corresponds to the most recently decoded geometry payload.

tmc3/PCCTMC3Decoder.h

@@ -87,6 +87,9 @@ public:
   //==========================================================================
 
 private:
+  // Current identifier of payloads with the same geometry
+  int _sliceId;
+
   PCCVector3D minPositions;
 
   // The point cloud currently being decoded

tmc3/PCCTMC3Encoder.h

@@ -98,6 +98,9 @@ private:
   const SequenceParameterSet* _sps;
   const GeometryParameterSet* _gps;
   std::vector<const AttributeParameterSet*> _aps;
+
+  // Current identifier of payloads with the same geometry
+  int _sliceId;
 };
 
 //============================================================================

tmc3/decoder.cpp

@@ -162,6 +162,7 @@ PCCTMC3Decoder3::decodeGeometryBrick(const PayloadBuffer& buf)
 
   int gbhSize;
   GeometryBrickHeader gbh = parseGbh(*_gps, buf, &gbhSize);
+  _sliceId = gbh.geom_slice_id;
   minPositions.x() = gbh.geomBoxOrigin.x();
   minPositions.y() = gbh.geomBoxOrigin.y();
   minPositions.z() = gbh.geomBoxOrigin.z();
@@ -203,8 +204,11 @@ PCCTMC3Decoder3::decodeAttributeBrick(const PayloadBuffer& buf)
   assert(_sps);
   assert(_gps);
 
-  // todo(df): validate that sps activation is not changed via the APS
+  // verify that this corresponds to the correct geometry slice
   AttributeBrickHeader abh = parseAbh(buf, nullptr);
+  assert(abh.attr_geom_slice_id == _sliceId);
+
+  // todo(df): validate that sps activation is not changed via the APS
   const auto it_attr_aps = _apss.find(abh.attr_attr_parameter_set_id);
 
   assert(it_attr_aps != _apss.cend());

tmc3/encoder.cpp

@@ -123,13 +123,15 @@ PCCTMC3Encoder3::compress(
 
   // geometry compression consists of the following stages:
   //  - prefilter/quantize geometry (non-normative)
-  //  - encode geometry
+  //  - encode geometry (single slice, id = 0)
   //  - recolour
 
   // The quantization process will determine the bounding box
   quantization(inputPointCloud);
 
   // geometry encoding
+  _sliceId = 0;
+
   if (1) {
     PayloadBuffer payload(PayloadType::kGeometryBrick);
 
@@ -189,7 +191,7 @@ PCCTMC3Encoder3::compress(
     AttributeBrickHeader abh;
     abh.attr_attr_parameter_set_id = attr_aps.aps_attr_parameter_set_id;
     abh.attr_sps_attr_idx = attrIdx;
-    abh.attr_geom_brick_id = 0;
+    abh.attr_geom_slice_id = _sliceId;
     write(abh, &payload);
 
     AttributeEncoder attrEncoder;
@@ -210,6 +212,10 @@ PCCTMC3Encoder3::compress(
     outputFn(payload);
   }
 
+  // prevent re-use of this sliceId:  the next slice (geometry + attributes)
+  // should be distinguishable from the current slice.
+  _sliceId++;
+
   reconstructedPointCloud(reconstructedCloud);
 
   return 0;
@@ -232,6 +238,7 @@ PCCTMC3Encoder3::encodeGeometryBrick(PayloadBuffer* buf)
   gbh.geomBoxOrigin.x() = int(minPositions.x());
   gbh.geomBoxOrigin.y() = int(minPositions.y());
   gbh.geomBoxOrigin.z() = int(minPositions.z());
+  gbh.geom_slice_id = _sliceId;
   gbh.geom_box_log2_scale = 0;
   gbh.geom_max_node_size_log2 = nodeSizeLog2;
   gbh.geom_num_points = int(pointCloud.getPointCount());

tmc3/hls.h

@@ -205,7 +205,7 @@ struct GeometryParameterSet {
 
 struct GeometryBrickHeader {
   int geom_geom_parameter_set_id;
-  int geom_brick_id;  // todo(df): v2
+  int geom_slice_id;
 
   // derived from geom_box_origin_{x,y,z} * (1 << geom_box_log2_scale)
   PCCVector3<int> geomBoxOrigin;
@@ -249,7 +249,7 @@ struct AttributeParameterSet {
 struct AttributeBrickHeader {
   int attr_sps_attr_idx;
   int attr_attr_parameter_set_id;
-  int attr_geom_brick_id;
+  int attr_geom_slice_id;
 };
 
 //============================================================================

tmc3/io_hls.cpp

@@ -343,7 +343,7 @@ write(
   auto bs = makeBitWriter(std::back_inserter(*buf));
 
   bs.writeUe(gbh.geom_geom_parameter_set_id);
-  //bs.writeUe(gbh.geom_brick_id);
+  bs.writeUe(gbh.geom_slice_id);
 
   if (gps.geom_box_present_flag) {
     int geom_box_origin_x = gbh.geomBoxOrigin.x() >> gbh.geom_box_log2_scale;
@@ -372,7 +372,7 @@ parseGbh(
   auto bs = makeBitReader(buf.begin(), buf.end());
 
   bs.readUe(&gbh.geom_geom_parameter_set_id);
-  //bs.readUe(&gbh.geom_brick_id);
+  bs.readUe(&gbh.geom_slice_id);
 
   if (gps.geom_box_present_flag) {
     bs.readUe(&gbh.geom_box_log2_scale);
@@ -408,7 +408,7 @@ write(const AttributeBrickHeader& abh, PayloadBuffer* buf)
 
   bs.writeUe(abh.attr_attr_parameter_set_id);
   bs.writeUe(abh.attr_sps_attr_idx);
-  //bs.writeUe(abh.attr_geom_brick_id);
+  bs.writeUe(abh.attr_geom_slice_id);
 
   bs.byteAlign();
 }
@@ -424,7 +424,7 @@ parseAbh(const PayloadBuffer& buf, int* bytesRead)
 
   bs.readUe(&abh.attr_attr_parameter_set_id);
   bs.readUe(&abh.attr_sps_attr_idx);
-  //bs.readUe(&abh.attr_geom_brick_id);
+  bs.readUe(&abh.attr_geom_slice_id);
 
   bs.byteAlign();