attr/m49605: add inter component prediction for predicting coder

This adoption permits prediction of residuals between components of
the same attribute, coding the residual resulting from this second
prediction.

cfg/octree-predt-ctc-lossless-geom-lossless-attrs.yaml

@@ -43,6 +43,7 @@ categories:
        - positionQuantizationScaleAdjustsDist2: 1
        - dist2: ${seq_dist2}
        - intraLodPredictionEnabled: 1
+       - interComponentPredictionEnabled: 1
 
        ##
        # attribute coding -- reflectance

cfg/octree-predt-ctc-lossless-geom-nearlossless-attrs.yaml

@@ -39,6 +39,7 @@ categories:
      - positionQuantizationScaleAdjustsDist2: 1
      - dist2: ${seq_dist2}
      - intraLodPredictionEnabled: 1
+     - interComponentPredictionEnabled: 1
 
      ##
      # attribute coding -- reflectance

doc/README.options.md

@@ -317,6 +317,10 @@ Neighbouring attribute value difference that enables choice of
 single|multi predictors. Applies to transformType=2 only.
 A value of -1 is replaced by 2**(bitdepth-2).
 
+### `--interComponentPredictionEnabled=0|1`
+Controls the use of an in-loop inter-component prediction of attribute
+residuals.  Applies to `transformType=1` and `attribute=color` only.
+
 ### `--attributeSearchRange=INT-VALUE`
 Range for nearest neighbour search.
 

tmc3/AttributeDecoder.cpp

@@ -403,12 +403,16 @@ AttributeDecoder::decodeColorsPred(
       predictor.predictColor(pointCloud, indexesLOD);
 
     int64_t clipMax = (1 << desc.attr_bitdepth) - 1;
+    int64_t residual0 = 0;
     for (int k = 0; k < 3; ++k) {
       const auto& q = quant[std::min(k, 1)];
       const int64_t residual = divExp2RoundHalfUp(
         q.scale(UIntToInt(values[k])), kFixedPointAttributeShift);
-      const int64_t recon = predictedColor[k] + residual;
+      const int64_t recon = predictedColor[k] + residual + residual0;
       color[k] = uint8_t(PCCClip(recon, int64_t(0), clipMax));
+
+      if (!k && aps.inter_component_prediction_enabled_flag)
+        residual0 = residual;
     }
   }
 }

tmc3/AttributeEncoder.cpp

@@ -699,6 +699,7 @@ AttributeEncoder::encodeColorsPred(
       predictor.predictColor(pointCloud, indexesLOD);
 
     Vec3<uint8_t> reconstructedColor;
+    int64_t residual0 = 0;
     for (int k = 0; k < 3; ++k) {
       const auto& q = quant[std::min(k, 1)];
       int64_t residual = color[k] - predictedColor[k];
@@ -707,6 +708,16 @@ AttributeEncoder::encodeColorsPred(
       int64_t residualR =
         divExp2RoundHalfUp(q.scale(residualQ), kFixedPointAttributeShift);
 
+      if (aps.inter_component_prediction_enabled_flag && k > 0) {
+        residual = residualR - residual0;
+        residualQ = q.quantize(residual << kFixedPointAttributeShift);
+        residualR = residual0
+          + divExp2RoundHalfUp(q.scale(residualQ), kFixedPointAttributeShift);
+      }
+
+      if (k == 0)
+        residual0 = residualR;
+
       values[k] = uint32_t(IntToUInt(long(residualQ)));
 
       int64_t recon = predictedColor[k] + residualR;

tmc3/TMC3.cpp

@@ -584,6 +584,11 @@ ParseParameters(int argc, char* argv[], Parameters& params)
     params_attr.aps.intra_lod_prediction_enabled_flag, false,
     "Permits referring to points in same LoD")
 
+  ("interComponentPredictionEnabled",
+    params_attr.aps.inter_component_prediction_enabled_flag, false,
+    "Use primary attribute component to predict values of subsequent "
+    "components")
+
   ("aps_scalable_enable_flag",
     params_attr.aps.scalable_lifting_enabled_flag, false,
     "Enable scalable attritube coding")

tmc3/hls.h

@@ -281,6 +281,7 @@ struct AttributeParameterSet {
   int search_range;
   Vec3<double> lod_neigh_bias;
   bool intra_lod_prediction_enabled_flag;
+  bool inter_component_prediction_enabled_flag;
 
   // NB: derived from num_detail_levels_minus1
   int num_detail_levels;

tmc3/io_hls.cpp

@@ -299,6 +299,7 @@ write(const AttributeParameterSet& aps)
   if (aps.attr_encoding == AttributeEncoding::kPredictingTransform) {
     bs.writeUe(aps.adaptive_prediction_threshold);
     bs.write(aps.intra_lod_prediction_enabled_flag);
+    bs.write(aps.inter_component_prediction_enabled_flag);
     bs.writeUe(aps.max_num_direct_predictors);
   }
 
@@ -359,6 +360,7 @@ parseAps(const PayloadBuffer& buf)
   if (aps.attr_encoding == AttributeEncoding::kPredictingTransform) {
     bs.readUe(&aps.adaptive_prediction_threshold);
     bs.read(&aps.intra_lod_prediction_enabled_flag);
+    bs.read(&aps.inter_component_prediction_enabled_flag);
     bs.readUe(&aps.max_num_direct_predictors);
   }