entropy: introduce o3dgc::Adaptive_Bit_Model_Fast abstraction

This commit provides an encapsulated interface to the fast update option
of the o3dgc context models with a statistic halving period of 128
symbols (max_count).

dependencies/arithmetic-coding/inc/ArithmeticCodec.h

@@ -135,6 +135,25 @@ private: //  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
     friend class Arithmetic_Codec;
 };
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// adaptive model for binary data, probability update each bin
+
+class Adaptive_Bit_Model_Fast : public Adaptive_Bit_Model
+    {
+public:
+    Adaptive_Bit_Model_Fast(void)
+    : Adaptive_Bit_Model()
+    {
+        reset();
+    }
+
+    // reset to equiprobable model
+    void reset(void)
+    {
+        Adaptive_Bit_Model::reset(true);
+    }
+};
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
 class Adaptive_Data_Model // adaptive model for binary data

tmc3/geometry_octree.cpp

@@ -196,28 +196,6 @@ updateGeometryNeighState(
   }
 }
 
-//---------------------------------------------------------------------------
-
-CtxModelOctreeOccupancy::CtxModelOctreeOccupancy()
-{
-  for (auto& ctx : b0)
-    ctx.reset(true);
-  for (auto& ctx : b1)
-    ctx.reset(true);
-  for (auto& ctx : b2)
-    ctx.reset(true);
-  for (auto& ctx : b3)
-    ctx.reset(true);
-  for (auto& ctx : b4)
-    ctx.reset(true);
-  for (auto& ctx : b5)
-    ctx.reset(true);
-  for (auto& ctx : b6)
-    ctx.reset(true);
-  for (auto& ctx : b7)
-    ctx.reset(true);
-}
-
 //============================================================================
 
 }  // namespace pcc

tmc3/geometry_octree.h

@@ -130,16 +130,14 @@ isDirectModeEligible(
 //---------------------------------------------------------------------------
 
 struct CtxModelOctreeOccupancy {
-  o3dgc::Adaptive_Bit_Model b0[10];
-  o3dgc::Adaptive_Bit_Model b1[2 * 10];
-  o3dgc::Adaptive_Bit_Model b2[4 * 10];
-  o3dgc::Adaptive_Bit_Model b3[8 * 10];
-  o3dgc::Adaptive_Bit_Model b4[75];
-  o3dgc::Adaptive_Bit_Model b5[112];
-  o3dgc::Adaptive_Bit_Model b6[117];
-  o3dgc::Adaptive_Bit_Model b7[127];
-
-  CtxModelOctreeOccupancy();
+  o3dgc::Adaptive_Bit_Model_Fast b0[10];
+  o3dgc::Adaptive_Bit_Model_Fast b1[2 * 10];
+  o3dgc::Adaptive_Bit_Model_Fast b2[4 * 10];
+  o3dgc::Adaptive_Bit_Model_Fast b3[8 * 10];
+  o3dgc::Adaptive_Bit_Model_Fast b4[75];
+  o3dgc::Adaptive_Bit_Model_Fast b5[112];
+  o3dgc::Adaptive_Bit_Model_Fast b6[117];
+  o3dgc::Adaptive_Bit_Model_Fast b7[127];
 
   o3dgc::Adaptive_Bit_Model* operator[](int bit_pos)
   {