Unit test for transform set indices

src/ImageSharp/Formats/Heif/Av1/Entropy/Av1SymbolContextHelper.cs

@@ -19,6 +19,15 @@ internal static class Av1SymbolContextHelper
         [7, 8, 9, 12, 10, 11, 13, 14, 15, 0, 1, 2, 3, 4, 5, 6],
     ];
 
+    public static readonly int[][] ExtendedTransformIndicesInverse = [
+        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
+        [9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
+        [9, 0, 3, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
+        [9, 0, 10, 11, 3, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0],
+        [9, 10, 11, 0, 1, 2, 4, 5, 3, 6, 7, 8, 0, 0, 0, 0],
+        [9, 10, 11, 12, 13, 14, 15, 0, 1, 2, 4, 5, 3, 6, 7, 8],
+    ];
+
     public static readonly int[] EndOfBlockOffsetBits = [0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
     public static readonly int[] EndOfBlockGroupStart = [0, 1, 2, 3, 5, 9, 17, 33, 65, 129, 257, 513];
     private static readonly int[] TransformCountInSet = [1, 2, 5, 7, 12, 16];
@@ -216,6 +225,9 @@ internal static class Av1SymbolContextHelper
         return Av1NzMap.GetNzMapContextFromStats(stats, levels, position, transformSize, transformClass);
     }
 
+    /// <summary>
+    /// SVT: get_ext_tx_set_type
+    /// </summary>
     internal static Av1TransformSetType GetExtendedTransformSetType(Av1TransformSize transformSize, bool useReducedSet)
     {
         Av1TransformSize squareUpSize = transformSize.GetSquareUpSize();
@@ -285,52 +297,14 @@ internal static class Av1SymbolContextHelper
     }
 
     /// <summary>
-    /// SVT: get_ext_tx_set_type
+    /// SVT: get_ext_tx_types
     /// </summary>
-    internal static Av1TransformSetType GetExtendedTransformSetType(Av1TransformSize transformSize, bool isInter, bool useReducedTransformSet)
+    internal static int GetExtendedTransformTypeCount(Av1TransformSetType setType) => TransformCountInSet[(int)setType];
-    {
-        Av1TransformSize transformSizeSquareUp = transformSize.GetSquareUpSize();
-
-        if (transformSizeSquareUp > Av1TransformSize.Size32x32)
-        {
-            return Av1TransformSetType.DctOnly;
-        }
-
-        if (transformSizeSquareUp == Av1TransformSize.Size32x32)
-        {
-            return isInter ? Av1TransformSetType.DctIdentity : Av1TransformSetType.DctOnly;
-        }
-
-        if (useReducedTransformSet)
-        {
-            return isInter ? Av1TransformSetType.DctIdentity : Av1TransformSetType.Dtt4Identity;
-        }
-
-        Av1TransformSize transformSizeSquare = transformSize.GetSquareSize();
-        if (isInter)
-        {
-            return transformSizeSquare == Av1TransformSize.Size16x16 ? Av1TransformSetType.Dtt9Identity1dDct : Av1TransformSetType.All16;
-        }
-        else
-        {
-            return transformSizeSquare == Av1TransformSize.Size16x16 ? Av1TransformSetType.Dtt4Identity : Av1TransformSetType.Dtt4Identity1dDct;
-        }
-    }
-
-    internal static int GetExtendedTransformTypeCount(Av1TransformSize transformSize, bool useReducedTransformSet)
-    {
-        int setType = (int)GetExtendedTransformSetType(transformSize, useReducedTransformSet);
-        return TransformCountInSet[setType];
-    }
 
     /// <summary>
     /// SVT: get_ext_tx_set
     /// </summary>
-    internal static int GetExtendedTransformSet(Av1TransformSize transformSize, bool useReducedTransformSet)
+    internal static int GetExtendedTransformSet(Av1TransformSetType setType) => ExtendedTransformSetToIndex[(int)setType];
-    {
-        int setType = (int)GetExtendedTransformSetType(transformSize, useReducedTransformSet);
-        return ExtendedTransformSetToIndex[setType];
-    }
 
     /// <summary>
     /// SVT: set_dc_sign

src/ImageSharp/Formats/Heif/Av1/Entropy/Av1SymbolDecoder.cs

@@ -9,15 +9,6 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Entropy;
 
 internal ref struct Av1SymbolDecoder
 {
-    private static readonly int[][] ExtendedTransformIndicesInverse = [
-        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
-        [9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
-        [9, 0, 3, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
-        [9, 0, 10, 11, 3, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0],
-        [9, 10, 11, 0, 1, 2, 4, 5, 3, 6, 7, 8, 0, 0, 0, 0],
-        [9, 10, 11, 12, 13, 14, 15, 0, 1, 2, 4, 5, 3, 6, 7, 8],
-    ];
-
     private static readonly int[] IntraModeContext = [0, 1, 2, 3, 4, 4, 4, 4, 3, 0, 1, 2, 0];
     private static readonly int[] AlphaVContexts = [-1, 0, 3, -1, 1, 4, -1, 2, 5];
 
@@ -199,6 +190,9 @@ internal ref struct Av1SymbolDecoder
         return transformSize;
     }
 
+    /// <summary>
+    /// SVT: parse_transform_type
+    /// </summary>
     public Av1TransformType ReadTransformType(
         Av1TransformSize transformSize,
         bool useReducedTransformSet,
@@ -216,12 +210,17 @@ internal ref struct Av1SymbolDecoder
             return;
         */
 
+        if (baseQIndex == 0)
+        {
+            return transformType;
+        }
+
         // Ignoring INTER blocks here, as these should not end up here.
         // int inter_block = is_inter_block_dec(mbmi);
         Av1TransformSetType transformSetType = Av1SymbolContextHelper.GetExtendedTransformSetType(transformSize, useReducedTransformSet);
-        if (Av1SymbolContextHelper.GetExtendedTransformTypeCount(transformSize, useReducedTransformSet) > 1 && baseQIndex > 0)
+        if (Av1SymbolContextHelper.GetExtendedTransformTypeCount(transformSetType) > 1 && baseQIndex > 0)
         {
-            int extendedSet = Av1SymbolContextHelper.GetExtendedTransformSet(transformSize, useReducedTransformSet);
+            int extendedSet = Av1SymbolContextHelper.GetExtendedTransformSet(transformSetType);
 
             // eset == 0 should correspond to a set with only DCT_DCT and
             // there is no need to read the tx_type
@@ -233,7 +232,7 @@ internal ref struct Av1SymbolDecoder
                 : intraDirection;
             ref Av1SymbolReader r = ref this.reader;
             int symbol = r.ReadSymbol(this.intraExtendedTransform[extendedSet][(int)squareTransformSize][(int)intraMode]);
-            transformType = (Av1TransformType)ExtendedTransformIndicesInverse[(int)transformSetType][symbol];
+            transformType = (Av1TransformType)Av1SymbolContextHelper.ExtendedTransformIndicesInverse[(int)transformSetType][symbol];
         }
 
         return transformType;
@@ -311,7 +310,7 @@ internal ref struct Av1SymbolDecoder
 
         if (plane == (int)Av1Plane.Y)
         {
-            this.ReadTransformType(transformSize, useReducedTransformSet, modeInfo.FilterIntraModeInfo.UseFilterIntra, this.baseQIndex, modeInfo.FilterIntraModeInfo.Mode, modeInfo.YMode);
+            transformInfo.Type = this.ReadTransformType(transformSize, useReducedTransformSet, modeInfo.FilterIntraModeInfo.UseFilterIntra, this.baseQIndex, modeInfo.FilterIntraModeInfo.Mode, modeInfo.YMode);
         }
 
         transformInfo.Type = ComputeTransformType(planeType, modeInfo, isLossless, transformSize, transformInfo, useReducedTransformSet);

src/ImageSharp/Formats/Heif/Av1/Entropy/Av1SymbolEncoder.cs

@@ -11,15 +11,6 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Entropy;
 
 internal class Av1SymbolEncoder : IDisposable
 {
-    private static readonly int[][] ExtendedTransformIndices = [
-        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
-        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
-        [1, 3, 4, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
-        [1, 5, 6, 4, 0, 0, 0, 0, 0, 0, 2, 3, 0, 0, 0, 0],
-        [3, 4, 5, 8, 6, 7, 9, 10, 11, 0, 1, 2, 0, 0, 0, 0],
-        [7, 8, 9, 12, 10, 11, 13, 14, 15, 0, 1, 2, 3, 4, 5, 6],
-    ];
-
     private readonly Av1Distribution tileIntraBlockCopy = Av1DefaultDistributions.IntraBlockCopy;
     private readonly Av1Distribution[] tilePartitionTypes = Av1DefaultDistributions.PartitionTypes;
     private readonly Av1Distribution[][] keyFrameYMode = Av1DefaultDistributions.KeyFrameYMode;
@@ -289,35 +280,35 @@ internal class Av1SymbolEncoder : IDisposable
         Av1PredictionMode intraDirection)
     {
         // bool isInter = mbmi->block_mi.use_intrabc || is_inter_mode(mbmi->block_mi.mode);
-        ref Av1SymbolWriter w = ref this.writer;
+        Av1TransformSetType transformSetType = Av1SymbolContextHelper.GetExtendedTransformSetType(transformSize, useReducedTransformSet);
-        if (Av1SymbolContextHelper.GetExtendedTransformTypeCount(transformSize, useReducedTransformSet) > 1 && baseQIndex > 0)
+        if (Av1SymbolContextHelper.GetExtendedTransformTypeCount(transformSetType) > 1 && baseQIndex > 0)
         {
             Av1TransformSize squareTransformSize = transformSize.GetSquareSize();
             Guard.MustBeLessThanOrEqualTo((int)squareTransformSize, Av1Constants.ExtendedTransformCount, nameof(squareTransformSize));
 
-            Av1TransformSetType transformSetType = Av1SymbolContextHelper.GetExtendedTransformSetType(transformSize, useReducedTransformSet);
+            int extendedSet = Av1SymbolContextHelper.GetExtendedTransformSet(transformSetType);
-            int extendedSet = Av1SymbolContextHelper.GetExtendedTransformSet(transformSize, useReducedTransformSet);
 
             // eset == 0 should correspond to a set with only DCT_DCT and there
             // is no need to send the tx_type
             Guard.MustBeGreaterThan(extendedSet, 0, nameof(extendedSet));
 
             // assert(av1_ext_tx_used[tx_set_type][transformType]);
-            Av1PredictionMode intraMode;
+            Av1PredictionMode intraDirectionContext;
             if (filterIntraMode != Av1FilterIntraMode.AllFilterIntraModes)
             {
-                intraMode = filterIntraMode.ToIntraDirection();
+                intraDirectionContext = filterIntraMode.ToIntraDirection();
             }
             else
             {
-                intraMode = intraDirection;
+                intraDirectionContext = intraDirection;
             }
 
-            Guard.MustBeLessThan((int)intraMode, 13, nameof(intraMode));
+            Guard.MustBeLessThan((int)intraDirectionContext, 13, nameof(intraDirectionContext));
             Guard.MustBeLessThan((int)squareTransformSize, 4, nameof(squareTransformSize));
+            ref Av1SymbolWriter w = ref this.writer;
             w.WriteSymbol(
-                ExtendedTransformIndices[(int)transformSetType][(int)transformType],
+                Av1SymbolContextHelper.ExtendedTransformIndices[(int)transformSetType][(int)transformType],
-                this.intraExtendedTransform[extendedSet][(int)squareTransformSize][(int)intraMode]);
+                this.intraExtendedTransform[extendedSet][(int)squareTransformSize][(int)intraDirectionContext]);
         }
     }
 

tests/ImageSharp.Tests/Formats/Heif/Av1/Av1SymbolContextTests.cs

@@ -1,9 +1,11 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using Microsoft.Diagnostics.Symbols;
 using SixLabors.ImageSharp.Formats.Heif.Av1;
 using SixLabors.ImageSharp.Formats.Heif.Av1.Entropy;
 using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
+using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
 
 namespace SixLabors.ImageSharp.Tests.Formats.Heif.Av1;
 
@@ -11,8 +13,8 @@ namespace SixLabors.ImageSharp.Tests.Formats.Heif.Av1;
 public class Av1SymbolContextTests
 {
     [Theory]
-    [MemberData(nameof(GetCombinations))]
+    [MemberData(nameof(GetLowLevelContextEndOfBlockData))]
-    public void TestAccuracy(int width, int height, int index)
+    public void TestLowLevelContextEndOfBlockAccuracy(int width, int height, int index)
     {
         // Arrange
         Size size = new(width, height);
@@ -28,7 +30,22 @@ public class Av1SymbolContextTests
         Assert.Equal(expectedContext, actualContext);
     }
 
-    public static TheoryData<int, int, int> GetCombinations()
+    [Theory]
+    [MemberData(nameof(GetExtendedTransformIndicesData))]
+    public void RoundTripExtendedTransformIndices(int setType, int index)
+    {
+        // Arrange
+        Av1TransformSetType transformSetType = (Av1TransformSetType)setType;
+
+        // Act
+        int transformType = Av1SymbolContextHelper.ExtendedTransformIndicesInverse[(int)transformSetType][index];
+        int actualIndex = Av1SymbolContextHelper.ExtendedTransformIndices[(int)transformSetType][transformType];
+
+        // Assert
+        Assert.Equal(actualIndex, index);
+    }
+
+    public static TheoryData<int, int, int> GetLowLevelContextEndOfBlockData()
     {
         TheoryData<int, int, int> result = [];
         for (int y = 1; y < 6; y++)
@@ -46,6 +63,21 @@ public class Av1SymbolContextTests
         return result;
     }
 
+    public static TheoryData<int, int> GetExtendedTransformIndicesData()
+    {
+        TheoryData<int, int> result = [];
+        for (Av1TransformSetType setType = Av1TransformSetType.DctOnly; setType <= Av1TransformSetType.All16; setType++)
+        {
+            int count = Av1SymbolContextHelper.GetExtendedTransformTypeCount(setType);
+            for (int type = 1; type < count; type++)
+            {
+                result.Add((int)setType, type);
+            }
+        }
+
+        return result;
+    }
+
     /// <summary>
     /// SVT: get_lower_levels_ctx_eob
     /// </summary>