Introduce Frame buffer class

src/ImageSharp/Formats/Heif/Av1/Tiling/Av1FrameBuffer.cs

@@ -0,0 +1,137 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Heif.Av1.OpenBitstreamUnit;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Symbol;
+
+internal class Av1FrameBuffer
+{
+    // Number of Coefficients in a single ModeInfo 4x4 block of pixels (1 length + 4 x 4).
+    public const int CoefficientCountPerModeInfo = 1 + 16;
+
+    private readonly int[] coefficientsY = [];
+    private readonly int[] coefficientsU = [];
+    private readonly int[] coefficientsV = [];
+    private readonly int modeInfoSizePerSuperblock;
+    private readonly int modeInfoCountPerSuperblock;
+    private readonly int superblockColumnCount;
+    private readonly int superblockRowCount;
+    private readonly int subsamplingFactor;
+    private readonly Av1SuperblockInfo[] superblockInfos;
+    private readonly Av1BlockModeInfo[] modeInfos;
+    private readonly Av1TransformInfo[] transformInfosY;
+    private readonly Av1TransformInfo[] transformInfosUv;
+    private readonly int[] deltaQ;
+    private readonly int cdefStrengthFactorLog2;
+    private readonly int[] cdefStrength;
+    private readonly int deltaLoopFactorLog2 = 2;
+    private readonly int[] deltaLoopFilter;
+
+    public Av1FrameBuffer(ObuSequenceHeader sequenceHeader)
+    {
+        // init_main_frame_ctxt
+        int superblockSizeLog2 = sequenceHeader.SuperBlockSizeLog2;
+        int superblockAlignedWidth = Av1Math.AlignPowerOf2(sequenceHeader.MaxFrameWidth, superblockSizeLog2);
+        int superblockAlignedHeight = Av1Math.AlignPowerOf2(sequenceHeader.MaxFrameHeight, superblockSizeLog2);
+        this.superblockColumnCount = superblockAlignedWidth >> superblockSizeLog2;
+        this.superblockRowCount = superblockAlignedHeight >> superblockSizeLog2;
+        int superblockCount = this.superblockColumnCount * this.superblockRowCount;
+        this.modeInfoSizePerSuperblock = 1 << (superblockSizeLog2 - Av1Constants.ModeInfoSizeLog2);
+        this.modeInfoCountPerSuperblock = this.modeInfoSizePerSuperblock * this.modeInfoSizePerSuperblock;
+        this.superblockInfos = new Av1SuperblockInfo[superblockCount];
+        this.modeInfos = new Av1BlockModeInfo[superblockCount * this.modeInfoCountPerSuperblock];
+        this.transformInfosY = new Av1TransformInfo[superblockCount * this.modeInfoCountPerSuperblock];
+        this.transformInfosUv = new Av1TransformInfo[2 * superblockCount * this.modeInfoCountPerSuperblock];
+        this.coefficientsY = new int[superblockCount * this.modeInfoCountPerSuperblock * CoefficientCountPerModeInfo];
+        bool subX = sequenceHeader.ColorConfig.SubSamplingX;
+        bool subY = sequenceHeader.ColorConfig.SubSamplingY;
+
+        // Factor: 444 => 0, 422 => 1, 420 => 2.
+        this.subsamplingFactor = (subX && subY) ? 2 : (subX && !subY) ? 1 : (!subX && !subY) ? 0 : -1;
+        Guard.IsFalse(this.subsamplingFactor == -1, nameof(this.subsamplingFactor), "Invalid combination of subsampling.");
+        this.coefficientsU = new int[(this.modeInfoCountPerSuperblock * CoefficientCountPerModeInfo) >> this.subsamplingFactor];
+        this.coefficientsV = new int[(this.modeInfoCountPerSuperblock * CoefficientCountPerModeInfo) >> this.subsamplingFactor];
+        this.deltaQ = new int[superblockCount];
+
+        // Superblock size: 128x128 has sizelog2 = 7, 64x64 = 6. Factor should be 128x128 => 4 and 64x64 => 1.
+        this.cdefStrengthFactorLog2 = (superblockSizeLog2 - 6) << 2;
+        this.cdefStrength = new int[superblockCount << this.cdefStrengthFactorLog2];
+        Array.Fill(this.cdefStrength, -1);
+        this.deltaLoopFilter = new int[superblockCount << this.deltaLoopFactorLog2];
+    }
+
+    public Av1SuperblockInfo GetSuperblock(Point index)
+    {
+        Span<Av1SuperblockInfo> span = this.superblockInfos;
+        int i = (index.Y * this.superblockColumnCount) + index.X;
+        return span[i];
+    }
+
+    public Av1BlockModeInfo GetModeInfo(Point superblockIndex, Point modeInfoIndex)
+    {
+        Span<Av1BlockModeInfo> span = this.modeInfos;
+        int baseIndex = ((superblockIndex.Y * this.superblockColumnCount) + superblockIndex.X) * this.modeInfoCountPerSuperblock;
+        int offset = (modeInfoIndex.Y * this.modeInfoSizePerSuperblock) + modeInfoIndex.X;
+        return span[baseIndex + offset];
+    }
+
+    public Av1TransformInfo GetTransformY(Point index)
+    {
+        Span<Av1TransformInfo> span = this.transformInfosY;
+        int i = (index.Y * this.superblockColumnCount) + index.X;
+        return span[i * this.modeInfoCountPerSuperblock];
+    }
+
+    public void GetTransformUv(Point index, out Av1TransformInfo transformU, out Av1TransformInfo transformV)
+    {
+        Span<Av1TransformInfo> span = this.transformInfosUv;
+        int i = 2 * ((index.Y * this.superblockColumnCount) + index.X) * this.modeInfoCountPerSuperblock;
+        transformU = span[i];
+        transformV = span[i + 1];
+    }
+
+    public Span<int> GetCoefficientsY(Point index)
+    {
+        Span<int> span = this.coefficientsY;
+        int i = ((index.Y * this.modeInfoCountPerSuperblock) + index.X) * CoefficientCountPerModeInfo;
+        return span.Slice(i, CoefficientCountPerModeInfo);
+    }
+
+    public Span<int> GetCoefficientsU(Point index)
+    {
+        Span<int> span = this.coefficientsU;
+        int i = ((index.Y * this.modeInfoCountPerSuperblock) + index.X) * CoefficientCountPerModeInfo;
+        return span.Slice(i >> this.subsamplingFactor, CoefficientCountPerModeInfo);
+    }
+
+    public Span<int> GetCoefficientsV(Point index)
+    {
+        Span<int> span = this.coefficientsV;
+        int i = ((index.Y * this.modeInfoCountPerSuperblock) + index.X) * CoefficientCountPerModeInfo;
+        return span.Slice(i >> this.subsamplingFactor, CoefficientCountPerModeInfo);
+    }
+
+    public ref int GetDeltaQuantizationIndex(Point index)
+    {
+        Span<int> span = this.deltaQ;
+        int i = (index.Y * this.superblockColumnCount) + index.X;
+        return ref span[i];
+    }
+
+    public Span<int> GetCdefStrength(Point index)
+    {
+        Span<int> span = this.cdefStrength;
+        int i = ((index.Y * this.superblockColumnCount) + index.X) << this.cdefStrengthFactorLog2;
+        return span.Slice(i, 1 << this.cdefStrengthFactorLog2);
+    }
+
+    public Span<int> GetDeltaLoopFilter(Point index)
+    {
+        Span<int> span = this.deltaLoopFilter;
+        int i = ((index.Y * this.superblockColumnCount) + index.X) << this.deltaLoopFactorLog2;
+        return span.Slice(i, 1 << this.deltaLoopFactorLog2);
+    }
+
+    internal void ClearDeltaLoopFilter() => Array.Fill(this.deltaLoopFilter, 0);
+}

src/ImageSharp/Formats/Heif/Av1/Tiling/Av1SuperblockInfo.cs

@@ -5,27 +5,31 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.Symbol;
 
 internal class Av1SuperblockInfo
 {
-    public Av1SuperblockInfo(Av1BlockModeInfo superblockModeInfo, Av1TransformInfo superblockTransformInfo)
+    private readonly Av1FrameBuffer frameBuffer;
+
+    public Av1SuperblockInfo(Av1FrameBuffer frameBuffer, Point position)
     {
-        this.SuperblockModeInfo = superblockModeInfo;
+        this.Position = position;
-        this.SuperblockTransformInfo = superblockTransformInfo;
+        this.frameBuffer = frameBuffer;
     }
 
-    public int SuperblockDeltaQ { get; internal set; }
+    public Point Position { get; }
+
+    public ref int SuperblockDeltaQ => ref this.frameBuffer.GetDeltaQuantizationIndex(this.Position);
 
-    public Av1BlockModeInfo SuperblockModeInfo { get; set; }
+    public Av1BlockModeInfo SuperblockModeInfo => this.GetModeInfo(default);
 
-    public int[] CoefficientsY { get; set; } = [];
+    public Span<int> CoefficientsY => this.frameBuffer.GetCoefficientsY(this.Position);
 
-    public int[] CoefficientsU { get; set; } = [];
+    public Span<int> CoefficientsU => this.frameBuffer.GetCoefficientsU(this.Position);
 
-    public int[] CoefficientsV { get; set; } = [];
+    public Span<int> CoefficientsV => this.frameBuffer.GetCoefficientsV(this.Position);
 
-    public Av1TransformInfo SuperblockTransformInfo { get; set; }
+    public Av1TransformInfo SuperblockTransformInfo => this.frameBuffer.GetTransformY(this.Position);
 
-    public int CdefStrength { get; internal set; }
+    public Span<int> CdefStrength => this.frameBuffer.GetCdefStrength(this.Position);
 
-    public int SuperblockDeltaLoopFilter { get; set; }
+    public Span<int> SuperblockDeltaLoopFilter => this.frameBuffer.GetDeltaLoopFilter(this.Position);
 
-    public Av1BlockModeInfo GetModeInfo(int rowIndex, int columnIndex) => throw new NotImplementedException();
+    public Av1BlockModeInfo GetModeInfo(Point index) => this.frameBuffer.GetModeInfo(this.Position, index);
 }

src/ImageSharp/Formats/Heif/Av1/Tiling/Av1TileDecoder.cs

@@ -14,9 +14,6 @@ internal class Av1TileDecoder : IAv1TileDecoder
     private static readonly int[] WienerTapsMid = [3, -7, 15];
     private const int PartitionProbabilitySet = 4;
 
-    // Number of Coefficients in a single ModeInfo 4x4 block of pixels (1 DC + 16 AC).
-    private const int NumberofCoefficients = 1 + 16;
-
     private bool[][][] blockDecoded = [];
     private int[][] referenceSgrXqd = [];
     private int[][][] referenceLrWiener = [];
@@ -32,19 +29,7 @@ internal class Av1TileDecoder : IAv1TileDecoder
     private int maxLumaHeight;
     private int deltaLoopFilterResolution = -1;
     private int deltaQuantizerResolution = -1;
-    private int[] coefficientsY = [];
+    private readonly Av1FrameBuffer frameBuffer;
-    private int[] coefficientsU = [];
-    private int[] coefficientsV = [];
-    private int numModeInfosInSuperblock;
-    private int superblockColumnCount;
-    private int superblockRowCount;
-    private Av1SuperblockInfo[] superblockInfos;
-    private Av1BlockModeInfo[] modeInfos;
-    private Av1TransformInfo[] transformInfosY;
-    private Av1TransformInfo[] transformInfosUv;
-    private int[] deltaQ;
-    private int[] cdefStrength;
-    private int[] deltaLoopFilter;
 
     public Av1TileDecoder(ObuSequenceHeader sequenceHeader, ObuFrameHeader frameInfo, ObuTileInfo tileInfo)
     {
@@ -53,29 +38,7 @@ internal class Av1TileDecoder : IAv1TileDecoder
         this.TileInfo = tileInfo;
 
         // init_main_frame_ctxt
-        int superblockSizeLog2 = this.SequenceHeader.SuperBlockSizeLog2;
+        this.frameBuffer = new(this.SequenceHeader);
-        int superblockAlignedWidth = Av1Math.AlignPowerOf2(this.SequenceHeader.MaxFrameWidth, superblockSizeLog2);
-        int superblockAlignedHeight = Av1Math.AlignPowerOf2(this.SequenceHeader.MaxFrameHeight, superblockSizeLog2);
-        this.superblockColumnCount = superblockAlignedWidth >> superblockSizeLog2;
-        this.superblockRowCount = superblockAlignedHeight >> superblockSizeLog2;
-        int superblockCount = this.superblockColumnCount * this.superblockRowCount;
-        this.numModeInfosInSuperblock = (1 << (superblockSizeLog2 - Av1Constants.ModeInfoSizeLog2)) * (1 << (superblockSizeLog2 - Av1Constants.ModeInfoSizeLog2));
-
-        this.superblockInfos = new Av1SuperblockInfo[superblockCount];
-        this.modeInfos = new Av1BlockModeInfo[superblockCount * this.numModeInfosInSuperblock];
-        this.transformInfosY = new Av1TransformInfo[superblockCount * this.numModeInfosInSuperblock];
-        this.transformInfosUv = new Av1TransformInfo[2 * superblockCount * this.numModeInfosInSuperblock];
-        this.coefficientsY = new int[superblockCount * this.numModeInfosInSuperblock * NumberofCoefficients];
-        int subsamplingFactor = (this.SequenceHeader.ColorConfig.SubSamplingX && this.SequenceHeader.ColorConfig.SubSamplingY) ? 2 :
-                (this.SequenceHeader.ColorConfig.SubSamplingX && !this.SequenceHeader.ColorConfig.SubSamplingY) ? 1 :
-                (!this.SequenceHeader.ColorConfig.SubSamplingX && !this.SequenceHeader.ColorConfig.SubSamplingY) ? 0 : -1;
-        Guard.IsFalse(subsamplingFactor == -1, nameof(subsamplingFactor), "Invalid combination of subsampling.");
-        this.coefficientsU = new int[(superblockCount * this.numModeInfosInSuperblock * NumberofCoefficients) >> subsamplingFactor];
-        this.coefficientsV = new int[(superblockCount * this.numModeInfosInSuperblock * NumberofCoefficients) >> subsamplingFactor];
-        this.deltaQ = new int[superblockCount];
-        this.cdefStrength = new int[superblockCount * (this.SequenceHeader.Use128x128SuperBlock ? 4 : 1)];
-        Array.Fill(this.cdefStrength, -1);
-        this.deltaLoopFilter = new int[superblockCount * Av1Constants.FrameLoopFilterCount];
     }
 
     public bool SequenceHeaderDone { get; set; }
@@ -129,17 +92,8 @@ internal class Av1TileDecoder : IAv1TileDecoder
 
                 this.ClearBlockDecodedFlags(row, column, superBlock4x4Size);
 
-                int superblockIndex = (superBlockRow * this.superblockColumnCount) + superBlockColumn;
+                Point superblockPosition = new Point(superBlockColumn, superBlockRow);
-                int cdefFactor = this.SequenceHeader.Use128x128SuperBlock ? 4 : 1;
+                Av1SuperblockInfo superblockInfo = new(this.frameBuffer, superblockPosition);
-                Av1SuperblockInfo superblockInfo = new(this.modeInfos[superblockIndex], this.transformInfosY[superblockIndex])
-                {
-                    CoefficientsY = this.coefficientsY,
-                    CoefficientsU = this.coefficientsU,
-                    CoefficientsV = this.coefficientsV,
-                    CdefStrength = this.cdefStrength[superblockIndex * cdefFactor],
-                    SuperblockDeltaLoopFilter = this.deltaLoopFilter[Av1Constants.FrameLoopFilterCount * superblockIndex],
-                    SuperblockDeltaQ = this.deltaQ[superblockIndex]
-                };
 
                 // Nothing to do for CDEF
                 // this.ClearCdef(row, column);
@@ -150,7 +104,7 @@ internal class Av1TileDecoder : IAv1TileDecoder
     }
 
     private void ClearLoopFilterDelta()
-        => this.deltaLoopFilter = new int[4];
+        => this.frameBuffer.ClearDeltaLoopFilter();
 
     private void ClearBlockDecodedFlags(int row, int column, int superBlock4x4Size)
     {
@@ -350,12 +304,12 @@ internal class Av1TileDecoder : IAv1TileDecoder
 
         if (partitionInfo.AvailableUp)
         {
-            partitionInfo.AboveModeInfo = superblockInfo.GetModeInfo(rowIndex - 1, columnIndex);
+            partitionInfo.AboveModeInfo = superblockInfo.GetModeInfo(new Point(rowIndex - 1, columnIndex));
         }
 
         if (partitionInfo.AvailableLeft)
         {
-            partitionInfo.LeftModeInfo = superblockInfo.GetModeInfo(rowIndex, columnIndex - 1);
+            partitionInfo.LeftModeInfo = superblockInfo.GetModeInfo(new Point(rowIndex, columnIndex - 1));
         }
 
         this.ReadModeInfo(ref reader, partitionInfo);
@@ -448,7 +402,7 @@ internal class Av1TileDecoder : IAv1TileDecoder
 
     private void TransformBlock(int plane, int baseX, int baseY, Av1TransformSize transformSize, int x, int y)
     {
-        Av1PartitionInfo partitionInfo = new(new(1, Av1BlockSize.Invalid), new(new(1, Av1BlockSize.Invalid), new()), false, Av1PartitionType.None);
+        Av1PartitionInfo partitionInfo = new(new(1, Av1BlockSize.Invalid), new(this.frameBuffer, default), false, Av1PartitionType.None);
         int startX = (baseX + 4) * x;
         int startY = (baseY + 4) * y;
         bool subsamplingX = this.SequenceHeader.ColorConfig.SubSamplingX;
@@ -915,6 +869,7 @@ internal class Av1TileDecoder : IAv1TileDecoder
                 frameLoopFilterCount = this.SequenceHeader.ColorConfig.ChannelCount > 1 ? Av1Constants.FrameLoopFilterCount : Av1Constants.FrameLoopFilterCount - 2;
             }
 
+            Span<int> currentDeltaLoopFilter = partitionInfo.SuperblockInfo.SuperblockDeltaLoopFilter;
             for (int i = 0; i < frameLoopFilterCount; i++)
             {
                 int deltaLoopFilterAbsolute = reader.ReadDeltaLoopFilterAbsolute();
@@ -929,7 +884,7 @@ internal class Av1TileDecoder : IAv1TileDecoder
                 {
                     bool deltaLoopFilterSign = reader.ReadLiteral(1) > 0;
                     int reducedDeltaLoopFilterLevel = deltaLoopFilterSign ? -deltaLoopFilterAbsolute : deltaLoopFilterAbsolute;
-                    this.deltaLoopFilter[i] = Av1Math.Clip3(-Av1Constants.MaxLoopFilter, Av1Constants.MaxLoopFilter, this.deltaLoopFilter[i] + (reducedDeltaLoopFilterLevel << this.deltaLoopFilterResolution));
+                    currentDeltaLoopFilter[i] = Av1Math.Clip3(-Av1Constants.MaxLoopFilter, Av1Constants.MaxLoopFilter, currentDeltaLoopFilter[i] + (reducedDeltaLoopFilterLevel << this.deltaLoopFilterResolution));
                 }
             }
         }