diff --git a/src/ImageSharp/Formats/Heif/Av1/OpenBitstreamUnit/ObuReader.cs b/src/ImageSharp/Formats/Heif/Av1/OpenBitstreamUnit/ObuReader.cs
index cf3aa451d5..feb9cfc9cd 100644
--- a/src/ImageSharp/Formats/Heif/Av1/OpenBitstreamUnit/ObuReader.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/OpenBitstreamUnit/ObuReader.cs
@@ -370,9 +370,6 @@ internal class ObuReader
 
         // Video related flags removed
         sequenceHeader.Use128x128Superblock = reader.ReadBoolean();
-        sequenceHeader.SuperblockSize = sequenceHeader.Use128x128Superblock ? Av1BlockSize.Block128x128 : Av1BlockSize.Block64x64;
-        sequenceHeader.SuperblockModeInfoSize = sequenceHeader.Use128x128Superblock ? 32 : 16;
-        sequenceHeader.SuperblockSizeLog2 = sequenceHeader.Use128x128Superblock ? 7 : 6;
         sequenceHeader.EnableFilterIntra = reader.ReadBoolean();
         sequenceHeader.EnableIntraEdgeFilter = reader.ReadBoolean();
 
@@ -699,25 +696,15 @@ internal class ObuReader
         ObuTileGroupHeader tileInfo = new();
         int superBlockColumnCount;
         int superBlockRowCount;
-        int superBlockShift;
-        if (sequenceHeader.Use128x128Superblock)
-        {
-            superBlockColumnCount = (frameInfo.ModeInfoColumnCount + 31) >> 5;
-            superBlockRowCount = (frameInfo.ModeInfoRowCount + 31) >> 5;
-            superBlockShift = 5;
-        }
-        else
-        {
-            superBlockColumnCount = (frameInfo.ModeInfoColumnCount + 15) >> 4;
-            superBlockRowCount = (frameInfo.ModeInfoRowCount + 15) >> 4;
-            superBlockShift = 4;
-        }
+        int superBlockShift = sequenceHeader.SuperblockSizeLog2 - Av1Constants.ModeInfoSizeLog2;
+        superBlockColumnCount = (frameInfo.ModeInfoColumnCount + sequenceHeader.SuperblockModeInfoSize - 1) >> superBlockShift;
+        superBlockRowCount = (frameInfo.ModeInfoRowCount + sequenceHeader.SuperblockModeInfoSize - 1) >> superBlockShift;
 
-        int superBlockSize = superBlockShift + 2;
-        int maxTileAreaOfSuperBlock = Av1Constants.MaxTileArea >> (2 * superBlockSize);
+        int superBlockSizeLog2 = superBlockShift + 2;
+        int maxTileAreaOfSuperBlock = Av1Constants.MaxTileArea >> (2 * superBlockSizeLog2);
 
-        tileInfo.MaxTileWidthSuperBlock = Av1Constants.MaxTileWidth >> superBlockSize;
-        tileInfo.MaxTileHeightSuperBlock = (Av1Constants.MaxTileArea / Av1Constants.MaxTileWidth) >> superBlockSize;
+        tileInfo.MaxTileWidthSuperBlock = Av1Constants.MaxTileWidth >> superBlockSizeLog2;
+        tileInfo.MaxTileHeightSuperBlock = (Av1Constants.MaxTileArea / Av1Constants.MaxTileWidth) >> superBlockSizeLog2;
         tileInfo.MinLog2TileColumnCount = TileLog2(tileInfo.MaxTileWidthSuperBlock, superBlockColumnCount);
         tileInfo.MaxLog2TileColumnCount = TileLog2(1, Math.Min(superBlockColumnCount, Av1Constants.MaxTileColumnCount));
         tileInfo.MaxLog2TileRowCount = TileLog2(1, Math.Min(superBlockRowCount, Av1Constants.MaxTileRowCount));
diff --git a/src/ImageSharp/Formats/Heif/Av1/OpenBitstreamUnit/ObuSequenceHeader.cs b/src/ImageSharp/Formats/Heif/Av1/OpenBitstreamUnit/ObuSequenceHeader.cs
index 34ce917634..ac87eefe74 100644
--- a/src/ImageSharp/Formats/Heif/Av1/OpenBitstreamUnit/ObuSequenceHeader.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/OpenBitstreamUnit/ObuSequenceHeader.cs
@@ -5,6 +5,8 @@ namespace SixLabors.ImageSharp.Formats.Heif.Av1.OpenBitstreamUnit;
 
 internal class ObuSequenceHeader
 {
+    private bool use128x128Superblock;
+
     public bool EnableFilterIntra { get; set; }
 
     public bool EnableCdef { get; set; }
@@ -37,13 +39,23 @@ internal class ObuSequenceHeader
 
     public int MaxFrameHeight { get; set; }
 
-    public bool Use128x128Superblock { get; set; }
+    public bool Use128x128Superblock
+    {
+        get => this.use128x128Superblock;
+        set
+        {
+            this.use128x128Superblock = value;
+            this.SuperblockSize = value ? Av1BlockSize.Block128x128 : Av1BlockSize.Block64x64;
+            this.SuperblockSizeLog2 = value ? 7 : 6;
+            this.SuperblockModeInfoSize = 1 << (this.SuperblockSizeLog2 - Av1Constants.ModeInfoSizeLog2);
+        }
+    }
 
-    public Av1BlockSize SuperblockSize { get; set; }
+    public Av1BlockSize SuperblockSize { get; private set; }
 
-    public int SuperblockModeInfoSize { get; set; }
+    public int SuperblockModeInfoSize { get; private set; }
 
-    public int SuperblockSizeLog2 { get; set; }
+    public int SuperblockSizeLog2 { get; private set; }
 
     public int FilterIntraLevel { get; set; }
 
diff --git a/src/ImageSharp/Formats/Heif/Av1/Tiling/Av1TileDecoder.cs b/src/ImageSharp/Formats/Heif/Av1/Tiling/Av1TileDecoder.cs
index 10fdcdf6cf..a05aa63a04 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Tiling/Av1TileDecoder.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Tiling/Av1TileDecoder.cs
@@ -114,7 +114,6 @@ internal class Av1TileDecoder : IAv1TileDecoder
                 Point superblockPosition = new(superBlockColumn, superBlockRow);
                 Av1SuperblockInfo superblockInfo = this.FrameBuffer.GetSuperblock(superblockPosition);
 
-                // this.ClearBlockDecodedFlags(modeInfoLocation, superBlock4x4Size);
                 Point modeInfoPosition = new(column, row);
                 this.FrameBuffer.ClearCdef(superblockPosition);
                 this.firstTransformOffset[0] = 0;
@@ -128,14 +127,6 @@ internal class Av1TileDecoder : IAv1TileDecoder
     private void ClearLoopFilterDelta()
         => this.FrameBuffer.ClearDeltaLoopFilter();
 
-    /// <summary>
-    /// 5.11.3. Clear block decoded flags function.
-    /// </summary>
-    private static void ClearBlockDecodedFlags(Point modeInfoLocation, int superBlock4x4Size)
-    {
-        // Nothing to do here.
-    }
-
     private void ReadLoopRestoration(Point modeInfoLocation, Av1BlockSize superBlockSize)
     {
         int planesCount = this.SequenceHeader.ColorConfig.PlaneCount;