diff --git a/HEIF_IMPLEMENTATION_PLAN.md b/HEIF_IMPLEMENTATION_PLAN.md
index fe99ed305f..4306d1ff4d 100644
--- a/HEIF_IMPLEMENTATION_PLAN.md
+++ b/HEIF_IMPLEMENTATION_PLAN.md
@@ -870,6 +870,7 @@ Encoder verification contract:
 ### 7. Write complete AVIF output
 
 - [~] The encoder-side AV1 codec configuration is now derived directly from the encoded sequence header and writes the fixed four-byte `av1C` record with empty `configOBUs`. The image payload retains the required sequence header, so the property introduces no sequence-header allocation, retention, or copy. Four production-header cases cover main, high, and professional profiles; 8-, 10-, and 12-bit precision; monochrome, 4:2:0, 4:2:2, and 4:4:4 sampling; exact fixed bytes; decoder reparsing; and header/property equivalence through direct net11 Release VSTest. Property-container emission and public AVIF activation remain open.
+- [~] AV1 image properties now write `ispe`, `pixi`, `av1C`, `colr`, and `auxC` in current AVIF item order. Only `av1C` is essential; color and alpha items retain independent property sets and the registered alpha auxiliary type. The property container reacquires its span after nested expansion before patching `ipco`, removing the prior stale-buffer write, and selects compact or 15-bit `ipma` indices from the property count rather than the unrelated item count. A forced-growth color-plus-alpha case validates every property payload and association byte; a separate 43-item, 129-property case proves indices 127 through 129 and the extended essential bit. Both pass direct foreground net11 Release VSTest. Complete AVIF assembly remains open.
 - [ ] Write the correct AVIF file type, item information, locations, references, properties, AV1 configuration, dimensions, color, alpha, metadata, and media data.
 - [ ] Support single images, alpha auxiliary images, grids, multiple extents, and bounded image sequences in the final public scope.
 - [ ] Preserve ICC, Exif, and XMP according to encoder options.
diff --git a/src/ImageSharp/Formats/Heif/HeifEncoderCore.cs b/src/ImageSharp/Formats/Heif/HeifEncoderCore.cs
index cc3e955492..5fc2d18d61 100644
--- a/src/ImageSharp/Formats/Heif/HeifEncoderCore.cs
+++ b/src/ImageSharp/Formats/Heif/HeifEncoderCore.cs
@@ -2,9 +2,12 @@
 // Licensed under the Six Labors Split License.
 
 using System.Buffers.Binary;
+using System.Text;
+using SixLabors.ImageSharp.Formats.Heif.Av1;
 using SixLabors.ImageSharp.Formats.Jpeg;
 using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
+using SixLabors.ImageSharp.Metadata.Profiles.Cicp;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Formats.Heif;
@@ -303,7 +306,7 @@ internal sealed class HeifEncoderCore
     /// <param name="memoryOffset">The destination offset within the metadata box.</param>
     /// <param name="items">The items whose dimensions are written and associated.</param>
     /// <returns>The complete item-properties-box length.</returns>
-    private static int WriteItemPropertiesBox(AutoExpandingMemory<byte> memory, int memoryOffset, List<HeifItem> items)
+    public static int WriteItemPropertiesBox(AutoExpandingMemory<byte> memory, int memoryOffset, List<HeifItem> items)
     {
         Span<byte> buffer = memory.GetSpan(memoryOffset, 20);
         int bytesWritten = WriteBoxHeader(buffer, Heif4CharCode.Iprp);
@@ -314,12 +317,50 @@ internal sealed class HeifEncoderCore
         foreach (HeifItem item in items)
         {
             bytesWritten += WriteSpatialExtentPropertyBox(memory, memoryOffset + bytesWritten, item);
+
+            byte[]? channelBitDepths = item.ChannelBitDepths;
+            if (channelBitDepths is not null)
+            {
+                bytesWritten += WritePixelInformationPropertyBox(memory, memoryOffset + bytesWritten, channelBitDepths);
+            }
+
+            Av1CodecConfiguration? codecConfiguration = item.Av1CodecConfiguration;
+            if (codecConfiguration is not null)
+            {
+                bytesWritten += WriteAv1CodecConfigurationPropertyBox(memory, memoryOffset + bytesWritten, codecConfiguration);
+            }
+
+            string? auxiliaryType = item.AuxiliaryType;
+            if (auxiliaryType is not null)
+            {
+                bytesWritten += WriteAuxiliaryTypePropertyBox(memory, memoryOffset + bytesWritten, auxiliaryType);
+            }
+
+            CicpProfile? cicpProfile = item.CicpProfile;
+            if (cicpProfile is not null)
+            {
+                bytesWritten += WriteColorInformationPropertyBox(memory, memoryOffset + bytesWritten, cicpProfile);
+            }
         }
 
+        buffer = memory.GetSpan(memoryOffset, bytesWritten);
         BinaryPrimitives.WriteUInt32BigEndian(buffer[ipcoLengthOffset..], (uint)(bytesWritten - ipcoLengthOffset));
-        bool largePropertyIndex = items.Count > 0x7F;
-        int propertyIndexSize = largePropertyIndex ? 2 : 1;
-        buffer = memory.GetSpan(memoryOffset, bytesWritten + 16 + ((3 + propertyIndexSize) * items.Count));
+        int propertyCount = 0;
+        int associationBoxCapacity = 16;
+        foreach (HeifItem item in items)
+        {
+            int itemPropertyCount = GetPropertyCount(item);
+            propertyCount += itemPropertyCount;
+            associationBoxCapacity += 3 + itemPropertyCount;
+        }
+
+        bool largePropertyIndex = propertyCount > 0x7F;
+        if (largePropertyIndex)
+        {
+            associationBoxCapacity += propertyCount;
+        }
+
+        buffer = memory.GetSpan(memoryOffset, bytesWritten + associationBoxCapacity);
 
         // ipma uses a 15-bit index only when the property table cannot fit in the compact seven-bit form.
         int ipmaLengthOffset = bytesWritten;
@@ -331,18 +372,30 @@ internal sealed class HeifEncoderCore
         {
             BinaryPrimitives.WriteUInt16BigEndian(buffer[bytesWritten..], (ushort)item.Id);
             bytesWritten += 2;
-            buffer[bytesWritten++] = 1;
-            if (largePropertyIndex)
+
+            int itemPropertyCount = GetPropertyCount(item);
+            buffer[bytesWritten++] = (byte)itemPropertyCount;
+            WritePropertyAssociation(buffer, ref bytesWritten, propertyIndex++, largePropertyIndex, false);
+
+            if (item.ChannelBitDepths is not null)
             {
-                BinaryPrimitives.WriteUInt16BigEndian(buffer[bytesWritten..], propertyIndex);
-                bytesWritten += 2;
+                WritePropertyAssociation(buffer, ref bytesWritten, propertyIndex++, largePropertyIndex, false);
             }
-            else
+
+            if (item.Av1CodecConfiguration is not null)
+            {
+                WritePropertyAssociation(buffer, ref bytesWritten, propertyIndex++, largePropertyIndex, true);
+            }
+
+            if (item.AuxiliaryType is not null)
             {
-                buffer[bytesWritten++] = (byte)propertyIndex;
+                WritePropertyAssociation(buffer, ref bytesWritten, propertyIndex++, largePropertyIndex, false);
             }
 
-            propertyIndex++;
+            if (item.CicpProfile is not null)
+            {
+                WritePropertyAssociation(buffer, ref bytesWritten, propertyIndex++, largePropertyIndex, false);
+            }
         }
 
         BinaryPrimitives.WriteUInt32BigEndian(buffer[ipmaLengthOffset..], (uint)(bytesWritten - ipmaLengthOffset));
@@ -352,6 +405,141 @@ internal sealed class HeifEncoderCore
         return bytesWritten;
     }
 
+    /// <summary>
+    /// Gets the number of properties emitted for an item.
+    /// </summary>
+    /// <param name="item">The item whose populated properties are counted.</param>
+    /// <returns>The number of emitted properties.</returns>
+    private static int GetPropertyCount(HeifItem item)
+    {
+        int count = 1;
+        count += item.ChannelBitDepths is not null ? 1 : 0;
+        count += item.Av1CodecConfiguration is not null ? 1 : 0;
+        count += item.AuxiliaryType is not null ? 1 : 0;
+        count += item.CicpProfile is not null ? 1 : 0;
+        return count;
+    }
+
+    /// <summary>
+    /// Writes one compact or extended property association.
+    /// </summary>
+    /// <param name="buffer">The item-property-association destination.</param>
+    /// <param name="offset">The current destination offset, advanced past the association.</param>
+    /// <param name="propertyIndex">The one-based property index.</param>
+    /// <param name="largePropertyIndex">Whether the association uses a 15-bit property index.</param>
+    /// <param name="essential">Whether decoding the item requires understanding this property.</param>
+    private static void WritePropertyAssociation(
+        Span<byte> buffer,
+        ref int offset,
+        ushort propertyIndex,
+        bool largePropertyIndex,
+        bool essential)
+    {
+        if (largePropertyIndex)
+        {
+            ushort association = essential ? (ushort)(propertyIndex | 0x8000) : propertyIndex;
+            BinaryPrimitives.WriteUInt16BigEndian(buffer[offset..], association);
+            offset += 2;
+        }
+        else
+        {
+            buffer[offset++] = essential ? (byte)(propertyIndex | 0x80) : (byte)propertyIndex;
+        }
+    }
+
+    /// <summary>
+    /// Writes the encoded precision of each image channel.
+    /// </summary>
+    /// <param name="memory">The expanding metadata buffer.</param>
+    /// <param name="memoryOffset">The destination offset within the property container.</param>
+    /// <param name="channelBitDepths">The encoded precision of each channel.</param>
+    /// <returns>The complete pixel-information-box length.</returns>
+    private static int WritePixelInformationPropertyBox(
+        AutoExpandingMemory<byte> memory,
+        int memoryOffset,
+        ReadOnlySpan<byte> channelBitDepths)
+    {
+        Span<byte> buffer = memory.GetSpan(memoryOffset, 13 + channelBitDepths.Length);
+        int bytesWritten = WriteBoxHeader(buffer, Heif4CharCode.Pixi, 0, 0);
+        buffer[bytesWritten++] = (byte)channelBitDepths.Length;
+        channelBitDepths.CopyTo(buffer[bytesWritten..]);
+        bytesWritten += channelBitDepths.Length;
+
+        BinaryPrimitives.WriteUInt32BigEndian(buffer, (uint)bytesWritten);
+        return bytesWritten;
+    }
+
+    /// <summary>
+    /// Writes an AV1 codec-configuration property.
+    /// </summary>
+    /// <param name="memory">The expanding metadata buffer.</param>
+    /// <param name="memoryOffset">The destination offset within the property container.</param>
+    /// <param name="configuration">The fixed image configuration.</param>
+    /// <returns>The complete AV1 codec-configuration-box length.</returns>
+    private static int WriteAv1CodecConfigurationPropertyBox(
+        AutoExpandingMemory<byte> memory,
+        int memoryOffset,
+        Av1CodecConfiguration configuration)
+    {
+        Span<byte> buffer = memory.GetSpan(memoryOffset, 8 + Av1CodecConfiguration.FixedHeaderSize);
+        int bytesWritten = WriteBoxHeader(buffer, Heif4CharCode.Av1C);
+        configuration.WriteFixedHeader(buffer.Slice(bytesWritten, Av1CodecConfiguration.FixedHeaderSize));
+        bytesWritten += Av1CodecConfiguration.FixedHeaderSize;
+
+        BinaryPrimitives.WriteUInt32BigEndian(buffer, (uint)bytesWritten);
+        return bytesWritten;
+    }
+
+    /// <summary>
+    /// Writes the registered type of an auxiliary image item.
+    /// </summary>
+    /// <param name="memory">The expanding metadata buffer.</param>
+    /// <param name="memoryOffset">The destination offset within the property container.</param>
+    /// <param name="auxiliaryType">The null-terminated registered auxiliary type.</param>
+    /// <returns>The complete auxiliary-type-box length.</returns>
+    private static int WriteAuxiliaryTypePropertyBox(
+        AutoExpandingMemory<byte> memory,
+        int memoryOffset,
+        string auxiliaryType)
+    {
+        int auxiliaryTypeLength = Encoding.UTF8.GetByteCount(auxiliaryType);
+        Span<byte> buffer = memory.GetSpan(memoryOffset, 13 + auxiliaryTypeLength);
+        int bytesWritten = WriteBoxHeader(buffer, Heif4CharCode.AuxC, 0, 0);
+        bytesWritten += Encoding.UTF8.GetBytes(auxiliaryType, buffer[bytesWritten..]);
+        buffer[bytesWritten++] = 0;
+
+        BinaryPrimitives.WriteUInt32BigEndian(buffer, (uint)bytesWritten);
+        return bytesWritten;
+    }
+
+    /// <summary>
+    /// Writes an H.273 color description for a color image item.
+    /// </summary>
+    /// <param name="memory">The expanding metadata buffer.</param>
+    /// <param name="memoryOffset">The destination offset within the property container.</param>
+    /// <param name="profile">The color description to write.</param>
+    /// <returns>The complete color-information-box length.</returns>
+    private static int WriteColorInformationPropertyBox(
+        AutoExpandingMemory<byte> memory,
+        int memoryOffset,
+        CicpProfile profile)
+    {
+        Span<byte> buffer = memory.GetSpan(memoryOffset, 19);
+        int bytesWritten = WriteBoxHeader(buffer, Heif4CharCode.Colr);
+        BinaryPrimitives.WriteUInt32BigEndian(buffer[bytesWritten..], (uint)Heif4CharCode.Nclx);
+        bytesWritten += 4;
+        BinaryPrimitives.WriteUInt16BigEndian(buffer[bytesWritten..], (ushort)profile.ColorPrimaries);
+        bytesWritten += 2;
+        BinaryPrimitives.WriteUInt16BigEndian(buffer[bytesWritten..], (ushort)profile.TransferCharacteristics);
+        bytesWritten += 2;
+        BinaryPrimitives.WriteUInt16BigEndian(buffer[bytesWritten..], (ushort)profile.MatrixCoefficients);
+        bytesWritten += 2;
+        buffer[bytesWritten++] = profile.FullRange ? (byte)0x80 : (byte)0;
+
+        BinaryPrimitives.WriteUInt32BigEndian(buffer, (uint)bytesWritten);
+        return bytesWritten;
+    }
+
     /// <summary>
     /// Writes an item's display width and height as an image-spatial-extents property.
     /// </summary>
diff --git a/tests/ImageSharp.Tests/Formats/Heif/HeifEncoderTests.cs b/tests/ImageSharp.Tests/Formats/Heif/HeifEncoderTests.cs
index 6d6a8766bf..43eb593d3b 100644
--- a/tests/ImageSharp.Tests/Formats/Heif/HeifEncoderTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Heif/HeifEncoderTests.cs
@@ -1,7 +1,13 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Buffers.Binary;
+using System.Text;
 using SixLabors.ImageSharp.Formats.Heif;
+using SixLabors.ImageSharp.Formats.Heif.Av1;
+using SixLabors.ImageSharp.Formats.Heif.Av1.OpenBitstreamUnit;
+using SixLabors.ImageSharp.Memory;
+using SixLabors.ImageSharp.Metadata.Profiles.Cicp;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
 using SixLabors.ImageSharp.Tests.TestUtilities.ReferenceCodecs;
@@ -146,6 +152,186 @@ public class HeifEncoderTests
         Assert.Equal(0, stream.Length);
     }
 
+    [Fact]
+    public void Av1ItemPropertiesWriteRequiredTypesAndEssentialConfiguration()
+    {
+        ObuSequenceHeader colorHeader = new()
+        {
+            SequenceProfile = ObuSequenceProfile.Main,
+            OperatingPoint = [new ObuOperatingPoint { SequenceLevelIndex = 31 }],
+            ColorConfig = new ObuColorConfig
+            {
+                BitDepth = Av1BitDepth.TenBit,
+                SubSamplingX = true,
+                SubSamplingY = true
+            }
+        };
+
+        ObuSequenceHeader alphaHeader = new()
+        {
+            SequenceProfile = ObuSequenceProfile.Main,
+            OperatingPoint = [new ObuOperatingPoint { SequenceLevelIndex = 31 }],
+            ColorConfig = new ObuColorConfig
+            {
+                BitDepth = Av1BitDepth.TenBit,
+                IsMonochrome = true,
+                SubSamplingX = true,
+                SubSamplingY = true
+            }
+        };
+
+        HeifItem colorItem = new(Heif4CharCode.Av01, 1)
+        {
+            ChannelBitDepths = [10, 10, 10],
+            Av1CodecConfiguration = new Av1CodecConfiguration(colorHeader),
+            CicpProfile = new CicpProfile(1, 13, 6, true)
+        };
+
+        colorItem.SetExtent(new Size(64, 48));
+        HeifItem alphaItem = new(Heif4CharCode.Av01, 2)
+        {
+            ChannelBitDepths = [10],
+            Av1CodecConfiguration = new Av1CodecConfiguration(alphaHeader),
+            AuxiliaryType = HeifConstants.AlphaAuxiliaryType
+        };
+
+        alphaItem.SetExtent(new Size(64, 48));
+        List<HeifItem> items = [colorItem, alphaItem];
+        using AutoExpandingMemory<byte> memory = new(Configuration.Default, 16);
+        int length = HeifEncoderCore.WriteItemPropertiesBox(memory, 0, items);
+        ReadOnlySpan<byte> propertyBox = memory.GetSpan(length);
+
+        Assert.Equal(length, BinaryPrimitives.ReadInt32BigEndian(propertyBox));
+        Assert.Equal(Heif4CharCode.Iprp, (Heif4CharCode)BinaryPrimitives.ReadUInt32BigEndian(propertyBox[4..]));
+
+        const int IpcoOffset = 8;
+        int ipcoSize = BinaryPrimitives.ReadInt32BigEndian(propertyBox[IpcoOffset..]);
+        Assert.Equal(Heif4CharCode.Ipco, (Heif4CharCode)BinaryPrimitives.ReadUInt32BigEndian(propertyBox[(IpcoOffset + 4)..]));
+
+        Heif4CharCode[] expectedTypes =
+        [
+            Heif4CharCode.Ispe,
+            Heif4CharCode.Pixi,
+            Heif4CharCode.Av1C,
+            Heif4CharCode.Colr,
+            Heif4CharCode.Ispe,
+            Heif4CharCode.Pixi,
+            Heif4CharCode.Av1C,
+            Heif4CharCode.AuxC
+        ];
+
+        int propertyOffset = IpcoOffset + 8;
+        int ipcoEnd = IpcoOffset + ipcoSize;
+        int propertyIndex = 0;
+        while (propertyOffset < ipcoEnd)
+        {
+            int propertySize = BinaryPrimitives.ReadInt32BigEndian(propertyBox[propertyOffset..]);
+            Heif4CharCode propertyType = (Heif4CharCode)BinaryPrimitives.ReadUInt32BigEndian(propertyBox[(propertyOffset + 4)..]);
+            ReadOnlySpan<byte> payload = propertyBox.Slice(propertyOffset + 8, propertySize - 8);
+            Assert.Equal(expectedTypes[propertyIndex], propertyType);
+            switch (propertyIndex)
+            {
+                case 0:
+                case 4:
+                    Assert.Equal(0, BinaryPrimitives.ReadInt32BigEndian(payload));
+                    Assert.Equal(64, BinaryPrimitives.ReadInt32BigEndian(payload[4..]));
+                    Assert.Equal(48, BinaryPrimitives.ReadInt32BigEndian(payload[8..]));
+                    break;
+                case 1:
+                    Assert.Equal([0, 0, 0, 0, 3, 10, 10, 10], payload.ToArray());
+                    break;
+                case 2:
+                    Assert.Equal([0x81, 0x1F, 0x4C, 0], payload.ToArray());
+                    break;
+                case 3:
+                    Assert.Equal(Heif4CharCode.Nclx, (Heif4CharCode)BinaryPrimitives.ReadUInt32BigEndian(payload));
+                    Assert.Equal(1, BinaryPrimitives.ReadUInt16BigEndian(payload[4..]));
+                    Assert.Equal(13, BinaryPrimitives.ReadUInt16BigEndian(payload[6..]));
+                    Assert.Equal(6, BinaryPrimitives.ReadUInt16BigEndian(payload[8..]));
+                    Assert.Equal(0x80, payload[10]);
+                    break;
+                case 5:
+                    Assert.Equal([0, 0, 0, 0, 1, 10], payload.ToArray());
+                    break;
+                case 6:
+                    Assert.Equal([0x81, 0x1F, 0x5C, 0], payload.ToArray());
+                    break;
+                case 7:
+                    Assert.Equal(0, BinaryPrimitives.ReadInt32BigEndian(payload));
+                    Assert.Equal(HeifConstants.AlphaAuxiliaryType, Encoding.UTF8.GetString(payload[4..^1]));
+                    Assert.Equal(0, payload[^1]);
+                    break;
+            }
+
+            propertyOffset += propertySize;
+            propertyIndex++;
+        }
+
+        Assert.Equal(expectedTypes.Length, propertyIndex);
+        Assert.Equal(ipcoEnd, propertyOffset);
+
+        int ipmaOffset = ipcoEnd;
+        int ipmaSize = BinaryPrimitives.ReadInt32BigEndian(propertyBox[ipmaOffset..]);
+        Assert.Equal(length - ipmaOffset, ipmaSize);
+        Assert.Equal(Heif4CharCode.Ipma, (Heif4CharCode)BinaryPrimitives.ReadUInt32BigEndian(propertyBox[(ipmaOffset + 4)..]));
+        ReadOnlySpan<byte> ipmaPayload = propertyBox.Slice(ipmaOffset + 8, ipmaSize - 8);
+        Assert.Equal(0, BinaryPrimitives.ReadInt32BigEndian(ipmaPayload));
+        Assert.Equal(2, BinaryPrimitives.ReadInt32BigEndian(ipmaPayload[4..]));
+        Assert.Equal(
+            [0, 1, 4, 1, 2, 0x83, 4, 0, 2, 4, 5, 6, 0x87, 8],
+            ipmaPayload[8..].ToArray());
+    }
+
+    [Fact]
+    public void ItemPropertiesUseLargeAssociationsWhenPropertyCountExceedsCompactRange()
+    {
+        const int ItemCount = 43;
+        ObuSequenceHeader sequenceHeader = new()
+        {
+            SequenceProfile = ObuSequenceProfile.Main,
+            OperatingPoint = [new ObuOperatingPoint { SequenceLevelIndex = 31 }],
+            ColorConfig = new ObuColorConfig
+            {
+                BitDepth = Av1BitDepth.EightBit,
+                SubSamplingX = true,
+                SubSamplingY = true
+            }
+        };
+
+        Av1CodecConfiguration codecConfiguration = new(sequenceHeader);
+        byte[] channelBitDepths = [8, 8, 8];
+        List<HeifItem> items = new(ItemCount);
+        for (uint itemId = 1; itemId <= ItemCount; itemId++)
+        {
+            HeifItem item = new(Heif4CharCode.Av01, itemId)
+            {
+                ChannelBitDepths = channelBitDepths,
+                Av1CodecConfiguration = codecConfiguration
+            };
+
+            item.SetExtent(new Size(1, 1));
+            items.Add(item);
+        }
+
+        using AutoExpandingMemory<byte> memory = new(Configuration.Default, 16);
+        int length = HeifEncoderCore.WriteItemPropertiesBox(memory, 0, items);
+        ReadOnlySpan<byte> propertyBox = memory.GetSpan(length);
+        const int IpcoOffset = 8;
+        int ipcoSize = BinaryPrimitives.ReadInt32BigEndian(propertyBox[IpcoOffset..]);
+        int ipmaOffset = IpcoOffset + ipcoSize;
+
+        Assert.Equal(1, BinaryPrimitives.ReadInt32BigEndian(propertyBox[(ipmaOffset + 8)..]));
+        Assert.Equal(ItemCount, BinaryPrimitives.ReadInt32BigEndian(propertyBox[(ipmaOffset + 12)..]));
+
+        const int AssociationEntrySize = 9;
+        int finalEntryOffset = ipmaOffset + 16 + ((ItemCount - 1) * AssociationEntrySize);
+        Assert.Equal(ItemCount, BinaryPrimitives.ReadUInt16BigEndian(propertyBox[finalEntryOffset..]));
+        Assert.Equal(3, propertyBox[finalEntryOffset + 2]);
+        Assert.Equal(127, BinaryPrimitives.ReadUInt16BigEndian(propertyBox[(finalEntryOffset + 3)..]));
+        Assert.Equal(128, BinaryPrimitives.ReadUInt16BigEndian(propertyBox[(finalEntryOffset + 5)..]));
+        Assert.Equal(0x8081, BinaryPrimitives.ReadUInt16BigEndian(propertyBox[(finalEntryOffset + 7)..]));
+    }
+
     [Fact]
     public void LegacyJpegEncodingDoesNotMutateSourceHeifMetadata()
     {