From d8e7078bb994fb197aca2d27d2468d930b9f2f54 Mon Sep 17 00:00:00 2001
From: Brian Popow <popow@gmx.de>
Date: Sun, 23 Jun 2024 13:04:35 +0200
Subject: [PATCH] Implement reading AV1 Codec Configuration Record

---
 .../Formats/Heif/Av1/Av1CodecConfiguration.cs | 63 +++++++++++++++++++
 .../Formats/Heif/HeifDecoderCore.cs           |  6 +-
 2 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 src/ImageSharp/Formats/Heif/Av1/Av1CodecConfiguration.cs

diff --git a/src/ImageSharp/Formats/Heif/Av1/Av1CodecConfiguration.cs b/src/ImageSharp/Formats/Heif/Av1/Av1CodecConfiguration.cs
new file mode 100644
index 000000000..e0cef4775
--- /dev/null
+++ b/src/ImageSharp/Formats/Heif/Av1/Av1CodecConfiguration.cs
@@ -0,0 +1,63 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+namespace SixLabors.ImageSharp.Formats.Heif.Av1;
+
+/// <summary>
+/// Implementation of section 2.3.3 of AV1 Codec ISO Media File Format Binding specification v1.2.0.
+/// See https://aomediacodec.github.io/av1-isobmff/v1.2.0.html#av1codecconfigurationbox-syntax.
+/// </summary>
+internal struct Av1CodecConfiguration
+{
+    public Av1CodecConfiguration(Span<byte> boxBuffer)
+    {
+        Av1BitStreamReader reader = new(boxBuffer);
+
+        this.Marker = (byte)reader.ReadLiteral(1);
+        this.Version = (byte)reader.ReadLiteral(7);
+        this.SeqProfile = (byte)reader.ReadLiteral(3);
+        this.SeqLevelIdx0 = (byte)reader.ReadLiteral(5);
+        this.SeqTier0 = (byte)reader.ReadLiteral(1);
+        this.HighBitdepth = (byte)reader.ReadLiteral(1);
+        this.TwelveBit = reader.ReadLiteral(1) == 1;
+        this.MonoChrome = reader.ReadLiteral(1) == 1;
+        this.ChromaSubsamplingX = reader.ReadLiteral(1) == 1;
+        this.ChromaSubsamplingY = reader.ReadLiteral(1) == 1;
+        this.ChromaSamplePosition = (byte)reader.ReadLiteral(2);
+
+        // 3 bits are reserved.
+        reader.ReadLiteral(3);
+
+        this.InitialPresentationDelayPresent = reader.ReadLiteral(1) == 1;
+        if (this.InitialPresentationDelayPresent)
+        {
+            byte initialPresentationDelayMinusOne = (byte)reader.ReadLiteral(4);
+            this.InitialPresentationDelay = (byte)(initialPresentationDelayMinusOne + 1);
+        }
+    }
+
+    public byte Marker { get; }
+
+    public byte Version { get; }
+
+    public byte SeqProfile { get; }
+
+    public byte SeqLevelIdx0 { get; }
+
+    public byte SeqTier0 { get; }
+
+    public byte HighBitdepth { get; }
+
+    public bool TwelveBit { get; }
+
+    public bool MonoChrome { get; }
+
+    public bool ChromaSubsamplingX { get; }
+
+    public bool ChromaSubsamplingY { get; }
+
+    public byte ChromaSamplePosition { get; }
+
+    public bool InitialPresentationDelayPresent { get; }
+
+    public byte InitialPresentationDelay { get; }
+}
diff --git a/src/ImageSharp/Formats/Heif/HeifDecoderCore.cs b/src/ImageSharp/Formats/Heif/HeifDecoderCore.cs
index 7aeeac56b..bfc397bf8 100644
--- a/src/ImageSharp/Formats/Heif/HeifDecoderCore.cs
+++ b/src/ImageSharp/Formats/Heif/HeifDecoderCore.cs
@@ -1,11 +1,11 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System;
 using System.Buffers;
 using System.Buffers.Binary;
 using System.Text;
 using SixLabors.ImageSharp.Formats.Heif.Av1;
-using SixLabors.ImageSharp.Formats.Heif.Av1.OpenBitstreamUnit;
 using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.Metadata;
@@ -35,6 +35,8 @@ internal sealed class HeifDecoderCore : IImageDecoderInternals
 
     private readonly List<HeifItemLink> itemLinks;
 
+    private Av1CodecConfiguration av1CodecConfiguration;
+
     /// <summary>
     /// Initializes a new instance of the <see cref="HeifDecoderCore" /> class.
     /// </summary>
@@ -475,6 +477,8 @@ internal sealed class HeifDecoderCore : IImageDecoderInternals
                 case Heif4CharCode.Iscl:
                 case Heif4CharCode.HvcC:
                 case Heif4CharCode.Av1C:
+                    this.av1CodecConfiguration = new(boxBuffer);
+                    break;
                 case Heif4CharCode.Rloc:
                 case Heif4CharCode.Udes:
                     // TODO: Implement