Implement 5.5.4. read Decoder model info

src/ImageSharp/Formats/Heif/Av1/OpenBitstreamUnit/ObuDecoderModelInfo.cs

@@ -0,0 +1,29 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1;
+
+internal class ObuDecoderModelInfo
+{
+    /// <summary>
+    /// Gets or sets BufferDelayLength. Specifies the length of the decoder_buffer_delay and the encoder_buffer_delay
+    /// syntax elements, in bits.
+    /// </summary>
+    internal uint BufferDelayLength { get; set; }
+
+    /// <summary>
+    /// Gets or sets NumUnitsInDecodingTick. This is the number of time units of a decoding clock operating at the frequency time_scale Hz
+    /// that corresponds to one increment of a clock tick counter.
+    /// </summary>
+    internal uint NumUnitsInDecodingTick { get; set; }
+
+    /// <summary>
+    /// Gets or sets BufferRemovalTimeLength. Specifies the length of the buffer_removal_time syntax element, in bits.
+    /// </summary>
+    internal uint BufferRemovalTimeLength { get; set; }
+
+    /// <summary>
+    /// Gets or sets the FramePresentationTimeLength. Specifies the length of the frame_presentation_time syntax element, in bits.
+    /// </summary>
+    internal uint FramePresentationTimeLength { get; set; }
+}

src/ImageSharp/Formats/Heif/Av1/OpenBitstreamUnit/ObuReader.cs

@@ -292,7 +292,7 @@ internal class ObuReader
                 sequenceHeader.DecoderModelInfoPresentFlag = reader.ReadBoolean();
                 if (sequenceHeader.DecoderModelInfoPresentFlag)
                 {
-                    // TODO: read decoder_model_info( )
+                    ReadDecoderModelInfo(ref reader, sequenceHeader);
                 }
             }
 
@@ -461,6 +461,17 @@ internal class ObuReader
         return colorConfig;
     }
 
+    /// <summary>
+    /// 5.5.4. Decoder model info syntax.
+    /// </summary>
+    private static void ReadDecoderModelInfo(ref Av1BitStreamReader reader, ObuSequenceHeader sequenceHeader) => sequenceHeader.DecoderModelInfo = new ObuDecoderModelInfo
+    {
+        BufferDelayLength = reader.ReadLiteral(5) + 1,
+        NumUnitsInDecodingTick = reader.ReadLiteral(16),
+        BufferRemovalTimeLength = reader.ReadLiteral(5) + 1,
+        FramePresentationTimeLength = reader.ReadLiteral(5) + 1
+    };
+
     private static void ReadBitDepth(ref Av1BitStreamReader reader, ObuColorConfig colorConfig, ObuSequenceHeader sequenceHeader)
     {
         bool hasHighBitDepth = reader.ReadBoolean();

src/ImageSharp/Formats/Heif/Av1/OpenBitstreamUnit/ObuSequenceHeader.cs

@@ -17,6 +17,8 @@ internal class ObuSequenceHeader
 
     public ObuOperatingPoint[] OperatingPoint { get; set; } = new ObuOperatingPoint[1];
 
+    public ObuDecoderModelInfo? DecoderModelInfo { get; set; }
+
     public bool InitialDisplayDelayPresentFlag { get; set; }
 
     public bool DecoderModelInfoPresentFlag { get; set; }