diff --git a/src/ImageSharp/Formats/Webp/Lossy/Vp8BandProbas.cs b/src/ImageSharp/Formats/Webp/Lossy/Vp8BandProbas.cs
index 90506efb8..86304d4bd 100644
--- a/src/ImageSharp/Formats/Webp/Lossy/Vp8BandProbas.cs
+++ b/src/ImageSharp/Formats/Webp/Lossy/Vp8BandProbas.cs
@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Text.Json.Serialization;
+
 namespace SixLabors.ImageSharp.Formats.Webp.Lossy;
 
 /// <summary>
@@ -20,6 +22,13 @@ internal class Vp8BandProbas
         }
     }
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Vp8BandProbas"/> class.
+    /// Only used for unit tests.
+    /// </summary>
+    [JsonConstructor]
+    public Vp8BandProbas(Vp8ProbaArray[] probabilities) => this.Probabilities = probabilities;
+
     /// <summary>
     /// Gets the Probabilities.
     /// </summary>
diff --git a/src/ImageSharp/Formats/Webp/Lossy/Vp8CostArray.cs b/src/ImageSharp/Formats/Webp/Lossy/Vp8CostArray.cs
index 2c8d723d7..8268e1c02 100644
--- a/src/ImageSharp/Formats/Webp/Lossy/Vp8CostArray.cs
+++ b/src/ImageSharp/Formats/Webp/Lossy/Vp8CostArray.cs
@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Text.Json.Serialization;
+
 namespace SixLabors.ImageSharp.Formats.Webp.Lossy;
 
 internal class Vp8CostArray
@@ -10,5 +12,12 @@ internal class Vp8CostArray
     /// </summary>
     public Vp8CostArray() => this.Costs = new ushort[67 + 1];
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Vp8CostArray"/> class.
+    /// Only used for unit tests.
+    /// </summary>
+    [JsonConstructor]
+    public Vp8CostArray(ushort[] costs) => this.Costs = costs;
+
     public ushort[] Costs { get; }
 }
diff --git a/src/ImageSharp/Formats/Webp/Lossy/Vp8Costs.cs b/src/ImageSharp/Formats/Webp/Lossy/Vp8Costs.cs
index eee22159e..2441436fb 100644
--- a/src/ImageSharp/Formats/Webp/Lossy/Vp8Costs.cs
+++ b/src/ImageSharp/Formats/Webp/Lossy/Vp8Costs.cs
@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Text.Json.Serialization;
+
 namespace SixLabors.ImageSharp.Formats.Webp.Lossy;
 
 internal class Vp8Costs
@@ -17,6 +19,13 @@ internal class Vp8Costs
         }
     }
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Vp8Costs"/> class.
+    /// Only used for unit tests.
+    /// </summary>
+    [JsonConstructor]
+    public Vp8Costs(Vp8CostArray[] costs) => this.Costs = costs;
+
     /// <summary>
     /// Gets the Costs.
     /// </summary>
diff --git a/src/ImageSharp/Formats/Webp/Lossy/Vp8ProbaArray.cs b/src/ImageSharp/Formats/Webp/Lossy/Vp8ProbaArray.cs
index 337527542..a19f9742f 100644
--- a/src/ImageSharp/Formats/Webp/Lossy/Vp8ProbaArray.cs
+++ b/src/ImageSharp/Formats/Webp/Lossy/Vp8ProbaArray.cs
@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Text.Json.Serialization;
+
 namespace SixLabors.ImageSharp.Formats.Webp.Lossy;
 
 /// <summary>
@@ -13,6 +15,13 @@ internal class Vp8ProbaArray
     /// </summary>
     public Vp8ProbaArray() => this.Probabilities = new byte[WebpConstants.NumProbas];
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Vp8ProbaArray"/> class.
+    /// Only used for unit tests.
+    /// </summary>
+    [JsonConstructor]
+    public Vp8ProbaArray(byte[] probabilities) => this.Probabilities = probabilities;
+
     /// <summary>
     /// Gets the probabilities.
     /// </summary>
diff --git a/src/ImageSharp/Formats/Webp/Lossy/Vp8Residual.cs b/src/ImageSharp/Formats/Webp/Lossy/Vp8Residual.cs
index 68bf09f94..c00d7dbdd 100644
--- a/src/ImageSharp/Formats/Webp/Lossy/Vp8Residual.cs
+++ b/src/ImageSharp/Formats/Webp/Lossy/Vp8Residual.cs
@@ -7,6 +7,7 @@ using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Runtime.Intrinsics;
 using System.Runtime.Intrinsics.X86;
+using System.Text.Json.Serialization;
 
 namespace SixLabors.ImageSharp.Formats.Webp.Lossy;
 
@@ -15,6 +16,22 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy;
 /// </summary>
 internal class Vp8Residual
 {
+    public Vp8Residual()
+    {
+    }
+
+    [JsonConstructor]
+    public Vp8Residual(int first, int last, int coeffType, short[] coeffs, Vp8BandProbas[] prob, Vp8Stats[] stats, Vp8Costs[] costs)
+    {
+        this.First = first;
+        this.Last = last;
+        this.CoeffType = coeffType;
+        this.Coeffs = coeffs;
+        this.Prob = prob;
+        this.Stats = stats;
+        this.Costs = costs;
+    }
+
     public int First { get; set; }
 
     public int Last { get; set; }
@@ -156,6 +173,55 @@ internal class Vp8Residual
             return LossyUtils.Vp8BitCost(0, (byte)p0);
         }
 
+        if (false)
+        {
+            Span<byte> scratch = stackalloc byte[32];
+            Span<byte> ctxs = scratch.Slice(0, 16);
+            Span<byte> levels = scratch.Slice(16);
+            Span<ushort> absLevels = stackalloc ushort[16];
+
+            // Precompute clamped levels and contexts, packed to 8b.
+            ref short outputRef = ref MemoryMarshal.GetReference<short>(this.Coeffs);
+            Vector256<short> c0 = Unsafe.As<short, Vector256<byte>>(ref outputRef).AsInt16();
+            Vector256<short> d0 = Avx2.Subtract(Vector256<short>.Zero, c0);
+            Vector256<short> e0 = Avx2.Max(c0, d0); // abs(v), 16b
+            Vector256<sbyte> f = Avx2.PackSignedSaturate(e0, e0);
+            Vector256<byte> g = Avx2.Min(f.AsByte(), Vector256.Create((byte)2));
+            Vector256<byte> h = Avx2.Min(f.AsByte(), Vector256.Create((byte)67)); // clampLevel in [0..67]
+
+            ref byte ctxsRef = ref MemoryMarshal.GetReference(ctxs);
+            ref byte levelsRef = ref MemoryMarshal.GetReference(levels);
+            ref ushort absLevelsRef = ref MemoryMarshal.GetReference(absLevels);
+            Unsafe.As<byte, Vector128<byte>>(ref ctxsRef) = g.GetLower();
+            Unsafe.As<byte, Vector128<byte>>(ref levelsRef) = h.GetLower();
+            Unsafe.As<ushort, Vector256<ushort>>(ref absLevelsRef) = e0.AsUInt16();
+
+            int level;
+            int flevel;
+            for (; n < this.Last; ++n)
+            {
+                int ctx = ctxs[n];
+                level = levels[n];
+                flevel = absLevels[n];
+                cost += WebpLookupTables.Vp8LevelFixedCosts[flevel] + t.Costs[level];
+                t = costs[n + 1].Costs[ctx];
+            }
+
+            // Last coefficient is always non-zero.
+            level = levels[n];
+            flevel = absLevels[n];
+            cost += WebpLookupTables.Vp8LevelFixedCosts[flevel] + t.Costs[level];
+            if (n < 15)
+            {
+                int b = WebpConstants.Vp8EncBands[n + 1];
+                int ctx = ctxs[n];
+                int lastP0 = this.Prob[b].Probabilities[ctx].Probabilities[0];
+                cost += LossyUtils.Vp8BitCost(0, (byte)lastP0);
+            }
+
+            return cost;
+        }
+
         if (Sse2.IsSupported)
         {
             Span<byte> scratch = stackalloc byte[32];
diff --git a/src/ImageSharp/Formats/Webp/Lossy/Vp8Stats.cs b/src/ImageSharp/Formats/Webp/Lossy/Vp8Stats.cs
index dda921a7c..b6c05f2d4 100644
--- a/src/ImageSharp/Formats/Webp/Lossy/Vp8Stats.cs
+++ b/src/ImageSharp/Formats/Webp/Lossy/Vp8Stats.cs
@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Text.Json.Serialization;
+
 namespace SixLabors.ImageSharp.Formats.Webp.Lossy;
 
 internal class Vp8Stats
@@ -17,5 +19,12 @@ internal class Vp8Stats
         }
     }
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Vp8Stats"/> class.
+    /// Only used for unit tests.
+    /// </summary>
+    [JsonConstructor]
+    public Vp8Stats(Vp8StatsArray[] stats) => this.Stats = stats;
+
     public Vp8StatsArray[] Stats { get; }
 }
diff --git a/src/ImageSharp/Formats/Webp/Lossy/Vp8StatsArray.cs b/src/ImageSharp/Formats/Webp/Lossy/Vp8StatsArray.cs
index 2fbba6996..864248dd8 100644
--- a/src/ImageSharp/Formats/Webp/Lossy/Vp8StatsArray.cs
+++ b/src/ImageSharp/Formats/Webp/Lossy/Vp8StatsArray.cs
@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Text.Json.Serialization;
+
 namespace SixLabors.ImageSharp.Formats.Webp.Lossy;
 
 internal class Vp8StatsArray
@@ -10,5 +12,12 @@ internal class Vp8StatsArray
     /// </summary>
     public Vp8StatsArray() => this.Stats = new uint[WebpConstants.NumProbas];
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Vp8StatsArray"/> class.
+    /// Only used for unit tests.
+    /// </summary>
+    [JsonConstructor]
+    public Vp8StatsArray(uint[] stats) => this.Stats = stats;
+
     public uint[] Stats { get; }
 }