From 43035256d784c5e5d3ed25b67f2bffa68311d2da Mon Sep 17 00:00:00 2001
From: James Jackson-South <james_south@hotmail.com>
Date: Wed, 2 Sep 2026 22:19:25 +1000
Subject: [PATCH] Correct AV1 distortion cost scaling

---
 .../Formats/Heif/Av1/Entropy/Av1RateDistortion.cs           | 2 +-
 tests/ImageSharp.Tests/Formats/Heif/Av1/Av1EntropyTests.cs  | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/ImageSharp/Formats/Heif/Av1/Entropy/Av1RateDistortion.cs b/src/ImageSharp/Formats/Heif/Av1/Entropy/Av1RateDistortion.cs
index c0edfb1ccd..d25f972d7c 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Entropy/Av1RateDistortion.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Entropy/Av1RateDistortion.cs
@@ -19,6 +19,6 @@ internal static class Av1RateDistortion
     {
         long weightedRate = (long)rate * rateMultiplier;
         long roundedRate = (weightedRate + (1 << (Av1ProbabilityCost.CostShift - 1))) >> Av1ProbabilityCost.CostShift;
-        return roundedRate + distortion;
+        return roundedRate + (distortion << 7);
     }
 }
diff --git a/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1EntropyTests.cs b/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1EntropyTests.cs
index 966d78d8df..cbde2bf2d3 100644
--- a/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1EntropyTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1EntropyTests.cs
@@ -522,9 +522,9 @@ public class Av1EntropyTests
     [Theory]
     [InlineData(1, 255, 0L, 0L)]
     [InlineData(1, 256, 0L, 1L)]
-    [InlineData(128, 512, 1000L, 1128L)]
-    [InlineData(512, 512, 1000L, 1512L)]
-    [InlineData(64, 1024, 4_000_000_000L, 4_000_000_128L)]
+    [InlineData(128, 512, 1000L, 128_128L)]
+    [InlineData(512, 512, 1000L, 128_512L)]
+    [InlineData(64, 1024, 4_000_000_000L, 512_000_000_128L)]
     public void RateDistortionCostMatchesCurrentLibaom(
         int rateMultiplier,
         int rate,