Complete AV1 inter-intra decoding checkpoint

HEIF_IMPLEMENTATION_PLAN.md

@@ -177,8 +177,8 @@ foreach ($aomEntry in $aomEnvironment)
 The single-reference syntax, buffer, reconstruction, and ownership foundation is verified by `54bb6cbe59bd113058854a3ee31448cf61f462ca`. Reverify the existing downstream implementations in this exact order, treating each as locally implemented but unverified until its current-main evidence is recorded.
 
 - [x] Compound reference selection, paired reference-MV derivation, and equal averaging.
-- [~] Inter-intra prediction. Current item.
+- [x] Inter-intra prediction.
-- [~] Distance-weighted compound prediction.
+- [~] Distance-weighted compound prediction. Current item.
 - [~] Wedge compound prediction.
 - [~] Difference-weighted compound prediction.
 - [~] OBMC.
@@ -220,6 +220,37 @@ Verified equal-average compound checkpoint evidence on 2026-08-31:
   failures or skips. Scoped analyzer and whitespace verification pass for every changed C# file,
   Roslynk reports zero compiler errors and no diagnostics in the changed files, and `git diff --check`
   passes. `.gitattributes` is unchanged.
+- [x] The completed checkpoint was committed as `4075a0844836e863a93cb2e2f3ca42d202c7df1b`
+  with author and committer `James Jackson-South <james_south@hotmail.com>`.
+
+Verified inter-intra checkpoint evidence on 2026-08-31:
+
+- [x] Audited syntax against current libaom `av1/decoder/decodemv.c` and
+  `av1/common/blockd.h`. ImageSharp applies the same sequence enable, skip-mode, block-size, and
+  single-reference gates, reads the same four-mode CDF, and reads wedge syntax only within libaom's
+  wedge-supported `BLOCK_8X8` through `BLOCK_32X32` range.
+- [x] Audited reconstruction against `ii_weights1d`, `ii_size_scales`,
+  `build_smooth_interintra_mask`, and `combine_interintra` in current
+  `av1/common/reconinter.c`. The ImageSharp weights, plane-size scaling, smooth-mask direction,
+  complemented destination orientation, wedge sign, subsampling, and final 6-bit blend match. No
+  production change was required.
+- [x] The mask tests cover all four inter-intra modes, complemented orientation, row-padding
+  sentinels, and the 32-wide curve. FeatureTestRunner covers byte and high-bit-depth selectable
+  blending under SIMD and scalar dispatch, and complete `Av1BlockDecoder.DecodeBlock` tests execute
+  smooth inter-intra reconstruction at 8, 10, and 12 bits.
+- [x] Extracted the fixture's 5,327-byte AV1 `mdat` payload and decoded it with the refreshed current
+  libaom `aomdec`, using one thread with row threading disabled. All 19 frames decoded. The final
+  19,200 YUV444 samples have SHA-256
+  `E8B776C2751DC30CA838931A4B74535FC6E681179568A1278747A38CFF2E5BFA` and match the retained
+  native reference with zero differing samples.
+- [x] The real production sequence requires both smooth and wedge inter-intra blocks, compares the
+  final native Y, Cb, and Cr planes exactly, and compares final RGBA presentation through
+  ImageSharp's established reference-output API. Its constrained 1,024-byte tracked-allocator run
+  proves motion-field allocation and exactly one return for every allocation.
+- [x] The focused Release checkpoint set passes 50/50 on net10.0 and 50/50 on net11.0, with zero
+  failures or skips. Scoped analyzer and whitespace verification pass for both changed C# files.
+  Roslynk reports zero compiler errors and no diagnostics in the changed files, `git diff --check`
+  passes, and `.gitattributes` is unchanged.
 
 For every item:
 

tests/ImageSharp.Tests/Formats/Heif/Av1/Av1CompoundInterPredictorTests.cs

@@ -60,7 +60,7 @@ public class Av1CompoundInterPredictorTests
     /// Verifies the four smooth inter-intra modes and their complemented destination orientation.
     /// </summary>
     [Fact]
-    public void SmoothInterIntraMasksMatchPinnedWeights()
+    public void SmoothInterIntraMasksMatchCurrentLibaomWeights()
     {
         ReadOnlySpan<byte> weights = [60, 34, 19, 11, 6, 4, 2, 1];
 
@@ -103,10 +103,10 @@ public class Av1CompoundInterPredictorTests
     }
 
     /// <summary>
-    /// Verifies the pinned horizontal curve at the index exercised by a 32-by-16 inter-intra block.
+    /// Verifies the current libaom horizontal curve at the index exercised by a 32-by-16 inter-intra block.
     /// </summary>
     [Fact]
-    public void HorizontalInterIntraMaskMatchesPinnedThirtyTwoWideCurve()
+    public void HorizontalInterIntraMaskMatchesCurrentLibaomThirtyTwoWideCurve()
     {
         const int width = 32;
         const int height = 16;

tests/ImageSharp.Tests/Formats/Heif/Av1/Av1ReconstructionConformanceTests.cs

@@ -1002,14 +1002,14 @@ public class Av1ReconstructionConformanceTests
     }
 
     /// <summary>
-    /// Verifies every selectable compound and inter-intra production branch against pinned native and presentation references.
+    /// Verifies every selectable compound and inter-intra production branch against retained native and presentation references.
     /// </summary>
     [Theory]
     [WithFile(TestImages.Heif.Av1DistanceWeightedCompoundSequenceAvif, PixelTypes.Rgba32)]
     [WithFile(TestImages.Heif.Av1WedgeCompoundSequenceAvif, PixelTypes.Rgba32)]
     [WithFile(TestImages.Heif.Av1DifferenceWeightedCompoundSequenceAvif, PixelTypes.Rgba32)]
     [WithFile(TestImages.Heif.Av1InterIntraSequenceAvif, PixelTypes.Rgba32)]
-    public void DecodeRealLibavifSequencesWithSelectableCompoundAndInterIntraMatchesPinnedReferences(
+    public void DecodeRealLibavifSequencesWithSelectableCompoundAndInterIntraMatchesRetainedReferences(
         TestImageProvider<Rgba32> provider)
 
         => FeatureTestRunner.RunWithHwIntrinsicsFeature(

tests/Images/Input/Heif/Av1/Conformance/README.md

@@ -118,7 +118,11 @@ only and is not used to establish AV1 reconstruction arithmetic.
 
 ## Selectable compound and inter-intra fixtures
 
-The four selectable-compound fixtures use the same pinned `tests/data/webp_logo_animated.y4m` source and its `0872208D9C19B68B10A1647FA6849CFC4E2B21A19561ACD672E0629C70EFACA2` SHA-256. They were encoded at speed zero after disabling later inter-mode checkpoints. Each command also disables competing prediction tools that would prevent the resulting stream from isolating its named mode:
+The four AVIF files are retained solely as interoperability inputs. Their original creation commands
+used the same `tests/data/webp_logo_animated.y4m` source and encoded at speed zero after disabling later
+inter-mode checkpoints. These commands record container-fixture provenance only; they are not codec
+implementation references. Each command also disables competing prediction tools that would prevent the
+resulting stream from isolating its named mode:
 
 ```text
 ./avifenc -j 1 -c aom -s 0 -q 80 -a enable-obmc=0 -a enable-warped-motion=0 -a enable-global-motion=0 -a enable-masked-comp=0 -a enable-interintra-comp=0 tests/data/webp_logo_animated.y4m libavif-webp-logo-distance-weighted-compound.avif
@@ -127,21 +131,24 @@ The four selectable-compound fixtures use the same pinned `tests/data/webp_logo_
 ./avifenc -j 1 -c aom -s 0 -q 80 -a enable-obmc=0 -a enable-warped-motion=0 -a enable-global-motion=0 -a enable-dist-wtd-comp=0 -a enable-masked-comp=0 tests/data/webp_logo_animated.y4m libavif-webp-logo-inter-intra.avif
 ```
 
-Pinned scalar libavif generated each final native and presentation reference with:
+| Fixture | AVIF SHA-256 | Retained frame-18 Y4M SHA-256 | Retained frame-18 PNG SHA-256 |
-
-```text
-./avifdec -j 1 -c aom --index 18 <fixture>.avif <fixture>-libaom.y4m
-./avifdec -j 1 -c aom --index 18 <fixture>.avif <fixture>-libavif.png
-```
-
-| Fixture | AVIF SHA-256 | Frame-18 Y4M SHA-256 | Frame-18 PNG SHA-256 |
 | --- | --- | --- | --- |
 | `libavif-webp-logo-distance-weighted-compound` | `DA710D11C60F03EEA209E4360E2FC807B89C49AD50671F0DFB1BCF4AD5EF76DD` | `904D1B5B3E7F334CE8D44040F9A7BDCAC1F7773122FF1C5F06A5B4DD31A62A97` | `D2CB388C9092EF17C4F0382C0150DD30D6F9D0EE247FF45AB5D7D4D312CEB23C` |
 | `libavif-webp-logo-wedge-compound` | `98640640A445055FEA3D9E2F4A78FEEF54E97F8171B472CF57D99156E1C553B2` | `904D1B5B3E7F334CE8D44040F9A7BDCAC1F7773122FF1C5F06A5B4DD31A62A97` | `D2CB388C9092EF17C4F0382C0150DD30D6F9D0EE247FF45AB5D7D4D312CEB23C` |
 | `libavif-webp-logo-difference-weighted-compound` | `FC6459CD334762D74D9D2654640221E80C463CC01B82B29A5866C9E725ABE273` | `904D1B5B3E7F334CE8D44040F9A7BDCAC1F7773122FF1C5F06A5B4DD31A62A97` | `D2CB388C9092EF17C4F0382C0150DD30D6F9D0EE247FF45AB5D7D4D312CEB23C` |
 | `libavif-webp-logo-inter-intra` | `71DF22E63626B5BC9001FF1E88076B90F11BB47D18089750853E66F0CBBB084B` | `502265688138641A7B12C8C4190B66C76CD4808D9AED05B06486056B39D7E9A0` | `F0DE4CCDFB6D95A400E69B69FA4C57F0BEEEEE75825722C31613385F0B3FD9FC` |
 
-Pinned libaom block tracing confirms that these streams select distance weighting, both wedge signs, both difference-mask types, and both smooth and wedge inter-intra prediction. The production test independently requires those decoded mode states, decodes all preceding samples, compares the final native Y, U, and V planes exactly, compares the final RGBA presentation exactly, and repeats reconstruction with constrained tracked allocation.
+The inter-intra fixture's 5,327-byte AV1 `mdat` payload was decoded directly with the current official
+libaom `main` checkout observed at `441c439b9916474cac15d2822af47a9ad70674a8`, using one thread and
+with row threading disabled. Current `aomdec` produced all 19 YUV444 frames. The final frame's 19,200
+native samples have SHA-256 `E8B776C2751DC30CA838931A4B74535FC6E681179568A1278747A38CFF2E5BFA`
+and match the retained Y4M with zero differing samples.
+
+The production tests independently require their decoded mode states. The inter-intra input must exercise
+both smooth and wedge inter-intra prediction, decode all preceding samples, compare the final native Y,
+Cb, and Cr planes exactly, compare final RGBA presentation through ImageSharp's established
+reference-output API, and repeat reconstruction with constrained tracked allocation. The retained PNG is
+presentation evidence only and is not an AV1 reconstruction reference.
 
 ## Overlapping motion-compensation fixture