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Add regular AV1 quantization across sample precisions 

Implement zero-bin thresholds, sharpness rounding, reciprocal correction, and dequantization through scalar and SIMD operators. Fix the .NET 11 AVX-512 test switch so narrower hardware paths actually execute.

Verified in the current worktree with Release .NET 11 VSTest: 379 focused cases passed. Temporary native comparison matched all quantized coefficients, dequantized coefficients, and end positions in 5184 cases across scalar, 128-, 256-, and 512-bit paths. This is a motion-winner dependency checkpoint; production controller integration and encoder parity remain open.
pull/2633/head
James Jackson-South 4 weeks ago
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6 changed files with 679 additions and 0 deletions
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  1. 131
      src/ImageSharp/Formats/Heif/Av1/Pipeline/Quantizers/Av1ForwardQuantizer.HighBitDepthRegularQuantizationOperator.cs
  2. 175
      src/ImageSharp/Formats/Heif/Av1/Pipeline/Quantizers/Av1ForwardQuantizer.Regular.cs
  3. 103
      src/ImageSharp/Formats/Heif/Av1/Pipeline/Quantizers/Av1ForwardQuantizer.RegularOperator.cs
  4. 116
      src/ImageSharp/Formats/Heif/Av1/Pipeline/Quantizers/Av1ForwardQuantizer.RegularQuantizationOperator.cs
  5. 148
      tests/ImageSharp.Tests/Formats/Heif/Av1/Av1RegularQuantizerTests.cs
  6. 6
      tests/ImageSharp.Tests/TestUtilities/FeatureTesting/FeatureTestRunner.cs

131
src/ImageSharp/Formats/Heif/Av1/Pipeline/Quantizers/Av1ForwardQuantizer.HighBitDepthRegularQuantizationOperator.cs
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// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.
using System.Runtime.Intrinsics;
namespace SixLabors.ImageSharp.Formats.Heif.Av1.Pipeline.Quantizers;
internal static partial class Av1ForwardQuantizer
{
/// <summary>
/// Quantizes high-bit-depth magnitudes without the sixteen-bit saturation used for byte samples.
/// </summary>
public readonly struct HighBitDepthRegularQuantizationOperator : IRegularQuantizationOperator
{
/// <inheritdoc/>
public static Vector128<int> Quantize(
Vector128<int> coefficients,
Vector128<int> zeroBin,
Vector128<int> rounding,
Vector128<int> quantizer,
Vector128<int> shift,
Vector128<int> dequantizer,
int logScale,
out Vector128<int> dequantizedCoefficients)
{
Vector128<int> sign = coefficients >> 31;
Vector128<int> magnitude = Vector128.Abs(coefficients);
Vector128<int> mask = ~Vector128.GreaterThan(zeroBin, magnitude);
Vector128<int> rounded = magnitude + rounding;
// Preserve signed products in two widened halves. The reciprocal correction can be negative;
// an arithmetic Q16 shift restores its implicit leading bit before the second multiplication.
Vector128<long> lower = Vector128.WidenLower(rounded);
Vector128<long> upper = Vector128.WidenUpper(rounded);
lower += (lower * Vector128.WidenLower(quantizer)) >> 16;
upper += (upper * Vector128.WidenUpper(quantizer)) >> 16;
lower = (lower * Vector128.WidenLower(shift)) >> (16 - logScale);
upper = (upper * Vector128.WidenUpper(shift)) >> (16 - logScale);
Vector128<int> quantizedMagnitude = Vector128.Narrow(lower, upper) & mask;
Vector128<int> dequantizedMagnitude = (quantizedMagnitude * dequantizer) >> logScale;
dequantizedCoefficients = (dequantizedMagnitude ^ sign) - sign;
return (quantizedMagnitude ^ sign) - sign;
}
/// <inheritdoc/>
public static Vector256<int> Quantize(
Vector256<int> coefficients,
Vector256<int> zeroBin,
Vector256<int> rounding,
Vector256<int> quantizer,
Vector256<int> shift,
Vector256<int> dequantizer,
int logScale,
out Vector256<int> dequantizedCoefficients)
{
Vector256<int> sign = coefficients >> 31;
Vector256<int> magnitude = Vector256.Abs(coefficients);
Vector256<int> mask = ~Vector256.GreaterThan(zeroBin, magnitude);
Vector256<int> rounded = magnitude + rounding;
// Preserve signed products in two widened halves. The reciprocal correction can be negative;
// an arithmetic Q16 shift restores its implicit leading bit before the second multiplication.
Vector256<long> lower = Vector256.WidenLower(rounded);
Vector256<long> upper = Vector256.WidenUpper(rounded);
lower += (lower * Vector256.WidenLower(quantizer)) >> 16;
upper += (upper * Vector256.WidenUpper(quantizer)) >> 16;
lower = (lower * Vector256.WidenLower(shift)) >> (16 - logScale);
upper = (upper * Vector256.WidenUpper(shift)) >> (16 - logScale);
Vector256<int> quantizedMagnitude = Vector256.Narrow(lower, upper) & mask;
Vector256<int> dequantizedMagnitude = (quantizedMagnitude * dequantizer) >> logScale;
dequantizedCoefficients = (dequantizedMagnitude ^ sign) - sign;
return (quantizedMagnitude ^ sign) - sign;
}
/// <inheritdoc/>
public static Vector512<int> Quantize(
Vector512<int> coefficients,
Vector512<int> zeroBin,
Vector512<int> rounding,
Vector512<int> quantizer,
Vector512<int> shift,
Vector512<int> dequantizer,
int logScale,
out Vector512<int> dequantizedCoefficients)
{
Vector512<int> sign = coefficients >> 31;
Vector512<int> magnitude = Vector512.Abs(coefficients);
Vector512<int> mask = ~Vector512.GreaterThan(zeroBin, magnitude);
Vector512<int> rounded = magnitude + rounding;
// Preserve signed products in two widened halves. The reciprocal correction can be negative;
// an arithmetic Q16 shift restores its implicit leading bit before the second multiplication.
Vector512<long> lower = Vector512.WidenLower(rounded);
Vector512<long> upper = Vector512.WidenUpper(rounded);
lower += (lower * Vector512.WidenLower(quantizer)) >> 16;
upper += (upper * Vector512.WidenUpper(quantizer)) >> 16;
lower = (lower * Vector512.WidenLower(shift)) >> (16 - logScale);
upper = (upper * Vector512.WidenUpper(shift)) >> (16 - logScale);
Vector512<int> quantizedMagnitude = Vector512.Narrow(lower, upper) & mask;
Vector512<int> dequantizedMagnitude = (quantizedMagnitude * dequantizer) >> logScale;
dequantizedCoefficients = (dequantizedMagnitude ^ sign) - sign;
return (quantizedMagnitude ^ sign) - sign;
}
/// <inheritdoc/>
public static int Quantize(
int coefficients,
int zeroBin,
int rounding,
int quantizer,
int shift,
int dequantizer,
int logScale,
out int dequantizedCoefficients)
{
int sign = coefficients >> 31;
int magnitude = (coefficients ^ sign) - sign;
int quantizedMagnitude = 0;
if (magnitude >= zeroBin)
{
long rounded = (long)magnitude + rounding;
long corrected = rounded + ((rounded * quantizer) >> 16);
quantizedMagnitude = (int)((corrected * shift) >> (16 - logScale));
}
int dequantizedMagnitude = (quantizedMagnitude * dequantizer) >> logScale;
dequantizedCoefficients = (dequantizedMagnitude ^ sign) - sign;
return (quantizedMagnitude ^ sign) - sign;
}
}
}

175
src/ImageSharp/Formats/Heif/Av1/Pipeline/Quantizers/Av1ForwardQuantizer.Regular.cs
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// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Intrinsics;
using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
namespace SixLabors.ImageSharp.Formats.Heif.Av1.Pipeline.Quantizers;
internal static partial class Av1ForwardQuantizer
{
/// <summary>
/// Quantizes a transform with the regular zero-bin and reciprocal-correction arithmetic.
/// </summary>
/// <param name="coefficients">The raster-order transformed coefficients.</param>
/// <param name="quantizedCoefficients">The raster-order coding coefficients.</param>
/// <param name="dequantizedCoefficients">The raster-order reconstruction coefficients.</param>
/// <param name="transformSize">The transform dimensions.</param>
/// <param name="transformType">The transform type selecting coefficient scan order.</param>
/// <param name="qIndex">The base quantizer index.</param>
/// <param name="dcDeltaQ">The DC index adjustment.</param>
/// <param name="acDeltaQ">The AC index adjustment.</param>
/// <param name="bitDepth">The coded sample precision.</param>
/// <param name="sharpness">The encoder sharpness setting from zero through seven.</param>
/// <returns>The one-based final nonzero scan position.</returns>
public static ushort QuantizeRegular(
ReadOnlySpan<int> coefficients,
Span<int> quantizedCoefficients,
Span<int> dequantizedCoefficients,
Av1TransformSize transformSize,
Av1TransformType transformType,
int qIndex,
int dcDeltaQ,
int acDeltaQ,
Av1BitDepth bitDepth,
int sharpness)
=> bitDepth == Av1BitDepth.EightBit
? QuantizeRegular<RegularQuantizationOperator>(
coefficients, quantizedCoefficients, dequantizedCoefficients, transformSize, transformType, qIndex, dcDeltaQ, acDeltaQ, bitDepth, sharpness)
: QuantizeRegular<HighBitDepthRegularQuantizationOperator>(
coefficients, quantizedCoefficients, dequantizedCoefficients, transformSize, transformType, qIndex, dcDeltaQ, acDeltaQ, bitDepth, sharpness);
/// <summary>
/// Traverses regular quantization with one DC coefficient followed by contiguous AC vectors and a scalar tail.
/// </summary>
private static ushort QuantizeRegular<TOperator>(
ReadOnlySpan<int> coefficients,
Span<int> quantizedCoefficients,
Span<int> dequantizedCoefficients,
Av1TransformSize transformSize,
Av1TransformType transformType,
int qIndex,
int dcDeltaQ,
int acDeltaQ,
Av1BitDepth bitDepth,
int sharpness)
where TOperator : struct, IRegularQuantizationOperator
{
int count = transformSize.GetAdjusted().GetSize2d();
int logScale = transformSize.GetScale();
int zeroBinFactor = Av1InverseTransformMath.GetQzbinFactor(qIndex, bitDepth);
int roundingFactor = qIndex == 0 ? 64 : sharpness == 0 ? 48 : 64 - (16 * (7 - sharpness) / 7);
int dcDequantizer = Av1QuantizationLookup.GetDcQuant(qIndex, dcDeltaQ, bitDepth);
int acDequantizer = Av1QuantizationLookup.GetAcQuant(qIndex, acDeltaQ, bitDepth);
Av1InverseTransformMath.InvertQuantization(out int dcQuantizer, out int dcShift, dcDequantizer);
Av1InverseTransformMath.InvertQuantization(out int acQuantizer, out int acShift, acDequantizer);
// Zero-bin constants round twice: once from Q7 and once for the transform scale. Rounding
// constants first truncate from Q7, then round for that same scale. Combining either pair of
// shifts would change coefficients at the quantization boundary.
int dcZeroBin = RoundPowerOfTwo(RoundPowerOfTwo(zeroBinFactor * dcDequantizer, 7), logScale);
int acZeroBin = RoundPowerOfTwo(RoundPowerOfTwo(zeroBinFactor * acDequantizer, 7), logScale);
int dcRounding = RoundPowerOfTwo((roundingFactor * dcDequantizer) >> 7, logScale);
int acRounding = RoundPowerOfTwo((roundingFactor * acDequantizer) >> 7, logScale);
ref int sourceBase = ref MemoryMarshal.GetReference(coefficients);
ref int quantizedBase = ref MemoryMarshal.GetReference(quantizedCoefficients);
ref int dequantizedBase = ref MemoryMarshal.GetReference(dequantizedCoefficients);
// DC has different constants. Processing it once leaves a uniform AC traversal with no lane masks
// for DC and no scratch coefficient copy; every output position is overwritten on each candidate.
quantizedBase = TOperator.Quantize(
sourceBase, dcZeroBin, dcRounding, dcQuantizer, dcShift, dcDequantizer, logScale, out dequantizedBase);
int index = 1;
if (Vector512.IsHardwareAccelerated)
{
Vector512<int> zeroBin = Vector512.Create(acZeroBin);
Vector512<int> rounding = Vector512.Create(acRounding);
Vector512<int> quantizer = Vector512.Create(acQuantizer);
Vector512<int> shift = Vector512.Create(acShift);
Vector512<int> dequantizer = Vector512.Create(acDequantizer);
// Each lane owns one contiguous coefficient. Narrower tiers resume at the first unread
// coefficient so unaligned starts and vector tails need neither padding nor overlapping stores.
for (; index <= count - Vector512<int>.Count; index += Vector512<int>.Count)
{
Vector512<int> values = Vector512.LoadUnsafe(ref sourceBase, (nuint)index);
Vector512<int> quantized = TOperator.Quantize(
values, zeroBin, rounding, quantizer, shift, dequantizer, logScale, out Vector512<int> dequantized);
quantized.StoreUnsafe(ref quantizedBase, (nuint)index);
dequantized.StoreUnsafe(ref dequantizedBase, (nuint)index);
}
}
if (Vector256.IsHardwareAccelerated)
{
Vector256<int> zeroBin = Vector256.Create(acZeroBin);
Vector256<int> rounding = Vector256.Create(acRounding);
Vector256<int> quantizer = Vector256.Create(acQuantizer);
Vector256<int> shift = Vector256.Create(acShift);
Vector256<int> dequantizer = Vector256.Create(acDequantizer);
// Each lane owns one contiguous coefficient. Narrower tiers resume at the first unread
// coefficient so unaligned starts and vector tails need neither padding nor overlapping stores.
for (; index <= count - Vector256<int>.Count; index += Vector256<int>.Count)
{
Vector256<int> values = Vector256.LoadUnsafe(ref sourceBase, (nuint)index);
Vector256<int> quantized = TOperator.Quantize(
values, zeroBin, rounding, quantizer, shift, dequantizer, logScale, out Vector256<int> dequantized);
quantized.StoreUnsafe(ref quantizedBase, (nuint)index);
dequantized.StoreUnsafe(ref dequantizedBase, (nuint)index);
}
}
if (Vector128.IsHardwareAccelerated)
{
Vector128<int> zeroBin = Vector128.Create(acZeroBin);
Vector128<int> rounding = Vector128.Create(acRounding);
Vector128<int> quantizer = Vector128.Create(acQuantizer);
Vector128<int> shift = Vector128.Create(acShift);
Vector128<int> dequantizer = Vector128.Create(acDequantizer);
// Each lane owns one contiguous coefficient. Narrower tiers resume at the first unread
// coefficient so unaligned starts and vector tails need neither padding nor overlapping stores.
for (; index <= count - Vector128<int>.Count; index += Vector128<int>.Count)
{
Vector128<int> values = Vector128.LoadUnsafe(ref sourceBase, (nuint)index);
Vector128<int> quantized = TOperator.Quantize(
values, zeroBin, rounding, quantizer, shift, dequantizer, logScale, out Vector128<int> dequantized);
quantized.StoreUnsafe(ref quantizedBase, (nuint)index);
dequantized.StoreUnsafe(ref dequantizedBase, (nuint)index);
}
}
for (; index < count; index++)
{
Unsafe.Add(ref quantizedBase, index) = TOperator.Quantize(
Unsafe.Add(ref sourceBase, index),
acZeroBin,
acRounding,
acQuantizer,
acShift,
acDequantizer,
logScale,
out Unsafe.Add(ref dequantizedBase, index));
}
// Coding and reconstruction retain raster order. Only the end position is reduced in scan order.
ReadOnlySpan<short> scan = Av1ScanOrderConstants.GetScanOrder(transformSize, transformType).Scan;
for (int scanIndex = count - 1; scanIndex >= 0; scanIndex--)
{
if (Unsafe.Add(ref quantizedBase, scan[scanIndex]) != 0)
{
return (ushort)(scanIndex + 1);
}
}
return 0;
}
}

103
src/ImageSharp/Formats/Heif/Av1/Pipeline/Quantizers/Av1ForwardQuantizer.RegularOperator.cs
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// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.
using System.Runtime.Intrinsics;
namespace SixLabors.ImageSharp.Formats.Heif.Av1.Pipeline.Quantizers;
internal static partial class Av1ForwardQuantizer
{
/// <summary>
/// Applies regular quantization while preserving the precision-specific rounded-magnitude contract.
/// </summary>
public interface IRegularQuantizationOperator
{
/// <summary>
/// Applies the zero bin, corrected reciprocal, dequantization, and coefficient sign.
/// </summary>
/// <param name="coefficients">The signed transform coefficients.</param>
/// <param name="zeroBin">The inclusive magnitude threshold after transform scaling.</param>
/// <param name="rounding">The rounded magnitude adjustment.</param>
/// <param name="quantizer">The signed reciprocal correction below its implicit leading bit.</param>
/// <param name="shift">The power-of-two reciprocal scale.</param>
/// <param name="dequantizer">The reconstruction quantizer.</param>
/// <param name="logScale">The transform coefficient scale.</param>
/// <param name="dequantizedCoefficients">The signed reconstruction coefficients.</param>
/// <returns>The signed coding coefficients.</returns>
static abstract Vector128<int> Quantize(
Vector128<int> coefficients,
Vector128<int> zeroBin,
Vector128<int> rounding,
Vector128<int> quantizer,
Vector128<int> shift,
Vector128<int> dequantizer,
int logScale,
out Vector128<int> dequantizedCoefficients);
/// <summary>
/// Applies the zero bin, corrected reciprocal, dequantization, and coefficient sign.
/// </summary>
/// <param name="coefficients">The signed transform coefficients.</param>
/// <param name="zeroBin">The inclusive magnitude threshold after transform scaling.</param>
/// <param name="rounding">The rounded magnitude adjustment.</param>
/// <param name="quantizer">The signed reciprocal correction below its implicit leading bit.</param>
/// <param name="shift">The power-of-two reciprocal scale.</param>
/// <param name="dequantizer">The reconstruction quantizer.</param>
/// <param name="logScale">The transform coefficient scale.</param>
/// <param name="dequantizedCoefficients">The signed reconstruction coefficients.</param>
/// <returns>The signed coding coefficients.</returns>
static abstract Vector256<int> Quantize(
Vector256<int> coefficients,
Vector256<int> zeroBin,
Vector256<int> rounding,
Vector256<int> quantizer,
Vector256<int> shift,
Vector256<int> dequantizer,
int logScale,
out Vector256<int> dequantizedCoefficients);
/// <summary>
/// Applies the zero bin, corrected reciprocal, dequantization, and coefficient sign.
/// </summary>
/// <param name="coefficients">The signed transform coefficients.</param>
/// <param name="zeroBin">The inclusive magnitude threshold after transform scaling.</param>
/// <param name="rounding">The rounded magnitude adjustment.</param>
/// <param name="quantizer">The signed reciprocal correction below its implicit leading bit.</param>
/// <param name="shift">The power-of-two reciprocal scale.</param>
/// <param name="dequantizer">The reconstruction quantizer.</param>
/// <param name="logScale">The transform coefficient scale.</param>
/// <param name="dequantizedCoefficients">The signed reconstruction coefficients.</param>
/// <returns>The signed coding coefficients.</returns>
static abstract Vector512<int> Quantize(
Vector512<int> coefficients,
Vector512<int> zeroBin,
Vector512<int> rounding,
Vector512<int> quantizer,
Vector512<int> shift,
Vector512<int> dequantizer,
int logScale,
out Vector512<int> dequantizedCoefficients);
/// <summary>
/// Applies the zero bin, corrected reciprocal, dequantization, and coefficient sign.
/// </summary>
/// <param name="coefficients">The signed transform coefficients.</param>
/// <param name="zeroBin">The inclusive magnitude threshold after transform scaling.</param>
/// <param name="rounding">The rounded magnitude adjustment.</param>
/// <param name="quantizer">The signed reciprocal correction below its implicit leading bit.</param>
/// <param name="shift">The power-of-two reciprocal scale.</param>
/// <param name="dequantizer">The reconstruction quantizer.</param>
/// <param name="logScale">The transform coefficient scale.</param>
/// <param name="dequantizedCoefficients">The signed reconstruction coefficients.</param>
/// <returns>The signed coding coefficients.</returns>
static abstract int Quantize(
int coefficients,
int zeroBin,
int rounding,
int quantizer,
int shift,
int dequantizer,
int logScale,
out int dequantizedCoefficients);
}
}

116
src/ImageSharp/Formats/Heif/Av1/Pipeline/Quantizers/Av1ForwardQuantizer.RegularQuantizationOperator.cs
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// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.
using System.Runtime.Intrinsics;
namespace SixLabors.ImageSharp.Formats.Heif.Av1.Pipeline.Quantizers;
internal static partial class Av1ForwardQuantizer
{
/// <summary>
/// Quantizes byte-source coefficients with saturated sixteen-bit rounded magnitudes.
/// </summary>
public readonly struct RegularQuantizationOperator : IRegularQuantizationOperator
{
/// <inheritdoc/>
public static Vector128<int> Quantize(
Vector128<int> coefficients,
Vector128<int> zeroBin,
Vector128<int> rounding,
Vector128<int> quantizer,
Vector128<int> shift,
Vector128<int> dequantizer,
int logScale,
out Vector128<int> dequantizedCoefficients)
{
Vector128<int> sign = coefficients >> 31;
Vector128<int> magnitude = Vector128.Abs(coefficients);
Vector128<int> mask = ~Vector128.GreaterThan(zeroBin, magnitude);
Vector128<int> rounded = Vector128.Min(magnitude + rounding, Vector128.Create((int)short.MaxValue));
// Saturation bounds both signed products to 32-bit lanes. The first Q16 multiplication
// restores the reciprocal's implicit leading bit; the second removes its power-of-two scale.
Vector128<int> corrected = rounded + ((rounded * quantizer) >> 16);
Vector128<int> quantizedMagnitude = ((corrected * shift) >> (16 - logScale)) & mask;
Vector128<int> dequantizedMagnitude = (quantizedMagnitude * dequantizer) >> logScale;
dequantizedCoefficients = (dequantizedMagnitude ^ sign) - sign;
return (quantizedMagnitude ^ sign) - sign;
}
/// <inheritdoc/>
public static Vector256<int> Quantize(
Vector256<int> coefficients,
Vector256<int> zeroBin,
Vector256<int> rounding,
Vector256<int> quantizer,
Vector256<int> shift,
Vector256<int> dequantizer,
int logScale,
out Vector256<int> dequantizedCoefficients)
{
Vector256<int> sign = coefficients >> 31;
Vector256<int> magnitude = Vector256.Abs(coefficients);
Vector256<int> mask = ~Vector256.GreaterThan(zeroBin, magnitude);
Vector256<int> rounded = Vector256.Min(magnitude + rounding, Vector256.Create((int)short.MaxValue));
// Saturation bounds both signed products to 32-bit lanes. The first Q16 multiplication
// restores the reciprocal's implicit leading bit; the second removes its power-of-two scale.
Vector256<int> corrected = rounded + ((rounded * quantizer) >> 16);
Vector256<int> quantizedMagnitude = ((corrected * shift) >> (16 - logScale)) & mask;
Vector256<int> dequantizedMagnitude = (quantizedMagnitude * dequantizer) >> logScale;
dequantizedCoefficients = (dequantizedMagnitude ^ sign) - sign;
return (quantizedMagnitude ^ sign) - sign;
}
/// <inheritdoc/>
public static Vector512<int> Quantize(
Vector512<int> coefficients,
Vector512<int> zeroBin,
Vector512<int> rounding,
Vector512<int> quantizer,
Vector512<int> shift,
Vector512<int> dequantizer,
int logScale,
out Vector512<int> dequantizedCoefficients)
{
Vector512<int> sign = coefficients >> 31;
Vector512<int> magnitude = Vector512.Abs(coefficients);
Vector512<int> mask = ~Vector512.GreaterThan(zeroBin, magnitude);
Vector512<int> rounded = Vector512.Min(magnitude + rounding, Vector512.Create((int)short.MaxValue));
// Saturation bounds both signed products to 32-bit lanes. The first Q16 multiplication
// restores the reciprocal's implicit leading bit; the second removes its power-of-two scale.
Vector512<int> corrected = rounded + ((rounded * quantizer) >> 16);
Vector512<int> quantizedMagnitude = ((corrected * shift) >> (16 - logScale)) & mask;
Vector512<int> dequantizedMagnitude = (quantizedMagnitude * dequantizer) >> logScale;
dequantizedCoefficients = (dequantizedMagnitude ^ sign) - sign;
return (quantizedMagnitude ^ sign) - sign;
}
/// <inheritdoc/>
public static int Quantize(
int coefficients,
int zeroBin,
int rounding,
int quantizer,
int shift,
int dequantizer,
int logScale,
out int dequantizedCoefficients)
{
int sign = coefficients >> 31;
int magnitude = (coefficients ^ sign) - sign;
int quantizedMagnitude = 0;
if (magnitude >= zeroBin)
{
int rounded = Math.Min(magnitude + rounding, short.MaxValue);
int corrected = rounded + ((rounded * quantizer) >> 16);
quantizedMagnitude = (corrected * shift) >> (16 - logScale);
}
int dequantizedMagnitude = (quantizedMagnitude * dequantizer) >> logScale;
dequantizedCoefficients = (dequantizedMagnitude ^ sign) - sign;
return (quantizedMagnitude ^ sign) - sign;
}
}
}

148
tests/ImageSharp.Tests/Formats/Heif/Av1/Av1RegularQuantizerTests.cs
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// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.
using System.Runtime.InteropServices;
using System.Runtime.Intrinsics;
using SixLabors.ImageSharp.Formats.Heif.Av1;
using SixLabors.ImageSharp.Formats.Heif.Av1.Pipeline.Quantizers;
using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
using SixLabors.ImageSharp.Tests.TestUtilities;
namespace SixLabors.ImageSharp.Tests.Formats.Heif.Av1;
/// <summary>
/// Verifies regular quantization's precision, scan position, and buffer boundaries across hardware paths.
/// </summary>
[Trait("Format", "Avif")]
public class Av1RegularQuantizerTests
{
/// <summary>
/// Exercises regular quantization under each available vector width and scalar fallback.
/// </summary>
[Fact]
public void RegularQuantizationPreservesCoefficientContracts()
=> FeatureTestRunner.RunWithHwIntrinsicsFeature(
ValidateQuantization,
HwIntrinsics.AllowAll | HwIntrinsics.DisableAVX512F | HwIntrinsics.DisableAVX | HwIntrinsics.DisableHWIntrinsic);
/// <summary>
/// Exports inputs and results for independent native comparison while checking observable storage contracts.
/// </summary>
private static void ValidateQuantization()
{
string vectorWidth = Vector512.IsHardwareAccelerated ? "512"
: Vector256.IsHardwareAccelerated ? "256"
: Vector128.IsHardwareAccelerated ? "128" : "0";
string directory = Path.Combine(TestEnvironment.ActualOutputDirectoryFullPath, "Heif", "Av1", "RegularQuantization", vectorWidth);
Directory.CreateDirectory(directory);
foreach (Av1BitDepth bitDepth in new[] { Av1BitDepth.EightBit, Av1BitDepth.TenBit, Av1BitDepth.TwelveBit })
{
foreach (Av1TransformSize size in new[]
{
Av1TransformSize.Size4x4, Av1TransformSize.Size8x8, Av1TransformSize.Size16x16,
Av1TransformSize.Size32x32, Av1TransformSize.Size64x64, Av1TransformSize.Size8x16
})
{
int count = size.GetAdjusted().GetSize2d();
int[] input = new int[count + 2];
int[] quantized = new int[count + 2];
int[] dequantized = new int[count + 2];
ReadOnlySpan<short> scan = Av1ScanOrderConstants.GetScanOrder(size, Av1TransformType.DctDct).Scan;
foreach (int qIndex in new[] { 0, 1, 10, 90, 200, 255 })
{
foreach (int sharpness in new[] { 0, 3, 7 })
{
for (int pattern = 0; pattern < 4; pattern++)
{
int dcDelta = pattern == 1 ? -20 : pattern == 2 ? 17 : 0;
int acDelta = pattern == 1 ? 13 : pattern == 2 ? -11 : 0;
int bits = bitDepth.GetBitCount();
int maximum = (1 << (bits + 7)) - 1;
uint state = (uint)(qIndex + 123);
Array.Fill(input, int.MinValue);
Array.Fill(quantized, int.MinValue);
Array.Fill(dequantized, int.MinValue);
for (int index = 0; index < count; index++)
{
state = unchecked((state * 1664525) + 1013904223);
int magnitude = (int)(state % (uint)maximum);
if (pattern == 1)
{
int divisor = index == 0
? Av1QuantizationLookup.GetDcQuant(qIndex, dcDelta, bitDepth)
: Av1QuantizationLookup.GetAcQuant(qIndex, acDelta, bitDepth);
int threshold = ((Av1InverseTransformMath.GetQzbinFactor(qIndex, bitDepth) * divisor) + 64) >> 7;
int scale = size.GetScale();
threshold = scale == 0 ? threshold : (threshold + (1 << (scale - 1))) >> scale;
magnitude = threshold + (index % 3) - 1;
}
else if (pattern == 2)
{
magnitude = maximum;
}
else if (pattern == 3)
{
// A sparse final scan position exposes stale output coefficients across candidate reuse.
magnitude = index == scan[count / 3] ? 97 : 0;
}
input[index + 1] = (index & 1) == 0 ? magnitude : -magnitude;
}
int[] original = (int[])input.Clone();
ushort end = Av1ForwardQuantizer.QuantizeRegular(
input.AsSpan(1, count),
quantized.AsSpan(1, count),
dequantized.AsSpan(1, count),
size,
Av1TransformType.DctDct,
qIndex,
dcDelta,
acDelta,
bitDepth,
sharpness);
Assert.Equal(original, input);
Assert.Equal(int.MinValue, quantized[0]);
Assert.Equal(int.MinValue, quantized[^1]);
Assert.Equal(int.MinValue, dequantized[0]);
Assert.Equal(int.MinValue, dequantized[^1]);
int expectedEnd = 0;
for (int index = 0; index < count; index++)
{
int level = quantized[index + 1];
int divisor = index == 0
? Av1QuantizationLookup.GetDcQuant(qIndex, dcDelta, bitDepth)
: Av1QuantizationLookup.GetAcQuant(qIndex, acDelta, bitDepth);
// Signed dequantization truncates the magnitude before restoring sign.
int restored = (Math.Abs(level) * divisor) >> size.GetScale();
Assert.Equal(level < 0 ? -restored : restored, dequantized[index + 1]);
if (quantized[scan[index] + 1] != 0)
{
expectedEnd = index + 1;
}
}
Assert.Equal(expectedEnd, end);
using BinaryWriter output = new(File.Create(Path.Combine(
directory, $"{bits}-{(int)size}-{qIndex}-{sharpness}-{pattern}.bin")));
foreach (int value in new[] { bits, (int)size, qIndex, dcDelta, acDelta, sharpness, count, end })
{
output.Write(value);
}
output.Write(MemoryMarshal.AsBytes(input.AsSpan(1, count)));
output.Write(MemoryMarshal.AsBytes(quantized.AsSpan(1, count)));
output.Write(MemoryMarshal.AsBytes(dequantized.AsSpan(1, count)));
}
}
}
}
}
}
}

6
tests/ImageSharp.Tests/TestUtilities/FeatureTesting/FeatureTestRunner.cs
View File

@ -415,6 +415,12 @@ public static class FeatureTestRunner
features.Add(key, nameof(HwIntrinsics.AllowAll));
break;
#if NET11_0_OR_GREATER
case nameof(HwIntrinsics.DisableAVX512F):
// AVX-512's baseline features share one switch in .NET 11. The old F-only switch is
// ignored, which would run 512-bit code again instead of exercising narrower vectors.
features.Add(key, "EnableAVX512");
break;
case nameof(HwIntrinsics.DisableSSE42):
// SSE3 through SSE4.2 and POPCNT are x86-64-v2 baseline in .NET 11+ and the

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