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Merge bit-exact movie conversion vectorization

This commit is contained in:
kuba 2026-10-01 18:31:18 +02:00
parent a1f5e6ebef 932ef17981
commit cd15ee772b
2 changed files with 74 additions and 2 deletions
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56
src/SharpEmu.Libs/Media/HostMovieYuv420.cs
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@ -2,6 +2,7 @@
// SPDX-License-Identifier: GPL-2.0-or-later
using System.Runtime.CompilerServices;
using System.Runtime.Intrinsics;
namespace SharpEmu.Libs.Media;
@ -30,7 +31,8 @@ internal static unsafe class HostMovieYuv420
ReadOnlySpan<byte> bgra,
uint width,
uint height,
Span<byte> destination)
Span<byte> destination,
bool useVectorized = true)
{
if (width == 0 || height == 0)
{
@ -46,10 +48,60 @@ internal static unsafe class HostMovieYuv420
fixed (byte* source = bgra, luma = destination)
{
ConvertRowPairs(source, (int)width, (int)height, luma, luma + lumaLength);
if (useVectorized && Vector128.IsHardwareAccelerated && BitConverter.IsLittleEndian &&
width % 4 == 0 && height % 2 == 0)
ConvertVectorRowPairs(source, (int)width, (int)height, luma, luma + lumaLength);
else
ConvertRowPairs(source, (int)width, (int)height, luma, luma + lumaLength);
}
}
// Four pixels from each of two rows share one vectorized luma/chroma
// calculation. Keep the scalar path for odd edges and hosts without SIMD.
private static void ConvertVectorRowPairs(byte* bgra, int width, int height, byte* luma, byte* chroma)
{
var mask = Vector128.Create(255u);
for (var y = 0; y < height; y += 2)
{
var row0 = bgra + (nint)y * width * 4;
var row1 = row0 + (nint)width * 4;
var luma0 = luma + (nint)y * width;
var luma1 = luma0 + width;
var chromaRow = chroma + (nint)(y / 2) * width;
for (var x = 0; x < width; x += 4)
{
var pixels0 = Vector128.Load((uint*)(row0 + x * 4));
var pixels1 = Vector128.Load((uint*)(row1 + x * 4));
var b0 = pixels0 & mask;
var b1 = pixels1 & mask;
var g0 = (pixels0 >> 8) & mask;
var g1 = (pixels1 >> 8) & mask;
var r0 = (pixels0 >> 16) & mask;
var r1 = (pixels1 >> 16) & mask;
var y0 = (r0 * 54u + g0 * 183u + b0 * 19u + Vector128.Create(128u)) >> 8;
var y1 = (r1 * 54u + g1 * 183u + b1 * 19u + Vector128.Create(128u)) >> 8;
var packedY = Vector128.Narrow(Vector128.Narrow(y0, y1), Vector128<ushort>.Zero).AsUInt32();
Unsafe.WriteUnaligned(luma0 + x, packedY.GetElement(0));
Unsafe.WriteUnaligned(luma1 + x, packedY.GetElement(1));
var red = AveragePairs(r0 + r1).AsInt32();
var green = AveragePairs(g0 + g1).AsInt32();
var blue = AveragePairs(b0 + b1).AsInt32();
var cr = ((red * 128 - green * 116 - blue * 12 + Vector128.Create(128)) >> 8) + Vector128.Create(128);
var cb = ((blue * 128 - red * 29 - green * 99 + Vector128.Create(128)) >> 8) + Vector128.Create(128);
cr = Vector128.Min(Vector128.Max(cr, Vector128<int>.Zero), Vector128.Create(255));
cb = Vector128.Min(Vector128.Max(cb, Vector128<int>.Zero), Vector128.Create(255));
var packedChroma = (uint)(cr.GetElement(0) | (cb.GetElement(0) << 8) |
(cr.GetElement(2) << 16) | (cb.GetElement(2) << 24));
Unsafe.WriteUnaligned(chromaRow + x, packedChroma);
}
}
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static Vector128<uint> AveragePairs(Vector128<uint> sums) =>
(sums + Vector128.Shuffle(sums, Vector128.Create(1u, 0u, 3u, 2u))) >> 2;
private static void ConvertRowPairs(
byte* bgra,
int width,

20
tests/SharpEmu.Libs.Tests/Media/HostMovieYuv420Tests.cs
View File

@ -14,6 +14,9 @@ public sealed class HostMovieYuv420Tests
[InlineData(3u, 2u)]
[InlineData(7u, 5u)]
[InlineData(64u, 33u)]
[InlineData(4u, 2u)]
[InlineData(8u, 6u)]
[InlineData(1920u, 1080u)]
public void ConvertFromBgra_MatchesPerPixelReference(uint width, uint height)
{
var bgra = new byte[width * height * 4];
@ -24,6 +27,23 @@ public sealed class HostMovieYuv420Tests
HostMovieYuv420.ConvertFromBgra(bgra, width, height, actual);
Assert.Equal(expected, actual);
var scalar = new byte[actual.Length];
HostMovieYuv420.ConvertFromBgra(bgra, width, height, scalar, useVectorized: false);
Assert.Equal(scalar, actual);
}
[Fact]
public void ConvertFromBgra_VectorStoresRespectUnalignedDestinationBounds()
{
const uint width = 8, height = 4;
var source = new byte[width * height * 4 + 1];
new System.Random(731).NextBytes(source);
var length = HostMovieYuv420.FrameLength(width, height);
var destination = Enumerable.Repeat((byte)0xCD, length + 9).ToArray();
HostMovieYuv420.ConvertFromBgra(source.AsSpan(1), width, height, destination.AsSpan(3, length));
Assert.Equal(ReferenceConvert(source[1..], (int)width, (int)height), destination.AsSpan(3, length).ToArray());
Assert.All(destination[..3], value => Assert.Equal(0xCD, value));
Assert.All(destination[(3 + length)..], value => Assert.Equal(0xCD, value));
}
[Fact]