42 lines
1.6 KiB
HLSL
42 lines
1.6 KiB
HLSL
// Copyright Epic Games, Inc. All Rights Reserved.
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#include "/Engine/Public/Platform.ush"
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#include "/Engine/Private/ColorUtils.ush"
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Texture2D SourceTexture;
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SamplerState SourceSampler;
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float2 SourceDimensions;
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RWTexture2D<float> OutputY;
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RWTexture2D<float> OutputU;
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RWTexture2D<float> OutputV;
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static const float4x4 ColorTransform = float4x4( 0.257, 0.504, 0.098, 0.063,
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-0.148, -0.291, 0.439, 0.500,
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0.439, -0.368, -0.071, 0.500,
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0.000, 0.000, 0.000, 1.000);
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[numthreads(THREADGROUPSIZE_X, THREADGROUPSIZE_Y, THREADGROUPSIZE_Z)]
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void ExtractI420(uint3 Gid : SV_GroupID,
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uint3 DTid : SV_DispatchThreadID,
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uint3 GTid : SV_GroupThreadID,
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uint GI : SV_GroupIndex)
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{
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// i tried sampling here so we would only need to transform the colours
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// once, but it resulted in a very blurry image with the Y component sampled.
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// sampling the UV values but picking the Y value seems to give the best
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// result.
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float3 yuv00 = RgbToYuv(SourceTexture[DTid.xy].rgb, ColorTransform, 0);
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OutputY[DTid.xy] = yuv00.x;
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if (DTid.x % 2 == 0 && DTid.y % 2)
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{
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float2 uv = (DTid.xy + float2(1, 1)) / SourceDimensions;
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float3 sampledColor = SourceTexture.SampleLevel(SourceSampler, uv, 0).rgb;
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float3 yuvSampled = RgbToYuv(sampledColor, ColorTransform, 0);
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OutputU[DTid.xy / 2] = yuvSampled.y;
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OutputV[DTid.xy / 2] = yuvSampled.z;
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}
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}
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