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Corrects phase error in chrominance separation.

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Thomas Harte 2019-02-12 19:24:28 -05:00
parent 208ef70e31
commit 037cbd534e
1 changed files with 3 additions and 5 deletions
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8
Outputs/OpenGL/ScanTargetGLSLFragments.cpp
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@ -631,12 +631,10 @@ std::unique_ptr<Shader> ScanTarget::qam_separation_shader() const {
// Take the average to calculate luminance, then subtract that from all four samples to
// give chrominance.
"float luminance = dot(samples, vec4(0.25));"
"float chrominance = (samples.y - luminance) * oneOverCompositeAmplitude;"
"float chrominance = (dot(samples.yz, vec2(0.5)) - luminance) * oneOverCompositeAmplitude;"
"vec2 channels = vec2(cos(compositeAngle), sin(compositeAngle)) * chrominance;"
// Apply a colour space conversion to get RGB.
"fragColour = vec4(luminance, channels, 1.0);";
// Pack that all up and send it on its way.
"fragColour = vec4(luminance, vec2(cos(compositeAngle), sin(compositeAngle)) * chrominance, 1.0);";
};
fragment_shader +=