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Switched phase and amplitude varying to a 3d vector; the third component is 1/amplitude if amplitude is non-zero, and zero otherwise. So you can multiply by that to get chrominance, rather than dividing by amplitude. With the direct effect that detected chrominance should automatically be zero if the colour burst didn't exist (i.e. had zero amplitude).

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This commit is contained in:
Thomas Harte 2017-07-06 21:25:38 -04:00
parent 212ae60622
commit c6d00ec7d1
1 changed files with 9 additions and 7 deletions
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16
Outputs/CRT/Internals/Shaders/IntermediateShader.cpp
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@ -47,7 +47,7 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_shader(const std::s
"uniform float outputVerticalOffset;"
"uniform float textureHeightDivisor;"
"out vec2 phaseAndAmplitudeVarying;"
"out vec3 phaseAndAmplitudeVarying;"
"out vec2 inputPositionsVarying[11];"
"out vec2 iInputPositionVarying;"
"out vec2 delayLinePositionVarying;"
@ -94,9 +94,11 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_shader(const std::s
"delayLinePositionVarying = mappedInputPosition - vec2(0.0, 1.0);"
// setup phaseAndAmplitudeVarying.x as colour burst subcarrier phase, in radians;
// setup phaseAndAmplitudeVarying.x as colour burst amplitude
// setup phaseAndAmplitudeVarying.y as colour burst amplitude;
// setup phaseAndAmplitudeVarying.z as 1 / (colour burst amplitude), or 0.0 if amplitude is 0.0;
"phaseAndAmplitudeVarying.x = (extendedOutputPosition.x + (phaseTimeAndAmplitude.x / 64.0)) * 0.5 * 3.141592654;"
"phaseAndAmplitudeVarying.y = 0.33;" // TODO: reinstate connection with (phaseTimeAndAmplitude.y/256.0)
"phaseAndAmplitudeVarying.y = 0.33;" // TODO: reinstate connection with phaseTimeAndAmplitude.y / 255.0;"
"phaseAndAmplitudeVarying.z = (phaseAndAmplitudeVarying.y > 0.0) ? 1.0 / phaseAndAmplitudeVarying.y : 0.0;"
// determine output position by scaling the output position according to the texture size
"vec2 eyePosition = 2.0*(extendedOutputPosition / outputTextureSize) - vec2(1.0);"
@ -133,7 +135,7 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_source_conversion_s
"in vec2 inputPositionsVarying[11];"
"in vec2 iInputPositionVarying;"
"in vec2 phaseAndAmplitudeVarying;"
"in vec3 phaseAndAmplitudeVarying;"
"out vec4 fragColour;"
@ -161,7 +163,7 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_rgb_source_shader(c
"in vec2 inputPositionsVarying[11];"
"in vec2 iInputPositionVarying;"
"in vec2 phaseAndAmplitudeVarying;"
"in vec3 phaseAndAmplitudeVarying;"
"out vec3 fragColour;"
@ -185,7 +187,7 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_chroma_luma_separat
return make_shader(
"#version 150\n"
"in vec2 phaseAndAmplitudeVarying;"
"in vec3 phaseAndAmplitudeVarying;"
"in vec2 inputPositionsVarying[11];"
"out vec3 fragColour;"
@ -203,7 +205,7 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_chroma_luma_separat
"float luminance = dot(samples, vec4(0.25));"
// define chroma to be whatever was here, minus luma
"float chrominance = 0.5 * (samples.z - luminance) / phaseAndAmplitudeVarying.y;"
"float chrominance = 0.5 * (samples.z - luminance) * phaseAndAmplitudeVarying.z;"
"luminance /= (1.0 - phaseAndAmplitudeVarying.y);"
// split choma colours here, as the most direct place, writing out