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Thomas Harte
86 lines
2.1 KiB
C++
86 lines
2.1 KiB
C++
//
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// CompositionShader.hpp
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// Clock Signal Kiosk
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//
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// Created by Thomas Harte on 26/01/2026.
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// Copyright © 2026 Thomas Harte. All rights reserved.
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//
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#pragma once
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#include "Outputs/ScanTarget.hpp"
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#include "Outputs/OpenGL/Primitives/VertexArray.hpp"
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#include "Outputs/OpenGL/Primitives/Shader.hpp"
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namespace Outputs::Display::OpenGL {
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/*!
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A composition shader assembles scans into a line buffer. It can include a downard conversion
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from RGB to S-Video or composite, or from S-Video to composite.
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The shader is configured to accept a buffer of ScanTarget::Scan as vertex attributes.
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Output formats are:
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RGB: (r, g, b, 1)
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S-Video: (luma, chroma * cos(phase), luma * sin(phase), 1)
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Composite: (luma, cos(phase), sin(phase), chroma amplitude)
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Data flow:
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* the separation shader takes input in 'composite' form and produce output in 's-video' form;
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* the demodulation shader takes input in 's-video' form and produces output in 'RGB' form;
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* chroma amplitude = 0 from composite output means that no chrominance is known to be
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present; in practice it means that no colour burst was detected.
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Implementation notes:
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* phase carries forward in cos and sin form because those values will definitely be needed
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later in the pipeline and might be needed earlier.
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Aside: the demodulation shader only _finishes_ demodulation — the earlier multiply
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by cos and sin started it.
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*/
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Shader composition_shader(
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API,
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InputDataType,
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DisplayType,
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ColourSpace,
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float cycles_multiplier,
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float phase_linked_luminance_offset,
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int source_width,
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int source_height,
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int target_width,
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int target_height,
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const VertexArray &,
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GLenum source_texture_unit
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);
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class ScanOutputShader {
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public:
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ScanOutputShader(
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API,
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InputDataType,
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int expected_vertical_lines,
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int scale_x,
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int scale_y,
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int source_width,
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int source_height,
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const VertexArray &,
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GLenum source_texture_unit
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);
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ScanOutputShader() = default;
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void set_aspect_ratio_transformation(const std::array<float, 9> &);
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void set_alpha(float);
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void bind();
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void reset() { shader_.reset(); }
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bool empty() const { return shader_.empty(); }
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private:
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Shader shader_;
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};
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}
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