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Communicates the colour subcarrier frequency, and uses it to pick a buffer width.

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This commit is contained in:
Thomas Harte 2018-11-13 18:33:44 -05:00
parent 654a19ea15
commit 02f9cada43
4 changed files with 17 additions and 1 deletions
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2
Outputs/CRT/CRT.cpp
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@ -62,6 +62,8 @@ void CRT::set_new_timing(int cycles_per_line, int height_of_display, Outputs::Di
scan_target_modals_.output_scale.y = uint16_t(real_clock_scan_period / vertical_flywheel_output_divider_);
scan_target_modals_.expected_vertical_lines = height_of_display;
scan_target_modals_.composite_colour_space = colour_space;
scan_target_modals_.colour_cycle_numerator = colour_cycle_numerator;
scan_target_modals_.colour_cycle_denominator = colour_cycle_denominator;
scan_target_->set_modals(scan_target_modals_);
}

9
Outputs/OpenGL/ScanTarget.cpp
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@ -131,6 +131,15 @@ void ScanTarget::set_modals(Modals modals) {
write_pointers_.write_area = 0;
}
// Pick a processing width; this will be at least four times the
// colour subcarrier, and an integer multiple of the pixel clock and
// at most 2048.
const int colour_cycle_width = (modals.colour_cycle_numerator * 4 + modals.colour_cycle_denominator - 1) / modals.colour_cycle_denominator;
const int dot_clock = modals.cycles_per_line / modals.clocks_per_pixel_greatest_common_divisor;
const int overflow = colour_cycle_width % dot_clock;
processing_width_ = colour_cycle_width + (overflow ? dot_clock - overflow : 0);
processing_width_ = std::min(processing_width_, 2048);
// TODO: this, but not to the test shader.
test_shader_->set_uniform("scale", GLfloat(modals.output_scale.x), GLfloat(modals.output_scale.y));
test_shader_->set_uniform("rowHeight", GLfloat(1.0f / modals.expected_vertical_lines));

4
Outputs/OpenGL/ScanTarget.hpp
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@ -129,9 +129,11 @@ class ScanTarget: public Outputs::Display::ScanTarget {
*/
void enable_vertex_attributes(ShaderType type, Shader &target);
std::unique_ptr<Shader> test_shader_;
GLsync fence_ = nullptr;
std::atomic_flag is_drawing_;
int processing_width_ = 0;
std::unique_ptr<Shader> test_shader_;
};
}

3
Outputs/ScanTarget.hpp
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@ -129,6 +129,9 @@ struct ScanTarget {
/// the @c cycles_per_line are offered for sizing of intermediary buffers.
int clocks_per_pixel_greatest_common_divisor;
/// Provides the number of colour cycles in a line, as a quotient.
int colour_cycle_numerator, colour_cycle_denominator;
/// Provides a pre-estimate of the likely number of left-to-right scans per frame.
/// This isn't a guarantee, but it should provide a decent-enough estimate.
int expected_vertical_lines;