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468 lines
20 KiB
C++
468 lines
20 KiB
C++
//
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// CRT.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 19/07/2015.
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// Copyright 2015 Thomas Harte. All rights reserved.
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//
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#include "CRT.hpp"
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#include <cstdarg>
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#include <cmath>
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#include <algorithm>
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#include <cassert>
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using namespace Outputs::CRT;
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void CRT::set_new_timing(int cycles_per_line, int height_of_display, Outputs::Display::ColourSpace colour_space, int colour_cycle_numerator, int colour_cycle_denominator, int vertical_sync_half_lines, bool should_alternate) {
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const int millisecondsHorizontalRetraceTime = 7; // Source: Dictionary of Video and Television Technology, p. 234.
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const int scanlinesVerticalRetraceTime = 8; // Source: ibid.
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// To quote:
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//
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// "retrace interval; The interval of time for the return of the blanked scanning beam of
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// a TV picture tube or camera tube to the starting point of a line or field. It is about
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// 7 microseconds for horizontal retrace and 500 to 750 microseconds for vertical retrace
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// in NTSC and PAL TV."
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time_multiplier_ = 65535 / cycles_per_line;
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phase_denominator_ = int64_t(cycles_per_line) * int64_t(colour_cycle_denominator) * int64_t(time_multiplier_);
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phase_numerator_ = 0;
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colour_cycle_numerator_ = int64_t(colour_cycle_numerator);
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phase_alternates_ = should_alternate;
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is_alernate_line_ &= phase_alternates_;
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cycles_per_line_ = cycles_per_line;
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const int multiplied_cycles_per_line = cycles_per_line * time_multiplier_;
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// Allow sync to be detected (and acted upon) a line earlier than the specified requirement,
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// as a simple way of avoiding not-quite-exact comparison issues while still being true enough to
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// the gist for simple debugging.
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sync_capacitor_charge_threshold_ = ((vertical_sync_half_lines - 2) * cycles_per_line) >> 1;
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// Create the two flywheels:
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//
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// The horizontal flywheel has an ideal period of `multiplied_cycles_per_line`, will accept syncs
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// within 1/32nd of that (i.e. tolerates 3.125% error) and takes millisecondsHorizontalRetraceTime
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// to retrace.
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//
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// The vertical slywheel has an ideal period of `multiplied_cycles_per_line * height_of_display`,
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// will accept syncs within 1/8th of that (i.e. tolerates 12.5% error) and takes scanlinesVerticalRetraceTime
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// to retrace.
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horizontal_flywheel_.reset(new Flywheel(multiplied_cycles_per_line, (millisecondsHorizontalRetraceTime * multiplied_cycles_per_line) >> 6, multiplied_cycles_per_line >> 5));
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vertical_flywheel_.reset(new Flywheel(multiplied_cycles_per_line * height_of_display, scanlinesVerticalRetraceTime * multiplied_cycles_per_line, (multiplied_cycles_per_line * height_of_display) >> 3));
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// Figure out the divisor necessary to get the horizontal flywheel into a 16-bit range.
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const int real_clock_scan_period = vertical_flywheel_->get_scan_period();
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vertical_flywheel_output_divider_ = (real_clock_scan_period + 65534) / 65535;
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// Communicate relevant fields to the scan target.
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scan_target_modals_.output_scale.x = uint16_t(horizontal_flywheel_->get_scan_period());
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scan_target_modals_.output_scale.y = uint16_t(real_clock_scan_period / vertical_flywheel_output_divider_);
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scan_target_modals_.expected_vertical_lines = height_of_display;
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scan_target_modals_.composite_colour_space = colour_space;
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scan_target_modals_.colour_cycle_numerator = colour_cycle_numerator;
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scan_target_modals_.colour_cycle_denominator = colour_cycle_denominator;
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scan_target_->set_modals(scan_target_modals_);
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}
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void CRT::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
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scan_target_ = scan_target;
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if(!scan_target_) scan_target_ = &Outputs::Display::NullScanTarget::singleton;
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scan_target_->set_modals(scan_target_modals_);
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}
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void CRT::set_new_data_type(Outputs::Display::InputDataType data_type) {
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scan_target_modals_.input_data_type = data_type;
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scan_target_->set_modals(scan_target_modals_);
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}
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void CRT::set_aspect_ratio(float aspect_ratio) {
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scan_target_modals_.aspect_ratio = aspect_ratio;
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scan_target_->set_modals(scan_target_modals_);
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}
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void CRT::set_visible_area(Outputs::Display::Rect visible_area) {
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scan_target_modals_.visible_area = visible_area;
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scan_target_->set_modals(scan_target_modals_);
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}
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void CRT::set_display_type(Outputs::Display::DisplayType display_type) {
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scan_target_modals_.display_type = display_type;
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scan_target_->set_modals(scan_target_modals_);
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}
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void CRT::set_phase_linked_luminance_offset(float offset) {
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scan_target_modals_.input_data_tweaks.phase_linked_luminance_offset = offset;
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scan_target_->set_modals(scan_target_modals_);
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}
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void CRT::set_input_data_type(Outputs::Display::InputDataType input_data_type) {
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scan_target_modals_.input_data_type = input_data_type;
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scan_target_->set_modals(scan_target_modals_);
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}
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void CRT::set_brightness(float brightness) {
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scan_target_modals_.brightness = brightness;
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scan_target_->set_modals(scan_target_modals_);
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}
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void CRT::set_new_display_type(int cycles_per_line, Outputs::Display::Type displayType) {
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switch(displayType) {
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case Outputs::Display::Type::PAL50:
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scan_target_modals_.intended_gamma = 2.8f;
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set_new_timing(cycles_per_line, 312, Outputs::Display::ColourSpace::YUV, 709379, 2500, 5, true); // i.e. 283.7516 colour cycles per line; 2.5 lines = vertical sync.
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break;
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case Outputs::Display::Type::NTSC60:
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scan_target_modals_.intended_gamma = 2.2f;
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set_new_timing(cycles_per_line, 262, Outputs::Display::ColourSpace::YIQ, 455, 2, 6, false); // i.e. 227.5 colour cycles per line, 3 lines = vertical sync.
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break;
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}
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}
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void CRT::set_composite_function_type(CompositeSourceType type, float offset_of_first_sample) {
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if(type == DiscreteFourSamplesPerCycle) {
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colour_burst_phase_adjustment_ = static_cast<uint8_t>(offset_of_first_sample * 256.0f) & 63;
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} else {
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colour_burst_phase_adjustment_ = 0xff;
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}
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}
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void CRT::set_input_gamma(float gamma) {
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scan_target_modals_.intended_gamma = gamma;
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scan_target_->set_modals(scan_target_modals_);
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}
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CRT::CRT( int cycles_per_line,
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int clocks_per_pixel_greatest_common_divisor,
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int height_of_display,
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Outputs::Display::ColourSpace colour_space,
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int colour_cycle_numerator, int colour_cycle_denominator,
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int vertical_sync_half_lines,
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bool should_alternate,
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Outputs::Display::InputDataType data_type) {
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scan_target_modals_.input_data_type = data_type;
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scan_target_modals_.cycles_per_line = cycles_per_line;
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scan_target_modals_.clocks_per_pixel_greatest_common_divisor = clocks_per_pixel_greatest_common_divisor;
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set_new_timing(cycles_per_line, height_of_display, colour_space, colour_cycle_numerator, colour_cycle_denominator, vertical_sync_half_lines, should_alternate);
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}
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CRT::CRT( int cycles_per_line,
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int clocks_per_pixel_greatest_common_divisor,
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Outputs::Display::Type display_type,
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Outputs::Display::InputDataType data_type) {
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scan_target_modals_.input_data_type = data_type;
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scan_target_modals_.cycles_per_line = cycles_per_line;
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scan_target_modals_.clocks_per_pixel_greatest_common_divisor = clocks_per_pixel_greatest_common_divisor;
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set_new_display_type(cycles_per_line, display_type);
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}
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// MARK: - Sync loop
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Flywheel::SyncEvent CRT::get_next_vertical_sync_event(bool vsync_is_requested, int cycles_to_run_for, int *cycles_advanced) {
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return vertical_flywheel_->get_next_event_in_period(vsync_is_requested, cycles_to_run_for, cycles_advanced);
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}
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Flywheel::SyncEvent CRT::get_next_horizontal_sync_event(bool hsync_is_requested, int cycles_to_run_for, int *cycles_advanced) {
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return horizontal_flywheel_->get_next_event_in_period(hsync_is_requested, cycles_to_run_for, cycles_advanced);
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}
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Outputs::Display::ScanTarget::Scan::EndPoint CRT::end_point(uint16_t data_offset) {
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Display::ScanTarget::Scan::EndPoint end_point;
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end_point.x = uint16_t(horizontal_flywheel_->get_current_output_position());
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end_point.y = uint16_t(vertical_flywheel_->get_current_output_position() / vertical_flywheel_output_divider_);
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end_point.data_offset = data_offset;
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// TODO: this is a workaround for the limited precision that can be posted onwards;
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// it'd be better to make time_multiplier_ an explicit modal and just not divide by it.
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const auto lost_precision = cycles_since_horizontal_sync_ % time_multiplier_;
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end_point.composite_angle = int16_t(((phase_numerator_ - lost_precision * colour_cycle_numerator_) << 6) / phase_denominator_) * (is_alernate_line_ ? -1 : 1);
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end_point.cycles_since_end_of_horizontal_retrace = uint16_t(cycles_since_horizontal_sync_ / time_multiplier_);
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return end_point;
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}
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void CRT::advance_cycles(int number_of_cycles, bool hsync_requested, bool vsync_requested, const Scan::Type type, int number_of_samples) {
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number_of_cycles *= time_multiplier_;
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const bool is_output_run = ((type == Scan::Type::Level) || (type == Scan::Type::Data));
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const auto total_cycles = number_of_cycles;
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bool did_output = false;
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while(number_of_cycles) {
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// Get time until next horizontal and vertical sync generator events.
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int time_until_vertical_sync_event, time_until_horizontal_sync_event;
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const Flywheel::SyncEvent next_vertical_sync_event = get_next_vertical_sync_event(vsync_requested, number_of_cycles, &time_until_vertical_sync_event);
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const Flywheel::SyncEvent next_horizontal_sync_event = get_next_horizontal_sync_event(hsync_requested, time_until_vertical_sync_event, &time_until_horizontal_sync_event);
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// Whichever event is scheduled to happen first is the one to advance to.
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const int next_run_length = std::min(time_until_vertical_sync_event, time_until_horizontal_sync_event);
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hsync_requested = false;
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vsync_requested = false;
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// Determine whether to output any data for this portion of the output; if so then grab somewhere to put it.
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const bool is_output_segment = ((is_output_run && next_run_length) && !horizontal_flywheel_->is_in_retrace() && !vertical_flywheel_->is_in_retrace());
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Outputs::Display::ScanTarget::Scan *const next_scan = is_output_segment ? scan_target_->begin_scan() : nullptr;
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did_output |= is_output_segment;
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// If outputting, store the start location and scan constants.
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if(next_scan) {
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next_scan->end_points[0] = end_point(uint16_t((total_cycles - number_of_cycles) * number_of_samples / total_cycles));
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next_scan->composite_amplitude = colour_burst_amplitude_;
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}
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// Advance time: that'll affect both the colour subcarrier position and the number of cycles left to run.
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phase_numerator_ += next_run_length * colour_cycle_numerator_;
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number_of_cycles -= next_run_length;
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cycles_since_horizontal_sync_ += next_run_length;
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// React to the incoming event.
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horizontal_flywheel_->apply_event(next_run_length, (next_run_length == time_until_horizontal_sync_event) ? next_horizontal_sync_event : Flywheel::SyncEvent::None);
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vertical_flywheel_->apply_event(next_run_length, (next_run_length == time_until_vertical_sync_event) ? next_vertical_sync_event : Flywheel::SyncEvent::None);
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// End the scan if necessary.
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if(next_scan) {
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next_scan->end_points[1] = end_point(uint16_t((total_cycles - number_of_cycles) * number_of_samples / total_cycles));
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scan_target_->end_scan();
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}
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// Announce horizontal retrace events.
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if(next_run_length == time_until_horizontal_sync_event && next_horizontal_sync_event != Flywheel::SyncEvent::None) {
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// Reset the cycles-since-sync counter if this is the end of retrace.
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if(next_horizontal_sync_event == Flywheel::SyncEvent::EndRetrace) {
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cycles_since_horizontal_sync_ = 0;
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// This is unnecessary, strictly speaking, but seeks to help ScanTargets fit as
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// much as possible into a fixed range.
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phase_numerator_ %= phase_denominator_;
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if(!phase_numerator_) phase_numerator_ += phase_denominator_;
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}
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// Announce event.
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const auto event =
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(next_horizontal_sync_event == Flywheel::SyncEvent::StartRetrace)
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? Outputs::Display::ScanTarget::Event::BeginHorizontalRetrace : Outputs::Display::ScanTarget::Event::EndHorizontalRetrace;
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scan_target_->announce(
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event,
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!(horizontal_flywheel_->is_in_retrace() || vertical_flywheel_->is_in_retrace()),
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end_point(uint16_t((total_cycles - number_of_cycles) * number_of_samples / total_cycles)),
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colour_burst_amplitude_);
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// If retrace is starting, update phase if required and mark no colour burst spotted yet.
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if(next_horizontal_sync_event == Flywheel::SyncEvent::StartRetrace) {
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is_alernate_line_ ^= phase_alternates_;
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colour_burst_amplitude_ = 0;
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}
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}
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// Also announce vertical retrace events.
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if(next_run_length == time_until_vertical_sync_event && next_vertical_sync_event != Flywheel::SyncEvent::None) {
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const auto event =
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(next_vertical_sync_event == Flywheel::SyncEvent::StartRetrace)
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? Outputs::Display::ScanTarget::Event::BeginVerticalRetrace : Outputs::Display::ScanTarget::Event::EndVerticalRetrace;
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scan_target_->announce(
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event,
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!(horizontal_flywheel_->is_in_retrace() || vertical_flywheel_->is_in_retrace()),
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end_point(uint16_t((total_cycles - number_of_cycles) * number_of_samples / total_cycles)),
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colour_burst_amplitude_);
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}
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// if this is vertical retrace then adcance a field
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if(next_run_length == time_until_vertical_sync_event && next_vertical_sync_event == Flywheel::SyncEvent::EndRetrace) {
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if(delegate_) {
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frames_since_last_delegate_call_++;
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if(frames_since_last_delegate_call_ == 20) {
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delegate_->crt_did_end_batch_of_frames(this, frames_since_last_delegate_call_, vertical_flywheel_->get_and_reset_number_of_surprises());
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frames_since_last_delegate_call_ = 0;
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}
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}
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}
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}
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if(did_output) {
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scan_target_->submit();
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}
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}
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// MARK: - stream feeding methods
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void CRT::output_scan(const Scan *const scan) {
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// Simplified colour burst logic: if it's within the back porch we'll take it.
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if(scan->type == Scan::Type::ColourBurst) {
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if(!colour_burst_amplitude_ && horizontal_flywheel_->get_current_time() < (horizontal_flywheel_->get_standard_period() * 12) >> 6) {
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// Load phase_numerator_ as a fixed-point quantity in the range [0, 255].
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phase_numerator_ = scan->phase;
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if(colour_burst_phase_adjustment_ != 0xff)
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phase_numerator_ = (phase_numerator_ & ~63) + colour_burst_phase_adjustment_;
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// Multiply the phase_numerator_ up to be to the proper scale.
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phase_numerator_ = (phase_numerator_ * phase_denominator_) >> 8;
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// Crib the colour burst amplitude.
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colour_burst_amplitude_ = scan->amplitude;
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}
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}
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// TODO: inspect raw data for potential colour burst if required; the DPLL and some zero crossing logic
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// will probably be sufficient but some test data would be helpful
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// sync logic: mark whether this is currently sync and check for a leading edge
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const bool this_is_sync = (scan->type == Scan::Type::Sync);
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const bool is_leading_edge = (!is_receiving_sync_ && this_is_sync);
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is_receiving_sync_ = this_is_sync;
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// Horizontal sync is recognised on any leading edge that is not 'near' the expected vertical sync;
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// the second limb is to avoid slightly horizontal sync shifting from the common pattern of
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// equalisation pulses as the inverse of ordinary horizontal sync.
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bool hsync_requested = is_leading_edge && !vertical_flywheel_->is_near_expected_sync();
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if(this_is_sync) {
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// If this is sync then either begin or continue a sync accumulation phase.
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is_accumulating_sync_ = true;
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cycles_since_sync_ = 0;
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} else {
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// If this is not sync then check how long it has been since sync. If it's more than
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// half a line then end sync accumulation and zero out the accumulating count.
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cycles_since_sync_ += scan->number_of_cycles;
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if(cycles_since_sync_ > (cycles_per_line_ >> 2)) {
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cycles_of_sync_ = 0;
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is_accumulating_sync_ = false;
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is_refusing_sync_ = false;
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}
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}
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int number_of_cycles = scan->number_of_cycles;
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bool vsync_requested = false;
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// If sync is being accumulated then accumulate it; if it crosses the vertical sync threshold then
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// divide this line at the crossing point and indicate vertical sync there.
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if(is_accumulating_sync_ && !is_refusing_sync_) {
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cycles_of_sync_ += scan->number_of_cycles;
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if(this_is_sync && cycles_of_sync_ >= sync_capacitor_charge_threshold_) {
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const int overshoot = std::min(cycles_of_sync_ - sync_capacitor_charge_threshold_, number_of_cycles);
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if(overshoot) {
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number_of_cycles -= overshoot;
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advance_cycles(number_of_cycles, hsync_requested, false, scan->type, 0);
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hsync_requested = false;
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number_of_cycles = overshoot;
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}
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is_refusing_sync_ = true;
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vsync_requested = true;
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}
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}
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advance_cycles(number_of_cycles, hsync_requested, vsync_requested, scan->type, scan->number_of_samples);
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}
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/*
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These all merely channel into advance_cycles, supplying appropriate arguments
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*/
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void CRT::output_sync(int number_of_cycles) {
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Scan scan;
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scan.type = Scan::Type::Sync;
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scan.number_of_cycles = number_of_cycles;
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output_scan(&scan);
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}
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void CRT::output_blank(int number_of_cycles) {
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Scan scan;
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scan.type = Scan::Type::Blank;
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scan.number_of_cycles = number_of_cycles;
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output_scan(&scan);
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}
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void CRT::output_level(int number_of_cycles) {
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scan_target_->end_data(1);
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Scan scan;
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scan.type = Scan::Type::Level;
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scan.number_of_cycles = number_of_cycles;
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scan.number_of_samples = 1;
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output_scan(&scan);
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}
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void CRT::output_colour_burst(int number_of_cycles, uint8_t phase, uint8_t amplitude) {
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Scan scan;
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scan.type = Scan::Type::ColourBurst;
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scan.number_of_cycles = number_of_cycles;
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scan.phase = phase;
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scan.amplitude = amplitude >> 1;
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output_scan(&scan);
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}
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void CRT::output_default_colour_burst(int number_of_cycles, uint8_t amplitude) {
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// TODO: avoid applying a rounding error here?
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output_colour_burst(number_of_cycles, static_cast<uint8_t>((phase_numerator_ * 256) / phase_denominator_), amplitude);
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}
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void CRT::set_immediate_default_phase(float phase) {
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phase = fmodf(phase, 1.0f);
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phase_numerator_ = static_cast<int>(phase * static_cast<float>(phase_denominator_));
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}
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void CRT::output_data(int number_of_cycles, size_t number_of_samples) {
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#ifndef NDEBUG
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assert(number_of_samples > 0 && number_of_samples <= allocated_data_length_);
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allocated_data_length_ = std::numeric_limits<size_t>::min();
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#endif
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scan_target_->end_data(number_of_samples);
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Scan scan;
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scan.type = Scan::Type::Data;
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scan.number_of_cycles = number_of_cycles;
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scan.number_of_samples = int(number_of_samples);
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output_scan(&scan);
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}
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Outputs::Display::Rect CRT::get_rect_for_area(int first_line_after_sync, int number_of_lines, int first_cycle_after_sync, int number_of_cycles, float aspect_ratio) {
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first_cycle_after_sync *= time_multiplier_;
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number_of_cycles *= time_multiplier_;
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first_line_after_sync -= 2;
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number_of_lines += 4;
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// determine prima facie x extent
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const int horizontal_period = horizontal_flywheel_->get_standard_period();
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const int horizontal_scan_period = horizontal_flywheel_->get_scan_period();
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const int horizontal_retrace_period = horizontal_period - horizontal_scan_period;
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// make sure that the requested range is visible
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if(static_cast<int>(first_cycle_after_sync) < horizontal_retrace_period) first_cycle_after_sync = static_cast<int>(horizontal_retrace_period);
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if(static_cast<int>(first_cycle_after_sync + number_of_cycles) > horizontal_scan_period) number_of_cycles = static_cast<int>(horizontal_scan_period - static_cast<int>(first_cycle_after_sync));
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float start_x = static_cast<float>(static_cast<int>(first_cycle_after_sync) - horizontal_retrace_period) / static_cast<float>(horizontal_scan_period);
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float width = static_cast<float>(number_of_cycles) / static_cast<float>(horizontal_scan_period);
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// determine prima facie y extent
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const int vertical_period = vertical_flywheel_->get_standard_period();
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const int vertical_scan_period = vertical_flywheel_->get_scan_period();
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const int vertical_retrace_period = vertical_period - vertical_scan_period;
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// make sure that the requested range is visible
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// if(static_cast<int>(first_line_after_sync) * horizontal_period < vertical_retrace_period)
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// first_line_after_sync = (vertical_retrace_period + horizontal_period - 1) / horizontal_period;
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// if((first_line_after_sync + number_of_lines) * horizontal_period > vertical_scan_period)
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// number_of_lines = static_cast<int>(horizontal_scan_period - static_cast<int>(first_cycle_after_sync));
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float start_y = static_cast<float>((static_cast<int>(first_line_after_sync) * horizontal_period) - vertical_retrace_period) / static_cast<float>(vertical_scan_period);
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float height = static_cast<float>(static_cast<int>(number_of_lines) * horizontal_period) / vertical_scan_period;
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// adjust to ensure aspect ratio is correct
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const float adjusted_aspect_ratio = (3.0f*aspect_ratio / 4.0f);
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const float ideal_width = height * adjusted_aspect_ratio;
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if(ideal_width > width) {
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start_x -= (ideal_width - width) * 0.5f;
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width = ideal_width;
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} else {
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float ideal_height = width / adjusted_aspect_ratio;
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start_y -= (ideal_height - height) * 0.5f;
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height = ideal_height;
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}
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return Outputs::Display::Rect(start_x, start_y, width, height);
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}
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