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CLK/Outputs/CRT/CRT.cpp
2024-09-06 22:12:19 -04:00

518 lines
22 KiB
C++

//
// CRT.cpp
// Clock Signal
//
// Created by Thomas Harte on 19/07/2015.
// Copyright 2015 Thomas Harte. All rights reserved.
//
#include "CRT.hpp"
#include <cstdarg>
#include <cmath>
#include <algorithm>
#include <cassert>
using namespace Outputs::CRT;
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) {
constexpr int millisecondsHorizontalRetraceTime = 7; // Source: Dictionary of Video and Television Technology, p. 234.
constexpr int scanlinesVerticalRetraceTime = 8; // Source: ibid.
// To quote:
//
// "retrace interval; The interval of time for the return of the blanked scanning beam of
// a TV picture tube or camera tube to the starting point of a line or field. It is about
// 7 microseconds for horizontal retrace and 500 to 750 microseconds for vertical retrace
// in NTSC and PAL TV."
time_multiplier_ = 63487 / cycles_per_line; // 63475 = 65535 * 31/32, i.e. the same 1/32 error as below is permitted.
phase_denominator_ = int64_t(cycles_per_line) * int64_t(colour_cycle_denominator) * int64_t(time_multiplier_);
phase_numerator_ = 0;
colour_cycle_numerator_ = int64_t(colour_cycle_numerator);
phase_alternates_ = should_alternate;
should_be_alternate_line_ &= phase_alternates_;
cycles_per_line_ = cycles_per_line;
const int multiplied_cycles_per_line = cycles_per_line * time_multiplier_;
// Allow sync to be detected (and acted upon) a line earlier than the specified requirement,
// as a simple way of avoiding not-quite-exact comparison issues while still being true enough to
// the gist for simple debugging.
sync_capacitor_charge_threshold_ = ((vertical_sync_half_lines - 2) * cycles_per_line) >> 1;
// Create the two flywheels:
//
// The horizontal flywheel has an ideal period of `multiplied_cycles_per_line`, will accept syncs
// within 1/32nd of that (i.e. tolerates 3.125% error) and takes millisecondsHorizontalRetraceTime
// to retrace.
//
// The vertical slywheel has an ideal period of `multiplied_cycles_per_line * height_of_display`,
// will accept syncs within 1/8th of that (i.e. tolerates 12.5% error) and takes scanlinesVerticalRetraceTime
// to retrace.
horizontal_flywheel_ = std::make_unique<Flywheel>(multiplied_cycles_per_line, (millisecondsHorizontalRetraceTime * multiplied_cycles_per_line) >> 6, multiplied_cycles_per_line >> 5);
vertical_flywheel_ = std::make_unique<Flywheel>(multiplied_cycles_per_line * height_of_display, scanlinesVerticalRetraceTime * multiplied_cycles_per_line, (multiplied_cycles_per_line * height_of_display) >> 3);
// Figure out the divisor necessary to get the horizontal flywheel into a 16-bit range.
const int real_clock_scan_period = vertical_flywheel_->get_scan_period();
vertical_flywheel_output_divider_ = (real_clock_scan_period + 65534) / 65535;
// Communicate relevant fields to the scan target.
scan_target_modals_.cycles_per_line = cycles_per_line;
scan_target_modals_.output_scale.x = uint16_t(horizontal_flywheel_->get_scan_period());
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_);
}
void CRT::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
scan_target_ = scan_target;
if(!scan_target_) scan_target_ = &Outputs::Display::NullScanTarget::singleton;
scan_target_->set_modals(scan_target_modals_);
}
void CRT::set_new_data_type(Outputs::Display::InputDataType data_type) {
scan_target_modals_.input_data_type = data_type;
scan_target_->set_modals(scan_target_modals_);
}
void CRT::set_aspect_ratio(float aspect_ratio) {
scan_target_modals_.aspect_ratio = aspect_ratio;
scan_target_->set_modals(scan_target_modals_);
}
void CRT::set_visible_area(Outputs::Display::Rect visible_area) {
scan_target_modals_.visible_area = visible_area;
scan_target_->set_modals(scan_target_modals_);
}
void CRT::set_display_type(Outputs::Display::DisplayType display_type) {
scan_target_modals_.display_type = display_type;
scan_target_->set_modals(scan_target_modals_);
}
Outputs::Display::DisplayType CRT::get_display_type() const {
return scan_target_modals_.display_type;
}
void CRT::set_phase_linked_luminance_offset(float offset) {
scan_target_modals_.input_data_tweaks.phase_linked_luminance_offset = offset;
scan_target_->set_modals(scan_target_modals_);
}
void CRT::set_input_data_type(Outputs::Display::InputDataType input_data_type) {
scan_target_modals_.input_data_type = input_data_type;
scan_target_->set_modals(scan_target_modals_);
}
void CRT::set_brightness(float brightness) {
scan_target_modals_.brightness = brightness;
scan_target_->set_modals(scan_target_modals_);
}
void CRT::set_new_display_type(int cycles_per_line, Outputs::Display::Type displayType) {
switch(displayType) {
case Outputs::Display::Type::PAL50:
case Outputs::Display::Type::PAL60:
scan_target_modals_.intended_gamma = 2.8f;
set_new_timing(
cycles_per_line,
(displayType == Outputs::Display::Type::PAL50) ? 312 : 262,
PAL::ColourSpace,
PAL::ColourCycleNumerator,
PAL::ColourCycleDenominator,
PAL::VerticalSyncLength,
PAL::AlternatesPhase);
break;
case Outputs::Display::Type::NTSC60:
scan_target_modals_.intended_gamma = 2.2f;
set_new_timing(
cycles_per_line,
262,
NTSC::ColourSpace,
NTSC::ColourCycleNumerator,
NTSC::ColourCycleDenominator,
NTSC::VerticalSyncLength,
NTSC::AlternatesPhase);
break;
}
}
void CRT::set_composite_function_type(CompositeSourceType type, float offset_of_first_sample) {
if(type == DiscreteFourSamplesPerCycle) {
colour_burst_phase_adjustment_ = uint8_t(offset_of_first_sample * 256.0f) & 63;
} else {
colour_burst_phase_adjustment_ = 0xff;
}
}
void CRT::set_input_gamma(float gamma) {
scan_target_modals_.intended_gamma = gamma;
scan_target_->set_modals(scan_target_modals_);
}
CRT::CRT( int cycles_per_line,
int clocks_per_pixel_greatest_common_divisor,
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,
Outputs::Display::InputDataType data_type) {
scan_target_modals_.input_data_type = data_type;
scan_target_modals_.clocks_per_pixel_greatest_common_divisor = clocks_per_pixel_greatest_common_divisor;
set_new_timing(cycles_per_line, height_of_display, colour_space, colour_cycle_numerator, colour_cycle_denominator, vertical_sync_half_lines, should_alternate);
}
CRT::CRT( int cycles_per_line,
int clocks_per_pixel_greatest_common_divisor,
Outputs::Display::Type display_type,
Outputs::Display::InputDataType data_type) {
scan_target_modals_.input_data_type = data_type;
scan_target_modals_.clocks_per_pixel_greatest_common_divisor = clocks_per_pixel_greatest_common_divisor;
set_new_display_type(cycles_per_line, display_type);
}
CRT::CRT(int cycles_per_line,
int clocks_per_pixel_greatest_common_divisor,
int height_of_display,
int vertical_sync_half_lines,
Outputs::Display::InputDataType data_type) {
scan_target_modals_.input_data_type = data_type;
scan_target_modals_.clocks_per_pixel_greatest_common_divisor = clocks_per_pixel_greatest_common_divisor;
set_new_timing(cycles_per_line, height_of_display, Outputs::Display::ColourSpace::YIQ, 1, 1, vertical_sync_half_lines, false);
}
// Use some from-thin-air arbitrary constants for default timing, otherwise passing
// construction off to one of the other constructors.
CRT::CRT(Outputs::Display::InputDataType data_type) : CRT(100, 1, 100, 1, data_type) {}
// MARK: - Sync loop
Flywheel::SyncEvent CRT::get_next_vertical_sync_event(bool vsync_is_requested, int cycles_to_run_for, int *cycles_advanced) {
return vertical_flywheel_->get_next_event_in_period(vsync_is_requested, cycles_to_run_for, cycles_advanced);
}
Flywheel::SyncEvent CRT::get_next_horizontal_sync_event(bool hsync_is_requested, int cycles_to_run_for, int *cycles_advanced) {
return horizontal_flywheel_->get_next_event_in_period(hsync_is_requested, cycles_to_run_for, cycles_advanced);
}
Outputs::Display::ScanTarget::Scan::EndPoint CRT::end_point(uint16_t data_offset) {
Display::ScanTarget::Scan::EndPoint end_point;
// Clamp the available range on endpoints. These will almost always be within range, but may go
// out during times of resync.
end_point.x = uint16_t(std::min(horizontal_flywheel_->get_current_output_position(), 65535));
end_point.y = uint16_t(std::min(vertical_flywheel_->get_current_output_position() / vertical_flywheel_output_divider_, 65535));
end_point.data_offset = data_offset;
// Ensure .composite_angle is sampled at the location indicated by .cycles_since_end_of_horizontal_retrace.
// TODO: I could supply time_multiplier_ as a modal and just not round .cycles_since_end_of_horizontal_retrace. Would that be better?
const auto lost_precision = cycles_since_horizontal_sync_ % time_multiplier_;
end_point.composite_angle = int16_t(((phase_numerator_ - lost_precision * colour_cycle_numerator_) << 6) / phase_denominator_) * (is_alternate_line_ ? -1 : 1);
end_point.cycles_since_end_of_horizontal_retrace = uint16_t(cycles_since_horizontal_sync_ / time_multiplier_);
return end_point;
}
void CRT::advance_cycles(int number_of_cycles, bool hsync_requested, bool vsync_requested, const Scan::Type type, int number_of_samples) {
number_of_cycles *= time_multiplier_;
const bool is_output_run = ((type == Scan::Type::Level) || (type == Scan::Type::Data));
const auto total_cycles = number_of_cycles;
bool did_output = false;
while(number_of_cycles) {
// Get time until next horizontal and vertical sync generator events.
int time_until_vertical_sync_event, time_until_horizontal_sync_event;
const Flywheel::SyncEvent next_vertical_sync_event = get_next_vertical_sync_event(vsync_requested, number_of_cycles, &time_until_vertical_sync_event);
const Flywheel::SyncEvent next_horizontal_sync_event = get_next_horizontal_sync_event(hsync_requested, time_until_vertical_sync_event, &time_until_horizontal_sync_event);
// Whichever event is scheduled to happen first is the one to advance to.
const int next_run_length = std::min(time_until_vertical_sync_event, time_until_horizontal_sync_event);
hsync_requested = false;
vsync_requested = false;
// Determine whether to output any data for this portion of the output; if so then grab somewhere to put it.
const bool is_output_segment = ((is_output_run && next_run_length) && !horizontal_flywheel_->is_in_retrace() && !vertical_flywheel_->is_in_retrace());
Outputs::Display::ScanTarget::Scan *const next_scan = is_output_segment ? scan_target_->begin_scan() : nullptr;
did_output |= is_output_segment;
// If outputting, store the start location and scan constants.
if(next_scan) {
next_scan->end_points[0] = end_point(uint16_t((total_cycles - number_of_cycles) * number_of_samples / total_cycles));
next_scan->composite_amplitude = colour_burst_amplitude_;
}
// Advance time: that'll affect both the colour subcarrier position and the number of cycles left to run.
phase_numerator_ += next_run_length * colour_cycle_numerator_;
number_of_cycles -= next_run_length;
cycles_since_horizontal_sync_ += next_run_length;
// React to the incoming event.
horizontal_flywheel_->apply_event(next_run_length, (next_run_length == time_until_horizontal_sync_event) ? next_horizontal_sync_event : Flywheel::SyncEvent::None);
vertical_flywheel_->apply_event(next_run_length, (next_run_length == time_until_vertical_sync_event) ? next_vertical_sync_event : Flywheel::SyncEvent::None);
// End the scan if necessary.
if(next_scan) {
next_scan->end_points[1] = end_point(uint16_t((total_cycles - number_of_cycles) * number_of_samples / total_cycles));
scan_target_->end_scan();
}
// Announce horizontal retrace events.
if(next_run_length == time_until_horizontal_sync_event && next_horizontal_sync_event != Flywheel::SyncEvent::None) {
// Reset the cycles-since-sync counter if this is the end of retrace.
if(next_horizontal_sync_event == Flywheel::SyncEvent::EndRetrace) {
cycles_since_horizontal_sync_ = 0;
// This is unnecessary, strictly speaking, but seeks to help ScanTargets fit as
// much as possible into a fixed range.
phase_numerator_ %= phase_denominator_;
if(!phase_numerator_) phase_numerator_ += phase_denominator_;
}
// Announce event.
const auto event =
(next_horizontal_sync_event == Flywheel::SyncEvent::StartRetrace)
? Outputs::Display::ScanTarget::Event::BeginHorizontalRetrace : Outputs::Display::ScanTarget::Event::EndHorizontalRetrace;
scan_target_->announce(
event,
!(horizontal_flywheel_->is_in_retrace() || vertical_flywheel_->is_in_retrace()),
end_point(uint16_t((total_cycles - number_of_cycles) * number_of_samples / total_cycles)),
colour_burst_amplitude_);
// If retrace is starting, update phase if required and mark no colour burst spotted yet.
if(next_horizontal_sync_event == Flywheel::SyncEvent::StartRetrace) {
should_be_alternate_line_ ^= phase_alternates_;
colour_burst_amplitude_ = 0;
}
}
// Also announce vertical retrace events.
if(next_run_length == time_until_vertical_sync_event && next_vertical_sync_event != Flywheel::SyncEvent::None) {
const auto event =
(next_vertical_sync_event == Flywheel::SyncEvent::StartRetrace)
? Outputs::Display::ScanTarget::Event::BeginVerticalRetrace : Outputs::Display::ScanTarget::Event::EndVerticalRetrace;
scan_target_->announce(
event,
!(horizontal_flywheel_->is_in_retrace() || vertical_flywheel_->is_in_retrace()),
end_point(uint16_t((total_cycles - number_of_cycles) * number_of_samples / total_cycles)),
colour_burst_amplitude_);
}
// if this is vertical retrace then advance a field
if(next_run_length == time_until_vertical_sync_event && next_vertical_sync_event == Flywheel::SyncEvent::EndRetrace) {
if(delegate_) {
frames_since_last_delegate_call_++;
if(frames_since_last_delegate_call_ == 20) {
delegate_->crt_did_end_batch_of_frames(this, frames_since_last_delegate_call_, vertical_flywheel_->get_and_reset_number_of_surprises());
frames_since_last_delegate_call_ = 0;
}
}
}
}
if(did_output) {
scan_target_->submit();
}
}
// MARK: - stream feeding methods
void CRT::output_scan(const Scan *const scan) {
assert(scan->number_of_cycles >= 0);
// Simplified colour burst logic: if it's within the back porch we'll take it.
if(scan->type == Scan::Type::ColourBurst) {
if(!colour_burst_amplitude_ && horizontal_flywheel_->get_current_time() < (horizontal_flywheel_->get_standard_period() * 12) >> 6) {
// Load phase_numerator_ as a fixed-point quantity in the range [0, 255].
phase_numerator_ = scan->phase;
if(colour_burst_phase_adjustment_ != 0xff)
phase_numerator_ = (phase_numerator_ & ~63) + colour_burst_phase_adjustment_;
// Multiply the phase_numerator_ up to be to the proper scale.
phase_numerator_ = (phase_numerator_ * phase_denominator_) >> 8;
// Crib the colour burst amplitude.
colour_burst_amplitude_ = scan->amplitude;
}
}
// TODO: inspect raw data for potential colour burst if required; the DPLL and some zero crossing logic
// will probably be sufficient but some test data would be helpful
// sync logic: mark whether this is currently sync and check for a leading edge
const bool this_is_sync = (scan->type == Scan::Type::Sync);
const bool is_leading_edge = (!is_receiving_sync_ && this_is_sync);
is_receiving_sync_ = this_is_sync;
// Horizontal sync is recognised on any leading edge that is not 'near' the expected vertical sync;
// the second limb is to avoid slightly horizontal sync shifting from the common pattern of
// equalisation pulses as the inverse of ordinary horizontal sync.
bool hsync_requested = is_leading_edge && !vertical_flywheel_->is_near_expected_sync();
if(this_is_sync) {
// If this is sync then either begin or continue a sync accumulation phase.
is_accumulating_sync_ = true;
cycles_since_sync_ = 0;
} else {
// If this is not sync then check how long it has been since sync. If it's more than
// half a line then end sync accumulation and zero out the accumulating count.
cycles_since_sync_ += scan->number_of_cycles;
if(cycles_since_sync_ > (cycles_per_line_ >> 2)) {
cycles_of_sync_ = 0;
is_accumulating_sync_ = false;
is_refusing_sync_ = false;
}
}
int number_of_cycles = scan->number_of_cycles;
bool vsync_requested = false;
// If sync is being accumulated then accumulate it; if it crosses the vertical sync threshold then
// divide this line at the crossing point and indicate vertical sync there.
if(is_accumulating_sync_ && !is_refusing_sync_) {
cycles_of_sync_ += scan->number_of_cycles;
if(this_is_sync && cycles_of_sync_ >= sync_capacitor_charge_threshold_) {
const int overshoot = std::min(cycles_of_sync_ - sync_capacitor_charge_threshold_, number_of_cycles);
if(overshoot) {
number_of_cycles -= overshoot;
advance_cycles(number_of_cycles, hsync_requested, false, scan->type, 0);
hsync_requested = false;
number_of_cycles = overshoot;
}
is_refusing_sync_ = true;
vsync_requested = true;
}
}
advance_cycles(number_of_cycles, hsync_requested, vsync_requested, scan->type, scan->number_of_samples);
}
/*
These all merely channel into advance_cycles, supplying appropriate arguments
*/
void CRT::output_sync(int number_of_cycles) {
Scan scan;
scan.type = Scan::Type::Sync;
scan.number_of_cycles = number_of_cycles;
output_scan(&scan);
}
void CRT::output_blank(int number_of_cycles) {
Scan scan;
scan.type = Scan::Type::Blank;
scan.number_of_cycles = number_of_cycles;
output_scan(&scan);
}
void CRT::output_level(int number_of_cycles) {
scan_target_->end_data(1);
Scan scan;
scan.type = Scan::Type::Level;
scan.number_of_cycles = number_of_cycles;
scan.number_of_samples = 1;
output_scan(&scan);
}
void CRT::output_colour_burst(int number_of_cycles, uint8_t phase, bool is_alternate_line, uint8_t amplitude) {
Scan scan;
scan.type = Scan::Type::ColourBurst;
scan.number_of_cycles = number_of_cycles;
scan.phase = phase;
scan.amplitude = amplitude >> 1;
is_alternate_line_ = is_alternate_line;
output_scan(&scan);
}
void CRT::output_default_colour_burst(int number_of_cycles, uint8_t amplitude) {
// TODO: avoid applying a rounding error here?
output_colour_burst(number_of_cycles, uint8_t((phase_numerator_ * 256) / phase_denominator_), should_be_alternate_line_, amplitude);
}
void CRT::set_immediate_default_phase(float phase) {
phase = fmodf(phase, 1.0f);
phase_numerator_ = int(phase * float(phase_denominator_));
}
void CRT::output_data(int number_of_cycles, size_t number_of_samples) {
#ifndef NDEBUG
// assert(number_of_samples > 0);
// assert(number_of_samples <= allocated_data_length_);
// allocated_data_length_ = std::numeric_limits<size_t>::min();
#endif
scan_target_->end_data(number_of_samples);
Scan scan;
scan.type = Scan::Type::Data;
scan.number_of_cycles = number_of_cycles;
scan.number_of_samples = int(number_of_samples);
output_scan(&scan);
}
// MARK: - Getters.
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) const {
first_cycle_after_sync *= time_multiplier_;
number_of_cycles *= time_multiplier_;
first_line_after_sync -= 2;
number_of_lines += 4;
// determine prima facie x extent
const int horizontal_period = horizontal_flywheel_->get_standard_period();
const int horizontal_scan_period = horizontal_flywheel_->get_scan_period();
const int horizontal_retrace_period = horizontal_period - horizontal_scan_period;
// make sure that the requested range is visible
if(int(first_cycle_after_sync) < horizontal_retrace_period) first_cycle_after_sync = int(horizontal_retrace_period);
if(int(first_cycle_after_sync + number_of_cycles) > horizontal_scan_period) number_of_cycles = int(horizontal_scan_period - int(first_cycle_after_sync));
float start_x = float(int(first_cycle_after_sync) - horizontal_retrace_period) / float(horizontal_scan_period);
float width = float(number_of_cycles) / float(horizontal_scan_period);
// determine prima facie y extent
const int vertical_period = vertical_flywheel_->get_standard_period();
const int vertical_scan_period = vertical_flywheel_->get_scan_period();
const int vertical_retrace_period = vertical_period - vertical_scan_period;
// make sure that the requested range is visible
// if(int(first_line_after_sync) * horizontal_period < vertical_retrace_period)
// first_line_after_sync = (vertical_retrace_period + horizontal_period - 1) / horizontal_period;
// if((first_line_after_sync + number_of_lines) * horizontal_period > vertical_scan_period)
// number_of_lines = int(horizontal_scan_period - int(first_cycle_after_sync));
float start_y = float((int(first_line_after_sync) * horizontal_period) - vertical_retrace_period) / float(vertical_scan_period);
float height = float(int(number_of_lines) * horizontal_period) / vertical_scan_period;
// adjust to ensure aspect ratio is correct
const float adjusted_aspect_ratio = (3.0f*aspect_ratio / 4.0f);
const float ideal_width = height * adjusted_aspect_ratio;
if(ideal_width > width) {
start_x -= (ideal_width - width) * 0.5f;
width = ideal_width;
} else {
float ideal_height = width / adjusted_aspect_ratio;
start_y -= (ideal_height - height) * 0.5f;
height = ideal_height;
}
return Outputs::Display::Rect(start_x, start_y, width, height);
}
Outputs::Display::ScanStatus CRT::get_scaled_scan_status() const {
Outputs::Display::ScanStatus status;
status.field_duration = float(vertical_flywheel_->get_locked_period()) / float(time_multiplier_);
status.field_duration_gradient = float(vertical_flywheel_->get_last_period_adjustment()) / float(time_multiplier_);
status.retrace_duration = float(vertical_flywheel_->get_retrace_period()) / float(time_multiplier_);
status.current_position = float(vertical_flywheel_->get_current_phase()) / float(vertical_flywheel_->get_locked_scan_period());
status.hsync_count = vertical_flywheel_->get_number_of_retraces();
return status;
}