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CLK/Machines/Atari/ST/Video.cpp
Thomas Harte e787c03530 Slightly shortens NTSC frame.
Either: (i) 263 is incorrect; or (ii) my logic as to frame height is incorrect. Given that the horizontal side of things is really well documented, I'm currently guessing (i). Research to do.
2019-11-18 23:47:27 -05:00

583 lines
18 KiB
C++

//
// Video.cpp
// Clock Signal
//
// Created by Thomas Harte on 04/10/2019.
// Copyright © 2019 Thomas Harte. All rights reserved.
//
#include "Video.hpp"
#include "../../../Outputs/Log.hpp"
#include <algorithm>
#include <cstring>
using namespace Atari::ST;
namespace {
/*!
Defines the line counts at which mode-specific events will occur:
vertical enable being set and being reset, and the line on which
the frame will end.
*/
const struct VerticalParams {
const int set_enable;
const int reset_enable;
const int height;
} vertical_params[3] = {
{63, 263, 313}, // 47 rather than 63 on early machines.
{34, 234, 262}, // TODO: is 262 correct? If it's 263, how does that interact with opening the bottom border?
{1, 401, 500} // 72 Hz mode: who knows?
};
/// @returns The correct @c VerticalParams for output at @c frequency.
const VerticalParams &vertical_parameters(Video::FieldFrequency frequency) {
return vertical_params[int(frequency)];
}
/*!
Defines the horizontal counts at which mode-specific events will occur:
horizontal enable being set and being reset, blank being set and reset, and the
intended length of this ine.
The caller should:
* latch line length at cycle 54 (TODO: also for 72Hz mode?);
* at (line length - 50), start sync and reset enable (usually for the second time);
* at (line length - 10), disable sync.
*/
const struct HorizontalParams {
const int set_enable;
const int reset_enable;
const int set_blank;
const int reset_blank;
const int length;
} horizontal_params[3] = {
{56*2, 376*2, 450*2, 28*2, 512*2},
{52*2, 372*2, 450*2, 24*2, 508*2},
{4*2, 164*2, 184*2, 2*2, 224*2}
};
const HorizontalParams &horizontal_parameters(Video::FieldFrequency frequency) {
return horizontal_params[int(frequency)];
}
#ifndef NDEBUG
struct Checker {
Checker() {
for(int c = 0; c < 3; ++c) {
// Expected horizontal order of events: reset blank, enable display, disable display, enable blank (at least 50 before end of line), end of line
const auto horizontal = horizontal_parameters(Video::FieldFrequency(c));
assert(horizontal.reset_blank < horizontal.set_enable);
assert(horizontal.set_enable < horizontal.reset_enable);
assert(horizontal.reset_enable < horizontal.set_blank);
assert(horizontal.set_blank+50 < horizontal.length);
// Expected vertical order of events: reset blank, enable display, disable display, enable blank (at least 50 before end of line), end of line
const auto vertical = vertical_parameters(Video::FieldFrequency(c));
assert(vertical.set_enable < vertical.reset_enable);
assert(vertical.reset_enable < vertical.height);
}
}
} checker;
#endif
const int de_delay_period = 28*2;
}
Video::Video() :
crt_(1024, 1, Outputs::Display::Type::PAL50, Outputs::Display::InputDataType::Red4Green4Blue4),
shifter_(crt_, palette_) {
// Show a total of 260 lines; a little short for PAL but a compromise between that and the ST's
// usual output height of 200 lines.
crt_.set_visible_area(crt_.get_rect_for_area(33, 260, 216, 850, 4.0f / 3.0f));
}
void Video::set_ram(uint16_t *ram, size_t size) {
ram_ = ram;
}
void Video::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
crt_.set_scan_target(scan_target);
}
void Video::run_for(HalfCycles duration) {
const auto horizontal_timings = horizontal_parameters(field_frequency_);
const auto vertical_timings = vertical_parameters(field_frequency_);
int integer_duration = int(duration.as_integral());
// Effect any changes in visible state out here; they're not relevant in the inner loop.
if(!pending_events_.empty()) {
auto erase_iterator = pending_events_.begin();
int duration_remaining = integer_duration;
while(erase_iterator != pending_events_.end()) {
erase_iterator->delay -= duration_remaining;
if(erase_iterator->delay <= 0) {
duration_remaining = -erase_iterator->delay;
erase_iterator->apply(public_state_);
++erase_iterator;
} else {
break;
}
}
if(erase_iterator != pending_events_.begin()) {
pending_events_.erase(pending_events_.begin(), erase_iterator);
}
}
while(integer_duration) {
// Seed next event to end of line.
int next_event = line_length_;
// Check the explicitly-placed events.
if(horizontal_timings.reset_blank > x_) next_event = std::min(next_event, horizontal_timings.reset_blank);
if(horizontal_timings.set_blank > x_) next_event = std::min(next_event, horizontal_timings.set_blank);
if(horizontal_timings.reset_enable > x_) next_event = std::min(next_event, horizontal_timings.reset_enable);
if(horizontal_timings.set_enable > x_) next_event = std::min(next_event, horizontal_timings.set_enable);
// Check for events that are relative to existing latched state.
if(line_length_ - 50*2 > x_) next_event = std::min(next_event, line_length_ - 50*2);
if(line_length_ - 10*2 > x_) next_event = std::min(next_event, line_length_ - 10*2);
// Also, a vertical sync event might intercede.
if(vertical_.sync_schedule != VerticalState::SyncSchedule::None && x_ < 30*2 && next_event >= 30*2) {
next_event = 30*2;
}
// Determine current output mode and number of cycles to output for.
const int run_length = std::min(integer_duration, next_event - x_);
const bool display_enable = vertical_.enable && horizontal_.enable;
if(horizontal_.sync || vertical_.sync) {
shifter_.output_sync(run_length);
} else if(horizontal_.blank || vertical_.blank) {
shifter_.output_blank(run_length);
} else if(!vertical_.enable || !horizontal_.enable) {
shifter_.output_border(run_length, output_bpp_);
} else {
// There will be pixels this line, subject to the shifter pipeline.
// Divide into 8-[half-]cycle windows; at the start of each window fetch a word,
// and during the rest of the window, shift out.
int start_column = x_ >> 3;
const int end_column = (x_ + run_length) >> 3;
// Rules obeyed below:
//
// Video fetches occur as the first act of business in a column. Each
// fetch is then followed by 8 shift clocks. Whether or not the shifter
// was reloaded by the fetch depends on the FIFO.
if(start_column == end_column) {
shifter_.output_pixels(run_length, output_bpp_);
} else {
// Continue the current column if partway across.
if(x_&7) {
// If at least one column boundary is crossed, complete this column.
shifter_.output_pixels(8 - (x_ & 7), output_bpp_);
++start_column; // This starts a new column, so latch a new word.
latch_word();
}
// Run for all columns that have their starts in this time period.
int complete_columns = end_column - start_column;
while(complete_columns--) {
shifter_.output_pixels(8, output_bpp_);
latch_word();
}
// Output the start of the next column, if necessary.
if((x_ + run_length) & 7) {
shifter_.output_pixels((x_ + run_length) & 7, output_bpp_);
}
}
}
// Check for whether line length should have been latched during this run.
if(x_ <= 54*2 && (x_ + run_length) > 54*2) line_length_ = horizontal_timings.length;
// Make a decision about vertical state on cycle 502.
if(x_ <= 502*2 && (x_ + run_length) > 502*2) {
next_y_ = y_ + 1;
next_vertical_ = vertical_;
next_vertical_.sync_schedule = VerticalState::SyncSchedule::None;
// Use vertical_parameters to get parameters for the current output frequency.
if(next_y_ == vertical_timings.set_enable) {
next_vertical_.enable = true;
} else if(next_y_ == vertical_timings.reset_enable) {
next_vertical_.enable = false;
} else if(next_y_ == vertical_timings.height) {
next_y_ = 0;
next_vertical_.sync_schedule = VerticalState::SyncSchedule::Begin;
current_address_ = base_address_ >> 1;
} else if(next_y_ == 3) {
next_vertical_.sync_schedule = VerticalState::SyncSchedule::End;
}
}
// Apply the next event.
x_ += run_length;
integer_duration -= run_length;
// Check horizontal events.
if(horizontal_timings.reset_blank == x_) horizontal_.blank = false;
else if(horizontal_timings.set_blank == x_) horizontal_.blank = true;
else if(horizontal_timings.reset_enable == x_) horizontal_.enable = false;
else if(horizontal_timings.set_enable == x_) horizontal_.enable = true;
else if(line_length_ - 50*2 == x_) horizontal_.sync = true;
else if(line_length_ - 10*2 == x_) horizontal_.sync = false;
// Check vertical events.
if(vertical_.sync_schedule != VerticalState::SyncSchedule::None && x_ == 30*2) {
vertical_.sync = vertical_.sync_schedule == VerticalState::SyncSchedule::Begin;
vertical_.enable &= !vertical_.sync;
}
// Check whether the terminating event was end-of-line; if so then advance
// the vertical bits of state.
if(x_ == line_length_) {
x_ = 0;
vertical_ = next_vertical_;
y_ = next_y_;
}
// Chuck any deferred output changes into the queue.
const bool next_display_enable = vertical_.enable && horizontal_.enable;
if(display_enable != next_display_enable) {
add_event(de_delay_period - integer_duration, next_display_enable ? Event::Type::SetDisplayEnable : Event::Type::ResetDisplayEnable);
}
}
}
void Video::latch_word() {
data_latch_[data_latch_position_] = ram_[current_address_ & 262143];
++current_address_;
++data_latch_position_;
if(data_latch_position_ == 4) {
data_latch_position_ = 0;
shifter_.load(
(uint64_t(data_latch_[0]) << 48) |
(uint64_t(data_latch_[1]) << 32) |
(uint64_t(data_latch_[2]) << 16) |
uint64_t(data_latch_[3])
);
}
}
bool Video::hsync() {
return horizontal_.sync;
}
bool Video::vsync() {
return vertical_.sync;
}
bool Video::display_enabled() {
return public_state_.display_enable;
}
HalfCycles Video::get_next_sequence_point() {
// The next sequence point will be whenever display_enabled, vsync or hsync next changes.
// Sequence of events within a standard line:
//
// 1) blank disabled;
// 2) display enabled;
// 3) display disabled;
// 4) blank enabled;
// 5) sync enabled;
// 6) sync disabled;
// 7) end-of-line, potential vertical event.
//
// If this line has a vertical sync event on it, there will also be an event at cycle 30,
// which will always falls somewhere between (1) and (4) but might or might not be in the
// visible area.
const auto horizontal_timings = horizontal_parameters(field_frequency_);
int event_time = line_length_; // Worst case: report end of line.
// If any events are pending, give the first of those the chance to be next.
if(!pending_events_.empty()) {
event_time = std::min(event_time, x_ + event_time);
}
// If this is a vertically-enabled line, check for the display enable boundaries, + the standard delay.
if(vertical_.enable) {
if(x_ < horizontal_timings.set_enable + de_delay_period) {
event_time = std::min(event_time, horizontal_timings.set_enable + de_delay_period);
}
else if(x_ < horizontal_timings.reset_enable + de_delay_period) {
event_time = std::min(event_time, horizontal_timings.reset_enable + de_delay_period);
}
}
// If a vertical sync event is scheduled, test for that.
if(vertical_.sync_schedule != VerticalState::SyncSchedule::None && (x_ < 30*2)) {
event_time = std::min(event_time, 30*2);
}
// Test for beginning and end of horizontal sync.
if(x_ < line_length_ - 50*2) event_time = std::min(line_length_ - 50*2, event_time);
else if(x_ < line_length_ - 10*2) event_time = std::min(line_length_ - 10*2, event_time);
// It wasn't any of those, so as a temporary expedient, just supply end of line.
return HalfCycles(event_time - x_);
}
// MARK: - IO dispatch
uint16_t Video::read(int address) {
address &= 0x3f;
switch(address) {
default:
break;
case 0x00: return uint16_t(0xff00 | (base_address_ >> 16));
case 0x01: return uint16_t(0xff00 | (base_address_ >> 8));
case 0x02: return uint16_t(0xff00 | (current_address_ >> 15)); // Current address is kept in word precision internally;
case 0x03: return uint16_t(0xff00 | (current_address_ >> 7)); // the shifts here represent a conversion back to
case 0x04: return uint16_t(0xff00 | (current_address_ << 1)); // byte precision.
case 0x05: return sync_mode_ | 0xfcff;
case 0x30: return video_mode_ | 0xfcff;
case 0x20: case 0x21: case 0x22: case 0x23:
case 0x24: case 0x25: case 0x26: case 0x27:
case 0x28: case 0x29: case 0x2a: case 0x2b:
case 0x2c: case 0x2d: case 0x2e: case 0x2f: return raw_palette_[address - 0x20];
}
return 0xff;
}
void Video::write(int address, uint16_t value) {
address &= 0x3f;
switch(address) {
default: break;
// Start address.
case 0x00: base_address_ = (base_address_ & 0x00ffff) | ((value & 0xff) << 16); break;
case 0x01: base_address_ = (base_address_ & 0xff00ff) | ((value & 0xff) << 8); break;
// Sync mode and pixel mode.
case 0x05:
sync_mode_ = value;
update_output_mode();
break;
case 0x30:
video_mode_ = value;
update_output_mode();
break;
// Palette.
case 0x20: case 0x21: case 0x22: case 0x23:
case 0x24: case 0x25: case 0x26: case 0x27:
case 0x28: case 0x29: case 0x2a: case 0x2b:
case 0x2c: case 0x2d: case 0x2e: case 0x2f: {
raw_palette_[address - 0x20] = value;
uint8_t *const entry = reinterpret_cast<uint8_t *>(&palette_[address - 0x20]);
entry[0] = uint8_t((value & 0x700) >> 7);
entry[1] = uint8_t((value & 0x77) << 1);
} break;
}
}
void Video::update_output_mode() {
// If this is black and white mode, that's that.
switch((video_mode_ >> 8) & 3) {
case 0: output_bpp_ = OutputBpp::Four; break;
case 1: output_bpp_ = OutputBpp::Two; break;
// 1bpp mode ignores the otherwise-programmed frequency.
default:
case 2:
output_bpp_ = OutputBpp::One;
field_frequency_ = FieldFrequency::SeventyTwo;
return;
}
field_frequency_ = (sync_mode_ & 0x200) ? FieldFrequency::Fifty : FieldFrequency::Sixty;
}
// MARK: - The shifter
void Video::Shifter::flush_output(OutputMode next_mode) {
switch(output_mode_) {
case OutputMode::Sync: crt_.output_sync(duration_); break;
case OutputMode::Blank: crt_.output_blank(duration_); break;
case OutputMode::Border: {
// if(!border_colour_) {
// crt_.output_blank(duration_);
// } else {
uint16_t *const colour_pointer = reinterpret_cast<uint16_t *>(crt_.begin_data(1));
if(colour_pointer) *colour_pointer = border_colour_;
crt_.output_level(duration_);
// }
} break;
case OutputMode::Pixels: {
crt_.output_data(duration_, pixel_pointer_);
pixel_buffer_ = nullptr;
pixel_pointer_ = 0;
} break;
}
duration_ = 0;
output_mode_ = next_mode;
}
void Video::Shifter::output_blank(int duration) {
if(output_mode_ != OutputMode::Blank) {
flush_output(OutputMode::Blank);
}
duration_ += duration;
}
void Video::Shifter::output_sync(int duration) {
if(output_mode_ != OutputMode::Sync) {
flush_output(OutputMode::Sync);
}
duration_ += duration;
}
void Video::Shifter::output_border(int duration, OutputBpp bpp) {
// If there's still anything in the shifter, redirect this to an output_pixels call.
if(output_shifter_) {
// This doesn't take an opinion on how much of the shifter remains populated;
// it assumes the worst case.
const int pixel_length = std::min(32, duration);
output_pixels(pixel_length, bpp);
duration -= pixel_length;
if(!duration) {
return;
}
}
// Flush anything that isn't level output *in the current border colour*.
if(output_mode_ != OutputMode::Border || border_colour_ != palette_[0]) {
flush_output(OutputMode::Border);
border_colour_ = palette_[0];
}
duration_ += duration;
}
void Video::Shifter::output_pixels(int duration, OutputBpp bpp) {
// If the shifter is empty and there's no pixel buffer at present,
// redirect this to an output_level call. Otherwise, do a quick
// memset-type fill, since the special case has been detected anyway.
if(!output_shifter_) {
if(!pixel_buffer_) {
output_border(duration, bpp);
} else {
duration_ += duration;
switch(bpp_) {
case OutputBpp::One: {
const size_t pixels = size_t(duration << 1);
memset(&pixel_buffer_[pixel_pointer_], 0, pixels * sizeof(uint16_t));
pixel_pointer_ += pixels;
} break;
default:
case OutputBpp::Four:
assert(!(duration & 1));
duration >>= 1;
case OutputBpp::Two: {
while(duration--) {
pixel_buffer_[pixel_pointer_] = palette_[0];
++pixel_pointer_;
}
} break;
}
}
return;
}
// Flush anything that isn't pixel output in the proper bpp; also flush if there's nowhere
// left to put pixels.
if(output_mode_ != OutputMode::Pixels || bpp_ != bpp || pixel_pointer_ >= 320) {
flush_output(OutputMode::Pixels);
bpp_ = bpp;
pixel_buffer_ = reinterpret_cast<uint16_t *>(crt_.begin_data(320 + 32));
}
duration_ += duration;
switch(bpp_) {
case OutputBpp::One: {
int pixels = duration << 1;
if(pixel_buffer_) {
while(pixels--) {
pixel_buffer_[pixel_pointer_] = ((output_shifter_ >> 63) & 1) * 0xffff;
output_shifter_ <<= 1;
++pixel_pointer_;
}
} else {
pixel_pointer_ += size_t(pixels);
output_shifter_ <<= pixels;
}
} break;
case OutputBpp::Two: {
#if TARGET_RT_BIG_ENDIAN
const int upper = 0;
#else
const int upper = 1;
#endif
if(pixel_buffer_) {
while(duration--) {
pixel_buffer_[pixel_pointer_] = palette_[
((output_shifter_ >> 63) & 1) |
((output_shifter_ >> 46) & 2)
];
// This ensures that the top two words shift one to the left;
// their least significant bits are fed from the most significant bits
// of the bottom two words, respectively.
shifter_halves_[upper] = (shifter_halves_[upper] << 1) & 0xfffefffe;
shifter_halves_[upper] |= (shifter_halves_[upper^1] & 0x80008000) >> 15;
shifter_halves_[upper^1] = (shifter_halves_[upper^1] << 1) & 0xfffefffe;
++pixel_pointer_;
}
} else {
pixel_pointer_ += size_t(duration);
while(duration--) {
shifter_halves_[upper] = (shifter_halves_[upper] << 1) & 0xfffefffe;
shifter_halves_[upper] |= (shifter_halves_[upper^1] & 0x80008000) >> 15;
shifter_halves_[upper^1] = (shifter_halves_[upper^1] << 1) & 0xfffefffe;
}
}
} break;
default:
case OutputBpp::Four:
assert(!(duration & 1));
if(pixel_buffer_) {
while(duration) {
pixel_buffer_[pixel_pointer_] = palette_[
((output_shifter_ >> 63) & 1) |
((output_shifter_ >> 46) & 2) |
((output_shifter_ >> 29) & 4) |
((output_shifter_ >> 12) & 8)
];
output_shifter_ = (output_shifter_ << 1) & 0xfffefffefffefffe;
++pixel_pointer_;
duration -= 2;
}
} else {
pixel_pointer_ += size_t(duration >> 1);
while(duration) {
output_shifter_ = (output_shifter_ << 1) & 0xfffefffefffefffe;
duration -= 2;
}
}
break;
}
}
void Video::Shifter::load(uint64_t value) {
output_shifter_ = value;
}