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Made a quick attempt to allow vsync triggers only on the raising edge of a sync signal. Will need to investigate more thoroughly.

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This commit is contained in:
Thomas Harte 2015-08-03 08:42:05 -04:00
parent 55017b78a5
commit 04c2640b15
2 changed files with 32 additions and 28 deletions
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56
Outputs/CRT.cpp
View File

@ -20,7 +20,7 @@ static const uint32_t kCRTFixedPointOffset = 0x08000000;
void CRT::set_new_timing(int cycles_per_line, int height_of_display)
{
const int syncCapacityLineChargeThreshold = 4;
const int syncCapacityLineChargeThreshold = 5;
const int millisecondsHorizontalRetraceTime = 10; // source: Dictionary of Video and Television Technology, p. 234
const int scanlinesVerticalRetraceTime = 7; // source: ibid
@ -28,13 +28,13 @@ void CRT::set_new_timing(int cycles_per_line, int height_of_display)
height_of_display += (height_of_display / 20); // this is the overrun area we'll use to
// store fundamental display configuration properties
_height_of_display = height_of_display;// + (height_of_display / 10);
_height_of_display = height_of_display + 10;
_cycles_per_line = cycles_per_line * _time_multiplier;
// generate timing values implied by the given arbuments
_hsync_error_window = _cycles_per_line >> 5;
_sync_capacitor_charge_threshold = (syncCapacityLineChargeThreshold * _cycles_per_line) >> 1;
_sync_capacitor_charge_threshold = ((syncCapacityLineChargeThreshold * _cycles_per_line) * 50) >> 7;
_horizontal_retrace_time = (millisecondsHorizontalRetraceTime * _cycles_per_line) >> 6;
const int vertical_retrace_time = scanlinesVerticalRetraceTime * _cycles_per_line;
const float halfLineWidth = (float)_height_of_display * 1.0f;
@ -96,19 +96,29 @@ CRT::~CRT()
#pragma mark - Sync loop
CRT::SyncEvent CRT::get_next_vertical_sync_event(bool vsync_is_charging, int cycles_to_run_for, int *cycles_advanced)
CRT::SyncEvent CRT::get_next_vertical_sync_event(bool vsync_is_requested, int cycles_to_run_for, int *cycles_advanced)
{
SyncEvent proposedEvent = SyncEvent::None;
int proposedSyncTime = cycles_to_run_for;
// will an acceptable vertical sync be triggered?
if (vsync_is_requested && !_is_in_vsync) {
if (_sync_capacitor_charge_level >= _sync_capacitor_charge_threshold) {// && _rasterPosition.y >= (kCRTFixedPointRange * 7) >> 3) {
// printf("%d v %d\n", _sync_capacitor_charge_level, _sync_capacitor_charge_threshold);
proposedSyncTime = 0;
proposedEvent = SyncEvent::StartVSync;
_did_detect_vsync = true;
}
}
// have we overrun the maximum permitted number of horizontal syncs for this frame?
if (!_is_in_vsync) {
int time_until_end_of_frame = (kCRTFixedPointRange - _rasterPosition.y) / _scanSpeed[0].y;
/* int time_until_end_of_frame = (kCRTFixedPointRange - _rasterPosition.y) / _scanSpeed[0].y;
if(time_until_end_of_frame < proposedSyncTime) {
proposedSyncTime = time_until_end_of_frame;
proposedEvent = SyncEvent::StartVSync;
}
}*/
} else {
int time_until_start_of_frame = _rasterPosition.y / _scanSpeed[kRetraceYMask].y;
@ -118,19 +128,6 @@ CRT::SyncEvent CRT::get_next_vertical_sync_event(bool vsync_is_charging, int cyc
}
}
// will an acceptable vertical sync be triggered?
if (vsync_is_charging && !_is_in_vsync) {
if (_sync_capacitor_charge_level < _sync_capacitor_charge_threshold && _sync_capacitor_charge_level + proposedSyncTime >= _sync_capacitor_charge_threshold) {
uint32_t proposed_sync_y = _rasterPosition.y + (_sync_capacitor_charge_threshold - _sync_capacitor_charge_level) * _scanSpeed[0].y;
if(proposed_sync_y >= (kCRTFixedPointRange * 7) >> 3) {
proposedSyncTime = _sync_capacitor_charge_threshold - _sync_capacitor_charge_level;
proposedEvent = SyncEvent::StartVSync;
_did_detect_vsync = true;
}
}
}
*cycles_advanced = proposedSyncTime;
return proposedEvent;
}
@ -166,7 +163,7 @@ CRT::SyncEvent CRT::get_next_horizontal_sync_event(bool hsync_is_requested, int
return proposedEvent;
}
void CRT::advance_cycles(int number_of_cycles, bool hsync_requested, const bool vsync_charging, const Type type, const char *data_type)
void CRT::advance_cycles(int number_of_cycles, bool hsync_requested, bool vsync_requested, const bool vsync_charging, const Type type, const char *data_type)
{
number_of_cycles *= _time_multiplier;
@ -182,14 +179,18 @@ void CRT::advance_cycles(int number_of_cycles, bool hsync_requested, const bool
while(number_of_cycles) {
int time_until_vertical_sync_event, time_until_horizontal_sync_event;
SyncEvent next_vertical_sync_event = this->get_next_vertical_sync_event(vsync_charging, number_of_cycles, &time_until_vertical_sync_event);
SyncEvent next_vertical_sync_event = this->get_next_vertical_sync_event(vsync_requested, number_of_cycles, &time_until_vertical_sync_event);
SyncEvent next_horizontal_sync_event = this->get_next_horizontal_sync_event(hsync_requested, time_until_vertical_sync_event, &time_until_horizontal_sync_event);
hsync_requested = false;
// get the next sync event and its timing; hsync request is instantaneous (being edge triggered) so
// set it to false for the next run through this loop (if any)
int next_run_length = std::min(time_until_vertical_sync_event, time_until_horizontal_sync_event);
// if(next_run_length) {
hsync_requested = false;
vsync_requested = false;
// }
uint16_t *next_run = (is_output_run && _current_frame_builder && next_run_length) ? _current_frame_builder->get_next_run() : nullptr;
int lengthMask = (_is_in_hsync ? kRetraceXMask : 0) | (_is_in_vsync ? kRetraceXMask : 0);
@ -342,25 +343,28 @@ void CRT::output_sync(int number_of_cycles)
{
bool _hsync_requested = !_is_receiving_sync; // ensure this really is edge triggered; someone calling output_sync twice in succession shouldn't trigger it twice
_is_receiving_sync = true;
advance_cycles(number_of_cycles, _hsync_requested, true, Type::Sync, nullptr);
advance_cycles(number_of_cycles, _hsync_requested, false, true, Type::Sync, nullptr);
}
void CRT::output_blank(int number_of_cycles)
{
bool _vsync_requested = _is_receiving_sync;
_is_receiving_sync = false;
advance_cycles(number_of_cycles, false, false, Type::Blank, nullptr);
advance_cycles(number_of_cycles, false, _vsync_requested, false, Type::Blank, nullptr);
}
void CRT::output_level(int number_of_cycles, const char *type)
{
bool _vsync_requested = _is_receiving_sync;
_is_receiving_sync = false;
advance_cycles(number_of_cycles, false, false, Type::Level, type);
advance_cycles(number_of_cycles, false, _vsync_requested, false, Type::Level, type);
}
void CRT::output_data(int number_of_cycles, const char *type)
{
bool _vsync_requested = _is_receiving_sync;
_is_receiving_sync = false;
advance_cycles(number_of_cycles, false, false, Type::Data, type);
advance_cycles(number_of_cycles, false, _vsync_requested, false, Type::Data, type);
}
#pragma mark - Buffer supply

4
Outputs/CRT.hpp
View File

@ -110,7 +110,7 @@ class CRT {
enum Type {
Sync, Level, Data, Blank
} type;
void advance_cycles(int number_of_cycles, bool hsync_requested, bool vsync_charging, Type type, const char *data_type);
void advance_cycles(int number_of_cycles, bool hsync_requested, bool vsync_requested, bool vsync_charging, Type type, const char *data_type);
// the inner entry point that determines whether and when the next sync event will occur within
// the current output window
@ -119,7 +119,7 @@ class CRT {
StartHSync, EndHSync,
StartVSync, EndVSync
};
SyncEvent get_next_vertical_sync_event(bool vsync_is_charging, int cycles_to_run_for, int *cycles_advanced);
SyncEvent get_next_vertical_sync_event(bool vsync_is_requested, int cycles_to_run_for, int *cycles_advanced);
SyncEvent get_next_horizontal_sync_event(bool hsync_is_requested, int cycles_to_run_for, int *cycles_advanced);
};