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Merge pull request #125 from TomHarte/SampledComposite

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Formalises reasoning for the colour phase clamp and offset...
This commit is contained in:
Thomas Harte 2017-05-16 20:47:20 -04:00 committed by GitHub
commit 67ec0b9e6c
4 changed files with 33 additions and 3 deletions
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2
Machines/Atari2600/TIA.cpp
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@ -137,7 +137,7 @@ void TIA::set_output_mode(Atari2600::TIA::OutputMode output_mode) {
"uint y = c & 14u;"
"uint iPhase = (c >> 4);"
"float phaseOffset = 6.283185308 * (float(iPhase) + 3.0) / 13.0 + 5.074880441076923;"
"float phaseOffset = 6.283185308 * float(iPhase) / 13.0 + 5.074880441076923;"
"return mix(float(y) / 14.0, step(1, iPhase) * cos(phase + phaseOffset), amplitude);"
"}");
display_type = Outputs::CRT::DisplayType::NTSC60;

1
Machines/Oric/Video.cpp
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@ -42,6 +42,7 @@ VideoOutput::VideoOutput(uint8_t *memory) :
"return (float(texValue) - 4.0) / 20.0;"
"}"
);
crt_->set_composite_function_type(Outputs::CRT::CRT::CompositeSourceType::DiscreteFourSamplesPerCycle, 0.0f);
set_output_device(Outputs::CRT::Television);
crt_->set_visible_area(crt_->get_rect_for_area(50, 224, 16 * 6, 40 * 6, 4.0f / 3.0f));

11
Outputs/CRT/CRT.cpp
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@ -62,6 +62,14 @@ void CRT::set_new_display_type(unsigned int cycles_per_line, DisplayType display
}
}
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;
}
}
CRT::CRT(unsigned int common_output_divisor, unsigned int buffer_depth) :
sync_capacitor_charge_level_(0),
is_receiving_sync_(false),
@ -272,7 +280,8 @@ void CRT::output_scan(const Scan *const scan) {
colour_burst_phase_ = (position_phase + scan->phase) & 255;
colour_burst_amplitude_ = scan->amplitude;
colour_burst_phase_ = (colour_burst_phase_ & ~63) + 32;
if(colour_burst_phase_adjustment_ != 0xff)
colour_burst_phase_ = (colour_burst_phase_ & ~63) + colour_burst_phase_adjustment_;
}
}

22
Outputs/CRT/CRT.hpp
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@ -59,7 +59,7 @@ class CRT {
};
void output_scan(const Scan *scan);
uint8_t colour_burst_phase_, colour_burst_amplitude_;
uint8_t colour_burst_phase_, colour_burst_amplitude_, colour_burst_phase_adjustment_;
bool is_writing_composite_run_;
unsigned int phase_denominator_, phase_numerator_, colour_cycle_numerator_;
@ -252,6 +252,26 @@ class CRT {
});
}
enum CompositeSourceType {
/// The composite function provides continuous output.
Continuous,
/// The composite function provides discrete output with four unique values per colour cycle.
DiscreteFourSamplesPerCycle
};
/*! Provides information about the type of output the composite sampling function provides — discrete or continuous.
This is necessary because the CRT implementation samples discretely and therefore can use fewer intermediate
samples if it can exactly duplicate the sampling rate and placement of the composite sampling function.
A continuous function is assumed by default.
@param type The type of output provided by the function supplied to `set_composite_sampling_function`.
@param offset_of_first_sample The relative position within a full cycle of the colour subcarrier at which the
first sample falls. E.g. 0.125 means "at 1/8th of the way through the complete cycle".
*/
void set_composite_function_type(CompositeSourceType type, float offset_of_first_sample = 0.0f);
/*! Sets a function that will map from whatever data the machine provided to an RGB signal.
If the output mode is composite then a default mapping from RGB to the display's composite