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118 lines
3.5 KiB
C++
118 lines
3.5 KiB
C++
//
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// Video.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 06/06/2017.
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// Copyright 2017 Thomas Harte. All rights reserved.
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//
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#include "Video.hpp"
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using namespace ZX8081;
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namespace {
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/*!
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The number of bytes of PCM data to allocate at once; if/when more are required,
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the class will simply allocate another batch.
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*/
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const std::size_t StandardAllocationSize = 320;
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}
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Video::Video() :
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crt_(new Outputs::CRT::CRT(207 * 2, 1, Outputs::CRT::DisplayType::PAL50, 1)) {
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// Set a composite sampling function that assumes two-level input; either a byte is 0, which is black,
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// or it is non-zero, which is white.
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crt_->set_composite_sampling_function(
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"float composite_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate, float phase, float amplitude)"
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"{"
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"return texture(sampler, coordinate).r;"
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"}");
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// Show only the centre 80% of the TV frame.
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crt_->set_video_signal(Outputs::CRT::VideoSignal::Composite);
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crt_->set_visible_area(Outputs::CRT::Rect(0.1f, 0.1f, 0.8f, 0.8f));
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}
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void Video::run_for(const HalfCycles half_cycles) {
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// Just keep a running total of the amount of time that remains owed to the CRT.
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time_since_update_ += half_cycles;
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}
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void Video::flush() {
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flush(sync_);
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}
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void Video::flush(bool next_sync) {
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if(sync_) {
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// If in sync, that takes priority. Output the proper amount of sync.
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crt_->output_sync(static_cast<unsigned int>(time_since_update_.as_int()));
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} else {
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// If not presently in sync, then...
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if(line_data_) {
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// If there is output data queued, output it either if it's being interrupted by
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// sync, or if we're past its end anyway. Otherwise let it be.
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int data_length = static_cast<int>(line_data_pointer_ - line_data_);
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if(data_length < time_since_update_.as_int() || next_sync) {
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auto output_length = std::min(data_length, time_since_update_.as_int());
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crt_->output_data(static_cast<unsigned int>(output_length), static_cast<unsigned int>(output_length));
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line_data_pointer_ = line_data_ = nullptr;
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time_since_update_ -= HalfCycles(output_length);
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} else return;
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}
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// Any pending pixels being dealt with, pad with the white level.
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uint8_t *colour_pointer = static_cast<uint8_t *>(crt_->allocate_write_area(1));
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if(colour_pointer) *colour_pointer = 0xff;
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crt_->output_level(static_cast<unsigned int>(time_since_update_.as_int()));
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}
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time_since_update_ = 0;
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}
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void Video::set_sync(bool sync) {
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// Do nothing if sync hasn't changed.
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if(sync_ == sync) return;
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// Complete whatever was being drawn, and update sync.
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flush(sync);
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sync_ = sync;
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}
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void Video::output_byte(uint8_t byte) {
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// Complete whatever was going on.
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if(sync_) return;
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flush();
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// Grab a buffer if one isn't already available.
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if(!line_data_) {
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line_data_pointer_ = line_data_ = crt_->allocate_write_area(StandardAllocationSize);
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}
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// If a buffer was obtained, serialise the new pixels.
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if(line_data_) {
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// If the buffer is full, output it now and obtain a new one
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if(line_data_pointer_ - line_data_ == StandardAllocationSize) {
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crt_->output_data(StandardAllocationSize, StandardAllocationSize);
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time_since_update_ -= StandardAllocationSize;
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line_data_pointer_ = line_data_ = crt_->allocate_write_area(StandardAllocationSize);
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if(!line_data_) return;
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}
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// Convert to one-byte-per-pixel where any non-zero value will act as white.
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uint8_t mask = 0x80;
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for(int c = 0; c < 8; c++) {
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line_data_pointer_[c] = byte & mask;
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mask >>= 1;
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}
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line_data_pointer_ += 8;
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}
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}
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Outputs::CRT::CRT *Video::get_crt() {
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return crt_.get();
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}
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