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Merge pull request #118 from TomHarte/HighResolutionAtariAudio

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Introduces a higher source sampling rate for Atari audio
This commit is contained in:
Thomas Harte 2017-04-15 21:21:58 -04:00 committed by GitHub
commit 4127350abe
5 changed files with 22 additions and 19 deletions
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6
Machines/Atari2600/Atari2600.cpp
View File

@ -38,7 +38,7 @@ Machine::Machine() :
void Machine::setup_output(float aspect_ratio) {
bus_->tia_.reset(new TIA);
bus_->speaker_.reset(new Speaker);
bus_->speaker_->set_input_rate((float)(get_clock_rate() / 38.0));
bus_->speaker_->set_input_rate((float)(get_clock_rate() / (double)CPUTicksPerAudioTick));
bus_->tia_->get_crt()->set_delegate(this);
}
@ -149,8 +149,8 @@ void Machine::crt_did_end_batch_of_frames(Outputs::CRT::CRT *crt, unsigned int n
bus_->tia_->set_output_mode(TIA::OutputMode::PAL);
}
bus_->speaker_->set_input_rate((float)(clock_rate / 38.0));
bus_->speaker_->set_high_frequency_cut_off((float)(clock_rate / (38.0 * 2.0)));
bus_->speaker_->set_input_rate((float)(clock_rate / (double)CPUTicksPerAudioTick));
bus_->speaker_->set_high_frequency_cut_off((float)(clock_rate / ((double)CPUTicksPerAudioTick * 2.0)));
set_clock_rate(clock_rate);
}
}

3
Machines/Atari2600/Atari2600.hpp
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@ -23,9 +23,6 @@
namespace Atari2600 {
const unsigned int number_of_upcoming_events = 6;
const unsigned int number_of_recorded_counters = 7;
class Machine:
public CRTMachine::Machine,
public ConfigurationTarget::Machine,

7
Machines/Atari2600/Bus.hpp
View File

@ -9,9 +9,10 @@
#ifndef Atari2600_Bus_hpp
#define Atari2600_Bus_hpp
#include "Atari2600.hpp"
#include "PIA.hpp"
#include "TIA.hpp"
#include "Speaker.hpp"
#include "TIA.hpp"
namespace Atari2600 {
@ -38,8 +39,8 @@ class Bus {
// speaker backlog accumlation counter
unsigned int cycles_since_speaker_update_;
inline void update_audio() {
unsigned int audio_cycles = cycles_since_speaker_update_ / 114;
cycles_since_speaker_update_ %= 114;
unsigned int audio_cycles = cycles_since_speaker_update_ / (CPUTicksPerAudioTick * 3);
cycles_since_speaker_update_ %= (CPUTicksPerAudioTick * 3);
speaker_->run_for_cycles(audio_cycles);
}

21
Machines/Atari2600/Speaker.cpp
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@ -44,6 +44,7 @@ void Atari2600::Speaker::get_samples(unsigned int number_of_samples, int16_t *ta
target[c] = 0;
for(int channel = 0; channel < 2; channel++) {
divider_counter_[channel] ++;
int divider_value = divider_counter_[channel] / (38 / CPUTicksPerAudioTick);
int level = 0;
switch(control_[channel]) {
case 0x0: case 0xb: // constant 1
@ -51,24 +52,24 @@ void Atari2600::Speaker::get_samples(unsigned int number_of_samples, int16_t *ta
break;
case 0x4: case 0x5: // div2 tone
level = (divider_counter_[channel] / (divider_[channel]+1))&1;
level = (divider_value / (divider_[channel]+1))&1;
break;
case 0xc: case 0xd: // div6 tone
level = (divider_counter_[channel] / ((divider_[channel]+1)*3))&1;
level = (divider_value / ((divider_[channel]+1)*3))&1;
break;
case 0x6: case 0xa: // div31 tone
level = (divider_counter_[channel] / (divider_[channel]+1))%30 <= 18;
level = (divider_value / (divider_[channel]+1))%30 <= 18;
break;
case 0xe: // div93 tone
level = (divider_counter_[channel] / ((divider_[channel]+1)*3))%30 <= 18;
level = (divider_value / ((divider_[channel]+1)*3))%30 <= 18;
break;
case 0x1: // 4-bit poly
level = poly4_counter_[channel]&1;
if(divider_counter_[channel] == divider_[channel]+1) {
if(divider_value == divider_[channel]+1) {
divider_counter_[channel] = 0;
advance_poly4(channel);
}
@ -76,14 +77,14 @@ void Atari2600::Speaker::get_samples(unsigned int number_of_samples, int16_t *ta
case 0x2: // 4-bit poly div31
level = poly4_counter_[channel]&1;
if(divider_counter_[channel]%(30*(divider_[channel]+1)) == 18) {
if(divider_value%(30*(divider_[channel]+1)) == 18) {
advance_poly4(channel);
}
break;
case 0x3: // 5/4-bit poly
level = output_state_[channel];
if(divider_counter_[channel] == divider_[channel]+1) {
if(divider_value == divider_[channel]+1) {
if(poly5_counter_[channel]&1) {
output_state_[channel] = poly4_counter_[channel]&1;
advance_poly4(channel);
@ -94,7 +95,7 @@ void Atari2600::Speaker::get_samples(unsigned int number_of_samples, int16_t *ta
case 0x7: case 0x9: // 5-bit poly
level = poly5_counter_[channel]&1;
if(divider_counter_[channel] == divider_[channel]+1) {
if(divider_value == divider_[channel]+1) {
divider_counter_[channel] = 0;
advance_poly5(channel);
}
@ -102,7 +103,7 @@ void Atari2600::Speaker::get_samples(unsigned int number_of_samples, int16_t *ta
case 0xf: // 5-bit poly div6
level = poly5_counter_[channel]&1;
if(divider_counter_[channel] == (divider_[channel]+1)*3) {
if(divider_value == (divider_[channel]+1)*3) {
divider_counter_[channel] = 0;
advance_poly5(channel);
}
@ -110,7 +111,7 @@ void Atari2600::Speaker::get_samples(unsigned int number_of_samples, int16_t *ta
case 0x8: // 9-bit poly
level = poly9_counter_[channel]&1;
if(divider_counter_[channel] == divider_[channel]+1) {
if(divider_value == divider_[channel]+1) {
divider_counter_[channel] = 0;
advance_poly9(channel);
}

4
Machines/Atari2600/Speaker.hpp
View File

@ -13,6 +13,10 @@
namespace Atari2600 {
// This should be a divisor of 38; audio counters are updated every 38 cycles — though lesser dividers
// will give greater resolution to changes in audio state. 1, 2 and 19 are the only divisors of 38.
const int CPUTicksPerAudioTick = 2;
class Speaker: public ::Outputs::Filter<Speaker> {
public:
Speaker();