Mercurial > repos > blastem
view psg.c @ 995:2bc27415565b
Fix some stuff with interrupt timing. The change in adjust_int_cycle gets Overdrive working again (vint was not being preferred over hint in some cases). One of the changes seems to have broken Fatal Rewind again, but no other regressions that I can see.
author | Michael Pavone <pavone@retrodev.com> |
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date | Sat, 30 Apr 2016 08:37:55 -0700 |
parents | e6dc30231b83 |
children | 8d032a368dd5 |
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/* Copyright 2013 Michael Pavone This file is part of BlastEm. BlastEm is free software distributed under the terms of the GNU General Public License version 3 or greater. See COPYING for full license text. */ #include "psg.h" #include "render.h" #include "blastem.h" #include <string.h> #include <stdlib.h> #include <stdio.h> #include <math.h> #define LOWPASS_CUTOFF 3390 void psg_init(psg_context * context, uint32_t sample_rate, uint32_t master_clock, uint32_t clock_div, uint32_t samples_frame) { memset(context, 0, sizeof(*context)); context->audio_buffer = malloc(sizeof(*context->audio_buffer) * samples_frame); context->back_buffer = malloc(sizeof(*context->audio_buffer) * samples_frame); context->clock_inc = clock_div; context->sample_rate = sample_rate; context->samples_frame = samples_frame; double rc = (1.0 / (double)LOWPASS_CUTOFF) / (2.0 * M_PI); double dt = 1.0 / ((double)master_clock / (double)clock_div); double alpha = dt / (dt + rc); context->lowpass_alpha = (int32_t)(((double)0x10000) * alpha); psg_adjust_master_clock(context, master_clock); for (int i = 0; i < 4; i++) { context->volume[i] = 0xF; } } void psg_free(psg_context *context) { free(context->audio_buffer); //TODO: Figure out how to make this 100% safe //audio thread could still be using this free(context->back_buffer); free(context); } #define BUFFER_INC_RES 0x40000000UL void psg_adjust_master_clock(psg_context * context, uint32_t master_clock) { uint64_t old_inc = context->buffer_inc; context->buffer_inc = ((BUFFER_INC_RES * (uint64_t)context->sample_rate) / (uint64_t)master_clock) * (uint64_t)context->clock_inc; } void psg_write(psg_context * context, uint8_t value) { if (value & 0x80) { context->latch = value & 0x70; uint8_t channel = value >> 5 & 0x3; if (value & 0x10) { context->volume[channel] = value & 0xF; } else { if (channel == 3) { switch(value & 0x3) { case 0: case 1: case 2: context->counter_load[3] = 0x10 << (value & 0x3); context->noise_use_tone = 0; break; default: context->counter_load[3] = context->counter_load[2]; context->noise_use_tone = 1; } context->noise_type = value & 0x4; context->lsfr = 0x8000; } else { context->counter_load[channel] = (context->counter_load[channel] & 0x3F0) | (value & 0xF); if (channel == 2 && context->noise_use_tone) { context->counter_load[3] = context->counter_load[2]; } } } } else { if (!(context->latch & 0x10)) { uint8_t channel = context->latch >> 5 & 0x3; if (channel != 3) { context->counter_load[channel] = (value << 4 & 0x3F0) | (context->counter_load[channel] & 0xF); if (channel == 2 && context->noise_use_tone) { context->counter_load[3] = context->counter_load[2]; } } } } } #define PSG_VOL_DIV 14 //table shamelessly swiped from PSG doc from smspower.org int16_t volume_table[16] = { 32767/PSG_VOL_DIV, 26028/PSG_VOL_DIV, 20675/PSG_VOL_DIV, 16422/PSG_VOL_DIV, 13045/PSG_VOL_DIV, 10362/PSG_VOL_DIV, 8231/PSG_VOL_DIV, 6568/PSG_VOL_DIV, 5193/PSG_VOL_DIV, 4125/PSG_VOL_DIV, 3277/PSG_VOL_DIV, 2603/PSG_VOL_DIV, 2067/PSG_VOL_DIV, 1642/PSG_VOL_DIV, 1304/PSG_VOL_DIV, 0 }; void psg_run(psg_context * context, uint32_t cycles) { while (context->cycles < cycles) { for (int i = 0; i < 4; i++) { if (context->counters[i]) { context->counters[i] -= 1; } if (!context->counters[i]) { context->counters[i] = context->counter_load[i]; context->output_state[i] = !context->output_state[i]; if (i == 3 && context->output_state[i]) { context->noise_out = context->lsfr & 1; context->lsfr = (context->lsfr >> 1) | (context->lsfr << 15); if (context->noise_type) { //white noise if (context->lsfr & 0x40) { context->lsfr ^= 0x8000; } } } } } context->last_sample = context->accum; context->accum = 0; for (int i = 0; i < 3; i++) { if (context->output_state[i]) { context->accum += volume_table[context->volume[i]]; } } if (context->noise_out) { context->accum += volume_table[context->volume[3]]; } int32_t tmp = context->accum * context->lowpass_alpha + context->last_sample * (0x10000 - context->lowpass_alpha); context->accum = tmp >> 16; context->buffer_fraction += context->buffer_inc; if (context->buffer_fraction >= BUFFER_INC_RES) { context->buffer_fraction -= BUFFER_INC_RES; int32_t tmp = context->last_sample * ((context->buffer_fraction << 16) / context->buffer_inc); tmp += context->accum * (0x10000 - ((context->buffer_fraction << 16) / context->buffer_inc)); context->audio_buffer[context->buffer_pos++] = tmp >> 16; if (context->buffer_pos == context->samples_frame) { if (!headless) { render_wait_psg(context); } } } context->cycles += context->clock_inc; } }