Mercurial > repos > blastem
view psg.c @ 505:b7b7a1cab44a
The local clone on my laptop got messed up and some changes had not been pushed. This commit represents the status of the working copy from that clone. It unfortunately contains some changes that I did not intend to commit yet, but this seems like the best option at the moment.
author | Michael Pavone <pavone@retrodev.com> |
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date | Mon, 06 Jan 2014 22:54:05 -0800 |
parents | 3e1573fa22cf |
children | 6a14c5a95648 |
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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> 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; psg_adjust_master_clock(context, master_clock); for (int i = 0; i < 4; i++) { context->volume[i] = 0xF; } } #define BUFFER_INC_RES 1000000000UL 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 6 //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->buffer_fraction += context->buffer_inc; if (context->buffer_fraction >= BUFFER_INC_RES) { context->buffer_fraction -= BUFFER_INC_RES; int16_t acc = 0; for (int i = 0; i < 3; i++) { if (context->output_state[i]) { acc += volume_table[context->volume[i]]; } } if (context->noise_out) { acc += volume_table[context->volume[3]]; } context->audio_buffer[context->buffer_pos++] = acc; if (context->buffer_pos == context->samples_frame) { if (!headless) { render_wait_psg(context); } } } context->cycles += context->clock_inc; } }