Mercurial > repos > blastem
view psg.c @ 922:913a6336ce20
Shift slot number to slot behavior mapping by six slots in H40 mode. This makes the line change slot align with the point at which the display turns on and off at the end of the active display area. Also fixed a regression in which an external slot got accidentally changed into a sprite draw slot
author | Michael Pavone <pavone@retrodev.com> |
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date | Thu, 28 Jan 2016 09:10:14 -0800 |
parents | 252dfd29831d |
children | bd549b25c362 |
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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> 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; } } 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 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 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; } } } } } 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]]; } context->sample_count++; context->buffer_fraction += context->buffer_inc; if (context->buffer_fraction >= BUFFER_INC_RES) { context->buffer_fraction -= BUFFER_INC_RES; context->audio_buffer[context->buffer_pos++] = context->accum / context->sample_count; context->accum = context->sample_count = 0; if (context->buffer_pos == context->samples_frame) { if (!headless) { render_wait_psg(context); } } } context->cycles += context->clock_inc; } }