mirror of
https://github.com/retro100/dosbox-wii.git
synced 2024-09-29 18:28:35 +02:00
335 lines
8.4 KiB
C++
335 lines
8.4 KiB
C++
/*
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* Copyright (C) 2002-2003 The DOSBox Team
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Library General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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/*
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Based of sn76496.c of the M.A.M.E. project
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*/
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#include <math.h>
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#include "dosbox.h"
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#include "inout.h"
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#include "mixer.h"
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#include "mem.h"
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#include "setup.h"
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#include "pic.h"
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#define MAX_OUTPUT 0x7fff
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#define STEP 0x10000
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/* Formulas for noise generator */
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/* bit0 = output */
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/* noise feedback for white noise mode (verified on real SN76489 by John Kortink) */
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#define FB_WNOISE 0x14002 /* (16bits) bit16 = bit0(out) ^ bit2 ^ bit15 */
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/* noise feedback for periodic noise mode */
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//#define FB_PNOISE 0x10000 /* 16bit rorate */
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#define FB_PNOISE 0x08000 /* JH 981127 - fixes Do Run Run */
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/*
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0x08000 is definitely wrong. The Master System conversion of Marble Madness
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uses periodic noise as a baseline. With a 15-bit rotate, the bassline is
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out of tune.
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The 16-bit rotate has been confirmed against a real PAL Sega Master System 2.
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Hope that helps the System E stuff, more news on the PSG as and when!
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*/
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/* noise generator start preset (for periodic noise) */
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#define NG_PRESET 0x0f35
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struct SN76496
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{
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int SampleRate;
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unsigned int UpdateStep;
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int VolTable[16]; /* volume table */
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int Register[8]; /* registers */
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int LastRegister; /* last register written */
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int Volume[4]; /* volume of voice 0-2 and noise */
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unsigned int RNG; /* noise generator */
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int NoiseFB; /* noise feedback mask */
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int Period[4];
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int Count[4];
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int Output[4];
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};
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static struct SN76496 sn;
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static struct {
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MIXER_Channel * chan;
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bool enabled;
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Bitu last_write;
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} tandy;
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static void SN76496Write(Bit32u port,Bit8u data)
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{
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struct SN76496 *R = &sn;
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tandy.last_write=PIC_Ticks;
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if (!tandy.enabled) {
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MIXER_Enable(tandy.chan,true);
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tandy.enabled=true;
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}
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/* update the output buffer before changing the registers */
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if (data & 0x80)
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{
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int r = (data & 0x70) >> 4;
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int c = r/2;
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R->LastRegister = r;
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R->Register[r] = (R->Register[r] & 0x3f0) | (data & 0x0f);
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switch (r)
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{
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case 0: /* tone 0 : frequency */
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case 2: /* tone 1 : frequency */
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case 4: /* tone 2 : frequency */
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R->Period[c] = R->UpdateStep * R->Register[r];
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if (R->Period[c] == 0) R->Period[c] = R->UpdateStep;
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if (r == 4)
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{
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/* update noise shift frequency */
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if ((R->Register[6] & 0x03) == 0x03)
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R->Period[3] = 2 * R->Period[2];
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}
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break;
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case 1: /* tone 0 : volume */
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case 3: /* tone 1 : volume */
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case 5: /* tone 2 : volume */
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case 7: /* noise : volume */
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R->Volume[c] = R->VolTable[data & 0x0f];
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break;
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case 6: /* noise : frequency, mode */
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{
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int n = R->Register[6];
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R->NoiseFB = (n & 4) ? FB_WNOISE : FB_PNOISE;
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n &= 3;
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/* N/512,N/1024,N/2048,Tone #3 output */
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R->Period[3] = (n == 3) ? 2 * R->Period[2] : (R->UpdateStep << (5+n));
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/* reset noise shifter */
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R->RNG = NG_PRESET;
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R->Output[3] = R->RNG & 1;
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}
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break;
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}
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}
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else
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{
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int r = R->LastRegister;
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int c = r/2;
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switch (r)
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{
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case 0: /* tone 0 : frequency */
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case 2: /* tone 1 : frequency */
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case 4: /* tone 2 : frequency */
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R->Register[r] = (R->Register[r] & 0x0f) | ((data & 0x3f) << 4);
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R->Period[c] = R->UpdateStep * R->Register[r];
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if (R->Period[c] == 0) R->Period[c] = R->UpdateStep;
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if (r == 4)
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{
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/* update noise shift frequency */
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if ((R->Register[6] & 0x03) == 0x03)
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R->Period[3] = 2 * R->Period[2];
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}
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break;
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}
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}
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}
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static void SN76496Update(Bit8u * stream,Bit32u length)
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{
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if ((tandy.last_write+1000)<PIC_Ticks) {
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tandy.enabled=false;
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MIXER_Enable(tandy.chan,false);
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}
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int i;
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struct SN76496 *R = &sn;
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Bit16s * buffer=(Bit16s *)stream;
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/* If the volume is 0, increase the counter */
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for (i = 0;i < 4;i++)
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{
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if (R->Volume[i] == 0)
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{
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/* note that I do count += length, NOT count = length + 1. You might think */
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/* it's the same since the volume is 0, but doing the latter could cause */
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/* interferencies when the program is rapidly modulating the volume. */
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if (R->Count[i] <= (int)length*STEP) R->Count[i] += length*STEP;
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}
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}
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while (length > 0)
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{
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int vol[4];
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unsigned int out;
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int left;
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/* vol[] keeps track of how long each square wave stays */
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/* in the 1 position during the sample period. */
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vol[0] = vol[1] = vol[2] = vol[3] = 0;
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for (i = 0;i < 3;i++)
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{
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if (R->Output[i]) vol[i] += R->Count[i];
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R->Count[i] -= STEP;
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/* Period[i] is the half period of the square wave. Here, in each */
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/* loop I add Period[i] twice, so that at the end of the loop the */
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/* square wave is in the same status (0 or 1) it was at the start. */
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/* vol[i] is also incremented by Period[i], since the wave has been 1 */
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/* exactly half of the time, regardless of the initial position. */
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/* If we exit the loop in the middle, Output[i] has to be inverted */
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/* and vol[i] incremented only if the exit status of the square */
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/* wave is 1. */
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while (R->Count[i] <= 0)
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{
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R->Count[i] += R->Period[i];
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if (R->Count[i] > 0)
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{
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R->Output[i] ^= 1;
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if (R->Output[i]) vol[i] += R->Period[i];
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break;
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}
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R->Count[i] += R->Period[i];
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vol[i] += R->Period[i];
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}
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if (R->Output[i]) vol[i] -= R->Count[i];
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}
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left = STEP;
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do
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{
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int nextevent;
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if (R->Count[3] < left) nextevent = R->Count[3];
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else nextevent = left;
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if (R->Output[3]) vol[3] += R->Count[3];
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R->Count[3] -= nextevent;
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if (R->Count[3] <= 0)
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{
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if (R->RNG & 1) R->RNG ^= R->NoiseFB;
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R->RNG >>= 1;
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R->Output[3] = R->RNG & 1;
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R->Count[3] += R->Period[3];
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if (R->Output[3]) vol[3] += R->Period[3];
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}
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if (R->Output[3]) vol[3] -= R->Count[3];
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left -= nextevent;
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} while (left > 0);
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out = vol[0] * R->Volume[0] + vol[1] * R->Volume[1] +
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vol[2] * R->Volume[2] + vol[3] * R->Volume[3];
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if (out > MAX_OUTPUT * STEP) out = MAX_OUTPUT * STEP;
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*(buffer++) = out / STEP;
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length--;
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}
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}
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static void SN76496_set_clock(int clock)
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{
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struct SN76496 *R = &sn;
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/* the base clock for the tone generators is the chip clock divided by 16; */
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/* for the noise generator, it is clock / 256. */
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/* Here we calculate the number of steps which happen during one sample */
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/* at the given sample rate. No. of events = sample rate / (clock/16). */
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/* STEP is a multiplier used to turn the fraction into a fixed point */
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/* number. */
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R->UpdateStep = (unsigned int)(((double)STEP * R->SampleRate * 16) / clock);
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}
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static void SN76496_set_gain(int gain)
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{
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struct SN76496 *R = &sn;
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int i;
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double out;
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gain &= 0xff;
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/* increase max output basing on gain (0.2 dB per step) */
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out = MAX_OUTPUT / 3;
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while (gain-- > 0)
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out *= 1.023292992; /* = (10 ^ (0.2/20)) */
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/* build volume table (2dB per step) */
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for (i = 0;i < 15;i++)
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{
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/* limit volume to avoid clipping */
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if (out > MAX_OUTPUT / 3) R->VolTable[i] = MAX_OUTPUT / 3;
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else R->VolTable[i] = (int)out;
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out /= 1.258925412; /* = 10 ^ (2/20) = 2dB */
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}
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R->VolTable[15] = 0;
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}
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void TANDYSOUND_Init(Section* sec) {
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Section_prop * section=static_cast<Section_prop *>(sec);
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if(!section->Get_bool("tandy")) return;
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IO_RegisterWriteHandler(0xc0,SN76496Write,"Tandy Sound");
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Bit32u sample_rate = section->Get_int("tandyrate");
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tandy.chan=MIXER_AddChannel(&SN76496Update,sample_rate,"TANDY");
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MIXER_Enable(tandy.chan,false);
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tandy.enabled=false;
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MIXER_SetMode(tandy.chan,MIXER_16MONO);
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Bitu i;
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struct SN76496 *R = &sn;
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R->SampleRate = sample_rate;
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SN76496_set_clock(2386360);
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for (i = 0;i < 4;i++) R->Volume[i] = 0;
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R->LastRegister = 0;
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for (i = 0;i < 8;i+=2)
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{
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R->Register[i] = 0;
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R->Register[i + 1] = 0x0f; /* volume = 0 */
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}
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for (i = 0;i < 4;i++)
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{
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R->Output[i] = 0;
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R->Period[i] = R->Count[i] = R->UpdateStep;
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}
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R->RNG = NG_PRESET;
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R->Output[3] = R->RNG & 1;
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SN76496_set_gain(0x1);
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}
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