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audio.c
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audio.c
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// Copyright 2008-2010 Segher Boessenkool <[email protected]>
// Licensed under the terms of the GNU GPL, version 2
// http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt
#include <stdio.h>
#include <math.h>
#include "types.h"
#include "emu.h"
#include "platform.h"
#include "audio.h"
int mute_audio;
void audio_store(u16 val, u32 addr)
{
if (addr == 0x340b)
mem[addr] &= ~val;
else
mem[addr] = val;
if (addr < 0x3200) { // XXX
return;
} else if (addr < 0x3400) { // XXX
return;
} else { // XXX control regs
return;
}
debug("AUDIO STORE %04x to %04x\n", val, addr);
}
u16 audio_load(u32 addr)
{
u16 val = mem[addr];
if (addr >= 0x3000 && addr < 0x3200) { // audio something
//debug("LOAD %04x from %04x\n", val, addr);
return val;
}
if (addr >= 0x3200 && addr < 0x3300) { // audio something
//debug("LOAD %04x from %04x\n", val, addr);
return val;
}
if (addr >= 0x3400 && addr < 0x3500) { // audio something
//debug("LOAD %04x from %04x\n", val, addr);
return val;
}
debug("UNKNOWN AUDIO LOAD from %04x\n", addr);
return val;
}
static u32 get_channel_bit(u32 ch, u32 reg)
{
reg += 0x3400;
if (ch >= 16) {
reg += 0x0100;
ch -= 16;
}
return (mem[reg] >> ch) & 1;
}
static u32 n_left[24];
static u16 bits_left[24];
static void do_next_sample(u32 ch)
{
loop:
if (n_left[ch] == 0) {
u32 addr = ((mem[0x3001 + 16*ch] & 0x3f) << 16) | mem[0x3000 + 16*ch];
bits_left[ch] = mem[addr];
if (bits_left[ch] == 0xffff) {
mem[0x3000 + 16*ch] = mem[0x3002 + 16*ch];
mem[0x3001 + 16*ch] &= 0xffc0;
mem[0x3001 + 16*ch] |= (mem[0x3001 + 16*ch] >> 6) & 0x3f;
goto loop;
}
n_left[ch] = 2;
mem[0x3000 + 16*ch]++;
if (mem[0x3000 + 16*ch] == 0)
mem[0x3001 + 16*ch]++; // XXX: mask?
//debug("--> addr = %06x\n", addr);
}
mem[0x300b + 16*ch] = bits_left[ch] << 8;
bits_left[ch] >>= 8;
n_left[ch]--;
}
#define FREQ 440
static u16 next_channel_sample(u32 ch)
{
// if (ch)
// return 0x8000;
// static u32 xxx[24] = {0};
// u16 sample = 0x8000 + (int)(20000*sin(2*M_PI*xxx[ch]*FREQ/281250));
// xxx[ch]++;
// if (xxx[ch] == 281250)
// xxx[ch] = 0;
// return sample;
u16 sample = mem[0x300b + 16*ch];
u32 acc = (mem[0x3201 + 16*ch] << 16) | mem[0x3205 + 16*ch];
u32 inc = (mem[0x3200 + 16*ch] << 16) | mem[0x3204 + 16*ch];
acc += inc;
if (acc >= 0x80000) {
do_next_sample(ch);
acc -= 0x80000;
}
mem[0x3201 + 16*ch] = acc >> 16;
mem[0x3205 + 16*ch] = acc;
return sample;
}
static u16 next_sample(void)
{
static u32 ch = 0;
u16 sample;
if (get_channel_bit(ch, 0))
sample = next_channel_sample(ch);
else
sample = 0x8000;
ch++;
if (ch == 24)
ch = 0;
return sample;
}
static s16 next_host_sample(void)
{
if (mem[0x3d20] & 0x0002) // audio DAC disable
return 0;
return 0;
u32 acc = 0;
u32 i;
for (i = 0; i < 153; i++)
acc += next_sample();
return (acc / 153) - 0x8000;
}
void audio_render(s16 *data, u32 n)
{
u32 i;
for (i = 0; i < n; i++)
data[i] = next_host_sample();
}
void audio_init(void)
{
}