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/*
* sound/softoss_rs.c
*
* Software based MIDI synthsesizer driver, the actual mixing loop.
* Keep the loop as simple as possible to make it easier to rewrite this
* routine in assembly.
*
*
* Copyright (C) by Hannu Savolainen 1993-1997
*
* OSS/Free for Linux is distributed under the GNU GENERAL PUBLIC LICENSE (GPL)
* Version 2 (June 1991). See the "COPYING" file distributed with this software
* for more info.
*/
#include <linux/config.h>
#include "sound_config.h"
#ifdef CONFIG_SOFTOSS
#include "softoss.h"
void softsynth_resample_loop(short *buf, int loops)
{
int iloop, voice;
volatile voice_info *v;
#ifdef OSS_BIG_ENDIAN
unsigned char *cbuf = (unsigned char *) buf;
#endif
for (iloop = 0; iloop < loops; iloop++)
{ /* Mix one sample */
int accum, left = 0, right = 0;
int ix, position;
for (voice = 0; voice < devc->maxvoice; voice++)
{
if (voice_active[voice])
{ /* Compute voice */
v = &softoss_voices[voice];
#ifdef SOFTOSS_TEST
ix = iloop << 3;
position = v->ptr;
#else
ix = (position = v->ptr) >> 9;
#endif
/* Interpolation (resolution of 512 steps) */
{
int fract = v->ptr & 0x1ff; /* 9 bits */
/* This method works with less arithmetic operations */
register int v1 = v->wave[ix];
accum = v1 + ((((v->wave[ix + 1] - v1)) * (fract)) >> 9);
}
left += (accum * v->leftvol);
right += (accum * v->rightvol);
/* Update sample pointer */
position += v->step;
if (position <= v->endloop)
v->ptr = position;
else if (v->mode & WAVE_LOOPING)
{
if (v->mode & WAVE_BIDIR_LOOP)
{ v->mode ^= WAVE_LOOP_BACK; /* Turn around */
v->step *= -1;
}
else
{
position -= v->looplen;
v->ptr = position;
}
}
/* else leave the voice looping the current sample */
if (v->mode & WAVE_LOOP_BACK && position < v->startloop)
{
if (v->mode & WAVE_BIDIR_LOOP)
{ v->mode ^= WAVE_LOOP_BACK; /* Turn around */
v->step *= -1;
}
else
{
position += v->looplen;
v->ptr = position;
}
}
} /* Compute voice */
}
#if 1 /* Delay */
left += left_delay[delayp];
right += right_delay[delayp];
left_delay[delayp] = right >> 2;
right_delay[delayp] = left >> 2;
delayp = (delayp + 1) % devc->delay_size;
#endif
#define AFTERSCALE devc->afterscale;
left >>= AFTERSCALE;
right >>= AFTERSCALE;
if (left > 32767)
left = 32767;
if (left < -32768)
left = -32768;
if (right > 32767)
right = 32767;
if (right < -32768)
right = -32768;
#ifdef OSS_BIG_ENDIAN
*cbuf++ = left & 0xff;
*cbuf++ = (left >> 8) & 0xff;
*cbuf++ = right & 0xff;
*cbuf++ = (right >> 8) & 0xff;
#else
*buf++ = left;
*buf++ = right;
#endif
if (devc->control_counter++ >= devc->control_rate)
{
devc->control_counter = 0;
softsyn_control_loop();
}
} /* Mix one sample */
}
#endif
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