sz81 Code

/* z81/xz81, Linux console and X ZX81/ZX80 emulators.
 * Copyright (C) 1994 Ian Collier. z81 changes (C) 1995-2001 Russell Marks.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *
 * sound.c - sound support, based on the beeper/AY code I
 *           wrote for Fuse.
 */

/* ZX81 sound routines seem to be based on using VSYNC; in Basic
 * you might do this by alternating FAST/SLOW mode quickly,
 * for example. So that's what's emulated here. Obviously this
 * won't be perfect, not least as it won't be as noisy... :-)
 */
 
/* some AY details (volume levels, white noise RNG algorithm) based on
 * info from MAME's ay8910.c - MAME's licence explicitly permits free
 * use of info (even encourages it).
 */

/* NB: I know some of this stuff looks fairly CPU-hogging.
 * For example, the AY code tracks changes with sub-frame timing
 * in a rather hairy way, and there's subsampling here and there.
 * But if you measure the CPU use, it doesn't actually seem
 * very high at all. And I speak as a Cyrix owner. :-)
 *
 * (I based that on testing in Fuse, but I doubt it's that much
 * worse in z81. Though in both, the AY code does cause cache oddities
 * on my machine, so I get the bizarre situation of z81 jumping
 * between <=2% CPU use and *30*% CPU use pretty much at random...)
 */

#ifdef OSS_SOUND_SUPPORT

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <sys/soundcard.h>

#include "common.h"
#include "sound.h"
#include "z80.h"


/* configuration */
int sound_enabled=0;
int sound_freq=32000;
int sound_stereo=0;
int sound_stereo_acb=0;		/* 1 for ACB stereo, else 0 */

/* sound_vsync and sound_ay are in common.c */


/* XXX don't know the clock rate for the QS sound board :-(
 * but this sounds pretty plausible, judging from the rather nice
 * effects in QS Defender...
 */
#define AY_CLOCK_QUICKSILVA	(3250000/4)

/* Bi-Pak Zon X-81, clock rate straight from the manual (thanks Hob!).
 * This is half of 3.25MHz, which is probably not a coincidence. ;-)
 */
#define AY_CLOCK_ZONX		1625000


/* assume all three tone channels together match the beeper volume.
 * Must be <=127 for all channels; 4 x 31 = 124.
 */
#define AMPL_BEEPER		31
#define AMPL_AY_TONE		31	/* three of these */

/* full range of beeper volume */
#define VOL_BEEPER		(AMPL_BEEPER*2)

/* max. number of sub-frame AY port writes allowed;
 * given the number of port writes theoretically possible in a
 * 50th I think this should be plenty.
 */
#define AY_CHANGE_MAX		8000

static int sound_framesiz;

static unsigned char ay_tone_levels[16];

static unsigned char *sound_buf;
static unsigned char *sound_ptr;
static int sound_oldpos,sound_fillpos,sound_oldval,sound_oldval_orig;

/* timer used for fadeout after beeper-toggle;
 * fixed-point with low 24 bits as fractional part.
 */
static unsigned int beeper_tick,beeper_tick_incr;

/* tick/incr/periods are all fixed-point with low 16 bits as
 * fractional part, except ay_env_{tick,period} which count as the chip does.
 */
static unsigned int ay_tone_tick[3],ay_noise_tick;
static unsigned int ay_env_tick,ay_env_subcycles;
static unsigned int ay_tick_incr;
static unsigned int ay_tone_period[3],ay_noise_period,ay_env_period;

static int env_held=0,env_alternating=0;

static int beeper_last_subpos=0;

/* AY registers */
/* we have 16 so we can fake an 8910 if needed */
static unsigned char sound_ay_registers[16];

struct ay_change_tag
  {
  unsigned long tstates;
  unsigned short ofs;
  unsigned char reg,val;
  };

static struct ay_change_tag ay_change[AY_CHANGE_MAX];
static int ay_change_count;


static int soundfd=-1;
static int sixteenbit=0;


/* using (8) 64 byte frags for 8kHz, scale up for higher */
#define BASE_SOUND_FRAG_PWR	6



/* returns non-zero on success, and adjusts freq/stereo args to reflect
 * what we've actually got.
 */
int osssound_init(int *freqptr,int *stereoptr)
{
int frag,tmp;

if((soundfd=open("/dev/dsp",O_WRONLY))<0)
  return(0);

tmp=AFMT_U8;
if(ioctl(soundfd,SNDCTL_DSP_SETFMT,&tmp)==-1)
  {
  /* try 16-bit - may be a 16-bit-only device */
  tmp=AFMT_S16_LE;
  if((ioctl(soundfd,SNDCTL_DSP_SETFMT,&tmp))==-1)
    {
    close(soundfd);
    return(0);
    }

  sixteenbit=1;
  }

tmp=(*stereoptr)?1:0;
if(ioctl(soundfd,SNDCTL_DSP_STEREO,&tmp)<0)
  {
  /* if it failed, make sure the opposite is ok */
  tmp=(*stereoptr)?0:1;
  if(ioctl(soundfd,SNDCTL_DSP_STEREO,&tmp)<0)
    {
    close(soundfd);
    return(0);
    }
  *stereoptr=tmp;
  }

frag=(0x80000|BASE_SOUND_FRAG_PWR);

if(ioctl(soundfd,SNDCTL_DSP_SPEED,freqptr)<0)
  {
  close(soundfd);
  return(0);
  }

if(*freqptr>8250) frag++;
if(*freqptr>16500) frag++;
if(*freqptr>33000) frag++;
if(*stereoptr) frag++;
if(sixteenbit) frag++;

if(ioctl(soundfd,SNDCTL_DSP_SETFRAGMENT,&frag)<0)
  {
  close(soundfd);
  return(0);
  }

return(1);	/* success */
}


void osssound_end(void)
{
if(soundfd!=-1)
  close(soundfd);
}


void osssound_frame(unsigned char *data,int len)
{
static unsigned char buf16[8192];
int ret=0,ofs=0;

if(sixteenbit)
  {
  unsigned char *src,*dst;
  int f;

  src=data; dst=buf16;
  for(f=0;f<len;f++)
    {
    *dst++=128;
    *dst++=*src++-128;
    }

  data=buf16;
  len<<=1;
  }

while(len)
  {
  ret=write(soundfd,data+ofs,len);
  if(ret>0)
    ofs+=ret,len-=ret;
  }
}


void sound_ay_init(void)
{
int f,clock;
double v;

/* logarithmic volume levels, 3dB per step */
v=AMPL_AY_TONE;
for(f=15;f>0;f--)
  {
  ay_tone_levels[f]=(int)(v+0.5);
  /* 10^3/20 = 3dB */
  v/=1.4125375446;
  }
ay_tone_levels[0]=0;

ay_noise_tick=ay_noise_period=0;
ay_env_tick=ay_env_period=0;
for(f=0;f<3;f++)
  ay_tone_tick[f]=ay_tone_period[f]=0;

switch(sound_ay_type)
  {
  case AY_TYPE_QUICKSILVA:
    clock=AY_CLOCK_QUICKSILVA;
    break;
  case AY_TYPE_ZONX:
    clock=AY_CLOCK_ZONX;
    break;
  default:
    fprintf(stderr,"AY type not specified - can't happen!\n");
    sound_ay=0;
    return;
  }

ay_tick_incr=(int)(65536.*clock/sound_freq);

ay_change_count=0;
}


void sound_init(void)
{
if(!osssound_init(&sound_freq,&sound_stereo))
  {
  /* XXX a bit vague, maybe I should put this check in osssound_init() */
  fprintf(stderr,"z81: warning: "
          "couldn't initialise sound device, sound disabled.\n");
  return;
  }

/* important to override this if not using stereo */
if(!sound_stereo)
  sound_stereo_acb=0;

sound_enabled=1;
sound_framesiz=sound_freq/50;

if((sound_buf=malloc(sound_framesiz*(sound_stereo+1)))==NULL)
  {
  sound_end();
  return;
  }

sound_oldval=sound_oldval_orig=128;
sound_oldpos=-1;
sound_fillpos=0;
sound_ptr=sound_buf;

beeper_tick=0;
beeper_tick_incr=(1<<24)/sound_freq;

if(sound_ay)
  sound_ay_init();
}


void sound_end(void)
{
if(sound_enabled)
  {
  if(sound_buf)
    free(sound_buf);
  osssound_end();
  sound_enabled=0;
  }
}



/* not great having this as a macro to inline it, but it's only
 * a fairly short routine, and it saves messing about.
 * (XXX ummm, possibly not so true any more :-))
 */
#define AY_GET_SUBVAL(tick,period) \
  (level*2*(tick-period)/ay_tick_incr)

#define AY_OVERLAY_TONE(ptr,chan,level) \
  was_high=0;								\
  if(level)								\
    {									\
    if(ay_tone_tick[chan]>=ay_tone_period[chan])			\
      (*(ptr))+=(level),was_high=1;					\
    else								\
      (*(ptr))-=(level);						\
    }									\
  									\
  ay_tone_tick[chan]+=ay_tick_incr;					\
  if(level && !was_high && ay_tone_tick[chan]>=ay_tone_period[chan])	\
    (*(ptr))+=AY_GET_SUBVAL(ay_tone_tick[chan],ay_tone_period[chan]);	\
  									\
  if(ay_tone_tick[chan]>=ay_tone_period[chan]*2)			\
    {									\
    ay_tone_tick[chan]-=ay_tone_period[chan]*2;				\
    /* sanity check needed to avoid making samples sound terrible */ 	\
    if(level && ay_tone_tick[chan]<ay_tone_period[chan]) 		\
      (*(ptr))-=AY_GET_SUBVAL(ay_tone_tick[chan],0);			\
    }


static void sound_ay_overlay(void)
{
static int rng=1;
static int noise_toggle=1;
static int env_level=0;
int tone_level[3];
int mixer,envshape;
int f,g,level;
int v=0;
unsigned char *ptr;
struct ay_change_tag *change_ptr=ay_change;
int changes_left=ay_change_count;
int reg,r;
int was_high;
int channels=(sound_stereo?2:1);

/* If no AY chip, don't produce any AY sound (!) */
if(!sound_ay) return;

/* convert change times to sample offsets */
for(f=0;f<ay_change_count;f++)
  ay_change[f].ofs=(ay_change[f].tstates*sound_freq)/3250000;

for(f=0,ptr=sound_buf;f<sound_framesiz;f++,ptr+=channels)
  {
  /* update ay registers. All this sub-frame change stuff
   * is pretty hairy, but how else would you handle the
   * samples in Robocop? :-) It also clears up some other
   * glitches.
   *
   * Ok, maybe that's no big deal on the ZX81, but even so. :-)
   * (Though, due to tstate-changing games in z80.c, we can
   * rarely `lose' one this way - hence "f==.." bit below
   * to catch any that slip through.)
   */
  while(changes_left && (f>=change_ptr->ofs || f==sound_framesiz-1))
    {
    sound_ay_registers[reg=change_ptr->reg]=change_ptr->val;
    change_ptr++; changes_left--;

    /* fix things as needed for some register changes */
    switch(reg)
      {
      case 0: case 1: case 2: case 3: case 4: case 5:
        r=reg>>1;
        ay_tone_period[r]=(8*(sound_ay_registers[reg&~1]|
                              (sound_ay_registers[reg|1]&15)<<8))<<16;

        /* important to get this right, otherwise e.g. Ghouls 'n' Ghosts
         * has really scratchy, horrible-sounding vibrato.
         */
        if(ay_tone_period[r] && ay_tone_tick[r]>=ay_tone_period[r]*2)
          ay_tone_tick[r]%=ay_tone_period[r]*2;
        break;
      case 6:
        ay_noise_tick=0;
        ay_noise_period=(16*(sound_ay_registers[reg]&31))<<16;
        break;
      case 11: case 12:
        /* this one *isn't* fixed-point */
        ay_env_period=sound_ay_registers[11]|(sound_ay_registers[12]<<8);
        break;
      case 13:
        ay_env_tick=ay_env_subcycles=0;
        env_held=env_alternating=0;
        env_level=0;
        break;
      }
    }
  
  /* the tone level if no enveloping is being used */
  for(g=0;g<3;g++)
    tone_level[g]=ay_tone_levels[sound_ay_registers[8+g]&15];

  /* envelope */
  envshape=sound_ay_registers[13];
  if(ay_env_period)
    {
    if(!env_held)
      {
      v=((int)ay_env_tick*15)/ay_env_period;
      if(v<0) v=0;
      if(v>15) v=15;
      if((envshape&4)==0) v=15-v;
      if(env_alternating) v=15-v;
      env_level=ay_tone_levels[v];
      }
    }
  
  for(g=0;g<3;g++)
    if(sound_ay_registers[8+g]&16)
      tone_level[g]=env_level;

  if(ay_env_period)
    {
    /* envelope gets incr'd every 256 AY cycles */
    ay_env_subcycles+=ay_tick_incr;
    if(ay_env_subcycles>=(256<<16))
      {
      ay_env_subcycles-=(256<<16);
      
      ay_env_tick++;
      if(ay_env_tick>=ay_env_period)
        {
        ay_env_tick-=ay_env_period;
        if(!env_held && ((envshape&1) || (envshape&8)==0))
          {
          env_held=1;
          if((envshape&2) || (envshape&0xc)==4)
            env_level=ay_tone_levels[15-v];
          }
        if(!env_held && (envshape&2))
          env_alternating=!env_alternating;
        }
      }
    }

  /* generate tone+noise */
  /* channel C first to make ACB easier */
  mixer=sound_ay_registers[7];
  if((mixer&4)==0 || (mixer&0x20)==0)
    {
    level=(noise_toggle || (mixer&0x20))?tone_level[2]:0;
    AY_OVERLAY_TONE(ptr,2,level);
    if(sound_stereo && sound_stereo_acb)
      ptr[1]=*ptr;
    }
  if((mixer&1)==0 || (mixer&0x08)==0)
    {
    level=(noise_toggle || (mixer&0x08))?tone_level[0]:0;
    AY_OVERLAY_TONE(ptr,0,level);
    }
  if((mixer&2)==0 || (mixer&0x10)==0)
    {
    level=(noise_toggle || (mixer&0x10))?tone_level[1]:0;
    AY_OVERLAY_TONE(ptr+sound_stereo_acb,1,level);
    }
  
  if(sound_stereo && !sound_stereo_acb)
    ptr[1]=*ptr;

  /* update noise RNG/filter */
  ay_noise_tick+=ay_tick_incr;
  if(ay_noise_tick>=ay_noise_period)
    {
    if((rng&1)^((rng&2)?1:0))
      noise_toggle=!noise_toggle;
    
    /* rng is 17-bit shift reg, bit 0 is output.
     * input is bit 0 xor bit 2.
     */
    rng|=((rng&1)^((rng&4)?1:0))?0x20000:0;
    rng>>=1;
    
    ay_noise_tick-=ay_noise_period;
    }
  }
}


/* don't make the change immediately; record it for later,
 * to be made by sound_frame() (via sound_ay_overlay()).
 */
void sound_ay_write(int reg,int val)
{
if(!sound_enabled || !sound_ay) return;

/* accept r15, in case of the two-I/O-port 8910 */
if(reg>=16) return;

if(tstates>=0 && ay_change_count<AY_CHANGE_MAX)
  {
  ay_change[ay_change_count].tstates=tstates;
  ay_change[ay_change_count].reg=reg;
  ay_change[ay_change_count].val=val;
  ay_change_count++;
  }
}


/* no need to call this initially, but should be called
 * on reset otherwise.
 */
void sound_ay_reset(void)
{
int f;

for(f=0;f<16;f++)
  sound_ay_write(f,0);
}


/* XXX currently using speccy beeper code verbatim for VSYNC.
 * Not sure how plausible this is, but for now it'll do.
 * It does *sound* pretty plausible.
 */

/* it should go without saying that the beeper was hardly capable of
 * generating perfect square waves. :-) What seems to have happened is
 * that after the `click' in the intended direction away from the rest
 * (zero) position, it faded out gradually over about 1/50th of a second
 * back down to zero - the bulk of the fade being over after about
 * a 1/500th.
 *
 * The true behaviour is awkward to model accurately, but a compromise
 * emulation (doing a linear fadeout over 1/150th) seems to work quite
 * well and IMHO sounds a little more like a real speccy than most
 * emulations. It also has the considerable advantage of having a zero
 * rest position, which I'm a lot happier with. :-)
 */

#define BEEPER_FADEOUT	(((1<<24)/150)/AMPL_BEEPER)

#define BEEPER_OLDVAL_ADJUST \
  beeper_tick+=beeper_tick_incr;	\
  if(beeper_tick>=BEEPER_FADEOUT)	\
    {					\
    beeper_tick-=BEEPER_FADEOUT;	\
    if(sound_oldval>128)		\
      sound_oldval--;			\
    else				\
      if(sound_oldval<128)		\
        sound_oldval++;			\
    }


void sound_frame(void)
{
unsigned char *ptr;
int f;

if(!sound_enabled) return;

if(sound_vsync)
  {
  ptr=sound_buf+(sound_stereo?sound_fillpos*2:sound_fillpos);
  for(f=sound_fillpos;f<sound_framesiz;f++)
    {
    BEEPER_OLDVAL_ADJUST;
    *ptr++=sound_oldval;
    if(sound_stereo)
      *ptr++=sound_oldval;
    }
  }
else
  /* must be AY then, so `zero' buffer ready for it */
  memset(sound_buf,128,sound_framesiz*(sound_stereo+1));

if(sound_ay)
  sound_ay_overlay();

osssound_frame(sound_buf,sound_framesiz*(sound_stereo+1));

sound_oldpos=-1;
sound_fillpos=0;
sound_ptr=sound_buf;

ay_change_count=0;
}


void sound_beeper(int on)
{
unsigned char *ptr;
int newpos,subpos;
int val,subval;
int f;

if(!sound_enabled || !sound_vsync) return;

val=(on?128+AMPL_BEEPER:128-AMPL_BEEPER);

if(val==sound_oldval_orig) return;

/* XXX a lookup table might help here... */
newpos=(tstates*sound_framesiz)/tsmax;
subpos=(tstates*sound_framesiz*VOL_BEEPER)/tsmax-VOL_BEEPER*newpos;

/* if we already wrote here, adjust the level.
 */
if(newpos==sound_oldpos)
  {
  /* adjust it as if the rest of the sample period were all in
   * the new state. (Often it will be, but if not, we'll fix
   * it later by doing this again.)
   */
  if(on)
    beeper_last_subpos+=VOL_BEEPER-subpos;
  else
    beeper_last_subpos-=VOL_BEEPER-subpos;
  }
else
  beeper_last_subpos=(on?VOL_BEEPER-subpos:subpos);

subval=128-AMPL_BEEPER+beeper_last_subpos;

if(newpos>=0)
  {
  /* fill gap from previous position */
  ptr=sound_buf+(sound_stereo?sound_fillpos*2:sound_fillpos);
  for(f=sound_fillpos;f<newpos && f<sound_framesiz;f++)
    {
    BEEPER_OLDVAL_ADJUST;
    *ptr++=sound_oldval;
    if(sound_stereo)
      *ptr++=sound_oldval;
    }

  if(newpos<sound_framesiz)
    {
    /* newpos may be less than sound_fillpos, so... */
    ptr=sound_buf+(sound_stereo?newpos*2:newpos);
    
    /* limit subval in case of faded beeper level,
     * to avoid slight spikes on ordinary tones.
     */
    if((sound_oldval<128 && subval<sound_oldval) ||
       (sound_oldval>=128 && subval>sound_oldval))
      subval=sound_oldval;

    /* write subsample value */
    *ptr=subval;
    if(sound_stereo)
      *++ptr=subval;
    }
  }

sound_oldpos=newpos;
sound_fillpos=newpos+1;
sound_oldval=sound_oldval_orig=val;
}

#endif	/* OSS_SOUND_SUPPORT */