i_sound.c

doom游戏

  for (i=0 ; i<128 ; i++)
    for (j=0 ; j<256 ; j++) {
      vol_lookup[i*256+j] = (i*(j-128)*256)/127;
//fprintf(stderr, "vol_lookup[%d*256+%d] = %d\n", i, j, vol_lookup[i*256+j]);
    }
}	

 
void I_SetSfxVolume(int volume)
{
  // Identical to DOS.
  // Basically, this should propagate
  //  the menu/config file setting
  //  to the state variable used in
  //  the mixing.
  snd_SfxVolume = volume;
}

// MUSIC API - dummy. Some code from DOS version.
void I_SetMusicVolume(int volume)
{
  // Internal state variable.
  snd_MusicVolume = volume;
  // Now set volume on output device.
  // Whatever( snd_MusciVolume );
}


//
// Retrieve the raw data lump index
//  for a given SFX name.
//
int I_GetSfxLumpNum(sfxinfo_t* sfx)
{
    char namebuf[9];
    sprintf(namebuf, "ds%s", sfx->name);
    return W_GetNumForName(namebuf);
}

//
// Starting a sound means adding it
//  to the current list of active sounds
//  in the internal channels.
// As the SFX info struct contains
//  e.g. a pointer to the raw data,
//  it is ignored.
// As our sound handling does not handle
//  priority, it is ignored.
// Pitching (that is, increased speed of playback)
//  is set, but currently not used by mixing.
//
int
I_StartSound
( int		id,
  int		vol,
  int		sep,
  int		pitch,
  int		priority )
{
#if 0 //!!
  // UNUSED
  priority = 0;
  
    // Debug.
    //fprintf( stderr, "starting sound %d", id );
    
    // Returns a handle (not used).
    SDL_LockAudio();
    id = addsfx( id, vol, steptable[pitch], sep );
    SDL_UnlockAudio();

    // fprintf( stderr, "/handle is %d\n", id );
#endif //!!    
    return id;
}



void I_StopSound (int handle)
{
  // You need the handle returned by StartSound.
  // Would be looping all channels,
  //  tracking down the handle,
  //  an setting the channel to zero.
  
  // UNUSED.
  handle = 0;
}


int I_SoundIsPlaying(int handle)
{
    // Ouch.
    return gametic < handle;
}


//
// This function loops all active (internal) sound
//  channels, retrieves a given number of samples
//  from the raw sound data, modifies it according
//  to the current (internal) channel parameters,
//  mixes the per channel samples into the given
//  mixing buffer, and clamping it to the allowed
//  range.
//
// This function currently supports only 16bit.
//
void I_UpdateSound(void *unused, Uint8 *stream, int len)
{
  // Mix current sound data.
  // Data, from raw sound, for right and left.
  register unsigned int	sample;
  register int		dl;
  register int		dr;
  
  // Pointers in audio stream, left, right, end.
  signed short*		leftout;
  signed short*		rightout;
  signed short*		leftend;
  // Step in stream, left and right, thus two.
  int				step;

  // Mixing channel index.
  int				chan;
    
    // Left and right channel
    //  are in audio stream, alternating.
    leftout = (signed short *)stream;
    rightout = ((signed short *)stream)+1;
    step = 2;

    // Determine end, for left channel only
    //  (right channel is implicit).
    leftend = leftout + SAMPLECOUNT*step;

    // Mix sounds into the mixing buffer.
    // Loop over step*SAMPLECOUNT,
    //  that is 512 values for two channels.
    while (leftout != leftend)
    {
	// Reset left/right value. 
	dl = 0;
	dr = 0;

	// Love thy L2 chache - made this a loop.
	// Now more channels could be set at compile time
	//  as well. Thus loop those  channels.
	for ( chan = 0; chan < NUM_CHANNELS; chan++ )
	{
	    // Check channel, if active.
	    if (channels[ chan ])
	    {
		// Get the raw data from the channel. 
		sample = *channels[ chan ];
		// Add left and right part
		//  for this channel (sound)
		//  to the current data.
		// Adjust volume accordingly.
		dl += channelleftvol_lookup[ chan ][sample];
		dr += channelrightvol_lookup[ chan ][sample];
		// Increment index ???
		channelstepremainder[ chan ] += channelstep[ chan ];
		// MSB is next sample???
		channels[ chan ] += channelstepremainder[ chan ] >> 16;
		// Limit to LSB???
		channelstepremainder[ chan ] &= 65536-1;

		// Check whether we are done.
		if (channels[ chan ] >= channelsend[ chan ])
		    channels[ chan ] = 0;
	    }
	}
	
	// Clamp to range. Left hardware channel.
	// Has been char instead of short.
	// if (dl > 127) *leftout = 127;
	// else if (dl < -128) *leftout = -128;
	// else *leftout = dl;

	if (dl > 0x7fff)
	    *leftout = 0x7fff;
	else if (dl < -0x8000)
	    *leftout = -0x8000;
	else
	    *leftout = dl;

	// Same for right hardware channel.
	if (dr > 0x7fff)
	    *rightout = 0x7fff;
	else if (dr < -0x8000)
	    *rightout = -0x8000;
	else
	    *rightout = dr;

	// Increment current pointers in stream
	leftout += step;
	rightout += step;
    }
}

void
I_UpdateSoundParams
( int	handle,
  int	vol,
  int	sep,
  int	pitch)
{
  // I fail too see that this is used.
  // Would be using the handle to identify
  //  on which channel the sound might be active,
  //  and resetting the channel parameters.

  // UNUSED.
  handle = vol = sep = pitch = 0;
}


void I_ShutdownSound(void)
{    
  //!!SDL_CloseAudio();
}


void
I_InitSound()
{ 
#if 0 //!!
  SDL_AudioSpec wanted;
  int i;
  
  // Secure and configure sound device first.
  fprintf( stderr, "I_InitSound: ");
  
  // Open the audio device
  wanted.freq = SAMPLERATE;
  if ( SDL_BYTEORDER == SDL_BIG_ENDIAN ) {
    wanted.format = AUDIO_S16MSB;
  } else {
    wanted.format = AUDIO_S16LSB;
  }
  wanted.channels = 2;
  wanted.samples = SAMPLECOUNT;
  wanted.callback = I_UpdateSound;
  if ( SDL_OpenAudio(&wanted, NULL) < 0 ) {
    fprintf(stderr, "couldn't open audio with desired format\n");
    return;
  }
  SAMPLECOUNT = wanted.samples;
  fprintf(stderr, " configured audio device with %d samples/slice\n", SAMPLECOUNT);

    
  // Initialize external data (all sounds) at start, keep static.
  fprintf( stderr, "I_InitSound: ");
  
  for (i=1 ; i<NUMSFX ; i++)
  { 
    // Alias? Example is the chaingun sound linked to pistol.
    if (!S_sfx[i].link)
    {
      // Load data from WAD file.
      S_sfx[i].data = getsfx( S_sfx[i].name, &lengths[i] );
    }	
    else
    {
      // Previously loaded already?
      S_sfx[i].data = S_sfx[i].link->data;
      lengths[i] = lengths[(S_sfx[i].link - S_sfx)/sizeof(sfxinfo_t)];
    }
  }

  fprintf( stderr, " pre-cached all sound data\n");
  
  // Finished initialization.
  fprintf(stderr, "I_InitSound: sound module ready\n");
  SDL_PauseAudio(0);
#endif //!!
}




//
// MUSIC API.
// Still no music done.
// Remains. Dummies.
//
void I_InitMusic(void)		{ }
void I_ShutdownMusic(void)	{ }

static int	looping=0;
static int	musicdies=-1;

void I_PlaySong(int handle, int looping)
{
  // UNUSED.
  handle = looping = 0;
  musicdies = gametic + TICRATE*30;
}

void I_PauseSong (int handle)
{
  // UNUSED.
  handle = 0;
}

void I_ResumeSong (int handle)
{
  // UNUSED.
  handle = 0;
}

void I_StopSong(int handle)
{
  // UNUSED.
  handle = 0;
  
  looping = 0;
  musicdies = 0;
}

void I_UnRegisterSong(int handle)
{
  // UNUSED.
  handle = 0;
}

int I_RegisterSong(void* data)
{
  // UNUSED.
  data = NULL;
  
  return 1;
}

// Is the song playing?
int I_QrySongPlaying(int handle)
{
  // UNUSED.
  handle = 0;
  return looping || musicdies > gametic;
}