Genesis-Plus-GX/source/gx/gx_audio.c

/****************************************************************************
 *  gx_audio.c
 *
 *  Genesis Plus GX audio support
 *
 *  Copyright Eke-Eke (2007-2011), based on original work from Softdev (2006)
 *
 *  Redistribution and use of this code or any derivative works are permitted
 *  provided that the following conditions are met:
 *
 *   - Redistributions may not be sold, nor may they be used in a commercial
 *     product or activity.
 *
 *   - Redistributions that are modified from the original source must include the
 *     complete source code, including the source code for all components used by a
 *     binary built from the modified sources. However, as a special exception, the
 *     source code distributed need not include anything that is normally distributed
 *     (in either source or binary form) with the major components (compiler, kernel,
 *     and so on) of the operating system on which the executable runs, unless that
 *     component itself accompanies the executable.
 *
 *   - Redistributions must reproduce the above copyright notice, this list of
 *     conditions and the following disclaimer in the documentation and/or other
 *     materials provided with the distribution.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************************/

#include "shared.h"

/* DMA soundbuffers (required to be 32-bytes aligned)
   Length is dimensionned for one frame of emulation (800/808 samples @60hz, 960 samples@50Hz)
   To prevent audio clashes, we use double buffering technique:
    one buffer is the active DMA buffer
    the other one is the current work buffer (updated during frame emulation)
   We do not need more since frame emulation and DMA operation are synchronized
*/
u8 soundbuffer[2][3840] ATTRIBUTE_ALIGN(32);

/* Current work soundbuffer */
u32 mixbuffer;

/* audio DMA status */
u32 audioStarted;

/* Background music */
static u8 *Bg_music_ogg = NULL;
static u32 Bg_music_ogg_size = 0;

/***************************************************************************************/
/*   Audio engine                                                                      */
/***************************************************************************************/

/* Audio DMA callback */
static void ai_callback(void)
{
  frameticker ++;
}

/* AUDIO engine initialization */
void gx_audio_Init(void)
{
  /* Initialize AUDIO processing library (ASNDLIB) */
  /* AUDIO & DSP hardware are initialized */
  /* Default samplerate is set to 48kHz */
  ASND_Init();

  /* Load background music from FAT device */
  char fname[MAXPATHLEN];
  sprintf(fname,"%s/Bg_music.ogg",DEFAULT_PATH);
  FILE *f = fopen(fname,"rb");
  if (f)
  {
    struct stat filestat;
    stat(fname, &filestat);
    Bg_music_ogg_size = filestat.st_size;
    Bg_music_ogg = memalign(32,Bg_music_ogg_size);
    if (Bg_music_ogg)
    {
      fread(Bg_music_ogg,1,Bg_music_ogg_size,f);
    }
    fclose(f);
  }
}

/* AUDIO engine shutdown */
void gx_audio_Shutdown(void)
{
  PauseOgg(1);
  StopOgg();
  ASND_Pause(1);
  ASND_End();
  if (Bg_music_ogg)
  {
    free(Bg_music_ogg);
  }
}

/*** 
      gx_audio_Update

     This function retrieves samples for the frame then set the next DMA parameters 
     Parameters will be taken in account only when current DMA operation is over
 ***/
void gx_audio_Update(void)
{
  /* retrieve audio samples */
  int size = audio_update() * 4;

  /* set next DMA soundbuffer */
  s16 *sb = (s16 *)(soundbuffer[mixbuffer]);
  DCFlushRange((void *)sb, size);
  AUDIO_InitDMA((u32) sb, size);
  mixbuffer ^= 1;

  /* Start Audio DMA */
  /* this is called once to kick-off DMA from external memory to audio interface        */
  /* DMA operation is automatically restarted when all samples have been sent.          */
  /* If DMA settings are not updated at that time, previous sound buffer will be used.  */
  /* Therefore we need to make sure frame emulation is completed before current DMA is  */
  /* completed, either by synchronizing frame emulation with DMA start or by syncing it */
  /* with Vertical Interrupt and outputing a suitable number of samples per frame.      */
  /*                                                                                    */
  /* In both cases, audio DMA need to be synchronized with VSYNC and therefore need to  */
  /* be resynchronized (restarted) every time video settings are changed (hopefully,    */
  /* this generally happens while no music is played.                                   */                    
  if (!audioStarted)
  {
    /* restart audio DMA */
    AUDIO_StopDMA();
    AUDIO_StartDMA();
    audioStarted = 1;

    /* resynchronize emulation */
    frameticker = 1;
  }
}

/*** 
      gx_audio_Start

     This function restart the audio engine
     This is called when coming back from Main Menu
 ***/
void gx_audio_Start(void)
{
  /* shutdown background music */
  PauseOgg(1);	
  StopOgg();	
  
  /* shutdown menu audio processing */
  ASND_Pause(1);
  AUDIO_StopDMA();
  AUDIO_RegisterDMACallback(NULL);
  DSP_Halt();

  /* when TV mode does not match emulated video mode, frame emulation is synchronized with Audio Interface DMA */
  if (gc_pal != vdp_pal)
  {
    AUDIO_RegisterDMACallback(ai_callback);
  }

  /* reset emulation audio processing */
  memset(soundbuffer, 0, 2 * 3840);
  audioStarted = 0;
  mixbuffer = 0;
}

/***
      gx_audio_Stop

     This function stops current Audio DMA process
     This is called when going back to Main Menu
     DMA need to be restarted when going back to the game (see above)
 ***/
void gx_audio_Stop(void)
{
  /* restart menu audio processing */
  DSP_Unhalt();
  ASND_Init();
  ASND_Pause(0);
	
  /* play background music */
  if (Bg_music_ogg && !Shutdown)
  {
    PauseOgg(0);	
    PlayOgg((char *)Bg_music_ogg, Bg_music_ogg_size, 0, OGG_INFINITE_TIME);	
    SetVolumeOgg(((int)config.bgm_volume * 255) / 100);	
  }
}