vbagx/source/ngc/mixer.cpp

/****************************************************************************
* VisualBoyAdvance
*
* Head and tail audio mixer
****************************************************************************/
#include <gccore.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/** Locals **/
static int head = 0;
static int tail = 0;

#define MIXBUFFSIZE 0x10000
static u8 mixerdata[MIXBUFFSIZE];
#define MIXERMASK ((MIXBUFFSIZE >> 2) - 1)

/****************************************************************************
* MIXER_AddSamples
*
* Upsample from 11025 to 48000
* 11025 == 15052
* 22050 == 30106
* 44100 == 60211
*
* Audio officianados should look away now !
****************************************************************************/
void MIXER_AddSamples( u8 *sampledata, int len )
{
  u32 *src = (u32 *)sampledata;
  u32 *dst = (u32 *)mixerdata;
  u32 intlen = (3200 >> 2);
  u32 fixofs = 0;
  u32 fixinc;

  if ( !len )
  	fixinc = 30106;
  else
        fixinc = 60211;

  do
    {
	/* Do simple linear interpolate */
	dst[head++] = src[fixofs >> 16];
	head &= MIXERMASK;
	fixofs += fixinc;
    }
  while( --intlen );

}

/****************************************************************************
* MIXER_GetSamples
****************************************************************************/
int MIXER_GetSamples( u8 *dstbuffer, int maxlen )
{
  u32 *src = (u32 *)mixerdata;
  u32 *dst = (u32 *)dstbuffer;
  u32 intlen = maxlen >> 2;

  memset(dstbuffer, 0, maxlen);

  while( ( head != tail ) && intlen )
    {
      *dst++ = src[tail++];
      tail &= MIXERMASK;
      intlen--;
    }

  return 3200;
}