void audio_set_rate(int samplerate, double framerate)
{
/* Number of M-cycles executed per second. */
/* All emulated chips are kept in sync by using a common oscillator (MCLOCK) */
/* */
/* The original console would run exactly 53693175 M-cycles per sec (53203424 for PAL), */
/* 3420 M-cycles per line and 262 (313 for PAL) lines per frame, which gives an exact */
/* framerate of 59.92 (49.70 for PAL) frames per second. */
/* */
/* Since audio samples are generated at the end of the frame, to prevent audio skipping */
/* or lag between emulated frames, number of samples rendered per frame must be set to */
/* output samplerate (number of samples played per second) divided by input framerate */
/* (number of frames emulated per seconds). */
/* */
/* On some systems, we may want to achieve 100% smooth video rendering by synchronizing */
/* frame emulation with VSYNC, which frequency is generally not exactly those values. */
/* In that case, input framerate (number of frames emulated per seconds) is the same as */
/* output framerate (number of frames rendered per seconds) by the host video hardware. */
/* */
/* When no framerate is specified, base clock is set to original master clock value. */
/* Otherwise, it is set to number of M-cycles emulated per line (fixed) multiplied by */
/* number of lines per frame (VDP mode specific) multiplied by input framerate. */
/* */
double mclk = framerate ? (MCYCLES_PER_LINE * (vdp_pal ? 313 : 262) * framerate) : system_clock;
/* For maximal accuracy, sound chips are running at their original rate using common */
/* master clock timebase so they remain perfectly synchronized together, while still */
/* being synchronized with 68K and Z80 CPUs as well. Mixed sound chip output is then */
/* resampled to desired rate at the end of each frame, using Blip Buffer. */
blip_set_rates(snd.blips[0], mclk, samplerate);
/* Mega CD sound hardware */
if (system_hw == SYSTEM_MCD)
{
/* number of SCD master clocks run per second */
mclk = (mclk / system_clock) * SCD_CLOCK;
/* PCM core */
pcm_init(mclk, samplerate);
/* CDD core */
cdd_init(samplerate);
}
/* Reinitialize internal rates */
snd.sample_rate = samplerate;
snd.frame_rate = framerate;
}
int audio_init(int samplerate, double framerate)
{
/* Number of M-cycles executed per second. */
/* All emulated chips are kept in sync by using a common oscillator (MCLOCK) */
/* */
/* The original console would run exactly 53693175 M-cycles per sec (53203424 for PAL), */
/* 3420 M-cycles per line and 262 (313 for PAL) lines per frame, which gives an exact */
/* framerate of 59.92 (49.70 for PAL) frames per second. */
/* */
/* Since audio samples are generated at the end of the frame, to prevent audio skipping */
/* or lag between emulated frames, number of samples rendered per frame must be set to */
/* output samplerate (number of samples played per second) divided by input framerate */
/* (number of frames emulated per seconds). */
/* */
/* On some systems, we may want to achieve 100% smooth video rendering by synchronizing */
/* frame emulation with VSYNC, which frequency is generally not exactly those values. */
/* In that case, input framerate (number of frames emulated per seconds) is the same as */
/* output framerate (number of frames rendered per seconds) by the host video hardware. */
/* */
/* When no framerate is specified, base clock is set to original master clock value. */
/* Otherwise, it is set to number of M-cycles emulated per line (fixed) multiplied by */
/* number of lines per frame (VDP mode specific) multiplied by input framerate. */
/* */
double mclk = framerate ? (MCYCLES_PER_LINE * (vdp_pal ? 313 : 262) * framerate) : system_clock;
/* Shutdown first */
audio_shutdown();
/* Clear the sound data context */
memset(&snd, 0, sizeof (snd));
/* Initialize audio rates */
snd.sample_rate = samplerate;
snd.frame_rate = framerate;
/* Initialize Blip Buffers */
snd.blips[0][0] = blip_new(samplerate / 10);
snd.blips[0][1] = blip_new(samplerate / 10);
if (!snd.blips[0][0] || !snd.blips[0][1])
{
audio_shutdown();
return -1;
}
/* For maximal accuracy, sound chips are running at their original rate using common */
/* master clock timebase so they remain perfectly synchronized together, while still */
/* being synchronized with 68K and Z80 CPUs as well. Mixed sound chip output is then */
/* resampled to desired rate at the end of each frame, using Blip Buffer. */
blip_set_rates(snd.blips[0][0], mclk, samplerate);
blip_set_rates(snd.blips[0][1], mclk, samplerate);
/* Initialize PSG core */
SN76489_Init(snd.blips[0][0], snd.blips[0][1], (system_hw < SYSTEM_MARKIII) ? SN_DISCRETE : SN_INTEGRATED);
/* Mega CD sound hardware */
if (system_hw == SYSTEM_MCD)
{
/* allocate blip buffers */
snd.blips[1][0] = blip_new(samplerate / 10);
snd.blips[1][1] = blip_new(samplerate / 10);
snd.blips[2][0] = blip_new(samplerate / 10);
snd.blips[2][1] = blip_new(samplerate / 10);
if (!snd.blips[1][0] || !snd.blips[1][1] || !snd.blips[2][0] || !snd.blips[2][1])
{
audio_shutdown();
return -1;
}
/* Initialize PCM core */
pcm_init(snd.blips[1][0], snd.blips[1][1]);
/* Initialize CDD core */
cdd_init(snd.blips[2][0], snd.blips[2][1]);
}
/* Set audio enable flag */
snd.enabled = 1;
/* Reset audio */
audio_reset();
return (0);
}
