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357 lines
11 KiB
C
357 lines
11 KiB
C
/***************************************************************************************
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* Genesis Plus
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* Sound Hardware
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*
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* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003 Charles Mac Donald (original code)
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* Copyright (C) 2007-2011 Eke-Eke (Genesis Plus GX)
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*
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* Redistribution and use of this code or any derivative works are permitted
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* provided that the following conditions are met:
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*
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* - Redistributions may not be sold, nor may they be used in a commercial
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* product or activity.
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*
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* - Redistributions that are modified from the original source must include the
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* complete source code, including the source code for all components used by a
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* binary built from the modified sources. However, as a special exception, the
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* source code distributed need not include anything that is normally distributed
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* (in either source or binary form) with the major components (compiler, kernel,
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* and so on) of the operating system on which the executable runs, unless that
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* component itself accompanies the executable.
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*
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* - Redistributions must reproduce the above copyright notice, this list of
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* conditions and the following disclaimer in the documentation and/or other
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* materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************************/
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#include "shared.h"
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#include "Fir_Resampler.h"
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/* Cycle-accurate samples */
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static unsigned int psg_cycles_ratio;
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static unsigned int psg_cycles_count;
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static unsigned int fm_cycles_ratio;
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static unsigned int fm_cycles_count;
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/* YM chip function pointers */
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static void (*YM_Reset)(void);
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static void (*YM_Update)(int *buffer, int length);
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static void (*YM_Write)(unsigned int a, unsigned int v);
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/* Run FM chip for required M-cycles */
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static __inline__ void fm_update(unsigned int cycles)
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{
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if (cycles > fm_cycles_count)
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{
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int32 *buffer;
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/* samples to run */
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unsigned int samples = (cycles - fm_cycles_count + fm_cycles_ratio - 1) / fm_cycles_ratio;
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/* update cycle count */
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fm_cycles_count += samples * fm_cycles_ratio;
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/* select input sample buffer */
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buffer = Fir_Resampler_buffer();
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if (buffer)
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{
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Fir_Resampler_write(samples << 1);
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}
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else
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{
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buffer = snd.fm.pos;
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snd.fm.pos += (samples << 1);
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}
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/* run FM chip & get samples */
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YM_Update(buffer, samples);
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}
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}
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/* Run PSG chip for required M-cycles */
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static __inline__ void psg_update(unsigned int cycles)
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{
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if (cycles > psg_cycles_count)
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{
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/* samples to run */
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unsigned int samples = (cycles - psg_cycles_count + psg_cycles_ratio - 1) / psg_cycles_ratio;
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/* update cycle count */
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psg_cycles_count += samples * psg_cycles_ratio;
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/* run PSG chip & get samples */
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SN76489_Update(snd.psg.pos, samples);
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snd.psg.pos += samples;
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}
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}
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/* Initialize sound chips emulation */
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void sound_init(void)
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{
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/* Number of M-cycles executed per second. */
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/* */
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/* The original Genesis would run exactly 53693175 M-cycles (53203424 for PAL), with */
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/* 3420 M-cycles per line and 262 (313 for PAL) lines per frame, which gives an exact */
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/* framerate of 59.92 (49.70 for PAL) fps. */
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/* */
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/* On some systems, the output framerate is not exactly 60 or 50 fps because we need */
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/* 100% smooth video and therefore frame emulation is synchronized with VSYNC, which */
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/* period is never exactly 1/60 or 1/50 seconds. */
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/* */
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/* For optimal sound rendering, input samplerate (number of samples rendered per frame) */
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/* is the exact output samplerate (number of samples played per second) divided by the */
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/* exact output framerate (number of frames emulated per seconds). */
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/* */
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/* This ensure there is no audio skipping or lag between emulated frames, while keeping */
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/* accurate timings for sound chips execution & synchronization. */
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/* */
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double mclk = MCYCLES_PER_LINE * lines_per_frame * snd.frame_rate;
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/* For better accuracy, sound chips run in synchronization with 68k and Z80 cpus */
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/* These values give the exact number of M-cycles between 2 rendered samples. */
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/* we use 21.11 fixed point precision (max. mcycle value is 3420*313 i.e 21 bits max) */
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psg_cycles_ratio = (unsigned int)(mclk / (double) snd.sample_rate * 2048.0);
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fm_cycles_ratio = psg_cycles_ratio;
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fm_cycles_count = 0;
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psg_cycles_count = 0;
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/* Initialize core emulation (input clock based on input frequency for 100% accuracy) */
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/* By default, both chips are running at the output frequency. */
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SN76489_Init(mclk/15.0,snd.sample_rate);
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if ((system_hw & SYSTEM_PBC) == SYSTEM_MD)
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{
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/* YM2612 */
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YM2612Init(mclk/7.0,snd.sample_rate);
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YM_Reset = YM2612ResetChip;
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YM_Update = YM2612Update;
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YM_Write = YM2612Write;
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/* In HQ mode, YM2612 is running at its original rate (one sample each 144*7 M-cycles) */
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/* FM stream is resampled to the output frequency at the end of a frame. */
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if (config.hq_fm)
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{
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fm_cycles_ratio = 144 * 7 * (1 << 11);
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Fir_Resampler_time_ratio(mclk / (double)snd.sample_rate / (144.0 * 7.0), config.rolloff);
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}
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}
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else
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{
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/* YM2413 */
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YM2413Init(mclk/15.0,snd.sample_rate);
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YM_Reset = YM2413ResetChip;
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YM_Update = YM2413Update;
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YM_Write = YM2413Write;
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/* In HQ mode, YM2413 is running at its original rate (one sample each 72*15 M-cycles) */
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/* FM stream is resampled to the output frequency at the end of a frame. */
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if (config.hq_fm)
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{
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fm_cycles_ratio = 72 * 15 * (1 << 11);
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Fir_Resampler_time_ratio(mclk / (double)snd.sample_rate / (72.0 * 15.0), config.rolloff);
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}
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}
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#ifdef LOGSOUND
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error("%d mcycles per PSG samples\n", psg_cycles_ratio);
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error("%d mcycles per FM samples\n", fm_cycles_ratio);
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#endif
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}
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/* Reset sound chips emulation */
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void sound_reset(void)
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{
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YM_Reset();
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SN76489_Reset();
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fm_cycles_count = 0;
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psg_cycles_count = 0;
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}
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void sound_restore()
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{
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int size;
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uint8 *ptr, *temp;
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/* save YM context */
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if ((system_hw & SYSTEM_PBC) == SYSTEM_MD)
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{
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size = YM2612GetContextSize();
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ptr = YM2612GetContextPtr();
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}
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else
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{
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size = YM2413GetContextSize();
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ptr = YM2413GetContextPtr();
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}
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temp = malloc(size);
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if (temp)
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{
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memcpy(temp, ptr, size);
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}
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/* reinitialize sound chips */
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sound_init();
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/* restore YM context */
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if (temp)
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{
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if ((system_hw & SYSTEM_PBC) == SYSTEM_MD)
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{
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YM2612Restore(temp);
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}
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else
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{
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YM2413Restore(temp);
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}
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free(temp);
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}
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}
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int sound_context_save(uint8 *state)
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{
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int bufferptr = 0;
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if ((system_hw & SYSTEM_PBC) == SYSTEM_MD)
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{
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bufferptr = YM2612SaveContext(state);
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}
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else
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{
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save_param(YM2413GetContextPtr(),YM2413GetContextSize());
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}
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save_param(SN76489_GetContextPtr(),SN76489_GetContextSize());
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save_param(&fm_cycles_count,sizeof(fm_cycles_count));
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save_param(&psg_cycles_count,sizeof(psg_cycles_count));
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return bufferptr;
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}
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int sound_context_load(uint8 *state)
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{
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int bufferptr = 0;
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if ((system_hw & SYSTEM_PBC) == SYSTEM_MD)
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{
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bufferptr = YM2612LoadContext(state);
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}
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else
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{
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load_param(YM2413GetContextPtr(),YM2413GetContextSize());
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}
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load_param(SN76489_GetContextPtr(),SN76489_GetContextSize());
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load_param(&fm_cycles_count,sizeof(fm_cycles_count));
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load_param(&psg_cycles_count,sizeof(psg_cycles_count));
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fm_cycles_count = psg_cycles_count;
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return bufferptr;
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}
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/* End of frame update, return the number of samples run so far. */
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int sound_update(unsigned int cycles)
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{
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int size;
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/* run PSG & FM chips until end of frame */
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cycles <<= 11;
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psg_update(cycles);
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fm_update(cycles);
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/* available PSG samples */
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size = snd.psg.pos - snd.psg.buffer;
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#ifdef LOGSOUND
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error("%d PSG samples available\n",size);
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#endif
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/* FM resampling */
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if (config.hq_fm)
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{
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/* get available FM samples */
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int avail = Fir_Resampler_avail();
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/* resynchronize FM & PSG chips */
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if (avail < size)
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{
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/* FM chip is late for one (or two) samples */
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do
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{
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YM_Update(Fir_Resampler_buffer(), 1);
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Fir_Resampler_write(2);
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avail = Fir_Resampler_avail();
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}
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while (avail < size);
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}
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else
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{
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/* FM chip is ahead */
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fm_cycles_count += (avail - size) * psg_cycles_ratio;
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}
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}
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#ifdef LOGSOUND
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if (config.hq_fm)
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error("%d FM samples (%d) available\n",Fir_Resampler_avail(), Fir_Resampler_written() >> 1);
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else
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error("%d FM samples available\n",(snd.fm.pos - snd.fm.buffer)>>1);
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#endif
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#ifdef LOGSOUND
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error("%lu PSG cycles run\n",psg_cycles_count);
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error("%lu FM cycles run \n",fm_cycles_count);
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#endif
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/* adjust PSG & FM cycle counts for next frame */
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psg_cycles_count -= cycles;
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fm_cycles_count -= cycles;
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#ifdef LOGSOUND
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error("%lu PSG cycles left\n",psg_cycles_count);
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error("%lu FM cycles left\n",fm_cycles_count);
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#endif
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return size;
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}
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/* Reset FM chip */
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void fm_reset(unsigned int cycles)
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{
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fm_update(cycles << 11);
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YM_Reset();
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}
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/* Write FM chip */
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void fm_write(unsigned int cycles, unsigned int address, unsigned int data)
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{
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if (address & 1) fm_update(cycles << 11);
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YM_Write(address, data);
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}
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/* Read FM status (YM2612 only) */
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unsigned int fm_read(unsigned int cycles, unsigned int address)
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{
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fm_update(cycles << 11);
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return YM2612Read();
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}
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/* Write PSG chip */
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void psg_write(unsigned int cycles, unsigned int data)
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{
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psg_update(cycles << 11);
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SN76489_Write(data);
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}
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