scummvm/backends/platform/dc/audio.cpp

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.

 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 */

#include <common/scummsys.h>
#include "engines/engine.h"
#include "audio/mixer_intern.h"
#include "dc.h"

EXTERN_C void *memcpy4s(void *s1, const void *s2, unsigned int n);

uint OSystem_Dreamcast::initSound()
{
  stop_sound();
  do_sound_command(CMD_SET_FREQ_EXP(FREQ_22050_EXP));
  do_sound_command(CMD_SET_STEREO(1));
  do_sound_command(CMD_SET_BUFFER(SOUND_BUFFER_SHIFT));
  return read_sound_int(&SOUNDSTATUS->freq);
}

void OSystem_Dreamcast::checkSound()
{
  int n;
  int curr_ring_buffer_samples;

  if (!_mixer)
    return;

  if (read_sound_int(&SOUNDSTATUS->mode) != MODE_PLAY)
    start_sound();

  curr_ring_buffer_samples = read_sound_int(&SOUNDSTATUS->ring_length);

  n = read_sound_int(&SOUNDSTATUS->samplepos);

  if ((n-=fillpos)<0)
    n += curr_ring_buffer_samples;

  n = ADJUST_BUFFER_SIZE(n-10);

  if (n<100)
    return;

  _mixer->mixCallback((byte*)temp_sound_buffer,
		      2*SAMPLES_TO_BYTES(n));

  if (fillpos+n > curr_ring_buffer_samples) {
    int r = curr_ring_buffer_samples - fillpos;
    memcpy4s(RING_BUF+fillpos, temp_sound_buffer, SAMPLES_TO_BYTES(r));
    fillpos = 0;
    n -= r;
    memcpy4s(RING_BUF, temp_sound_buffer+r, SAMPLES_TO_BYTES(n));
  } else {
    memcpy4s(RING_BUF+fillpos, temp_sound_buffer, SAMPLES_TO_BYTES(n));
  }
  if ((fillpos += n) >= curr_ring_buffer_samples)
    fillpos = 0;
}