mirror of
https://github.com/libretro/scummvm.git
synced 2024-12-15 06:08:35 +00:00
5cc2696deb
The CMS emulation assumes the chips run at 8 MHz clock, but in PCs they run at 7.15909 MHz, so the emulated pitch is too high. Adjusting the requested sampling rate higher by matching amount the pitch is lowered down to normal.
93 lines
2.9 KiB
C++
93 lines
2.9 KiB
C++
/* 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.
|
|
*
|
|
*/
|
|
|
|
#ifndef AUDIO_SOFTSYNTH_CMS_H
|
|
#define AUDIO_SOFTSYNTH_CMS_H
|
|
|
|
#include "common/scummsys.h"
|
|
|
|
/* this structure defines a channel */
|
|
struct saa1099_channel {
|
|
int frequency; /* frequency (0x00..0xff) */
|
|
int freq_enable; /* frequency enable */
|
|
int noise_enable; /* noise enable */
|
|
int octave; /* octave (0x00..0x07) */
|
|
int amplitude[2]; /* amplitude (0x00..0x0f) */
|
|
int envelope[2]; /* envelope (0x00..0x0f or 0x10 == off) */
|
|
|
|
/* vars to simulate the square wave */
|
|
double counter;
|
|
double freq;
|
|
int level;
|
|
};
|
|
|
|
/* this structure defines a noise channel */
|
|
struct saa1099_noise {
|
|
/* vars to simulate the noise generator output */
|
|
double counter;
|
|
double freq;
|
|
int level; /* noise polynomal shifter */
|
|
};
|
|
|
|
/* this structure defines a SAA1099 chip */
|
|
struct SAA1099 {
|
|
int stream; /* our stream */
|
|
int noise_params[2]; /* noise generators parameters */
|
|
int env_enable[2]; /* envelope generators enable */
|
|
int env_reverse_right[2]; /* envelope reversed for right channel */
|
|
int env_mode[2]; /* envelope generators mode */
|
|
int env_bits[2]; /* non zero = 3 bits resolution */
|
|
int env_clock[2]; /* envelope clock mode (non-zero external) */
|
|
int env_step[2]; /* current envelope step */
|
|
int all_ch_enable; /* all channels enable */
|
|
int sync_state; /* sync all channels */
|
|
int selected_reg; /* selected register */
|
|
struct saa1099_channel channels[6]; /* channels */
|
|
struct saa1099_noise noise[2]; /* noise generators */
|
|
};
|
|
|
|
class CMSEmulator {
|
|
public:
|
|
CMSEmulator(uint32 sampleRate) {
|
|
// In PCs the chips run at 7.15909 MHz instead of 8 MHz.
|
|
// Adjust sampling rate upwards to bring pitch down.
|
|
_sampleRate = (sampleRate * 352) / 315;
|
|
memset(_saa1099, 0, sizeof(SAA1099)*2);
|
|
}
|
|
|
|
~CMSEmulator() { }
|
|
|
|
void portWrite(int port, int val);
|
|
void readBuffer(int16 *buffer, const int numSamples);
|
|
private:
|
|
uint32 _sampleRate;
|
|
|
|
SAA1099 _saa1099[2];
|
|
|
|
void envelope(int chip, int ch);
|
|
void update(int chip, int16 *buffer, int length);
|
|
void portWriteIntern(int chip, int offset, int data);
|
|
};
|
|
|
|
|
|
#endif
|