ceab0b04eb
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@27208 a1c6a512-1295-4272-9138-f99709370657
124 lines
3.8 KiB
C
124 lines
3.8 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Pacbox - a Pacman Emulator for Rockbox
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*
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* Based on PIE - Pacman Instructional Emulator
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*
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* Namco custom waveform sound generator 3 (Pacman hardware)
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*
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* Copyright (c) 2003,2004 Alessandro Scotti
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* http://www.ascotti.org/
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#ifndef WSG3_H
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#define WSG3_H
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/**
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Namco 3-channel sound generator voice properties.
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This information is only needed by applications that want to do their own
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sound rendering, as the playSound() function already plays and mixes all
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three voices.
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@see PacmanMachine::playSound
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*/
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struct wsg3_voice
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{
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/** Volume (from 0 to 15) */
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unsigned volume;
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/** Index into the 4-bit 32-entry waveform table (0 to 7) */
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unsigned waveform;
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/** Frequency */
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unsigned frequency;
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};
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struct wsg3
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{
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unsigned master_clock;
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unsigned sampling_rate;
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unsigned char sound_regs[0x20];
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unsigned char sound_prom[32*8];
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unsigned resample_step;
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unsigned wave_offset[3];
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int16_t sound_wave_data[32*8]; /* sign-extended 4-bit, prenormalized */
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};
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extern struct wsg3 wsg3;
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/**
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Constructor.
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@param masterClock clock frequency of sound chip (in Hertz)
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@see #wsg3_play_sound
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*/
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void wsg3_init(unsigned master_clock);
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/**
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Sets the 256 byte PROM that contains the waveform table used by the sound chip.
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*/
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void wsg3_set_sound_prom( const unsigned char * prom );
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/**
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Sets the value of the specified register.
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*/
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static inline void wsg3_set_register(unsigned reg, unsigned char value)
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{ wsg3.sound_regs[reg] = value; }
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/**
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Returns the value of the specified register.
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*/
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static inline unsigned char wsg3_get_register(unsigned reg)
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{ return wsg3.sound_regs[reg]; }
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/**
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Reproduces the sound that is currently being generated by the sound
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chip into the specified buffer.
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The sound chip has three independent voices that generate 8-bit signed
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PCM audio. This function resamples the voices at the currently specified
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sampling rate and mixes them into the output buffer. The output buffer
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can be converted to 8-bit (signed) PCM by dividing each sample by 3 (since
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there are three voices) or it can be expanded to 16-bit by multiplying
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each sample by 85 (i.e. 256 divided by 3). If necessary, it is possible
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to approximate these values with 4 and 64 in order to use arithmetic
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shifts that are usually faster to execute.
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Note: this function does not clear the content of the output buffer before
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mixing voices into it.
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@param buf pointer to sound buffer that receives the audio samples
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@param len length of the sound buffer
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*/
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void wsg3_play_sound(int16_t * buf, int len);
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/**
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Returns the sampling rate currently in use for rendering sound.
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*/
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static inline unsigned wsg3_get_sampling_rate(void)
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{ return wsg3.sampling_rate; }
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/**
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Sets the output sampling rate for playSound().
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@param samplingRate sampling rate in Hertz (samples per second)
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*/
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void wsg3_set_sampling_rate(unsigned sampling_rate);
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#endif /* WSG3_H */
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