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-rw-r--r--lib/rbcodec/codecs/libgme/gb_oscs.h187
1 files changed, 187 insertions, 0 deletions
diff --git a/lib/rbcodec/codecs/libgme/gb_oscs.h b/lib/rbcodec/codecs/libgme/gb_oscs.h
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1// Private oscillators used by Gb_Apu
2
3// Gb_Snd_Emu 0.1.4
4#ifndef GB_OSCS_H
5#define GB_OSCS_H
6
7#include "blargg_common.h"
8#include "blip_buffer.h"
9
10#ifndef GB_APU_OVERCLOCK
11 #define GB_APU_OVERCLOCK 1
12#endif
13
14#if GB_APU_OVERCLOCK & (GB_APU_OVERCLOCK - 1)
15 #error "GB_APU_OVERCLOCK must be a power of 2"
16#endif
17
18enum { clk_mul = GB_APU_OVERCLOCK };
19enum { dac_bias = 7 };
20
21struct Gb_Osc {
22 struct Blip_Buffer* outputs [4];// NULL, right, left, center
23 struct Blip_Buffer* output; // where to output sound
24 uint8_t* regs; // osc's 5 registers
25 int mode; // mode_dmg, mode_cgb, mode_agb
26 int dac_off_amp;// amplitude when DAC is off
27 int last_amp; // current amplitude in Blip_Buffer
28
29 struct Blip_Synth* synth;
30
31 int delay; // clocks until frequency timer expires
32 int length_ctr; // length counter
33 unsigned phase; // waveform phase (or equivalent)
34 bool enabled; // internal enabled flag
35};
36
37// 11-bit frequency in NRx3 and NRx4
38static inline int Osc_frequency( struct Gb_Osc* this ) { return (this->regs [4] & 7) * 0x100 + this->regs [3]; }
39
40void Osc_clock_length( struct Gb_Osc* this );
41void Osc_reset( struct Gb_Osc* this );
42
43// Square
44
45enum { period_mask = 0x70 };
46enum { shift_mask = 0x07 };
47
48struct Gb_Square {
49 struct Gb_Osc osc;
50
51 int env_delay;
52 int volume;
53 bool env_enabled;
54
55 // Sweep square
56 int sweep_freq;
57 int sweep_delay;
58 bool sweep_enabled;
59 bool sweep_neg;
60};
61
62void Square_run( struct Gb_Square* this, blip_time_t, blip_time_t );
63void Square_clock_envelope( struct Gb_Square* this );
64
65static inline void Square_reset( struct Gb_Square* this )
66{
67 this->env_delay = 0;
68 this->volume = 0;
69 Osc_reset( &this->osc );
70 this->osc.delay = 0x40000000; // TODO: something less hacky (never clocked until first trigger)
71}
72// Frequency timer period
73static inline int Square_period( struct Gb_Square* this ) { return (2048 - Osc_frequency( &this->osc )) * (4 * clk_mul); }
74static inline int Square_dac_enabled( struct Gb_Square* this) { return this->osc.regs [2] & 0xF8; }
75static inline int Square_reload_env_timer( struct Gb_Square* this )
76{
77 int raw = this->osc.regs [2] & 7;
78 this->env_delay = (raw ? raw : 8);
79 return raw;
80}
81
82// Sweep square
83
84void clock_sweep( struct Gb_Square* this );
85
86static inline void Sweep_reset( struct Gb_Square* this )
87{
88 this->sweep_freq = 0;
89 this->sweep_delay = 0;
90 this->sweep_enabled = false;
91 this->sweep_neg = false;
92
93 this->env_delay = 0;
94 this->volume = 0;
95 Osc_reset( &this->osc );
96 this->osc.delay = 0x40000000; // TODO: something less hacky (never clocked until first trigger)
97}
98
99// Noise
100
101enum { period2_mask = 0x1FFFF };
102
103struct Gb_Noise {
104 struct Gb_Osc osc;
105
106 int env_delay;
107 int volume;
108 bool env_enabled;
109
110 int divider; // noise has more complex frequency divider setup
111};
112
113void Noise_run( struct Gb_Noise* this, blip_time_t, blip_time_t );
114
115static inline void Noise_reset( struct Gb_Noise* this )
116{
117 this->divider = 0;
118
119 this->env_delay = 0;
120 this->volume = 0;
121 Osc_reset( &this->osc );
122 this->osc.delay = 4 * clk_mul; // TODO: remove?
123}
124
125void Noise_clock_envelope( struct Gb_Noise* this );
126
127// Non-zero if DAC is enabled
128static inline int Noise_dac_enabled( struct Gb_Noise* this) { return this->osc.regs [2] & 0xF8; }
129static inline int Noise_reload_env_timer( struct Gb_Noise* this )
130{
131 int raw = this->osc.regs [2] & 7;
132 this->env_delay = (raw ? raw : 8);
133 return raw;
134}
135
136static inline int period2_index( struct Gb_Noise* this ) { return this->osc.regs [3] >> 4; }
137static inline int period2( struct Gb_Noise* this, int base ) { return base << period2_index( this ); }
138static inline unsigned lfsr_mask( struct Gb_Noise* this ) { return (this->osc.regs [3] & 0x08) ? ~0x4040 : ~0x4000; }
139
140// Wave
141
142enum { bank40_mask = 0x40 };
143enum { wave_bank_size = 32 };
144
145struct Gb_Wave {
146 struct Gb_Osc osc;
147
148 int sample_buf; // last wave RAM byte read (hardware has this as well)
149
150 int agb_mask; // 0xFF if AGB features enabled, 0 otherwise
151 uint8_t* wave_ram; // 32 bytes (64 nybbles), stored in APU
152};
153
154void Wave_run( struct Gb_Wave* this, blip_time_t, blip_time_t );
155
156static inline void Wave_reset( struct Gb_Wave* this )
157{
158 this->sample_buf = 0;
159 Osc_reset( &this->osc );
160}
161
162// Frequency timer period
163static inline int Wave_period( struct Gb_Wave* this ) { return (2048 - Osc_frequency( &this->osc )) * (2 * clk_mul); }
164
165// Non-zero if DAC is enabled
166static inline int Wave_dac_enabled( struct Gb_Wave* this ) { return this->osc.regs [0] & 0x80; }
167
168static inline uint8_t* wave_bank( struct Gb_Wave* this ) { return &this->wave_ram [(~this->osc.regs [0] & bank40_mask) >> 2 & this->agb_mask]; }
169
170// Wave index that would be accessed, or -1 if no access would occur
171int wave_access( struct Gb_Wave* this, int addr );
172
173// Reads/writes wave RAM
174static inline int Wave_read( struct Gb_Wave* this, int addr )
175{
176 int index = wave_access( this, addr );
177 return (index < 0 ? 0xFF : wave_bank( this ) [index]);
178}
179
180static inline void Wave_write( struct Gb_Wave* this, int addr, int data )
181{
182 int index = wave_access( this, addr );
183 if ( index >= 0 )
184 wave_bank( this ) [index] = data;;
185}
186
187#endif
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