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Diffstat (limited to 'apps/codecs/libgme/nes_oscs.c')
-rw-r--r-- | apps/codecs/libgme/nes_oscs.c | 583 |
1 files changed, 583 insertions, 0 deletions
diff --git a/apps/codecs/libgme/nes_oscs.c b/apps/codecs/libgme/nes_oscs.c new file mode 100644 index 0000000000..f04d5fa9ad --- /dev/null +++ b/apps/codecs/libgme/nes_oscs.c | |||
@@ -0,0 +1,583 @@ | |||
1 | // Nes_Snd_Emu 0.1.8. http://www.slack.net/~ant/ | ||
2 | |||
3 | #include "nes_apu.h" | ||
4 | |||
5 | /* Copyright (C) 2003-2006 Shay Green. This module is free software; you | ||
6 | can redistribute it and/or modify it under the terms of the GNU Lesser | ||
7 | General Public License as published by the Free Software Foundation; either | ||
8 | version 2.1 of the License, or (at your option) any later version. This | ||
9 | module is distributed in the hope that it will be useful, but WITHOUT ANY | ||
10 | WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS | ||
11 | FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more | ||
12 | details. You should have received a copy of the GNU Lesser General Public | ||
13 | License along with this module; if not, write to the Free Software Foundation, | ||
14 | Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ | ||
15 | |||
16 | #include "blargg_source.h" | ||
17 | |||
18 | // Nes_Osc | ||
19 | |||
20 | void Osc_clock_length( struct Nes_Osc* this, int halt_mask ) | ||
21 | { | ||
22 | if ( this->length_counter && !(this->regs [0] & halt_mask) ) | ||
23 | this->length_counter--; | ||
24 | } | ||
25 | |||
26 | // Nes_Square | ||
27 | |||
28 | void Square_clock_envelope( struct Nes_Square* this ) | ||
29 | { | ||
30 | struct Nes_Osc* osc = &this->osc; | ||
31 | int period = osc->regs [0] & 15; | ||
32 | if ( osc->reg_written [3] ) { | ||
33 | osc->reg_written [3] = false; | ||
34 | this->env_delay = period; | ||
35 | this->envelope = 15; | ||
36 | } | ||
37 | else if ( --this->env_delay < 0 ) { | ||
38 | this->env_delay = period; | ||
39 | if ( this->envelope | (osc->regs [0] & 0x20) ) | ||
40 | this->envelope = (this->envelope - 1) & 15; | ||
41 | } | ||
42 | } | ||
43 | |||
44 | int Square_volume( struct Nes_Square* this ) | ||
45 | { | ||
46 | struct Nes_Osc* osc = &this->osc; | ||
47 | return osc->length_counter == 0 ? 0 : (osc->regs [0] & 0x10) ? (osc->regs [0] & 15) : this->envelope; | ||
48 | } | ||
49 | |||
50 | void Square_clock_sweep( struct Nes_Square* this, int negative_adjust ) | ||
51 | { | ||
52 | struct Nes_Osc* osc = &this->osc; | ||
53 | int sweep = osc->regs [1]; | ||
54 | |||
55 | if ( --this->sweep_delay < 0 ) | ||
56 | { | ||
57 | osc->reg_written [1] = true; | ||
58 | |||
59 | int period = Osc_period( osc ); | ||
60 | int shift = sweep & shift_mask; | ||
61 | if ( shift && (sweep & 0x80) && period >= 8 ) | ||
62 | { | ||
63 | int offset = period >> shift; | ||
64 | |||
65 | if ( sweep & negate_flag ) | ||
66 | offset = negative_adjust - offset; | ||
67 | |||
68 | if ( period + offset < 0x800 ) | ||
69 | { | ||
70 | period += offset; | ||
71 | // rewrite period | ||
72 | osc->regs [2] = period & 0xFF; | ||
73 | osc->regs [3] = (osc->regs [3] & ~7) | ((period >> 8) & 7); | ||
74 | } | ||
75 | } | ||
76 | } | ||
77 | |||
78 | if ( osc->reg_written [1] ) { | ||
79 | osc->reg_written [1] = false; | ||
80 | this->sweep_delay = (sweep >> 4) & 7; | ||
81 | } | ||
82 | } | ||
83 | |||
84 | // TODO: clean up | ||
85 | inline nes_time_t Square_maintain_phase( struct Nes_Square* this, nes_time_t time, nes_time_t end_time, | ||
86 | nes_time_t timer_period ) | ||
87 | { | ||
88 | nes_time_t remain = end_time - time; | ||
89 | if ( remain > 0 ) | ||
90 | { | ||
91 | int count = (remain + timer_period - 1) / timer_period; | ||
92 | this->phase = (this->phase + count) & (square_phase_range - 1); | ||
93 | time += (blargg_long) count * timer_period; | ||
94 | } | ||
95 | return time; | ||
96 | } | ||
97 | |||
98 | void Square_run( struct Nes_Square* this, nes_time_t time, nes_time_t end_time ) | ||
99 | { | ||
100 | struct Nes_Osc* osc = &this->osc; | ||
101 | const int period = Osc_period( osc ); | ||
102 | const int timer_period = (period + 1) * 2; | ||
103 | |||
104 | if ( !osc->output ) | ||
105 | { | ||
106 | osc->delay = Square_maintain_phase( this, time + osc->delay, end_time, timer_period ) - end_time; | ||
107 | return; | ||
108 | } | ||
109 | |||
110 | Blip_set_modified( osc->output ); | ||
111 | |||
112 | int offset = period >> (osc->regs [1] & shift_mask); | ||
113 | if ( osc->regs [1] & negate_flag ) | ||
114 | offset = 0; | ||
115 | |||
116 | const int volume = Square_volume( this ); | ||
117 | if ( volume == 0 || period < 8 || (period + offset) >= 0x800 ) | ||
118 | { | ||
119 | if ( osc->last_amp ) { | ||
120 | Synth_offset( this->synth, time, -osc->last_amp, osc->output ); | ||
121 | osc->last_amp = 0; | ||
122 | } | ||
123 | |||
124 | time += osc->delay; | ||
125 | time = Square_maintain_phase( this, time, end_time, timer_period ); | ||
126 | } | ||
127 | else | ||
128 | { | ||
129 | // handle duty select | ||
130 | int duty_select = (osc->regs [0] >> 6) & 3; | ||
131 | int duty = 1 << duty_select; // 1, 2, 4, 2 | ||
132 | int amp = 0; | ||
133 | if ( duty_select == 3 ) { | ||
134 | duty = 2; // negated 25% | ||
135 | amp = volume; | ||
136 | } | ||
137 | if ( this->phase < duty ) | ||
138 | amp ^= volume; | ||
139 | |||
140 | { | ||
141 | int delta = Osc_update_amp( osc, amp ); | ||
142 | if ( delta ) | ||
143 | Synth_offset( this->synth, time, delta, osc->output ); | ||
144 | } | ||
145 | |||
146 | time += osc->delay; | ||
147 | if ( time < end_time ) | ||
148 | { | ||
149 | struct Blip_Buffer* const output = osc->output; | ||
150 | Synth* synth = this->synth; | ||
151 | int delta = amp * 2 - volume; | ||
152 | int phase = this->phase; | ||
153 | |||
154 | do { | ||
155 | phase = (phase + 1) & (square_phase_range - 1); | ||
156 | if ( phase == 0 || phase == duty ) { | ||
157 | delta = -delta; | ||
158 | Synth_offset_inline( synth, time, delta, output ); | ||
159 | } | ||
160 | time += timer_period; | ||
161 | } | ||
162 | while ( time < end_time ); | ||
163 | |||
164 | osc->last_amp = (delta + volume) >> 1; | ||
165 | this->phase = phase; | ||
166 | } | ||
167 | } | ||
168 | |||
169 | osc->delay = time - end_time; | ||
170 | } | ||
171 | |||
172 | // Nes_Triangle | ||
173 | |||
174 | void Triangle_clock_linear_counter( struct Nes_Triangle* this ) | ||
175 | { | ||
176 | struct Nes_Osc* osc = &this->osc; | ||
177 | if ( osc->reg_written [3] ) | ||
178 | this->linear_counter = osc->regs [0] & 0x7F; | ||
179 | else if ( this->linear_counter ) | ||
180 | this->linear_counter--; | ||
181 | |||
182 | if ( !(osc->regs [0] & 0x80) ) | ||
183 | osc->reg_written [3] = false; | ||
184 | } | ||
185 | |||
186 | inline int Triangle_calc_amp( struct Nes_Triangle* this ) | ||
187 | { | ||
188 | int amp = Triangle_phase_range - this->phase; | ||
189 | if ( amp < 0 ) | ||
190 | amp = this->phase - (Triangle_phase_range + 1); | ||
191 | return amp; | ||
192 | } | ||
193 | |||
194 | // TODO: clean up | ||
195 | inline nes_time_t Triangle_maintain_phase( struct Nes_Triangle* this, nes_time_t time, nes_time_t end_time, | ||
196 | nes_time_t timer_period ) | ||
197 | { | ||
198 | nes_time_t remain = end_time - time; | ||
199 | if ( remain > 0 ) | ||
200 | { | ||
201 | int count = (remain + timer_period - 1) / timer_period; | ||
202 | this->phase = ((unsigned) this->phase + 1 - count) & (Triangle_phase_range * 2 - 1); | ||
203 | this->phase++; | ||
204 | time += (blargg_long) count * timer_period; | ||
205 | } | ||
206 | return time; | ||
207 | } | ||
208 | |||
209 | void Triangle_run( struct Nes_Triangle* this, nes_time_t time, nes_time_t end_time ) | ||
210 | { | ||
211 | struct Nes_Osc* osc = &this->osc; | ||
212 | const int timer_period = Osc_period( osc ) + 1; | ||
213 | if ( !osc->output ) | ||
214 | { | ||
215 | time += osc->delay; | ||
216 | osc->delay = 0; | ||
217 | if ( osc->length_counter && this->linear_counter && timer_period >= 3 ) | ||
218 | osc->delay = Triangle_maintain_phase( this, time, end_time, timer_period ) - end_time; | ||
219 | return; | ||
220 | } | ||
221 | |||
222 | Blip_set_modified( osc->output ); | ||
223 | |||
224 | // to do: track phase when period < 3 | ||
225 | // to do: Output 7.5 on dac when period < 2? More accurate, but results in more clicks. | ||
226 | |||
227 | int delta = Osc_update_amp( osc, Triangle_calc_amp( this ) ); | ||
228 | if ( delta ) | ||
229 | Synth_offset( &this->synth, time, delta, osc->output ); | ||
230 | |||
231 | time += osc->delay; | ||
232 | if ( osc->length_counter == 0 || this->linear_counter == 0 || timer_period < 3 ) | ||
233 | { | ||
234 | time = end_time; | ||
235 | } | ||
236 | else if ( time < end_time ) | ||
237 | { | ||
238 | struct Blip_Buffer* const output = osc->output; | ||
239 | |||
240 | int phase = this->phase; | ||
241 | int volume = 1; | ||
242 | if ( phase > Triangle_phase_range ) { | ||
243 | phase -= Triangle_phase_range; | ||
244 | volume = -volume; | ||
245 | } | ||
246 | |||
247 | do { | ||
248 | if ( --phase == 0 ) { | ||
249 | phase = Triangle_phase_range; | ||
250 | volume = -volume; | ||
251 | } | ||
252 | else { | ||
253 | Synth_offset_inline( &this->synth, time, volume, output ); | ||
254 | } | ||
255 | |||
256 | time += timer_period; | ||
257 | } | ||
258 | while ( time < end_time ); | ||
259 | |||
260 | if ( volume < 0 ) | ||
261 | phase += Triangle_phase_range; | ||
262 | this->phase = phase; | ||
263 | osc->last_amp = Triangle_calc_amp( this ); | ||
264 | } | ||
265 | osc->delay = time - end_time; | ||
266 | } | ||
267 | |||
268 | // Nes_Dmc | ||
269 | |||
270 | void Dmc_reset( struct Nes_Dmc* this ) | ||
271 | { | ||
272 | this->address = 0; | ||
273 | this->dac = 0; | ||
274 | this->buf = 0; | ||
275 | this->bits_remain = 1; | ||
276 | this->bits = 0; | ||
277 | this->buf_full = false; | ||
278 | this->silence = true; | ||
279 | this->next_irq = apu_no_irq; | ||
280 | this->irq_flag = false; | ||
281 | this->irq_enabled = false; | ||
282 | |||
283 | Osc_reset( &this->osc ); | ||
284 | this->period = 0x1AC; | ||
285 | } | ||
286 | |||
287 | void Dmc_recalc_irq( struct Nes_Dmc* this ) | ||
288 | { | ||
289 | struct Nes_Osc* osc = &this->osc; | ||
290 | nes_time_t irq = apu_no_irq; | ||
291 | if ( this->irq_enabled && osc->length_counter ) | ||
292 | irq = this->apu->last_dmc_time + osc->delay + | ||
293 | ((osc->length_counter - 1) * 8 + this->bits_remain - 1) * (nes_time_t) (this->period) + 1; | ||
294 | if ( irq != this->next_irq ) { | ||
295 | this->next_irq = irq; | ||
296 | Apu_irq_changed( this->apu ); | ||
297 | } | ||
298 | } | ||
299 | |||
300 | int Dmc_count_reads( struct Nes_Dmc* this, nes_time_t time, nes_time_t* last_read ) | ||
301 | { | ||
302 | struct Nes_Osc* osc = &this->osc; | ||
303 | if ( last_read ) | ||
304 | *last_read = time; | ||
305 | |||
306 | if ( osc->length_counter == 0 ) | ||
307 | return 0; // not reading | ||
308 | |||
309 | nes_time_t first_read = Dmc_next_read_time( this ); | ||
310 | nes_time_t avail = time - first_read; | ||
311 | if ( avail <= 0 ) | ||
312 | return 0; | ||
313 | |||
314 | int count = (avail - 1) / (this->period * 8) + 1; | ||
315 | if ( !(osc->regs [0] & loop_flag) && count > osc->length_counter ) | ||
316 | count = osc->length_counter; | ||
317 | |||
318 | if ( last_read ) | ||
319 | { | ||
320 | *last_read = first_read + (count - 1) * (this->period * 8) + 1; | ||
321 | check( *last_read <= time ); | ||
322 | check( count == count_reads( *last_read, NULL ) ); | ||
323 | check( count - 1 == count_reads( *last_read - 1, NULL ) ); | ||
324 | } | ||
325 | |||
326 | return count; | ||
327 | } | ||
328 | |||
329 | static short const dmc_period_table [2] [16] ICONST_ATTR = { | ||
330 | {428, 380, 340, 320, 286, 254, 226, 214, // NTSC | ||
331 | 190, 160, 142, 128, 106, 84, 72, 54}, | ||
332 | |||
333 | {398, 354, 316, 298, 276, 236, 210, 198, // PAL | ||
334 | 176, 148, 132, 118, 98, 78, 66, 50} | ||
335 | }; | ||
336 | |||
337 | inline void Dmc_reload_sample( struct Nes_Dmc* this ) | ||
338 | { | ||
339 | this->address = 0x4000 + this->osc.regs [2] * 0x40; | ||
340 | this->osc.length_counter = this->osc.regs [3] * 0x10 + 1; | ||
341 | } | ||
342 | |||
343 | static byte const dac_table [128] ICONST_ATTR = | ||
344 | { | ||
345 | 0, 1, 2, 3, 4, 5, 6, 7, 7, 8, 9,10,11,12,13,14, | ||
346 | 15,15,16,17,18,19,20,20,21,22,23,24,24,25,26,27, | ||
347 | 27,28,29,30,31,31,32,33,33,34,35,36,36,37,38,38, | ||
348 | 39,40,41,41,42,43,43,44,45,45,46,47,47,48,48,49, | ||
349 | 50,50,51,52,52,53,53,54,55,55,56,56,57,58,58,59, | ||
350 | 59,60,60,61,61,62,63,63,64,64,65,65,66,66,67,67, | ||
351 | 68,68,69,70,70,71,71,72,72,73,73,74,74,75,75,75, | ||
352 | 76,76,77,77,78,78,79,79,80,80,81,81,82,82,82,83, | ||
353 | }; | ||
354 | |||
355 | void Dmc_write_register( struct Nes_Dmc* this, int addr, int data ) | ||
356 | { | ||
357 | if ( addr == 0 ) | ||
358 | { | ||
359 | this->period = dmc_period_table [this->pal_mode] [data & 15]; | ||
360 | this->irq_enabled = (data & 0xC0) == 0x80; // enabled only if loop disabled | ||
361 | this->irq_flag &= this->irq_enabled; | ||
362 | Dmc_recalc_irq( this ); | ||
363 | } | ||
364 | else if ( addr == 1 ) | ||
365 | { | ||
366 | int old_dac = this->dac; | ||
367 | this->dac = data & 0x7F; | ||
368 | |||
369 | // adjust last_amp so that "pop" amplitude will be properly non-linear | ||
370 | // with respect to change in dac | ||
371 | int faked_nonlinear = this->dac - (dac_table [this->dac] - dac_table [old_dac]); | ||
372 | if ( !this->nonlinear ) | ||
373 | this->osc.last_amp = faked_nonlinear; | ||
374 | } | ||
375 | } | ||
376 | |||
377 | void Dmc_start( struct Nes_Dmc* this ) | ||
378 | { | ||
379 | Dmc_reload_sample( this ); | ||
380 | Dmc_fill_buffer( this ); | ||
381 | Dmc_recalc_irq( this ); | ||
382 | } | ||
383 | |||
384 | void Dmc_fill_buffer( struct Nes_Dmc* this ) | ||
385 | { | ||
386 | if ( !this->buf_full && this->osc.length_counter ) | ||
387 | { | ||
388 | require( this->prg_reader ); // prg_reader must be set | ||
389 | this->buf = this->prg_reader( this->prg_reader_data, 0x8000u + this->address ); | ||
390 | this->address = (this->address + 1) & 0x7FFF; | ||
391 | this->buf_full = true; | ||
392 | if ( --this->osc.length_counter == 0 ) | ||
393 | { | ||
394 | if ( this->osc.regs [0] & loop_flag ) { | ||
395 | Dmc_reload_sample( this ); | ||
396 | } | ||
397 | else { | ||
398 | this->apu->osc_enables &= ~0x10; | ||
399 | this->irq_flag = this->irq_enabled; | ||
400 | this->next_irq = apu_no_irq; | ||
401 | Apu_irq_changed( this->apu ); | ||
402 | } | ||
403 | } | ||
404 | } | ||
405 | } | ||
406 | |||
407 | void Dmc_run( struct Nes_Dmc* this, nes_time_t time, nes_time_t end_time ) | ||
408 | { | ||
409 | struct Nes_Osc* osc = &this->osc; | ||
410 | int delta = Osc_update_amp( osc, this->dac ); | ||
411 | if ( !osc->output ) | ||
412 | { | ||
413 | this->silence = true; | ||
414 | } | ||
415 | else | ||
416 | { | ||
417 | Blip_set_modified( osc->output ); | ||
418 | if ( delta ) | ||
419 | Synth_offset( &this->synth, time, delta, osc->output ); | ||
420 | } | ||
421 | |||
422 | time += osc->delay; | ||
423 | if ( time < end_time ) | ||
424 | { | ||
425 | int bits_remain = this->bits_remain; | ||
426 | if ( this->silence && !this->buf_full ) | ||
427 | { | ||
428 | int count = (end_time - time + this->period - 1) / this->period; | ||
429 | bits_remain = (bits_remain - 1 + 8 - (count % 8)) % 8 + 1; | ||
430 | time += count * this->period; | ||
431 | } | ||
432 | else | ||
433 | { | ||
434 | struct Blip_Buffer* const output = osc->output; | ||
435 | const int period = this->period; | ||
436 | int bits = this->bits; | ||
437 | int dac = this->dac; | ||
438 | |||
439 | do | ||
440 | { | ||
441 | if ( !this->silence ) | ||
442 | { | ||
443 | int step = (bits & 1) * 4 - 2; | ||
444 | bits >>= 1; | ||
445 | if ( (unsigned) (dac + step) <= 0x7F ) { | ||
446 | dac += step; | ||
447 | Synth_offset_inline( &this->synth, time, step, output ); | ||
448 | } | ||
449 | } | ||
450 | |||
451 | time += period; | ||
452 | |||
453 | if ( --bits_remain == 0 ) | ||
454 | { | ||
455 | bits_remain = 8; | ||
456 | if ( !this->buf_full ) { | ||
457 | this->silence = true; | ||
458 | } | ||
459 | else { | ||
460 | this->silence = false; | ||
461 | bits = this->buf; | ||
462 | this->buf_full = false; | ||
463 | if ( !output ) | ||
464 | this->silence = true; | ||
465 | Dmc_fill_buffer( this ); | ||
466 | } | ||
467 | } | ||
468 | } | ||
469 | while ( time < end_time ); | ||
470 | |||
471 | this->dac = dac; | ||
472 | osc->last_amp = dac; | ||
473 | this->bits = bits; | ||
474 | } | ||
475 | this->bits_remain = bits_remain; | ||
476 | } | ||
477 | osc->delay = time - end_time; | ||
478 | } | ||
479 | |||
480 | // Nes_Noise | ||
481 | |||
482 | static short const noise_period_table [16] ICONST_ATTR = { | ||
483 | 0x004, 0x008, 0x010, 0x020, 0x040, 0x060, 0x080, 0x0A0, | ||
484 | 0x0CA, 0x0FE, 0x17C, 0x1FC, 0x2FA, 0x3F8, 0x7F2, 0xFE4 | ||
485 | }; | ||
486 | |||
487 | void Noise_clock_envelope( struct Nes_Noise* this ) | ||
488 | { | ||
489 | struct Nes_Osc* osc = &this->osc; | ||
490 | int period = osc->regs [0] & 15; | ||
491 | if ( osc->reg_written [3] ) { | ||
492 | osc->reg_written [3] = false; | ||
493 | this->env_delay = period; | ||
494 | this->envelope = 15; | ||
495 | } | ||
496 | else if ( --this->env_delay < 0 ) { | ||
497 | this->env_delay = period; | ||
498 | if ( this->envelope | (osc->regs [0] & 0x20) ) | ||
499 | this->envelope = (this->envelope - 1) & 15; | ||
500 | } | ||
501 | } | ||
502 | |||
503 | int Noise_volume( struct Nes_Noise* this ) | ||
504 | { | ||
505 | struct Nes_Osc* osc = &this->osc; | ||
506 | return osc->length_counter == 0 ? 0 : (osc->regs [0] & 0x10) ? (osc->regs [0] & 15) : this->envelope; | ||
507 | } | ||
508 | |||
509 | void Noise_run( struct Nes_Noise* this, nes_time_t time, nes_time_t end_time ) | ||
510 | { | ||
511 | struct Nes_Osc* osc = &this->osc; | ||
512 | int period = noise_period_table [osc->regs [2] & 15]; | ||
513 | |||
514 | if ( !osc->output ) | ||
515 | { | ||
516 | // TODO: clean up | ||
517 | time += osc->delay; | ||
518 | osc->delay = time + (end_time - time + period - 1) / period * period - end_time; | ||
519 | return; | ||
520 | } | ||
521 | |||
522 | Blip_set_modified( osc->output ); | ||
523 | |||
524 | const int volume = Noise_volume( this ); | ||
525 | int amp = (this->noise & 1) ? volume : 0; | ||
526 | { | ||
527 | int delta = Osc_update_amp( osc, amp ); | ||
528 | if ( delta ) | ||
529 | Synth_offset( &this->synth, time, delta, osc->output ); | ||
530 | } | ||
531 | |||
532 | time += osc->delay; | ||
533 | if ( time < end_time ) | ||
534 | { | ||
535 | const int mode_flag = 0x80; | ||
536 | |||
537 | if ( !volume ) | ||
538 | { | ||
539 | // round to next multiple of period | ||
540 | time += (end_time - time + period - 1) / period * period; | ||
541 | |||
542 | // approximate noise cycling while muted, by shuffling up noise register | ||
543 | // to do: precise muted noise cycling? | ||
544 | if ( !(osc->regs [2] & mode_flag) ) { | ||
545 | int feedback = (this->noise << 13) ^ (this->noise << 14); | ||
546 | this->noise = (feedback & 0x4000) | (this->noise >> 1); | ||
547 | } | ||
548 | } | ||
549 | else | ||
550 | { | ||
551 | struct Blip_Buffer* const output = osc->output; | ||
552 | |||
553 | // using resampled time avoids conversion in synth.offset() | ||
554 | blip_resampled_time_t rperiod = Blip_resampled_duration( output, period ); | ||
555 | blip_resampled_time_t rtime = Blip_resampled_time( output, time ); | ||
556 | |||
557 | int noise = this->noise; | ||
558 | int delta = amp * 2 - volume; | ||
559 | const int tap = (osc->regs [2] & mode_flag ? 8 : 13); | ||
560 | |||
561 | do { | ||
562 | int feedback = (noise << tap) ^ (noise << 14); | ||
563 | time += period; | ||
564 | |||
565 | if ( (noise + 1) & 2 ) { | ||
566 | // bits 0 and 1 of noise differ | ||
567 | delta = -delta; | ||
568 | Synth_offset_resampled( &this->synth, rtime, delta, output ); | ||
569 | } | ||
570 | |||
571 | rtime += rperiod; | ||
572 | noise = (feedback & 0x4000) | (noise >> 1); | ||
573 | } | ||
574 | while ( time < end_time ); | ||
575 | |||
576 | osc->last_amp = (delta + volume) >> 1; | ||
577 | this->noise = noise; | ||
578 | } | ||
579 | } | ||
580 | |||
581 | osc->delay = time - end_time; | ||
582 | } | ||
583 | |||