sound.c

   1 /* gameplaySP
   2  *
   3  * Copyright (C) 2006 Exophase <exophase@gmail.com>
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License as
   7  * published by the Free Software Foundation; either version 2 of
   8  * the License, or (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  18  */
  19
  20
  21 #include "common.h"
  22 #include <SDL.h>
  23 u32 global_enable_audio = 1;
  24
  25 direct_sound_struct direct_sound_channel[2];
  26 gbc_sound_struct gbc_sound_channel[4];
  27
  28 u32 sound_frequency = 44100;
  29
  30 SDL_mutex *sound_mutex;
  31 static SDL_cond *sound_cv;
  32
  33 #ifdef PSP_BUILD
  34 u32 audio_buffer_size_number = 1;
  35 #elif defined(POLLUX_BUILD)
  36 u32 audio_buffer_size_number = 7;
  37 #else
  38 u32 audio_buffer_size_number = 8;
  39 #endif
  40
  41 u32 sound_on;
  42 static u32 audio_buffer_size;
  43 static s16 sound_buffer[BUFFER_SIZE];
  44 static u32 sound_buffer_base;
  45
  46 static u32 sound_last_cpu_ticks;
  47 static fixed16_16 gbc_sound_tick_step;
  48
  49 static u32 sound_exit_flag;
  50
  51 // Queue 1, 2, or 4 samples to the top of the DS FIFO, wrap around circularly
  52
  53 #define sound_timer_queue(size, value)                                        \
  54   *((s##size *)(ds->fifo + ds->fifo_top)) = value;                            \
  55   ds->fifo_top = (ds->fifo_top + 1) % 32;                                     \
  56
  57 void sound_timer_queue8(u32 channel, u8 value)
  58 {
  59   direct_sound_struct *ds = direct_sound_channel + channel;
  60   sound_timer_queue(8, value);
  61 }
  62
  63 void sound_timer_queue16(u32 channel, u16 value)
  64 {
  65   direct_sound_struct *ds = direct_sound_channel + channel;
  66   sound_timer_queue(8, value & 0xFF);
  67   sound_timer_queue(8, value >> 8);
  68 }
  69
  70 void sound_timer_queue32(u32 channel, u32 value)
  71 {
  72   direct_sound_struct *ds = direct_sound_channel + channel;
  73
  74   sound_timer_queue(8, value & 0xFF);
  75   sound_timer_queue(8, (value >> 8) & 0xFF);
  76   sound_timer_queue(8, (value >> 16) & 0xFF);
  77   sound_timer_queue(8, value >> 24);
  78 }
  79
  80 // Unqueue 1 sample from the base of the DS FIFO and place it on the audio
  81 // buffer for as many samples as necessary. If the DS FIFO is 16 bytes or
  82 // smaller and if DMA is enabled for the sound channel initiate a DMA transfer
  83 // to the DS FIFO.
  84
  85 #define render_sample_null()                                                  \
  86
  87 #define render_sample_left()                                                  \
  88   sound_buffer[buffer_index] += current_sample +                              \
  89    fp16_16_to_u32((next_sample - current_sample) * (fifo_fractional >> 8))    \
  90
  91 #define render_sample_right()                                                 \
  92   sound_buffer[buffer_index + 1] += current_sample +                          \
  93    fp16_16_to_u32((next_sample - current_sample) * (fifo_fractional >> 8))    \
  94
  95 #define render_sample_both()                                                  \
  96   dest_sample = current_sample +                                              \
  97    fp16_16_to_u32((next_sample - current_sample) * (fifo_fractional >> 8));   \
  98   sound_buffer[buffer_index] += dest_sample;                                  \
  99   sound_buffer[buffer_index + 1] += dest_sample                               \
 100
 101 #define render_samples(type)                                                  \
 102   while(fifo_fractional <= 0xFFFFFF)                                          \
 103   {                                                                           \
 104     render_sample_##type();                                                   \
 105     fifo_fractional += frequency_step;                                        \
 106     buffer_index = (buffer_index + 2) % BUFFER_SIZE;                          \
 107   }                                                                           \
 108
 109 void sound_timer(fixed8_24 frequency_step, u32 channel)
 110 {
 111   direct_sound_struct *ds = direct_sound_channel + channel;
 112
 113   fixed8_24 fifo_fractional = ds->fifo_fractional;
 114   u32 buffer_index = ds->buffer_index;
 115   s16 current_sample, next_sample, dest_sample;
 116
 117   current_sample = ds->fifo[ds->fifo_base] << 4;
 118   ds->fifo_base = (ds->fifo_base + 1) % 32;
 119   next_sample = ds->fifo[ds->fifo_base] << 4;
 120
 121   if(sound_on == 1)
 122   {
 123     if(ds->volume == DIRECT_SOUND_VOLUME_50)
 124     {
 125       current_sample >>= 1;
 126       next_sample >>= 1;
 127     }
 128
 129     switch(ds->status)
 130     {
 131       case DIRECT_SOUND_INACTIVE:
 132         render_samples(null);
 133         break;
 134
 135       case DIRECT_SOUND_RIGHT:
 136         render_samples(right);
 137         break;
 138
 139       case DIRECT_SOUND_LEFT:
 140         render_samples(left);
 141         break;
 142
 143       case DIRECT_SOUND_LEFTRIGHT:
 144         render_samples(both);
 145         break;
 146     }
 147   }
 148   else
 149   {
 150     render_samples(null);
 151   }
 152
 153   ds->buffer_index = buffer_index;
 154   ds->fifo_fractional = fp8_24_fractional_part(fifo_fractional);
 155
 156   if(((ds->fifo_top - ds->fifo_base) % 32) <= 16)
 157   {
 158     if(dma[1].direct_sound_channel == channel)
 159       dma_transfer(dma + 1);
 160
 161     if(dma[2].direct_sound_channel == channel)
 162       dma_transfer(dma + 2);
 163   }
 164 }
 165
 166 void sound_reset_fifo(u32 channel)
 167 {
 168   direct_sound_struct *ds = direct_sound_channel;
 169
 170   memset(ds->fifo, 0, 32);
 171 }
 172
 173 // Initial pattern data = 4bits (signed)
 174 // Channel volume = 12bits
 175 // Envelope volume = 14bits
 176 // Master volume = 2bits
 177
 178 // Recalculate left and right volume as volume changes.
 179 // To calculate the current sample, use (sample * volume) >> 16
 180
 181 // Square waves range from -8 (low) to 7 (high)
 182
 183 s8 square_pattern_duty[4][8] =
 184 {
 185   { 0xF8, 0xF8, 0xF8, 0xF8, 0x07, 0xF8, 0xF8, 0xF8 },
 186   { 0xF8, 0xF8, 0xF8, 0xF8, 0x07, 0x07, 0xF8, 0xF8 },
 187   { 0xF8, 0xF8, 0x07, 0x07, 0x07, 0x07, 0xF8, 0xF8 },
 188   { 0x07, 0x07, 0x07, 0x07, 0xF8, 0xF8, 0x07, 0x07 },
 189 };
 190
 191 s8 wave_samples[64];
 192
 193 u32 noise_table15[1024];
 194 u32 noise_table7[4];
 195
 196 u32 gbc_sound_master_volume_table[4] = { 1, 2, 4, 0 };
 197
 198 u32 gbc_sound_channel_volume_table[8] =
 199 {
 200   fixed_div(0, 7, 12),
 201   fixed_div(1, 7, 12),
 202   fixed_div(2, 7, 12),
 203   fixed_div(3, 7, 12),
 204   fixed_div(4, 7, 12),
 205   fixed_div(5, 7, 12),
 206   fixed_div(6, 7, 12),
 207   fixed_div(7, 7, 12)
 208 };
 209
 210 u32 gbc_sound_envelope_volume_table[16] =
 211 {
 212   fixed_div(0, 15, 14),
 213   fixed_div(1, 15, 14),
 214   fixed_div(2, 15, 14),
 215   fixed_div(3, 15, 14),
 216   fixed_div(4, 15, 14),
 217   fixed_div(5, 15, 14),
 218   fixed_div(6, 15, 14),
 219   fixed_div(7, 15, 14),
 220   fixed_div(8, 15, 14),
 221   fixed_div(9, 15, 14),
 222   fixed_div(10, 15, 14),
 223   fixed_div(11, 15, 14),
 224   fixed_div(12, 15, 14),
 225   fixed_div(13, 15, 14),
 226   fixed_div(14, 15, 14),
 227   fixed_div(15, 15, 14)
 228 };
 229
 230 u32 gbc_sound_buffer_index = 0;
 231 u32 gbc_sound_last_cpu_ticks = 0;
 232 u32 gbc_sound_partial_ticks = 0;
 233
 234 u32 gbc_sound_master_volume_left;
 235 u32 gbc_sound_master_volume_right;
 236 u32 gbc_sound_master_volume;
 237
 238 #define update_volume_channel_envelope(channel)                               \
 239   volume_##channel = gbc_sound_envelope_volume_table[envelope_volume] *       \
 240    gbc_sound_channel_volume_table[gbc_sound_master_volume_##channel] *        \
 241    gbc_sound_master_volume_table[gbc_sound_master_volume]                     \
 242
 243 #define update_volume_channel_noenvelope(channel)                             \
 244   volume_##channel = gs->wave_volume *                                        \
 245    gbc_sound_channel_volume_table[gbc_sound_master_volume_##channel] *        \
 246    gbc_sound_master_volume_table[gbc_sound_master_volume]                     \
 247
 248 #define update_volume(type)                                                   \
 249   update_volume_channel_##type(left);                                         \
 250   update_volume_channel_##type(right)                                         \
 251
 252 #define update_tone_sweep()                                                   \
 253   if(gs->sweep_status)                                                        \
 254   {                                                                           \
 255     u32 sweep_ticks = gs->sweep_ticks - 1;                                    \
 256                                                                               \
 257     if(sweep_ticks == 0)                                                      \
 258     {                                                                         \
 259       u32 rate = gs->rate;                                                    \
 260                                                                               \
 261       if(gs->sweep_direction)                                                 \
 262         rate = rate - (rate >> gs->sweep_shift);                              \
 263       else                                                                    \
 264         rate = rate + (rate >> gs->sweep_shift);                              \
 265                                                                               \
 266       if(rate > 2048)                                                         \
 267         rate = 2048;                                                          \
 268                                                                               \
 269       frequency_step = float_to_fp16_16(((131072.0f / (2048 - rate)) * 8.0f)  \
 270        / sound_frequency);                                                    \
 271                                                                               \
 272       gs->frequency_step = frequency_step;                                    \
 273       gs->rate = rate;                                                        \
 274                                                                               \
 275       sweep_ticks = gs->sweep_initial_ticks;                                  \
 276     }                                                                         \
 277     gs->sweep_ticks = sweep_ticks;                                            \
 278   }                                                                           \
 279
 280 #define update_tone_nosweep()                                                 \
 281
 282 #define update_tone_envelope()                                                \
 283   if(gs->envelope_status)                                                     \
 284   {                                                                           \
 285     u32 envelope_ticks = gs->envelope_ticks - 1;                              \
 286     envelope_volume = gs->envelope_volume;                                    \
 287                                                                               \
 288     if(envelope_ticks == 0)                                                   \
 289     {                                                                         \
 290       if(gs->envelope_direction)                                              \
 291       {                                                                       \
 292         if(envelope_volume != 15)                                             \
 293           envelope_volume = gs->envelope_volume + 1;                          \
 294       }                                                                       \
 295       else                                                                    \
 296       {                                                                       \
 297         if(envelope_volume != 0)                                              \
 298           envelope_volume = gs->envelope_volume - 1;                          \
 299       }                                                                       \
 300                                                                               \
 301       update_volume(envelope);                                                \
 302                                                                               \
 303       gs->envelope_volume = envelope_volume;                                  \
 304       gs->envelope_ticks = gs->envelope_initial_ticks;                        \
 305     }                                                                         \
 306     else                                                                      \
 307     {                                                                         \
 308       gs->envelope_ticks = envelope_ticks;                                    \
 309     }                                                                         \
 310   }                                                                           \
 311
 312 #define update_tone_noenvelope()                                              \
 313
 314 #define update_tone_counters(envelope_op, sweep_op)                           \
 315   tick_counter += gbc_sound_tick_step;                                        \
 316   if(tick_counter > 0xFFFF)                                                   \
 317   {                                                                           \
 318     if(gs->length_status)                                                     \
 319     {                                                                         \
 320       u32 length_ticks = gs->length_ticks - 1;                                \
 321       gs->length_ticks = length_ticks;                                        \
 322                                                                               \
 323       if(length_ticks == 0)                                                   \
 324       {                                                                       \
 325         gs->active_flag = 0;                                                  \
 326         break;                                                                \
 327       }                                                                       \
 328     }                                                                         \
 329                                                                               \
 330     update_tone_##envelope_op();                                              \
 331     update_tone_##sweep_op();                                                 \
 332                                                                               \
 333     tick_counter &= 0xFFFF;                                                   \
 334   }                                                                           \
 335
 336 #define gbc_sound_render_sample_right()                                       \
 337   sound_buffer[buffer_index + 1] += (current_sample * volume_right) >> 22     \
 338
 339 #define gbc_sound_render_sample_left()                                        \
 340   sound_buffer[buffer_index] += (current_sample * volume_left) >> 22          \
 341
 342 #define gbc_sound_render_sample_both()                                        \
 343   gbc_sound_render_sample_right();                                            \
 344   gbc_sound_render_sample_left()                                              \
 345
 346 #define gbc_sound_render_samples(type, sample_length, envelope_op, sweep_op)  \
 347   for(i = 0; i < buffer_ticks; i++)                                           \
 348   {                                                                           \
 349     current_sample =                                                          \
 350      sample_data[fp16_16_to_u32(sample_index) % sample_length];               \
 351     gbc_sound_render_sample_##type();                                         \
 352                                                                               \
 353     sample_index += frequency_step;                                           \
 354     buffer_index = (buffer_index + 2) % BUFFER_SIZE;                          \
 355                                                                               \
 356     update_tone_counters(envelope_op, sweep_op);                              \
 357   }                                                                           \
 358
 359 #define gbc_noise_wrap_full 32767
 360
 361 #define gbc_noise_wrap_half 126
 362
 363 #define get_noise_sample_full()                                               \
 364   current_sample =                                                            \
 365    ((s32)(noise_table15[fp16_16_to_u32(sample_index) >> 5] <<                 \
 366    (fp16_16_to_u32(sample_index) & 0x1F)) >> 31) & 0x0F                       \
 367
 368 #define get_noise_sample_half()                                               \
 369   current_sample =                                                            \
 370    ((s32)(noise_table7[fp16_16_to_u32(sample_index) >> 5] <<                  \
 371    (fp16_16_to_u32(sample_index) & 0x1F)) >> 31) & 0x0F                       \
 372
 373 #define gbc_sound_render_noise(type, noise_type, envelope_op, sweep_op)       \
 374   for(i = 0; i < buffer_ticks; i++)                                           \
 375   {                                                                           \
 376     get_noise_sample_##noise_type();                                          \
 377     gbc_sound_render_sample_##type();                                         \
 378                                                                               \
 379     sample_index += frequency_step;                                           \
 380                                                                               \
 381     if(sample_index >= u32_to_fp16_16(gbc_noise_wrap_##noise_type))           \
 382       sample_index -= u32_to_fp16_16(gbc_noise_wrap_##noise_type);            \
 383                                                                               \
 384     buffer_index = (buffer_index + 2) % BUFFER_SIZE;                          \
 385     update_tone_counters(envelope_op, sweep_op);                              \
 386   }                                                                           \
 387
 388 #define gbc_sound_render_channel(type, sample_length, envelope_op, sweep_op)  \
 389   buffer_index = gbc_sound_buffer_index;                                      \
 390   sample_index = gs->sample_index;                                            \
 391   frequency_step = gs->frequency_step;                                        \
 392   tick_counter = gs->tick_counter;                                            \
 393                                                                               \
 394   update_volume(envelope_op);                                                 \
 395                                                                               \
 396   switch(gs->status)                                                          \
 397   {                                                                           \
 398     case GBC_SOUND_INACTIVE:                                                  \
 399       break;                                                                  \
 400                                                                               \
 401     case GBC_SOUND_LEFT:                                                      \
 402       gbc_sound_render_##type(left, sample_length, envelope_op, sweep_op);    \
 403       break;                                                                  \
 404                                                                               \
 405     case GBC_SOUND_RIGHT:                                                     \
 406       gbc_sound_render_##type(right, sample_length, envelope_op, sweep_op);   \
 407       break;                                                                  \
 408                                                                               \
 409     case GBC_SOUND_LEFTRIGHT:                                                 \
 410       gbc_sound_render_##type(both, sample_length, envelope_op, sweep_op);    \
 411       break;                                                                  \
 412   }                                                                           \
 413                                                                               \
 414   gs->sample_index = sample_index;                                            \
 415   gs->tick_counter = tick_counter;                                            \
 416
 417 #define gbc_sound_load_wave_ram(bank)                                         \
 418   wave_bank = wave_samples + (bank * 32);                                     \
 419   for(i = 0, i2 = 0; i < 16; i++, i2 += 2)                                    \
 420   {                                                                           \
 421     current_sample = wave_ram[i];                                             \
 422     wave_bank[i2] = (((current_sample >> 4) & 0x0F) - 8);                     \
 423     wave_bank[i2 + 1] = ((current_sample & 0x0F) - 8);                        \
 424   }                                                                           \
 425
 426 void update_gbc_sound(u32 cpu_ticks)
 427 {
 428   fixed16_16 buffer_ticks = float_to_fp16_16((float)(cpu_ticks -
 429    gbc_sound_last_cpu_ticks) * sound_frequency / GBC_BASE_RATE);
 430   u32 i, i2;
 431   gbc_sound_struct *gs = gbc_sound_channel;
 432   fixed16_16 sample_index, frequency_step;
 433   fixed16_16 tick_counter;
 434   u32 buffer_index;
 435   s32 volume_left, volume_right;
 436   u32 envelope_volume;
 437   s32 current_sample;
 438   u32 sound_status = address16(io_registers, 0x84) & 0xFFF0;
 439   s8 *sample_data;
 440   s8 *wave_bank;
 441   u8 *wave_ram = ((u8 *)io_registers) + 0x90;
 442
 443   gbc_sound_partial_ticks += fp16_16_fractional_part(buffer_ticks);
 444   buffer_ticks = fp16_16_to_u32(buffer_ticks);
 445
 446   if(gbc_sound_partial_ticks > 0xFFFF)
 447   {
 448     buffer_ticks += 1;
 449     gbc_sound_partial_ticks &= 0xFFFF;
 450   }
 451
 452   SDL_LockMutex(sound_mutex);
 453   if(synchronize_flag)
 454   {
 455     if(((gbc_sound_buffer_index - sound_buffer_base) % BUFFER_SIZE) >=
 456      (audio_buffer_size * 2))
 457     {
 458       while(((gbc_sound_buffer_index - sound_buffer_base) % BUFFER_SIZE) >
 459        (audio_buffer_size * 3 / 2))
 460       {
 461         SDL_CondWait(sound_cv, sound_mutex);
 462       }
 463
 464 #ifdef PSP_BUILD
 465       if(current_frameskip_type == auto_frameskip)
 466       {
 467         sceDisplayWaitVblankStart();
 468         real_frame_count = 0;
 469         virtual_frame_count = 0;
 470       }
 471 #else
 472       if(current_frameskip_type == auto_frameskip)
 473       {
 474 /*
 475         u64 current_ticks;
 476         u64 next_ticks;
 477         get_ticks_us(&current_ticks);
 478
 479         next_ticks = ((current_ticks + 16666) / 16667) * 16667;
 480         delay_us(next_ticks - current_ticks);
 481
 482         get_ticks_us(&frame_count_initial_timestamp);
 483 */
 484         /* prevent frameskip, or it will cause more audio,
 485          * then more waiting here, then frame skip again, ... */
 486         num_skipped_frames = 100;
 487       }
 488 #endif
 489
 490     }
 491   }
 492   if(sound_on == 1)
 493   {
 494     gs = gbc_sound_channel + 0;
 495     if(gs->active_flag)
 496     {
 497       sound_status |= 0x01;
 498       sample_data = gs->sample_data;
 499       envelope_volume = gs->envelope_volume;
 500       gbc_sound_render_channel(samples, 8, envelope, sweep);
 501     }
 502
 503     gs = gbc_sound_channel + 1;
 504     if(gs->active_flag)
 505     {
 506       sound_status |= 0x02;
 507       sample_data = gs->sample_data;
 508       envelope_volume = gs->envelope_volume;
 509       gbc_sound_render_channel(samples, 8, envelope, nosweep);
 510     }
 511
 512     gs = gbc_sound_channel + 2;
 513     if(gbc_sound_wave_update)
 514     {
 515       if(gs->wave_bank == 1)
 516       {
 517         gbc_sound_load_wave_ram(1);
 518       }
 519       else
 520       {
 521         gbc_sound_load_wave_ram(0);
 522       }
 523
 524       gbc_sound_wave_update = 0;
 525     }
 526
 527     if((gs->active_flag) && (gs->master_enable))
 528     {
 529       sound_status |= 0x04;
 530       sample_data = wave_samples;
 531       if(gs->wave_type == 0)
 532       {
 533         if(gs->wave_bank == 1)
 534           sample_data += 32;
 535
 536         gbc_sound_render_channel(samples, 32, noenvelope, nosweep);
 537       }
 538       else
 539       {
 540         gbc_sound_render_channel(samples, 64, noenvelope, nosweep);
 541       }
 542     }
 543
 544     gs = gbc_sound_channel + 3;
 545     if(gs->active_flag)
 546     {
 547       sound_status |= 0x08;
 548       envelope_volume = gs->envelope_volume;
 549
 550       if(gs->noise_type == 1)
 551       {
 552         gbc_sound_render_channel(noise, half, envelope, nosweep);
 553       }
 554       else
 555       {
 556         gbc_sound_render_channel(noise, full, envelope, nosweep);
 557       }
 558     }
 559   }
 560
 561   address16(io_registers, 0x84) = sound_status;
 562
 563   gbc_sound_last_cpu_ticks = cpu_ticks;
 564   gbc_sound_buffer_index =
 565    (gbc_sound_buffer_index + (buffer_ticks * 2)) % BUFFER_SIZE;
 566
 567   SDL_UnlockMutex(sound_mutex);
 568
 569   SDL_CondSignal(sound_cv);
 570 }
 571
 572 #define sound_copy_normal()                                                   \
 573   current_sample = source[i]                                                  \
 574
 575 #define sound_copy(source_offset, length, render_type)                        \
 576   _length = (length) / 2;                                                     \
 577   source = (s16 *)(sound_buffer + source_offset);                             \
 578   for(i = 0; i < _length; i++)                                                \
 579   {                                                                           \
 580     sound_copy_##render_type();                                               \
 581     if(current_sample > 2047)                                                 \
 582       current_sample = 2047;                                                  \
 583     if(current_sample < -2048)                                                \
 584       current_sample = -2048;                                                 \
 585                                                                               \
 586     stream_base[i] = current_sample << 4;                                     \
 587     source[i] = 0;                                                            \
 588   }                                                                           \
 589
 590 #define sound_copy_null(source_offset, length)                                \
 591   _length = (length) / 2;                                                     \
 592   source = (s16 *)(sound_buffer + source_offset);                             \
 593   for(i = 0; i < _length; i++)                                                \
 594   {                                                                           \
 595     stream_base[i] = 0;                                                       \
 596     source[i] = 0;                                                            \
 597   }                                                                           \
 598
 599
 600 void sound_callback(void *userdata, Uint8 *stream, int length)
 601 {
 602   u32 sample_length = length / 2;
 603   u32 _length;
 604   u32 i;
 605   s16 *stream_base = (s16 *)stream;
 606   s16 *source;
 607   s32 current_sample;
 608
 609   SDL_LockMutex(sound_mutex);
 610
 611   while(((gbc_sound_buffer_index - sound_buffer_base) % BUFFER_SIZE) <
 612    length && !sound_exit_flag)
 613   {
 614     SDL_CondWait(sound_cv, sound_mutex);
 615   }
 616
 617   if(global_enable_audio)
 618   {
 619     if((sound_buffer_base + sample_length) >= BUFFER_SIZE)
 620     {
 621       u32 partial_length = (BUFFER_SIZE - sound_buffer_base) * 2;
 622       sound_copy(sound_buffer_base, partial_length, normal);
 623       source = (s16 *)sound_buffer;
 624       sound_copy(0, length - partial_length, normal);
 625       sound_buffer_base = (length - partial_length) / 2;
 626     }
 627     else
 628     {
 629       sound_copy(sound_buffer_base, length, normal);
 630       sound_buffer_base += sample_length;
 631     }
 632   }
 633   else
 634   {
 635     if((sound_buffer_base + sample_length) >= BUFFER_SIZE)
 636     {
 637       u32 partial_length = (BUFFER_SIZE - sound_buffer_base) * 2;
 638       sound_copy_null(sound_buffer_base, partial_length);
 639       source = (s16 *)sound_buffer;
 640       sound_copy(0, length - partial_length, normal);
 641       sound_buffer_base = (length - partial_length) / 2;
 642     }
 643     else
 644     {
 645       sound_copy_null(sound_buffer_base, length);
 646       sound_buffer_base += sample_length;
 647     }
 648   }
 649
 650   SDL_CondSignal(sound_cv);
 651
 652   SDL_UnlockMutex(sound_mutex);
 653 }
 654
 655 // Special thanks to blarrg for the LSFR frequency used in Meridian, as posted
 656 // on the forum at http://meridian.overclocked.org:
 657 // http://meridian.overclocked.org/cgi-bin/wwwthreads/showpost.pl?Board=merid
 658 // angeneraldiscussion&Number=2069&page=0&view=expanded&mode=threaded&sb=4
 659 // Hope you don't mind me borrowing it ^_-
 660
 661 void init_noise_table(u32 *table, u32 period, u32 bit_length)
 662 {
 663   u32 shift_register = 0xFF;
 664   u32 mask = ~(1 << bit_length);
 665   s32 table_pos, bit_pos;
 666   u32 current_entry;
 667   u32 table_period = (period + 31) / 32;
 668
 669   // Bits are stored in reverse order so they can be more easily moved to
 670   // bit 31, for sign extended shift down.
 671
 672   for(table_pos = 0; table_pos < table_period; table_pos++)
 673   {
 674     current_entry = 0;
 675     for(bit_pos = 31; bit_pos >= 0; bit_pos--)
 676     {
 677       current_entry |= (shift_register & 0x01) << bit_pos;
 678
 679       shift_register =
 680        ((1 & (shift_register ^ (shift_register >> 1))) << bit_length) |
 681        ((shift_register >> 1) & mask);
 682     }
 683
 684     table[table_pos] = current_entry;
 685   }
 686 }
 687
 688 void reset_sound()
 689 {
 690   direct_sound_struct *ds = direct_sound_channel;
 691   gbc_sound_struct *gs = gbc_sound_channel;
 692   u32 i;
 693
 694   SDL_LockMutex(sound_mutex);
 695
 696   sound_on = 0;
 697   sound_buffer_base = 0;
 698   sound_last_cpu_ticks = 0;
 699   memset(sound_buffer, 0, sizeof(sound_buffer));
 700
 701   for(i = 0; i < 2; i++, ds++)
 702   {
 703     ds->buffer_index = 0;
 704     ds->status = DIRECT_SOUND_INACTIVE;
 705     ds->fifo_top = 0;
 706     ds->fifo_base = 0;
 707     ds->fifo_fractional = 0;
 708     ds->last_cpu_ticks = 0;
 709     memset(ds->fifo, 0, 32);
 710   }
 711
 712   gbc_sound_buffer_index = 0;
 713   gbc_sound_last_cpu_ticks = 0;
 714   gbc_sound_partial_ticks = 0;
 715
 716   gbc_sound_master_volume_left = 0;
 717   gbc_sound_master_volume_right = 0;
 718   gbc_sound_master_volume = 0;
 719   memset(wave_samples, 0, 64);
 720
 721   for(i = 0; i < 4; i++, gs++)
 722   {
 723     gs->status = GBC_SOUND_INACTIVE;
 724     gs->sample_data = square_pattern_duty[2];
 725     gs->active_flag = 0;
 726   }
 727
 728   SDL_UnlockMutex(sound_mutex);
 729 }
 730
 731 void sound_exit()
 732 {
 733   gbc_sound_buffer_index =
 734    (sound_buffer_base + audio_buffer_size) % BUFFER_SIZE;
 735   SDL_PauseAudio(1);
 736   sound_exit_flag = 1;
 737   SDL_CondSignal(sound_cv);
 738   SDL_CloseAudio();
 739   SDL_Delay(200);
 740   SDL_DestroyMutex(sound_mutex);
 741   sound_mutex = NULL;
 742   SDL_DestroyCond(sound_cv);
 743   sound_cv = NULL;
 744 }
 745
 746 void init_sound(int need_reset)
 747 {
 748   SDL_AudioSpec sound_settings;
 749
 750   sound_exit_flag = 0;
 751 #ifdef PSP_BUILD
 752   audio_buffer_size = (audio_buffer_size_number * 1024) + 3072;
 753 #else
 754   audio_buffer_size = 16 << audio_buffer_size_number;
 755 //  audio_buffer_size = 16384;
 756 #endif
 757
 758   SDL_AudioSpec desired_spec =
 759   {
 760     sound_frequency,
 761     AUDIO_S16,
 762     2,
 763     0,
 764     audio_buffer_size / 4,
 765     0,
 766     0,
 767     sound_callback,
 768     NULL
 769   };
 770
 771   sound_mutex = SDL_CreateMutex();
 772   sound_cv = SDL_CreateCond();
 773
 774   SDL_OpenAudio(&desired_spec, &sound_settings);
 775   sound_frequency = sound_settings.freq;
 776   audio_buffer_size = sound_settings.size;
 777   u32 i = audio_buffer_size / 16;
 778   for (audio_buffer_size_number = 0; i && (i & 1) == 0; i >>= 1)
 779     audio_buffer_size_number++;
 780 #ifndef PSP_BUILD
 781   printf("audio: freq %d, size %d\n", sound_frequency, audio_buffer_size);
 782 #endif
 783
 784   gbc_sound_tick_step =
 785    float_to_fp16_16(256.0f / sound_frequency);
 786
 787   init_noise_table(noise_table15, 32767, 14);
 788   init_noise_table(noise_table7, 127, 6);
 789
 790   if (need_reset)
 791     reset_sound();
 792
 793   SDL_PauseAudio(0);
 794 }
 795
 796 #define sound_savestate_builder(type)                                       \
 797 void sound_##type##_savestate(file_tag_type savestate_file)                 \
 798 {                                                                           \
 799   file_##type##_variable(savestate_file, sound_on);                         \
 800   file_##type##_variable(savestate_file, sound_buffer_base);                \
 801   file_##type##_variable(savestate_file, sound_last_cpu_ticks);             \
 802   file_##type##_variable(savestate_file, gbc_sound_buffer_index);           \
 803   file_##type##_variable(savestate_file, gbc_sound_last_cpu_ticks);         \
 804   file_##type##_variable(savestate_file, gbc_sound_partial_ticks);          \
 805   file_##type##_variable(savestate_file, gbc_sound_master_volume_left);     \
 806   file_##type##_variable(savestate_file, gbc_sound_master_volume_right);    \
 807   file_##type##_variable(savestate_file, gbc_sound_master_volume);          \
 808   file_##type##_array(savestate_file, wave_samples);                        \
 809   file_##type##_array(savestate_file, direct_sound_channel);                \
 810   file_##type##_array(savestate_file, gbc_sound_channel);                   \
 811 }                                                                           \
 812
 813 sound_savestate_builder(read);
 814 sound_savestate_builder(write_mem);
 815