snd_mix.c

   1 /*
   2 Copyright (C) 1996-1997 Id Software, Inc.
   3
   4 This program is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU General Public License
   6 as published by the Free Software Foundation; either version 2
   7 of the License, or (at your option) any later version.
   8
   9 This program is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  12
  13 See the GNU 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  18
  19 */
  20
  21 #include "quakedef.h"
  22 #include "snd_main.h"
  23
  24
  25 static portable_sampleframe_t paintbuffer[PAINTBUFFER_SIZE];
  26 static portable_sampleframe_t paintbuffer_unswapped[PAINTBUFFER_SIZE];
  27
  28 extern speakerlayout_t snd_speakerlayout; // for querying the listeners
  29
  30 extern void SCR_CaptureVideo_SoundFrame(const portable_sampleframe_t *paintbuffer, size_t length);
  31 static void S_CaptureAVISound(size_t length)
  32 {
  33         size_t i;
  34         unsigned int j;
  35
  36         if (!cls.capturevideo.active)
  37                 return;
  38
  39         // undo whatever swapping the channel layout (swapstereo, ALSA) did
  40         for(j = 0; j < snd_speakerlayout.channels; ++j)
  41         {
  42                 unsigned int j0 = snd_speakerlayout.listeners[j].channel_unswapped;
  43                 for(i = 0; i < length; ++i)
  44                         paintbuffer_unswapped[i].sample[j0] = paintbuffer[i].sample[j];
  45         }
  46
  47         SCR_CaptureVideo_SoundFrame(paintbuffer_unswapped, length);
  48 }
  49
  50 static void S_ConvertPaintBuffer(const portable_sampleframe_t *painted_ptr, void *rb_ptr, int nbframes, int width, int channels)
  51 {
  52         int i, val;
  53         if (width == 2)  // 16bit
  54         {
  55                 short *snd_out = (short*)rb_ptr;
  56                 if (channels == 8)  // 7.1 surround
  57                 {
  58                         for (i = 0;i < nbframes;i++, painted_ptr++)
  59                         {
  60                                 *snd_out++ = bound(-32768, painted_ptr->sample[0], 32767);
  61                                 *snd_out++ = bound(-32768, painted_ptr->sample[1], 32767);
  62                                 *snd_out++ = bound(-32768, painted_ptr->sample[2], 32767);
  63                                 *snd_out++ = bound(-32768, painted_ptr->sample[3], 32767);
  64                                 *snd_out++ = bound(-32768, painted_ptr->sample[4], 32767);
  65                                 *snd_out++ = bound(-32768, painted_ptr->sample[5], 32767);
  66                                 *snd_out++ = bound(-32768, painted_ptr->sample[6], 32767);
  67                                 *snd_out++ = bound(-32768, painted_ptr->sample[7], 32767);
  68                         }
  69                 }
  70                 else if (channels == 6)  // 5.1 surround
  71                 {
  72                         for (i = 0; i < nbframes; i++, painted_ptr++)
  73                         {
  74                                 *snd_out++ = bound(-32768, painted_ptr->sample[0], 32767);
  75                                 *snd_out++ = bound(-32768, painted_ptr->sample[1], 32767);
  76                                 *snd_out++ = bound(-32768, painted_ptr->sample[2], 32767);
  77                                 *snd_out++ = bound(-32768, painted_ptr->sample[3], 32767);
  78                                 *snd_out++ = bound(-32768, painted_ptr->sample[4], 32767);
  79                                 *snd_out++ = bound(-32768, painted_ptr->sample[5], 32767);
  80                         }
  81                 }
  82                 else if (channels == 4)  // 4.0 surround
  83                 {
  84                         for (i = 0; i < nbframes; i++, painted_ptr++)
  85                         {
  86                                 *snd_out++ = bound(-32768, painted_ptr->sample[0], 32767);
  87                                 *snd_out++ = bound(-32768, painted_ptr->sample[1], 32767);
  88                                 *snd_out++ = bound(-32768, painted_ptr->sample[2], 32767);
  89                                 *snd_out++ = bound(-32768, painted_ptr->sample[3], 32767);
  90                         }
  91                 }
  92                 else if (channels == 2)  // 2.0 stereo
  93                 {
  94                         for (i = 0; i < nbframes; i++, painted_ptr++)
  95                         {
  96                                 *snd_out++ = bound(-32768, painted_ptr->sample[0], 32767);
  97                                 *snd_out++ = bound(-32768, painted_ptr->sample[1], 32767);
  98                         }
  99                 }
 100                 else if (channels == 1)  // 1.0 mono
 101                 {
 102                         for (i = 0; i < nbframes; i++, painted_ptr++)
 103                         {
 104                                 val = (painted_ptr->sample[0] + painted_ptr->sample[1]) >> 1;
 105                                 *snd_out++ = bound(-32768, val, 32767);
 106                         }
 107                 }
 108
 109                 // noise is really really annoying
 110                 if (cls.timedemo)
 111                         memset(rb_ptr, 0, nbframes * channels * width);
 112         }
 113         else  // 8bit
 114         {
 115                 unsigned char *snd_out = (unsigned char*)rb_ptr;
 116                 if (channels == 8)  // 7.1 surround
 117                 {
 118                         for (i = 0; i < nbframes; i++, painted_ptr++)
 119                         {
 120                                 val = (painted_ptr->sample[0] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 121                                 val = (painted_ptr->sample[1] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 122                                 val = (painted_ptr->sample[2] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 123                                 val = (painted_ptr->sample[3] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 124                                 val = (painted_ptr->sample[4] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 125                                 val = (painted_ptr->sample[5] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 126                                 val = (painted_ptr->sample[6] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 127                                 val = (painted_ptr->sample[7] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 128                         }
 129                 }
 130                 else if (channels == 6)  // 5.1 surround
 131                 {
 132                         for (i = 0; i < nbframes; i++, painted_ptr++)
 133                         {
 134                                 val = (painted_ptr->sample[0] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 135                                 val = (painted_ptr->sample[1] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 136                                 val = (painted_ptr->sample[2] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 137                                 val = (painted_ptr->sample[3] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 138                                 val = (painted_ptr->sample[4] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 139                                 val = (painted_ptr->sample[5] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 140                         }
 141                 }
 142                 else if (channels == 4)  // 4.0 surround
 143                 {
 144                         for (i = 0; i < nbframes; i++, painted_ptr++)
 145                         {
 146                                 val = (painted_ptr->sample[0] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 147                                 val = (painted_ptr->sample[1] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 148                                 val = (painted_ptr->sample[2] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 149                                 val = (painted_ptr->sample[3] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 150                         }
 151                 }
 152                 else if (channels == 2)  // 2.0 stereo
 153                 {
 154                         for (i = 0; i < nbframes; i++, painted_ptr++)
 155                         {
 156                                 val = (painted_ptr->sample[0] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 157                                 val = (painted_ptr->sample[1] >> 8) + 128; *snd_out++ = bound(0, val, 255);
 158                         }
 159                 }
 160                 else if (channels == 1)  // 1.0 mono
 161                 {
 162                         for (i = 0;i < nbframes;i++, painted_ptr++)
 163                         {
 164                                 val = ((painted_ptr->sample[0] + painted_ptr->sample[1]) >> 9) + 128;
 165                                 *snd_out++ = bound(0, val, 255);
 166                         }
 167                 }
 168
 169                 // noise is really really annoying
 170                 if (cls.timedemo)
 171                         memset(rb_ptr, 128, nbframes * channels);
 172         }
 173 }
 174
 175
 176 /*
 177 ===============================================================================
 178
 179 CHANNEL MIXING
 180
 181 ===============================================================================
 182 */
 183
 184 static qboolean SND_PaintChannel (channel_t *ch, portable_sampleframe_t *paint, unsigned int count)
 185 {
 186         int vol[SND_LISTENERS];
 187         const snd_buffer_t *sb;
 188         unsigned int i, sb_offset;
 189         sfx_t *sfx;
 190
 191         sfx = ch->sfx; // fetch the volatile variable
 192         if (!sfx) // given that this is called by the mixer thread, this never happens, but...
 193                 return false;
 194
 195         // move to the stack (do we need to?)
 196         for (i = 0;i < SND_LISTENERS;i++)
 197                 vol[i] = ch->listener_volume[i];
 198
 199         // if volumes are all zero, just return
 200         for (i = 0;i < SND_LISTENERS;i++)
 201                 if (vol[i])
 202                         break;
 203         if (i == SND_LISTENERS)
 204                 return false;
 205
 206         sb_offset = ch->pos;
 207         sb = sfx->fetcher->getsb (sfx->fetcher_data, &ch->fetcher_data, &sb_offset, count);
 208         if (sb == NULL)
 209         {
 210                 Con_DPrintf("SND_PaintChannel: ERROR: can't get sound buffer from sfx \"%s\"\n",
 211                                         sfx->name); // , count); // or add this? FIXME
 212                 return false;
 213         }
 214         else
 215         {
 216 #if SND_LISTENERS != 8
 217 #               error the following code only supports up to 8 channels, update it
 218 #endif
 219                 if (sb->format.width == 1)
 220                 {
 221                         const signed char *samples = (signed char*)sb->samples + (ch->pos - sb_offset) * sb->format.channels;
 222
 223                         // Stereo sound support
 224                         if (sb->format.channels == 2)
 225                         {
 226                                 if (vol[6] + vol[7] > 0)
 227                                 {
 228                                         for (i = 0;i < count;i++)
 229                                         {
 230                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 8;
 231                                                 paint[i].sample[1] += (samples[1] * vol[1]) >> 8;
 232                                                 paint[i].sample[2] += (samples[0] * vol[2]) >> 8;
 233                                                 paint[i].sample[3] += (samples[1] * vol[3]) >> 8;
 234                                                 paint[i].sample[4] += ((samples[0] + samples[1]) * vol[4]) >> 9;
 235                                                 paint[i].sample[5] += ((samples[0] + samples[1]) * vol[5]) >> 9;
 236                                                 paint[i].sample[6] += (samples[0] * vol[6]) >> 8;
 237                                                 paint[i].sample[7] += (samples[1] * vol[7]) >> 8;
 238                                                 samples += 2;
 239                                         }
 240                                 }
 241                                 else if (vol[4] + vol[5] > 0)
 242                                 {
 243                                         for (i = 0;i < count;i++)
 244                                         {
 245                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 8;
 246                                                 paint[i].sample[1] += (samples[1] * vol[1]) >> 8;
 247                                                 paint[i].sample[2] += (samples[0] * vol[2]) >> 8;
 248                                                 paint[i].sample[3] += (samples[1] * vol[3]) >> 8;
 249                                                 paint[i].sample[4] += ((samples[0] + samples[1]) * vol[4]) >> 9;
 250                                                 paint[i].sample[5] += ((samples[0] + samples[1]) * vol[5]) >> 9;
 251                                                 samples += 2;
 252                                         }
 253                                 }
 254                                 else if (vol[2] + vol[3] > 0)
 255                                 {
 256                                         for (i = 0;i < count;i++)
 257                                         {
 258                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 8;
 259                                                 paint[i].sample[1] += (samples[1] * vol[1]) >> 8;
 260                                                 paint[i].sample[2] += (samples[0] * vol[2]) >> 8;
 261                                                 paint[i].sample[3] += (samples[1] * vol[3]) >> 8;
 262                                                 samples += 2;
 263                                         }
 264                                 }
 265                                 else if (vol[0] + vol[1] > 0 && ch->prologic_invert == -1)
 266                                 {
 267                                         for (i = 0;i < count;i++)
 268                                         {
 269                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 8;
 270                                                 paint[i].sample[1] -= (samples[1] * vol[1]) >> 8;
 271                                                 samples += 2;
 272                                         }
 273                                 }
 274                                 else if (vol[0] + vol[1] > 0)
 275                                 {
 276                                         for (i = 0;i < count;i++)
 277                                         {
 278                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 8;
 279                                                 paint[i].sample[1] += (samples[1] * vol[1]) >> 8;
 280                                                 samples += 2;
 281                                         }
 282                                 }
 283                         }
 284                         else if (sb->format.channels == 1)
 285                         {
 286                                 if (vol[6] + vol[7] > 0)
 287                                 {
 288                                         for (i = 0;i < count;i++)
 289                                         {
 290                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 8;
 291                                                 paint[i].sample[1] += (samples[0] * vol[1]) >> 8;
 292                                                 paint[i].sample[2] += (samples[0] * vol[2]) >> 8;
 293                                                 paint[i].sample[3] += (samples[0] * vol[3]) >> 8;
 294                                                 paint[i].sample[4] += (samples[0] * vol[4]) >> 8;
 295                                                 paint[i].sample[5] += (samples[0] * vol[5]) >> 8;
 296                                                 paint[i].sample[6] += (samples[0] * vol[6]) >> 8;
 297                                                 paint[i].sample[7] += (samples[0] * vol[7]) >> 8;
 298                                                 samples += 1;
 299                                         }
 300                                 }
 301                                 else if (vol[4] + vol[5] > 0)
 302                                 {
 303                                         for (i = 0;i < count;i++)
 304                                         {
 305                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 8;
 306                                                 paint[i].sample[1] += (samples[0] * vol[1]) >> 8;
 307                                                 paint[i].sample[2] += (samples[0] * vol[2]) >> 8;
 308                                                 paint[i].sample[3] += (samples[0] * vol[3]) >> 8;
 309                                                 paint[i].sample[4] += (samples[0] * vol[4]) >> 8;
 310                                                 paint[i].sample[5] += (samples[0] * vol[5]) >> 8;
 311                                                 samples += 1;
 312                                         }
 313                                 }
 314                                 else if (vol[2] + vol[3] > 0)
 315                                 {
 316                                         for (i = 0;i < count;i++)
 317                                         {
 318                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 8;
 319                                                 paint[i].sample[1] += (samples[0] * vol[1]) >> 8;
 320                                                 paint[i].sample[2] += (samples[0] * vol[2]) >> 8;
 321                                                 paint[i].sample[3] += (samples[0] * vol[3]) >> 8;
 322                                                 samples += 1;
 323                                         }
 324                                 }
 325                                 else if (vol[0] + vol[1] > 0 && ch->prologic_invert == -1)
 326                                 {
 327                                         for (i = 0;i < count;i++)
 328                                         {
 329                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 8;
 330                                                 paint[i].sample[1] -= (samples[0] * vol[1]) >> 8;
 331                                                 samples += 1;
 332                                         }
 333                                 }
 334                                 else if (vol[0] + vol[1] > 0)
 335                                 {
 336                                         for (i = 0;i < count;i++)
 337                                         {
 338                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 8;
 339                                                 paint[i].sample[1] += (samples[0] * vol[1]) >> 8;
 340                                                 samples += 1;
 341                                         }
 342                                 }
 343                         }
 344                         else
 345                                 return false; // unsupported number of channels in sound
 346                 }
 347                 else if (sb->format.width == 2)
 348                 {
 349                         const signed short *samples = (signed short*)sb->samples + (ch->pos - sb_offset) * sb->format.channels;
 350
 351                         // Stereo sound support
 352                         if (sb->format.channels == 2)
 353                         {
 354                                 if (vol[6] + vol[7] > 0)
 355                                 {
 356                                         for (i = 0;i < count;i++)
 357                                         {
 358                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 16;
 359                                                 paint[i].sample[1] += (samples[1] * vol[1]) >> 16;
 360                                                 paint[i].sample[2] += (samples[0] * vol[2]) >> 16;
 361                                                 paint[i].sample[3] += (samples[1] * vol[3]) >> 16;
 362                                                 paint[i].sample[4] += ((samples[0] + samples[1]) * vol[4]) >> 17;
 363                                                 paint[i].sample[5] += ((samples[0] + samples[1]) * vol[5]) >> 17;
 364                                                 paint[i].sample[6] += (samples[0] * vol[6]) >> 16;
 365                                                 paint[i].sample[7] += (samples[1] * vol[7]) >> 16;
 366                                                 samples += 2;
 367                                         }
 368                                 }
 369                                 else if (vol[4] + vol[5] > 0)
 370                                 {
 371                                         for (i = 0;i < count;i++)
 372                                         {
 373                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 16;
 374                                                 paint[i].sample[1] += (samples[1] * vol[1]) >> 16;
 375                                                 paint[i].sample[2] += (samples[0] * vol[2]) >> 16;
 376                                                 paint[i].sample[3] += (samples[1] * vol[3]) >> 16;
 377                                                 paint[i].sample[4] += ((samples[0] + samples[1]) * vol[4]) >> 17;
 378                                                 paint[i].sample[5] += ((samples[0] + samples[1]) * vol[5]) >> 17;
 379                                                 samples += 2;
 380                                         }
 381                                 }
 382                                 else if (vol[2] + vol[3] > 0)
 383                                 {
 384                                         for (i = 0;i < count;i++)
 385                                         {
 386                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 16;
 387                                                 paint[i].sample[1] += (samples[1] * vol[1]) >> 16;
 388                                                 paint[i].sample[2] += (samples[0] * vol[2]) >> 16;
 389                                                 paint[i].sample[3] += (samples[1] * vol[3]) >> 16;
 390                                                 samples += 2;
 391                                         }
 392                                 }
 393                                 else if (vol[0] + vol[1] > 0 && ch->prologic_invert == -1)
 394                                 {
 395                                         for (i = 0;i < count;i++)
 396                                         {
 397                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 16;
 398                                                 paint[i].sample[1] -= (samples[1] * vol[1]) >> 16;
 399                                                 samples += 2;
 400                                         }
 401                                 }
 402                                 else if (vol[0] + vol[1] > 0)
 403                                 {
 404                                         for (i = 0;i < count;i++)
 405                                         {
 406                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 16;
 407                                                 paint[i].sample[1] += (samples[1] * vol[1]) >> 16;
 408                                                 samples += 2;
 409                                         }
 410                                 }
 411                         }
 412                         else if (sb->format.channels == 1)
 413                         {
 414                                 if (vol[6] + vol[7] > 0)
 415                                 {
 416                                         for (i = 0;i < count;i++)
 417                                         {
 418                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 16;
 419                                                 paint[i].sample[1] += (samples[0] * vol[1]) >> 16;
 420                                                 paint[i].sample[2] += (samples[0] * vol[2]) >> 16;
 421                                                 paint[i].sample[3] += (samples[0] * vol[3]) >> 16;
 422                                                 paint[i].sample[4] += (samples[0] * vol[4]) >> 16;
 423                                                 paint[i].sample[5] += (samples[0] * vol[5]) >> 16;
 424                                                 paint[i].sample[6] += (samples[0] * vol[6]) >> 16;
 425                                                 paint[i].sample[7] += (samples[0] * vol[7]) >> 16;
 426                                                 samples += 1;
 427                                         }
 428                                 }
 429                                 else if (vol[4] + vol[5] > 0)
 430                                 {
 431                                         for (i = 0;i < count;i++)
 432                                         {
 433                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 16;
 434                                                 paint[i].sample[1] += (samples[0] * vol[1]) >> 16;
 435                                                 paint[i].sample[2] += (samples[0] * vol[2]) >> 16;
 436                                                 paint[i].sample[3] += (samples[0] * vol[3]) >> 16;
 437                                                 paint[i].sample[4] += (samples[0] * vol[4]) >> 16;
 438                                                 paint[i].sample[5] += (samples[0] * vol[5]) >> 16;
 439                                                 samples += 1;
 440                                         }
 441                                 }
 442                                 else if (vol[2] + vol[3] > 0)
 443                                 {
 444                                         for (i = 0;i < count;i++)
 445                                         {
 446                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 16;
 447                                                 paint[i].sample[1] += (samples[0] * vol[1]) >> 16;
 448                                                 paint[i].sample[2] += (samples[0] * vol[2]) >> 16;
 449                                                 paint[i].sample[3] += (samples[0] * vol[3]) >> 16;
 450                                                 samples += 1;
 451                                         }
 452                                 }
 453                                 else if (vol[0] + vol[1] > 0 && ch->prologic_invert == -1)
 454                                 {
 455                                         for (i = 0;i < count;i++)
 456                                         {
 457                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 16;
 458                                                 paint[i].sample[1] -= (samples[0] * vol[1]) >> 16;
 459                                                 samples += 1;
 460                                         }
 461                                 }
 462                                 else if (vol[0] + vol[1] > 0)
 463                                 {
 464                                         for (i = 0;i < count;i++)
 465                                         {
 466                                                 paint[i].sample[0] += (samples[0] * vol[0]) >> 16;
 467                                                 paint[i].sample[1] += (samples[0] * vol[1]) >> 16;
 468                                                 samples += 1;
 469                                         }
 470                                 }
 471                         }
 472                         else
 473                                 return false; // unsupported number of channels in sound
 474                 }
 475         }
 476         return true;
 477 }
 478
 479 void S_MixToBuffer(void *stream, unsigned int bufferframes)
 480 {
 481         unsigned int i;
 482         channel_t *ch;
 483         unsigned int frames;
 484         unsigned char *outbytes = (unsigned char *) stream;
 485
 486         // mix as many times as needed to fill the requested buffer
 487         while (bufferframes)
 488         {
 489                 // limit to the size of the paint buffer
 490                 frames = min(bufferframes, PAINTBUFFER_SIZE);
 491
 492                 // clear the paint buffer
 493                 memset (paintbuffer, 0, frames * sizeof (paintbuffer[0]));
 494
 495                 // paint in the channels.
 496                 // channels with zero volumes still advance in time but don't paint.
 497                 ch = channels;
 498                 for (i = 0; i < total_channels ; i++, ch++)
 499                 {
 500                         sfx_t *sfx;
 501                         int ltime;
 502                         int count;
 503
 504                         sfx = ch->sfx;
 505                         if (sfx == NULL)
 506                                 continue;
 507                         if (!S_LoadSound (sfx, true))
 508                                 continue;
 509                         if (ch->flags & CHANNELFLAG_PAUSED)
 510                                 continue;
 511                         if (!sfx->total_length)
 512                                 continue;
 513                         if (sfx->total_length > 1<<30)
 514                                 Sys_Error("S_MixToBuffer: sfx corrupt\n");
 515
 516                         ltime = 0;
 517                         if (ch->pos < 0)
 518                         {
 519                                 count = -ch->pos;
 520                                 count = min(count, (int)frames - ltime);
 521                                 ch->pos += count;
 522                                 ltime += count;
 523                         }
 524
 525                         while (ltime < (int)frames)
 526                         {
 527                                 // paint up to end of buffer or of input, whichever is lower
 528                                 count = sfx->total_length - ch->pos;
 529                                 count = bound(0, count, (int)frames - ltime);
 530                                 // mix the remaining samples
 531                                 if (count)
 532                                 {
 533                                         SND_PaintChannel (ch, paintbuffer + ltime, count);
 534                                         ch->pos += count;
 535                                         ltime += count;
 536                                 }
 537                                 // if at end of sfx, loop or stop the channel
 538                                 else
 539                                 {
 540                                         if (sfx->loopstart < sfx->total_length)
 541                                                 ch->pos = sfx->loopstart;
 542                                         else if (ch->flags & CHANNELFLAG_FORCELOOP)
 543                                                 ch->pos = 0;
 544                                         else
 545                                         {
 546                                                 S_StopChannel (ch - channels, false, false);
 547                                                 break;
 548                                         }
 549                                 }
 550                         }
 551                 }
 552
 553                 if (!snd_usethreadedmixing)
 554                         S_CaptureAVISound(frames);
 555
 556                 S_ConvertPaintBuffer(paintbuffer, outbytes, frames, snd_renderbuffer->format.width, snd_renderbuffer->format.channels);
 557
 558                 // advance the output pointer
 559                 outbytes += frames * snd_renderbuffer->format.width * snd_renderbuffer->format.channels;
 560                 bufferframes -= frames;
 561         }
 562 }