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 extern cvar_t snd_softclip;
  25
  26 static portable_sampleframe_t paintbuffer[PAINTBUFFER_SIZE];
  27 static portable_sampleframe_t paintbuffer_unswapped[PAINTBUFFER_SIZE];
  28
  29 extern speakerlayout_t snd_speakerlayout; // for querying the listeners
  30
  31 #ifdef CONFIG_VIDEO_CAPTURE
  32 static void S_CaptureAVISound(const portable_sampleframe_t *sampleframes, size_t length)
  33 {
  34         size_t i;
  35         unsigned int j;
  36
  37         if (!cls.capturevideo.active)
  38                 return;
  39
  40         // undo whatever swapping the channel layout (swapstereo, ALSA) did
  41         for(j = 0; j < snd_speakerlayout.channels; ++j)
  42         {
  43                 unsigned int j0 = snd_speakerlayout.listeners[j].channel_unswapped;
  44                 for(i = 0; i < length; ++i)
  45                         paintbuffer_unswapped[i].sample[j0] = sampleframes[i].sample[j];
  46         }
  47
  48         SCR_CaptureVideo_SoundFrame(paintbuffer_unswapped, length);
  49 }
  50 #endif
  51
  52 extern cvar_t snd_softclip;
  53
  54 static void S_SoftClipPaintBuffer(portable_sampleframe_t *painted_ptr, int nbframes, int width, int nchannels)
  55 {
  56         int i;
  57
  58         if((snd_softclip.integer == 1 && width <= 2) || snd_softclip.integer > 1)
  59         {
  60                 portable_sampleframe_t *p = painted_ptr;
  61
  62 #if 0
  63 /* Soft clipping, the sound of a dream, thanks to Jon Wattes
  64    post to Musicdsp.org */
  65 #define SOFTCLIP(x) (x) = sin(bound(-M_PI/2, (x), M_PI/2)) * 0.25
  66 #endif
  67
  68                 // let's do a simple limiter instead, seems to sound better
  69                 static float maxvol = 0;
  70                 maxvol = max(1.0f, maxvol * (1.0f - nbframes / (0.4f * snd_renderbuffer->format.speed)));
  71 #define SOFTCLIP(x) if(fabs(x)>maxvol) maxvol=fabs(x); (x) /= maxvol;
  72
  73                 if (nchannels == 8)  // 7.1 surround
  74                 {
  75                         for (i = 0;i < nbframes;i++, p++)
  76                         {
  77                                 SOFTCLIP(p->sample[0]);
  78                                 SOFTCLIP(p->sample[1]);
  79                                 SOFTCLIP(p->sample[2]);
  80                                 SOFTCLIP(p->sample[3]);
  81                                 SOFTCLIP(p->sample[4]);
  82                                 SOFTCLIP(p->sample[5]);
  83                                 SOFTCLIP(p->sample[6]);
  84                                 SOFTCLIP(p->sample[7]);
  85                         }
  86                 }
  87                 else if (nchannels == 6)  // 5.1 surround
  88                 {
  89                         for (i = 0; i < nbframes; i++, p++)
  90                         {
  91                                 SOFTCLIP(p->sample[0]);
  92                                 SOFTCLIP(p->sample[1]);
  93                                 SOFTCLIP(p->sample[2]);
  94                                 SOFTCLIP(p->sample[3]);
  95                                 SOFTCLIP(p->sample[4]);
  96                                 SOFTCLIP(p->sample[5]);
  97                         }
  98                 }
  99                 else if (nchannels == 4)  // 4.0 surround
 100                 {
 101                         for (i = 0; i < nbframes; i++, p++)
 102                         {
 103                                 SOFTCLIP(p->sample[0]);
 104                                 SOFTCLIP(p->sample[1]);
 105                                 SOFTCLIP(p->sample[2]);
 106                                 SOFTCLIP(p->sample[3]);
 107                         }
 108                 }
 109                 else if (nchannels == 2)  // 2.0 stereo
 110                 {
 111                         for (i = 0; i < nbframes; i++, p++)
 112                         {
 113                                 SOFTCLIP(p->sample[0]);
 114                                 SOFTCLIP(p->sample[1]);
 115                         }
 116                 }
 117                 else if (nchannels == 1)  // 1.0 mono
 118                 {
 119                         for (i = 0; i < nbframes; i++, p++)
 120                         {
 121                                 SOFTCLIP(p->sample[0]);
 122                         }
 123                 }
 124 #undef SOFTCLIP
 125         }
 126 }
 127
 128 static void S_ConvertPaintBuffer(portable_sampleframe_t *painted_ptr, void *rb_ptr, int nbframes, int width, int nchannels)
 129 {
 130         int i;
 131         float val;
 132         if (width == 4)  // 32bit float
 133         {
 134                 float *snd_out = (float*)rb_ptr;
 135                 if (nchannels == 8)  // 7.1 surround
 136                 {
 137                         for (i = 0; i < nbframes; i++, painted_ptr++)
 138                         {
 139                                 *snd_out++ = painted_ptr->sample[0];
 140                                 *snd_out++ = painted_ptr->sample[1];
 141                                 *snd_out++ = painted_ptr->sample[2];
 142                                 *snd_out++ = painted_ptr->sample[3];
 143                                 *snd_out++ = painted_ptr->sample[4];
 144                                 *snd_out++ = painted_ptr->sample[5];
 145                                 *snd_out++ = painted_ptr->sample[6];
 146                                 *snd_out++ = painted_ptr->sample[7];
 147                         }
 148                 }
 149                 else if (nchannels == 6)  // 5.1 surround
 150                 {
 151                         for (i = 0; i < nbframes; i++, painted_ptr++)
 152                         {
 153                                 *snd_out++ = painted_ptr->sample[0];
 154                                 *snd_out++ = painted_ptr->sample[1];
 155                                 *snd_out++ = painted_ptr->sample[2];
 156                                 *snd_out++ = painted_ptr->sample[3];
 157                                 *snd_out++ = painted_ptr->sample[4];
 158                                 *snd_out++ = painted_ptr->sample[5];
 159                         }
 160                 }
 161                 else if (nchannels == 4)  // 4.0 surround
 162                 {
 163                         for (i = 0; i < nbframes; i++, painted_ptr++)
 164                         {
 165                                 *snd_out++ = painted_ptr->sample[0];
 166                                 *snd_out++ = painted_ptr->sample[1];
 167                                 *snd_out++ = painted_ptr->sample[2];
 168                                 *snd_out++ = painted_ptr->sample[3];
 169                         }
 170                 }
 171                 else if (nchannels == 2)  // 2.0 stereo
 172                 {
 173                         for (i = 0; i < nbframes; i++, painted_ptr++)
 174                         {
 175                                 *snd_out++ = painted_ptr->sample[0];
 176                                 *snd_out++ = painted_ptr->sample[1];
 177                         }
 178                 }
 179                 else if (nchannels == 1)  // 1.0 mono
 180                 {
 181                         for (i = 0; i < nbframes; i++, painted_ptr++)
 182                         {
 183                                 *snd_out++ = painted_ptr->sample[0];
 184                         }
 185                 }
 186
 187                 // noise is really really annoying
 188                 if (cls.timedemo)
 189                         memset(rb_ptr, 0, nbframes * nchannels * width);
 190         }
 191         else if (width == 2)  // 16bit
 192         {
 193                 short *snd_out = (short*)rb_ptr;
 194                 if (nchannels == 8)  // 7.1 surround
 195                 {
 196                         for (i = 0;i < nbframes;i++, painted_ptr++)
 197                         {
 198                                 val = (int)(painted_ptr->sample[0] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 199                                 val = (int)(painted_ptr->sample[1] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 200                                 val = (int)(painted_ptr->sample[2] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 201                                 val = (int)(painted_ptr->sample[3] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 202                                 val = (int)(painted_ptr->sample[4] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 203                                 val = (int)(painted_ptr->sample[5] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 204                                 val = (int)(painted_ptr->sample[6] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 205                                 val = (int)(painted_ptr->sample[7] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 206                         }
 207                 }
 208                 else if (nchannels == 6)  // 5.1 surround
 209                 {
 210                         for (i = 0; i < nbframes; i++, painted_ptr++)
 211                         {
 212                                 val = (int)(painted_ptr->sample[0] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 213                                 val = (int)(painted_ptr->sample[1] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 214                                 val = (int)(painted_ptr->sample[2] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 215                                 val = (int)(painted_ptr->sample[3] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 216                                 val = (int)(painted_ptr->sample[4] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 217                                 val = (int)(painted_ptr->sample[5] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 218                         }
 219                 }
 220                 else if (nchannels == 4)  // 4.0 surround
 221                 {
 222                         for (i = 0; i < nbframes; i++, painted_ptr++)
 223                         {
 224                                 val = (int)(painted_ptr->sample[0] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 225                                 val = (int)(painted_ptr->sample[1] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 226                                 val = (int)(painted_ptr->sample[2] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 227                                 val = (int)(painted_ptr->sample[3] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 228                         }
 229                 }
 230                 else if (nchannels == 2)  // 2.0 stereo
 231                 {
 232                         for (i = 0; i < nbframes; i++, painted_ptr++)
 233                         {
 234                                 val = (int)(painted_ptr->sample[0] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 235                                 val = (int)(painted_ptr->sample[1] * 32768.0f);*snd_out++ = bound(-32768, val, 32767);
 236                         }
 237                 }
 238                 else if (nchannels == 1)  // 1.0 mono
 239                 {
 240                         for (i = 0; i < nbframes; i++, painted_ptr++)
 241                         {
 242                                 val = (int)((painted_ptr->sample[0] + painted_ptr->sample[1]) * 16384.0f);*snd_out++ = bound(-32768, val, 32767);
 243                         }
 244                 }
 245
 246                 // noise is really really annoying
 247                 if (cls.timedemo)
 248                         memset(rb_ptr, 0, nbframes * nchannels * width);
 249         }
 250         else  // 8bit
 251         {
 252                 unsigned char *snd_out = (unsigned char*)rb_ptr;
 253                 if (nchannels == 8)  // 7.1 surround
 254                 {
 255                         for (i = 0; i < nbframes; i++, painted_ptr++)
 256                         {
 257                                 val = (int)(painted_ptr->sample[0] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 258                                 val = (int)(painted_ptr->sample[1] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 259                                 val = (int)(painted_ptr->sample[2] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 260                                 val = (int)(painted_ptr->sample[3] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 261                                 val = (int)(painted_ptr->sample[4] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 262                                 val = (int)(painted_ptr->sample[5] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 263                                 val = (int)(painted_ptr->sample[6] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 264                                 val = (int)(painted_ptr->sample[7] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 265                         }
 266                 }
 267                 else if (nchannels == 6)  // 5.1 surround
 268                 {
 269                         for (i = 0; i < nbframes; i++, painted_ptr++)
 270                         {
 271                                 val = (int)(painted_ptr->sample[0] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 272                                 val = (int)(painted_ptr->sample[1] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 273                                 val = (int)(painted_ptr->sample[2] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 274                                 val = (int)(painted_ptr->sample[3] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 275                                 val = (int)(painted_ptr->sample[4] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 276                                 val = (int)(painted_ptr->sample[5] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 277                         }
 278                 }
 279                 else if (nchannels == 4)  // 4.0 surround
 280                 {
 281                         for (i = 0; i < nbframes; i++, painted_ptr++)
 282                         {
 283                                 val = (int)(painted_ptr->sample[0] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 284                                 val = (int)(painted_ptr->sample[1] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 285                                 val = (int)(painted_ptr->sample[2] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 286                                 val = (int)(painted_ptr->sample[3] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 287                         }
 288                 }
 289                 else if (nchannels == 2)  // 2.0 stereo
 290                 {
 291                         for (i = 0; i < nbframes; i++, painted_ptr++)
 292                         {
 293                                 val = (int)(painted_ptr->sample[0] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 294                                 val = (int)(painted_ptr->sample[1] * 128.0f) + 128; *snd_out++ = bound(0, val, 255);
 295                         }
 296                 }
 297                 else if (nchannels == 1)  // 1.0 mono
 298                 {
 299                         for (i = 0;i < nbframes;i++, painted_ptr++)
 300                         {
 301                                 val = (int)((painted_ptr->sample[0] + painted_ptr->sample[1]) * 64.0f) + 128; *snd_out++ = bound(0, val, 255);
 302                         }
 303                 }
 304
 305                 // noise is really really annoying
 306                 if (cls.timedemo)
 307                         memset(rb_ptr, 128, nbframes * nchannels);
 308         }
 309 }
 310
 311
 312 /*
 313 ===============================================================================
 314
 315 CHANNEL MIXING
 316
 317 ===============================================================================
 318 */
 319
 320 void S_MixToBuffer(void *stream, unsigned int bufferframes)
 321 {
 322         int channelindex;
 323         channel_t *ch;
 324         int totalmixframes;
 325         unsigned char *outbytes = (unsigned char *) stream;
 326         sfx_t *sfx;
 327         portable_sampleframe_t *paint;
 328         int wantframes;
 329         int i;
 330         int count;
 331         int fetched;
 332         int fetch;
 333         int istartframe;
 334         int iendframe;
 335         int ilengthframes;
 336         int totallength;
 337         int loopstart;
 338         int indexfrac;
 339         int indexfracstep;
 340 #define S_FETCHBUFFERSIZE 4096
 341         float fetchsampleframes[S_FETCHBUFFERSIZE*2];
 342         const float *fetchsampleframe;
 343         float vol[SND_LISTENERS];
 344         float lerp[2];
 345         float sample[3];
 346         double posd;
 347         double speedd;
 348         float maxvol;
 349         qboolean looping;
 350         qboolean silent;
 351
 352         // mix as many times as needed to fill the requested buffer
 353         while (bufferframes)
 354         {
 355                 // limit to the size of the paint buffer
 356                 totalmixframes = min(bufferframes, PAINTBUFFER_SIZE);
 357
 358                 // clear the paint buffer
 359                 memset(paintbuffer, 0, totalmixframes * sizeof(paintbuffer[0]));
 360
 361                 // paint in the channels.
 362                 // channels with zero volumes still advance in time but don't paint.
 363                 ch = channels; // cppcheck complains here but it is wrong, channels is a channel_t[MAX_CHANNELS] and not an int
 364                 for (channelindex = 0;channelindex < (int)total_channels;channelindex++, ch++)
 365                 {
 366                         sfx = ch->sfx;
 367                         if (sfx == NULL)
 368                                 continue;
 369                         if (!S_LoadSound (sfx, true))
 370                                 continue;
 371                         if (ch->flags & CHANNELFLAG_PAUSED)
 372                                 continue;
 373                         if (!sfx->total_length)
 374                                 continue;
 375
 376                         // copy the channel information to the stack for reference, otherwise the
 377                         // values might change during a mix if the spatializer is updating them
 378                         // (note: this still may get some old and some new values!)
 379                         posd = ch->position;
 380                         speedd = ch->mixspeed * sfx->format.speed / snd_renderbuffer->format.speed;
 381                         for (i = 0;i < SND_LISTENERS;i++)
 382                                 vol[i] = ch->volume[i];
 383
 384                         // check total volume level, because we can skip some code on silent sounds but other code must still run (position updates mainly)
 385                         maxvol = 0;
 386                         for (i = 0;i < SND_LISTENERS;i++)
 387                                 if(vol[i] > maxvol)
 388                                         maxvol = vol[i];
 389                         switch(snd_renderbuffer->format.width)
 390                         {
 391                                 case 1: // 8bpp
 392                                         silent = maxvol < (1.0f / (256.0f));
 393                                         // so silent it has zero effect
 394                                         break;
 395                                 case 2: // 16bpp
 396                                         silent = maxvol < (1.0f / (65536.0f));
 397                                         // so silent it has zero effect
 398                                         break;
 399                                 default: // floating point
 400                                         silent = maxvol < 1.0e-13f;
 401                                         // 130 dB is difference between hearing
 402                                         // threshold and a jackhammer from
 403                                         // working distance.
 404                                         // therefore, anyone who turns up
 405                                         // volume so much they notice this
 406                                         // cutoff, likely already has their
 407                                         // ear-drums blown out anyway.
 408                                         break;
 409                         }
 410
 411                         // when doing prologic mixing, some channels invert one side
 412                         if (ch->prologic_invert == -1)
 413                                 vol[1] *= -1.0f;
 414
 415                         // get some sfx info in a consistent form
 416                         totallength = sfx->total_length;
 417                         loopstart = (int)sfx->loopstart < totallength ? (int)sfx->loopstart : ((ch->flags & CHANNELFLAG_FORCELOOP) ? 0 : totallength);
 418                         looping = loopstart < totallength;
 419
 420                         // do the actual paint now (may skip work if silent)
 421                         paint = paintbuffer;
 422                         istartframe = 0;
 423                         for (wantframes = totalmixframes;wantframes > 0;posd += count * speedd, wantframes -= count)
 424                         {
 425                                 // check if this is a delayed sound
 426                                 if (posd < 0)
 427                                 {
 428                                         // for a delayed sound we have to eat into the delay first
 429                                         count = (int)floor(-posd / speedd) + 1;
 430                                         count = bound(1, count, wantframes);
 431                                         // let the for loop iterator apply the skip
 432                                         continue;
 433                                 }
 434
 435                                 // compute a fetch size that won't overflow our buffer
 436                                 count = wantframes;
 437                                 for (;;)
 438                                 {
 439                                         istartframe = (int)floor(posd);
 440                                         iendframe = (int)floor(posd + (count-1) * speedd);
 441                                         ilengthframes = count > 1 ? (iendframe - istartframe + 2) : 2;
 442                                         if (ilengthframes <= S_FETCHBUFFERSIZE)
 443                                                 break;
 444                                         // reduce count by 25% and try again
 445                                         count -= count >> 2;
 446                                 }
 447
 448                                 // zero whole fetch buffer for safety
 449                                 // (floating point noise from uninitialized memory = HORRIBLE)
 450                                 // otherwise we would only need to clear the excess
 451                                 if (!silent)
 452                                         memset(fetchsampleframes, 0, ilengthframes*sfx->format.channels*sizeof(fetchsampleframes[0]));
 453
 454                                 // if looping, do multiple fetches
 455                                 fetched = 0;
 456                                 for (;;)
 457                                 {
 458                                         fetch = min(ilengthframes - fetched, totallength - istartframe);
 459                                         if (fetch > 0)
 460                                         {
 461                                                 if (!silent)
 462                                                         sfx->fetcher->getsamplesfloat(ch, sfx, istartframe, fetch, fetchsampleframes + fetched*sfx->format.channels);
 463                                                 istartframe += fetch;
 464                                                 fetched += fetch;
 465                                         }
 466                                         if (istartframe == totallength && looping && fetched < ilengthframes)
 467                                         {
 468                                                 // loop and fetch some more
 469                                                 posd += loopstart - totallength;
 470                                                 istartframe = loopstart;
 471                                         }
 472                                         else
 473                                         {
 474                                                 break;
 475                                         }
 476                                 }
 477
 478                                 // set up our fixedpoint resampling variables (float to int conversions are expensive so do not do one per sampleframe)
 479                                 fetchsampleframe = fetchsampleframes;
 480                                 indexfrac = (int)floor((posd - floor(posd)) * 65536.0);
 481                                 indexfracstep = (int)floor(speedd * 65536.0);
 482                                 if (!silent)
 483                                 {
 484                                         if (sfx->format.channels == 2)
 485                                         {
 486                                                 // music is stereo
 487 #if SND_LISTENERS != 8
 488 #error the following code only supports up to 8 channels, update it
 489 #endif
 490                                                 if (snd_speakerlayout.channels > 2)
 491                                                 {
 492                                                         // surround mixing
 493                                                         for (i = 0;i < count;i++, paint++)
 494                                                         {
 495                                                                 lerp[1] = indexfrac * (1.0f / 65536.0f);
 496                                                                 lerp[0] = 1.0f - lerp[1];
 497                                                                 sample[0] = fetchsampleframe[0] * lerp[0] + fetchsampleframe[2] * lerp[1];
 498                                                                 sample[1] = fetchsampleframe[1] * lerp[0] + fetchsampleframe[3] * lerp[1];
 499                                                                 sample[2] = (sample[0] + sample[1]) * 0.5f;
 500                                                                 paint->sample[0] += sample[0] * vol[0];
 501                                                                 paint->sample[1] += sample[1] * vol[1];
 502                                                                 paint->sample[2] += sample[0] * vol[2];
 503                                                                 paint->sample[3] += sample[1] * vol[3];
 504                                                                 paint->sample[4] += sample[2] * vol[4];
 505                                                                 paint->sample[5] += sample[2] * vol[5];
 506                                                                 paint->sample[6] += sample[0] * vol[6];
 507                                                                 paint->sample[7] += sample[1] * vol[7];
 508                                                                 indexfrac += indexfracstep;
 509                                                                 fetchsampleframe += 2 * (indexfrac >> 16);
 510                                                                 indexfrac &= 0xFFFF;
 511                                                         }
 512                                                 }
 513                                                 else
 514                                                 {
 515                                                         // stereo mixing
 516                                                         for (i = 0;i < count;i++, paint++)
 517                                                         {
 518                                                                 lerp[1] = indexfrac * (1.0f / 65536.0f);
 519                                                                 lerp[0] = 1.0f - lerp[1];
 520                                                                 sample[0] = fetchsampleframe[0] * lerp[0] + fetchsampleframe[2] * lerp[1];
 521                                                                 sample[1] = fetchsampleframe[1] * lerp[0] + fetchsampleframe[3] * lerp[1];
 522                                                                 paint->sample[0] += sample[0] * vol[0];
 523                                                                 paint->sample[1] += sample[1] * vol[1];
 524                                                                 indexfrac += indexfracstep;
 525                                                                 fetchsampleframe += 2 * (indexfrac >> 16);
 526                                                                 indexfrac &= 0xFFFF;
 527                                                         }
 528                                                 }
 529                                         }
 530                                         else if (sfx->format.channels == 1)
 531                                         {
 532                                                 // most sounds are mono
 533 #if SND_LISTENERS != 8
 534 #error the following code only supports up to 8 channels, update it
 535 #endif
 536                                                 if (snd_speakerlayout.channels > 2)
 537                                                 {
 538                                                         // surround mixing
 539                                                         for (i = 0;i < count;i++, paint++)
 540                                                         {
 541                                                                 lerp[1] = indexfrac * (1.0f / 65536.0f);
 542                                                                 lerp[0] = 1.0f - lerp[1];
 543                                                                 sample[0] = fetchsampleframe[0] * lerp[0] + fetchsampleframe[1] * lerp[1];
 544                                                                 paint->sample[0] += sample[0] * vol[0];
 545                                                                 paint->sample[1] += sample[0] * vol[1];
 546                                                                 paint->sample[2] += sample[0] * vol[2];
 547                                                                 paint->sample[3] += sample[0] * vol[3];
 548                                                                 paint->sample[4] += sample[0] * vol[4];
 549                                                                 paint->sample[5] += sample[0] * vol[5];
 550                                                                 paint->sample[6] += sample[0] * vol[6];
 551                                                                 paint->sample[7] += sample[0] * vol[7];
 552                                                                 indexfrac += indexfracstep;
 553                                                                 fetchsampleframe += (indexfrac >> 16);
 554                                                                 indexfrac &= 0xFFFF;
 555                                                         }
 556                                                 }
 557                                                 else
 558                                                 {
 559                                                         // stereo mixing
 560                                                         for (i = 0;i < count;i++, paint++)
 561                                                         {
 562                                                                 lerp[1] = indexfrac * (1.0f / 65536.0f);
 563                                                                 lerp[0] = 1.0f - lerp[1];
 564                                                                 sample[0] = fetchsampleframe[0] * lerp[0] + fetchsampleframe[1] * lerp[1];
 565                                                                 paint->sample[0] += sample[0] * vol[0];
 566                                                                 paint->sample[1] += sample[0] * vol[1];
 567                                                                 indexfrac += indexfracstep;
 568                                                                 fetchsampleframe += (indexfrac >> 16);
 569                                                                 indexfrac &= 0xFFFF;
 570                                                         }
 571                                                 }
 572                                         }
 573                                 }
 574                         }
 575                         ch->position = posd;
 576                         if (!looping && istartframe == totallength)
 577                                 S_StopChannel(ch - channels, false, false);
 578                 }
 579
 580                 S_SoftClipPaintBuffer(paintbuffer, totalmixframes, snd_renderbuffer->format.width, snd_renderbuffer->format.channels);
 581
 582 #ifdef CONFIG_VIDEO_CAPTURE
 583                 if (!snd_usethreadedmixing)
 584                         S_CaptureAVISound(paintbuffer, totalmixframes);
 585 #endif
 586
 587                 S_ConvertPaintBuffer(paintbuffer, outbytes, totalmixframes, snd_renderbuffer->format.width, snd_renderbuffer->format.channels);
 588
 589                 // advance the output pointer
 590                 outbytes += totalmixframes * snd_renderbuffer->format.width * snd_renderbuffer->format.channels;
 591                 bufferframes -= totalmixframes;
 592         }
 593 }