examples/almultireverb.c

   1 /*
   2  * OpenAL Multi-Zone Reverb Example
   3  *
   4  * Copyright (c) 2018 by Chris Robinson <chris.kcat@gmail.com>
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24
  25 /* This file contains an example for controlling multiple reverb zones to
  26  * smoothly transition between reverb environments. The general concept is to
  27  * extend single-reverb by also tracking the closest adjacent environment, and
  28  * utilize EAX Reverb's panning vectors to position them relative to the
  29  * listener.
  30  */
  31
  32
  33 #include <assert.h>
  34 #include <inttypes.h>
  35 #include <limits.h>
  36 #include <math.h>
  37 #include <stdio.h>
  38 #include <stdlib.h>
  39 #include <string.h>
  40
  41 #include "sndfile.h"
  42
  43 #include "AL/al.h"
  44 #include "AL/alc.h"
  45 #include "AL/efx.h"
  46 #include "AL/efx-presets.h"
  47
  48 #include "common/alhelpers.h"
  49
  50
  51 #ifndef M_PI
  52 #define M_PI 3.14159265358979323846
  53 #endif
  54
  55
  56 /* Filter object functions */
  57 static LPALGENFILTERS alGenFilters;
  58 static LPALDELETEFILTERS alDeleteFilters;
  59 static LPALISFILTER alIsFilter;
  60 static LPALFILTERI alFilteri;
  61 static LPALFILTERIV alFilteriv;
  62 static LPALFILTERF alFilterf;
  63 static LPALFILTERFV alFilterfv;
  64 static LPALGETFILTERI alGetFilteri;
  65 static LPALGETFILTERIV alGetFilteriv;
  66 static LPALGETFILTERF alGetFilterf;
  67 static LPALGETFILTERFV alGetFilterfv;
  68
  69 /* Effect object functions */
  70 static LPALGENEFFECTS alGenEffects;
  71 static LPALDELETEEFFECTS alDeleteEffects;
  72 static LPALISEFFECT alIsEffect;
  73 static LPALEFFECTI alEffecti;
  74 static LPALEFFECTIV alEffectiv;
  75 static LPALEFFECTF alEffectf;
  76 static LPALEFFECTFV alEffectfv;
  77 static LPALGETEFFECTI alGetEffecti;
  78 static LPALGETEFFECTIV alGetEffectiv;
  79 static LPALGETEFFECTF alGetEffectf;
  80 static LPALGETEFFECTFV alGetEffectfv;
  81
  82 /* Auxiliary Effect Slot object functions */
  83 static LPALGENAUXILIARYEFFECTSLOTS alGenAuxiliaryEffectSlots;
  84 static LPALDELETEAUXILIARYEFFECTSLOTS alDeleteAuxiliaryEffectSlots;
  85 static LPALISAUXILIARYEFFECTSLOT alIsAuxiliaryEffectSlot;
  86 static LPALAUXILIARYEFFECTSLOTI alAuxiliaryEffectSloti;
  87 static LPALAUXILIARYEFFECTSLOTIV alAuxiliaryEffectSlotiv;
  88 static LPALAUXILIARYEFFECTSLOTF alAuxiliaryEffectSlotf;
  89 static LPALAUXILIARYEFFECTSLOTFV alAuxiliaryEffectSlotfv;
  90 static LPALGETAUXILIARYEFFECTSLOTI alGetAuxiliaryEffectSloti;
  91 static LPALGETAUXILIARYEFFECTSLOTIV alGetAuxiliaryEffectSlotiv;
  92 static LPALGETAUXILIARYEFFECTSLOTF alGetAuxiliaryEffectSlotf;
  93 static LPALGETAUXILIARYEFFECTSLOTFV alGetAuxiliaryEffectSlotfv;
  94
  95
  96 /* LoadEffect loads the given initial reverb properties into the given OpenAL
  97  * effect object, and returns non-zero on success.
  98  */
  99 static int LoadEffect(ALuint effect, const EFXEAXREVERBPROPERTIES *reverb)
 100 {
 101     ALenum err;
 102
 103     alGetError();
 104
 105     /* Prepare the effect for EAX Reverb (standard reverb doesn't contain
 106      * the needed panning vectors).
 107      */
 108     alEffecti(effect, AL_EFFECT_TYPE, AL_EFFECT_EAXREVERB);
 109     if((err=alGetError()) != AL_NO_ERROR)
 110     {
 111         fprintf(stderr, "Failed to set EAX Reverb: %s (0x%04x)\n", alGetString(err), err);
 112         return 0;
 113     }
 114
 115     /* Load the reverb properties. */
 116     alEffectf(effect, AL_EAXREVERB_DENSITY, reverb->flDensity);
 117     alEffectf(effect, AL_EAXREVERB_DIFFUSION, reverb->flDiffusion);
 118     alEffectf(effect, AL_EAXREVERB_GAIN, reverb->flGain);
 119     alEffectf(effect, AL_EAXREVERB_GAINHF, reverb->flGainHF);
 120     alEffectf(effect, AL_EAXREVERB_GAINLF, reverb->flGainLF);
 121     alEffectf(effect, AL_EAXREVERB_DECAY_TIME, reverb->flDecayTime);
 122     alEffectf(effect, AL_EAXREVERB_DECAY_HFRATIO, reverb->flDecayHFRatio);
 123     alEffectf(effect, AL_EAXREVERB_DECAY_LFRATIO, reverb->flDecayLFRatio);
 124     alEffectf(effect, AL_EAXREVERB_REFLECTIONS_GAIN, reverb->flReflectionsGain);
 125     alEffectf(effect, AL_EAXREVERB_REFLECTIONS_DELAY, reverb->flReflectionsDelay);
 126     alEffectfv(effect, AL_EAXREVERB_REFLECTIONS_PAN, reverb->flReflectionsPan);
 127     alEffectf(effect, AL_EAXREVERB_LATE_REVERB_GAIN, reverb->flLateReverbGain);
 128     alEffectf(effect, AL_EAXREVERB_LATE_REVERB_DELAY, reverb->flLateReverbDelay);
 129     alEffectfv(effect, AL_EAXREVERB_LATE_REVERB_PAN, reverb->flLateReverbPan);
 130     alEffectf(effect, AL_EAXREVERB_ECHO_TIME, reverb->flEchoTime);
 131     alEffectf(effect, AL_EAXREVERB_ECHO_DEPTH, reverb->flEchoDepth);
 132     alEffectf(effect, AL_EAXREVERB_MODULATION_TIME, reverb->flModulationTime);
 133     alEffectf(effect, AL_EAXREVERB_MODULATION_DEPTH, reverb->flModulationDepth);
 134     alEffectf(effect, AL_EAXREVERB_AIR_ABSORPTION_GAINHF, reverb->flAirAbsorptionGainHF);
 135     alEffectf(effect, AL_EAXREVERB_HFREFERENCE, reverb->flHFReference);
 136     alEffectf(effect, AL_EAXREVERB_LFREFERENCE, reverb->flLFReference);
 137     alEffectf(effect, AL_EAXREVERB_ROOM_ROLLOFF_FACTOR, reverb->flRoomRolloffFactor);
 138     alEffecti(effect, AL_EAXREVERB_DECAY_HFLIMIT, reverb->iDecayHFLimit);
 139
 140     /* Check if an error occured, and return failure if so. */
 141     if((err=alGetError()) != AL_NO_ERROR)
 142     {
 143         fprintf(stderr, "Error setting up reverb: %s\n", alGetString(err));
 144         return 0;
 145     }
 146
 147     return 1;
 148 }
 149
 150
 151 /* LoadBuffer loads the named audio file into an OpenAL buffer object, and
 152  * returns the new buffer ID.
 153  */
 154 static ALuint LoadSound(const char *filename)
 155 {
 156     ALenum err, format;
 157     ALuint buffer;
 158     SNDFILE *sndfile;
 159     SF_INFO sfinfo;
 160     short *membuf;
 161     sf_count_t num_frames;
 162     ALsizei num_bytes;
 163
 164     /* Open the audio file and check that it's usable. */
 165     sndfile = sf_open(filename, SFM_READ, &sfinfo);
 166     if(!sndfile)
 167     {
 168         fprintf(stderr, "Could not open audio in %s: %s\n", filename, sf_strerror(sndfile));
 169         return 0;
 170     }
 171     if(sfinfo.frames < 1 || sfinfo.frames > (sf_count_t)(INT_MAX/sizeof(short))/sfinfo.channels)
 172     {
 173         fprintf(stderr, "Bad sample count in %s (%" PRId64 ")\n", filename, sfinfo.frames);
 174         sf_close(sndfile);
 175         return 0;
 176     }
 177
 178     /* Get the sound format, and figure out the OpenAL format */
 179     if(sfinfo.channels == 1)
 180         format = AL_FORMAT_MONO16;
 181     else if(sfinfo.channels == 2)
 182         format = AL_FORMAT_STEREO16;
 183     else
 184     {
 185         fprintf(stderr, "Unsupported channel count: %d\n", sfinfo.channels);
 186         sf_close(sndfile);
 187         return 0;
 188     }
 189
 190     /* Decode the whole audio file to a buffer. */
 191     membuf = malloc((size_t)(sfinfo.frames * sfinfo.channels) * sizeof(short));
 192
 193     num_frames = sf_readf_short(sndfile, membuf, sfinfo.frames);
 194     if(num_frames < 1)
 195     {
 196         free(membuf);
 197         sf_close(sndfile);
 198         fprintf(stderr, "Failed to read samples in %s (%" PRId64 ")\n", filename, num_frames);
 199         return 0;
 200     }
 201     num_bytes = (ALsizei)(num_frames * sfinfo.channels) * (ALsizei)sizeof(short);
 202
 203     /* Buffer the audio data into a new buffer object, then free the data and
 204      * close the file.
 205      */
 206     buffer = 0;
 207     alGenBuffers(1, &buffer);
 208     alBufferData(buffer, format, membuf, num_bytes, sfinfo.samplerate);
 209
 210     free(membuf);
 211     sf_close(sndfile);
 212
 213     /* Check if an error occured, and clean up if so. */
 214     err = alGetError();
 215     if(err != AL_NO_ERROR)
 216     {
 217         fprintf(stderr, "OpenAL Error: %s\n", alGetString(err));
 218         if(buffer && alIsBuffer(buffer))
 219             alDeleteBuffers(1, &buffer);
 220         return 0;
 221     }
 222
 223     return buffer;
 224 }
 225
 226
 227 /* Helper to calculate the dot-product of the two given vectors. */
 228 static ALfloat dot_product(const ALfloat vec0[3], const ALfloat vec1[3])
 229 {
 230     return vec0[0]*vec1[0] + vec0[1]*vec1[1] + vec0[2]*vec1[2];
 231 }
 232
 233 /* Helper to normalize a given vector. */
 234 static void normalize(ALfloat vec[3])
 235 {
 236     ALfloat mag = sqrtf(dot_product(vec, vec));
 237     if(mag > 0.00001f)
 238     {
 239         vec[0] /= mag;
 240         vec[1] /= mag;
 241         vec[2] /= mag;
 242     }
 243     else
 244     {
 245         vec[0] = 0.0f;
 246         vec[1] = 0.0f;
 247         vec[2] = 0.0f;
 248     }
 249 }
 250
 251
 252 /* The main update function to update the listener and environment effects. */
 253 static void UpdateListenerAndEffects(float timediff, const ALuint slots[2], const ALuint effects[2], const EFXEAXREVERBPROPERTIES reverbs[2])
 254 {
 255     static const ALfloat listener_move_scale = 10.0f;
 256     /* Individual reverb zones are connected via "portals". Each portal has a
 257      * position (center point of the connecting area), a normal (facing
 258      * direction), and a radius (approximate size of the connecting area).
 259      */
 260     const ALfloat portal_pos[3] = { 0.0f, 0.0f, 0.0f };
 261     const ALfloat portal_norm[3] = { sqrtf(0.5f), 0.0f, -sqrtf(0.5f) };
 262     const ALfloat portal_radius = 2.5f;
 263     ALfloat other_dir[3], this_dir[3];
 264     ALfloat listener_pos[3];
 265     ALfloat local_norm[3];
 266     ALfloat local_dir[3];
 267     ALfloat near_edge[3];
 268     ALfloat far_edge[3];
 269     ALfloat dist, edist;
 270
 271     /* Update the listener position for the amount of time passed. This uses a
 272      * simple triangular LFO to offset the position (moves along the X axis
 273      * between -listener_move_scale and +listener_move_scale for each
 274      * transition).
 275      */
 276     listener_pos[0] = (fabsf(2.0f - timediff/2.0f) - 1.0f) * listener_move_scale;
 277     listener_pos[1] = 0.0f;
 278     listener_pos[2] = 0.0f;
 279     alListenerfv(AL_POSITION, listener_pos);
 280
 281     /* Calculate local_dir, which represents the listener-relative point to the
 282      * adjacent zone (should also include orientation). Because EAX Reverb uses
 283      * left-handed coordinates instead of right-handed like the rest of OpenAL,
 284      * negate Z for the local values.
 285      */
 286     local_dir[0] = portal_pos[0] - listener_pos[0];
 287     local_dir[1] = portal_pos[1] - listener_pos[1];
 288     local_dir[2] = -(portal_pos[2] - listener_pos[2]);
 289     /* A normal application would also rotate the portal's normal given the
 290      * listener orientation, to get the listener-relative normal.
 291      */
 292     local_norm[0] = portal_norm[0];
 293     local_norm[1] = portal_norm[1];
 294     local_norm[2] = -portal_norm[2];
 295
 296     /* Calculate the distance from the listener to the portal, and ensure it's
 297      * far enough away to not suffer severe floating-point precision issues.
 298      */
 299     dist = sqrtf(dot_product(local_dir, local_dir));
 300     if(dist > 0.00001f)
 301     {
 302         const EFXEAXREVERBPROPERTIES *other_reverb, *this_reverb;
 303         ALuint other_effect, this_effect;
 304         ALfloat magnitude, dir_dot_norm;
 305
 306         /* Normalize the direction to the portal. */
 307         local_dir[0] /= dist;
 308         local_dir[1] /= dist;
 309         local_dir[2] /= dist;
 310
 311         /* Calculate the dot product of the portal's local direction and local
 312          * normal, which is used for angular and side checks later on.
 313          */
 314         dir_dot_norm = dot_product(local_dir, local_norm);
 315
 316         /* Figure out which zone we're in. */
 317         if(dir_dot_norm <= 0.0f)
 318         {
 319             /* We're in front of the portal, so we're in Zone 0. */
 320             this_effect = effects[0];
 321             other_effect = effects[1];
 322             this_reverb = &reverbs[0];
 323             other_reverb = &reverbs[1];
 324         }
 325         else
 326         {
 327             /* We're behind the portal, so we're in Zone 1. */
 328             this_effect = effects[1];
 329             other_effect = effects[0];
 330             this_reverb = &reverbs[1];
 331             other_reverb = &reverbs[0];
 332         }
 333
 334         /* Calculate the listener-relative extents of the portal. */
 335         /* First, project the listener-to-portal vector onto the portal's plane
 336          * to get the portal-relative direction along the plane that goes away
 337          * from the listener (toward the farthest edge of the portal).
 338          */
 339         far_edge[0] = local_dir[0] - local_norm[0]*dir_dot_norm;
 340         far_edge[1] = local_dir[1] - local_norm[1]*dir_dot_norm;
 341         far_edge[2] = local_dir[2] - local_norm[2]*dir_dot_norm;
 342
 343         edist = sqrtf(dot_product(far_edge, far_edge));
 344         if(edist > 0.0001f)
 345         {
 346             /* Rescale the portal-relative vector to be at the radius edge. */
 347             ALfloat mag = portal_radius / edist;
 348             far_edge[0] *= mag;
 349             far_edge[1] *= mag;
 350             far_edge[2] *= mag;
 351
 352             /* Calculate the closest edge of the portal by negating the
 353              * farthest, and add an offset to make them both relative to the
 354              * listener.
 355              */
 356             near_edge[0] = local_dir[0]*dist - far_edge[0];
 357             near_edge[1] = local_dir[1]*dist - far_edge[1];
 358             near_edge[2] = local_dir[2]*dist - far_edge[2];
 359             far_edge[0] += local_dir[0]*dist;
 360             far_edge[1] += local_dir[1]*dist;
 361             far_edge[2] += local_dir[2]*dist;
 362
 363             /* Normalize the listener-relative extents of the portal, then
 364              * calculate the panning magnitude for the other zone given the
 365              * apparent size of the opening. The panning magnitude affects the
 366              * envelopment of the environment, with 1 being a point, 0.5 being
 367              * half coverage around the listener, and 0 being full coverage.
 368              */
 369             normalize(far_edge);
 370             normalize(near_edge);
 371             magnitude = 1.0f - acosf(dot_product(far_edge, near_edge))/(float)(M_PI*2.0);
 372
 373             /* Recalculate the panning direction, to be directly between the
 374              * direction of the two extents.
 375              */
 376             local_dir[0] = far_edge[0] + near_edge[0];
 377             local_dir[1] = far_edge[1] + near_edge[1];
 378             local_dir[2] = far_edge[2] + near_edge[2];
 379             normalize(local_dir);
 380         }
 381         else
 382         {
 383             /* If we get here, the listener is directly in front of or behind
 384              * the center of the portal, making all aperture edges effectively
 385              * equidistant. Calculating the panning magnitude is simplified,
 386              * using the arctangent of the radius and distance.
 387              */
 388             magnitude = 1.0f - (atan2f(portal_radius, dist) / (float)M_PI);
 389         }
 390
 391         /* Scale the other zone's panning vector. */
 392         other_dir[0] = local_dir[0] * magnitude;
 393         other_dir[1] = local_dir[1] * magnitude;
 394         other_dir[2] = local_dir[2] * magnitude;
 395         /* Pan the current zone to the opposite direction of the portal, and
 396          * take the remaining percentage of the portal's magnitude.
 397          */
 398         this_dir[0] = local_dir[0] * (magnitude-1.0f);
 399         this_dir[1] = local_dir[1] * (magnitude-1.0f);
 400         this_dir[2] = local_dir[2] * (magnitude-1.0f);
 401
 402         /* Now set the effects' panning vectors and gain. Energy is shared
 403          * between environments, so attenuate according to each zone's
 404          * contribution (note: gain^2 = energy).
 405          */
 406         alEffectf(this_effect, AL_EAXREVERB_REFLECTIONS_GAIN, this_reverb->flReflectionsGain * sqrtf(magnitude));
 407         alEffectf(this_effect, AL_EAXREVERB_LATE_REVERB_GAIN, this_reverb->flLateReverbGain * sqrtf(magnitude));
 408         alEffectfv(this_effect, AL_EAXREVERB_REFLECTIONS_PAN, this_dir);
 409         alEffectfv(this_effect, AL_EAXREVERB_LATE_REVERB_PAN, this_dir);
 410
 411         alEffectf(other_effect, AL_EAXREVERB_REFLECTIONS_GAIN, other_reverb->flReflectionsGain * sqrtf(1.0f-magnitude));
 412         alEffectf(other_effect, AL_EAXREVERB_LATE_REVERB_GAIN, other_reverb->flLateReverbGain * sqrtf(1.0f-magnitude));
 413         alEffectfv(other_effect, AL_EAXREVERB_REFLECTIONS_PAN, other_dir);
 414         alEffectfv(other_effect, AL_EAXREVERB_LATE_REVERB_PAN, other_dir);
 415     }
 416     else
 417     {
 418         /* We're practically in the center of the portal. Give the panning
 419          * vectors a 50/50 split, with Zone 0 covering the half in front of
 420          * the normal, and Zone 1 covering the half behind.
 421          */
 422         this_dir[0] = local_norm[0] / 2.0f;
 423         this_dir[1] = local_norm[1] / 2.0f;
 424         this_dir[2] = local_norm[2] / 2.0f;
 425
 426         other_dir[0] = local_norm[0] / -2.0f;
 427         other_dir[1] = local_norm[1] / -2.0f;
 428         other_dir[2] = local_norm[2] / -2.0f;
 429
 430         alEffectf(effects[0], AL_EAXREVERB_REFLECTIONS_GAIN, reverbs[0].flReflectionsGain * sqrtf(0.5f));
 431         alEffectf(effects[0], AL_EAXREVERB_LATE_REVERB_GAIN, reverbs[0].flLateReverbGain * sqrtf(0.5f));
 432         alEffectfv(effects[0], AL_EAXREVERB_REFLECTIONS_PAN, this_dir);
 433         alEffectfv(effects[0], AL_EAXREVERB_LATE_REVERB_PAN, this_dir);
 434
 435         alEffectf(effects[1], AL_EAXREVERB_REFLECTIONS_GAIN, reverbs[1].flReflectionsGain * sqrtf(0.5f));
 436         alEffectf(effects[1], AL_EAXREVERB_LATE_REVERB_GAIN, reverbs[1].flLateReverbGain * sqrtf(0.5f));
 437         alEffectfv(effects[1], AL_EAXREVERB_REFLECTIONS_PAN, other_dir);
 438         alEffectfv(effects[1], AL_EAXREVERB_LATE_REVERB_PAN, other_dir);
 439     }
 440
 441     /* Finally, update the effect slots with the updated effect parameters. */
 442     alAuxiliaryEffectSloti(slots[0], AL_EFFECTSLOT_EFFECT, (ALint)effects[0]);
 443     alAuxiliaryEffectSloti(slots[1], AL_EFFECTSLOT_EFFECT, (ALint)effects[1]);
 444 }
 445
 446
 447 int main(int argc, char **argv)
 448 {
 449     static const int MaxTransitions = 8;
 450     EFXEAXREVERBPROPERTIES reverbs[2] = {
 451         EFX_REVERB_PRESET_CARPETEDHALLWAY,
 452         EFX_REVERB_PRESET_BATHROOM
 453     };
 454     ALCdevice *device = NULL;
 455     ALCcontext *context = NULL;
 456     ALuint effects[2] = { 0, 0 };
 457     ALuint slots[2] = { 0, 0 };
 458     ALuint direct_filter = 0;
 459     ALuint buffer = 0;
 460     ALuint source = 0;
 461     ALCint num_sends = 0;
 462     ALenum state = AL_INITIAL;
 463     ALfloat direct_gain = 1.0f;
 464     int basetime = 0;
 465     int loops = 0;
 466
 467     /* Print out usage if no arguments were specified */
 468     if(argc < 2)
 469     {
 470         fprintf(stderr, "Usage: %s [-device <name>] [options] <filename>\n\n"
 471         "Options:\n"
 472         "\t-nodirect\tSilence direct path output (easier to hear reverb)\n\n",
 473         argv[0]);
 474         return 1;
 475     }
 476
 477     /* Initialize OpenAL, and check for EFX support with at least 2 auxiliary
 478      * sends (if multiple sends are supported, 2 are provided by default; if
 479      * you want more, you have to request it through alcCreateContext).
 480      */
 481     argv++; argc--;
 482     if(InitAL(&argv, &argc) != 0)
 483         return 1;
 484
 485     while(argc > 0)
 486     {
 487         if(strcmp(argv[0], "-nodirect") == 0)
 488             direct_gain = 0.0f;
 489         else
 490             break;
 491         argv++;
 492         argc--;
 493     }
 494     if(argc < 1)
 495     {
 496         fprintf(stderr, "No filename spacified.\n");
 497         CloseAL();
 498         return 1;
 499     }
 500
 501     context = alcGetCurrentContext();
 502     device = alcGetContextsDevice(context);
 503
 504     if(!alcIsExtensionPresent(device, "ALC_EXT_EFX"))
 505     {
 506         fprintf(stderr, "Error: EFX not supported\n");
 507         CloseAL();
 508         return 1;
 509     }
 510
 511     num_sends = 0;
 512     alcGetIntegerv(device, ALC_MAX_AUXILIARY_SENDS, 1, &num_sends);
 513     if(alcGetError(device) != ALC_NO_ERROR || num_sends < 2)
 514     {
 515         fprintf(stderr, "Error: Device does not support multiple sends (got %d, need 2)\n",
 516                 num_sends);
 517         CloseAL();
 518         return 1;
 519     }
 520
 521     /* Define a macro to help load the function pointers. */
 522 #define LOAD_PROC(T, x)  ((x) = FUNCTION_CAST(T, alGetProcAddress(#x)))
 523     LOAD_PROC(LPALGENFILTERS, alGenFilters);
 524     LOAD_PROC(LPALDELETEFILTERS, alDeleteFilters);
 525     LOAD_PROC(LPALISFILTER, alIsFilter);
 526     LOAD_PROC(LPALFILTERI, alFilteri);
 527     LOAD_PROC(LPALFILTERIV, alFilteriv);
 528     LOAD_PROC(LPALFILTERF, alFilterf);
 529     LOAD_PROC(LPALFILTERFV, alFilterfv);
 530     LOAD_PROC(LPALGETFILTERI, alGetFilteri);
 531     LOAD_PROC(LPALGETFILTERIV, alGetFilteriv);
 532     LOAD_PROC(LPALGETFILTERF, alGetFilterf);
 533     LOAD_PROC(LPALGETFILTERFV, alGetFilterfv);
 534
 535     LOAD_PROC(LPALGENEFFECTS, alGenEffects);
 536     LOAD_PROC(LPALDELETEEFFECTS, alDeleteEffects);
 537     LOAD_PROC(LPALISEFFECT, alIsEffect);
 538     LOAD_PROC(LPALEFFECTI, alEffecti);
 539     LOAD_PROC(LPALEFFECTIV, alEffectiv);
 540     LOAD_PROC(LPALEFFECTF, alEffectf);
 541     LOAD_PROC(LPALEFFECTFV, alEffectfv);
 542     LOAD_PROC(LPALGETEFFECTI, alGetEffecti);
 543     LOAD_PROC(LPALGETEFFECTIV, alGetEffectiv);
 544     LOAD_PROC(LPALGETEFFECTF, alGetEffectf);
 545     LOAD_PROC(LPALGETEFFECTFV, alGetEffectfv);
 546
 547     LOAD_PROC(LPALGENAUXILIARYEFFECTSLOTS, alGenAuxiliaryEffectSlots);
 548     LOAD_PROC(LPALDELETEAUXILIARYEFFECTSLOTS, alDeleteAuxiliaryEffectSlots);
 549     LOAD_PROC(LPALISAUXILIARYEFFECTSLOT, alIsAuxiliaryEffectSlot);
 550     LOAD_PROC(LPALAUXILIARYEFFECTSLOTI, alAuxiliaryEffectSloti);
 551     LOAD_PROC(LPALAUXILIARYEFFECTSLOTIV, alAuxiliaryEffectSlotiv);
 552     LOAD_PROC(LPALAUXILIARYEFFECTSLOTF, alAuxiliaryEffectSlotf);
 553     LOAD_PROC(LPALAUXILIARYEFFECTSLOTFV, alAuxiliaryEffectSlotfv);
 554     LOAD_PROC(LPALGETAUXILIARYEFFECTSLOTI, alGetAuxiliaryEffectSloti);
 555     LOAD_PROC(LPALGETAUXILIARYEFFECTSLOTIV, alGetAuxiliaryEffectSlotiv);
 556     LOAD_PROC(LPALGETAUXILIARYEFFECTSLOTF, alGetAuxiliaryEffectSlotf);
 557     LOAD_PROC(LPALGETAUXILIARYEFFECTSLOTFV, alGetAuxiliaryEffectSlotfv);
 558 #undef LOAD_PROC
 559
 560     /* Load the sound into a buffer. */
 561     buffer = LoadSound(argv[0]);
 562     if(!buffer)
 563     {
 564         CloseAL();
 565         return 1;
 566     }
 567
 568     /* Generate two effects for two "zones", and load a reverb into each one.
 569      * Note that unlike single-zone reverb, where you can store one effect per
 570      * preset, for multi-zone reverb you should have one effect per environment
 571      * instance, or one per audible zone. This is because we'll be changing the
 572      * effects' properties in real-time based on the environment instance
 573      * relative to the listener.
 574      */
 575     alGenEffects(2, effects);
 576     if(!LoadEffect(effects[0], &reverbs[0]) || !LoadEffect(effects[1], &reverbs[1]))
 577     {
 578         alDeleteEffects(2, effects);
 579         alDeleteBuffers(1, &buffer);
 580         CloseAL();
 581         return 1;
 582     }
 583
 584     /* Create the effect slot objects, one for each "active" effect. */
 585     alGenAuxiliaryEffectSlots(2, slots);
 586
 587     /* Tell the effect slots to use the loaded effect objects, with slot 0 for
 588      * Zone 0 and slot 1 for Zone 1. Note that this effectively copies the
 589      * effect properties. Modifying or deleting the effect object afterward
 590      * won't directly affect the effect slot until they're reapplied like this.
 591      */
 592     alAuxiliaryEffectSloti(slots[0], AL_EFFECTSLOT_EFFECT, (ALint)effects[0]);
 593     alAuxiliaryEffectSloti(slots[1], AL_EFFECTSLOT_EFFECT, (ALint)effects[1]);
 594     assert(alGetError()==AL_NO_ERROR && "Failed to set effect slot");
 595
 596     /* For the purposes of this example, prepare a filter that optionally
 597      * silences the direct path which allows us to hear just the reverberation.
 598      * A filter like this is normally used for obstruction, where the path
 599      * directly between the listener and source is blocked (the exact
 600      * properties depending on the type and thickness of the obstructing
 601      * material).
 602      */
 603     alGenFilters(1, &direct_filter);
 604     alFilteri(direct_filter, AL_FILTER_TYPE, AL_FILTER_LOWPASS);
 605     alFilterf(direct_filter, AL_LOWPASS_GAIN, direct_gain);
 606     assert(alGetError()==AL_NO_ERROR && "Failed to set direct filter");
 607
 608     /* Create the source to play the sound with, place it in front of the
 609      * listener's path in the left zone.
 610      */
 611     source = 0;
 612     alGenSources(1, &source);
 613     alSourcei(source, AL_LOOPING, AL_TRUE);
 614     alSource3f(source, AL_POSITION, -5.0f, 0.0f, -2.0f);
 615     alSourcei(source, AL_DIRECT_FILTER, (ALint)direct_filter);
 616     alSourcei(source, AL_BUFFER, (ALint)buffer);
 617
 618     /* Connect the source to the effect slots. Here, we connect source send 0
 619      * to Zone 0's slot, and send 1 to Zone 1's slot. Filters can be specified
 620      * to occlude the source from each zone by varying amounts; for example, a
 621      * source within a particular zone would be unfiltered, while a source that
 622      * can only see a zone through a window or thin wall may be attenuated for
 623      * that zone.
 624      */
 625     alSource3i(source, AL_AUXILIARY_SEND_FILTER, (ALint)slots[0], 0, AL_FILTER_NULL);
 626     alSource3i(source, AL_AUXILIARY_SEND_FILTER, (ALint)slots[1], 1, AL_FILTER_NULL);
 627     assert(alGetError()==AL_NO_ERROR && "Failed to setup sound source");
 628
 629     /* Get the current time as the base for timing in the main loop. */
 630     basetime = altime_get();
 631     loops = 0;
 632     printf("Transition %d of %d...\n", loops+1, MaxTransitions);
 633
 634     /* Play the sound for a while. */
 635     alSourcePlay(source);
 636     do {
 637         int curtime;
 638         ALfloat timediff;
 639
 640         /* Start a batch update, to ensure all changes apply simultaneously. */
 641         alcSuspendContext(context);
 642
 643         /* Get the current time to track the amount of time that passed.
 644          * Convert the difference to seconds.
 645          */
 646         curtime = altime_get();
 647         timediff = (float)(curtime - basetime) / 1000.0f;
 648
 649         /* Avoid negative time deltas, in case of non-monotonic clocks. */
 650         if(timediff < 0.0f)
 651             timediff = 0.0f;
 652         else while(timediff >= 4.0f*(float)((loops&1)+1))
 653         {
 654             /* For this example, each transition occurs over 4 seconds, and
 655              * there's 2 transitions per cycle.
 656              */
 657             if(++loops < MaxTransitions)
 658                 printf("Transition %d of %d...\n", loops+1, MaxTransitions);
 659             if(!(loops&1))
 660             {
 661                 /* Cycle completed. Decrease the delta and increase the base
 662                  * time to start a new cycle.
 663                  */
 664                 timediff -= 8.0f;
 665                 basetime += 8000;
 666             }
 667         }
 668
 669         /* Update the listener and effects, and finish the batch. */
 670         UpdateListenerAndEffects(timediff, slots, effects, reverbs);
 671         alcProcessContext(context);
 672
 673         al_nssleep(10000000);
 674
 675         alGetSourcei(source, AL_SOURCE_STATE, &state);
 676     } while(alGetError() == AL_NO_ERROR && state == AL_PLAYING && loops < MaxTransitions);
 677
 678     /* All done. Delete resources, and close down OpenAL. */
 679     alDeleteSources(1, &source);
 680     alDeleteAuxiliaryEffectSlots(2, slots);
 681     alDeleteEffects(2, effects);
 682     alDeleteFilters(1, &direct_filter);
 683     alDeleteBuffers(1, &buffer);
 684
 685     CloseAL();
 686
 687     return 0;
 688 }