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 /* C doesn't allow casting between function and non-function pointer types, so
  96  * with C99 we need to use a union to reinterpret the pointer type. Pre-C99
  97  * still needs to use a normal cast and live with the warning (C++ is fine with
  98  * a regular reinterpret_cast).
  99  */
 100 #if __STDC_VERSION__ >= 199901L
 101 #define FUNCTION_CAST(T, ptr) (union{void *p; T f;}){ptr}.f
 102 #else
 103 #define FUNCTION_CAST(T, ptr) (T)(ptr)
 104 #endif
 105
 106
 107 /* LoadEffect loads the given initial reverb properties into the given OpenAL
 108  * effect object, and returns non-zero on success.
 109  */
 110 static int LoadEffect(ALuint effect, const EFXEAXREVERBPROPERTIES *reverb)
 111 {
 112     ALenum err;
 113
 114     alGetError();
 115
 116     /* Prepare the effect for EAX Reverb (standard reverb doesn't contain
 117      * the needed panning vectors).
 118      */
 119     alEffecti(effect, AL_EFFECT_TYPE, AL_EFFECT_EAXREVERB);
 120     if((err=alGetError()) != AL_NO_ERROR)
 121     {
 122         fprintf(stderr, "Failed to set EAX Reverb: %s (0x%04x)\n", alGetString(err), err);
 123         return 0;
 124     }
 125
 126     /* Load the reverb properties. */
 127     alEffectf(effect, AL_EAXREVERB_DENSITY, reverb->flDensity);
 128     alEffectf(effect, AL_EAXREVERB_DIFFUSION, reverb->flDiffusion);
 129     alEffectf(effect, AL_EAXREVERB_GAIN, reverb->flGain);
 130     alEffectf(effect, AL_EAXREVERB_GAINHF, reverb->flGainHF);
 131     alEffectf(effect, AL_EAXREVERB_GAINLF, reverb->flGainLF);
 132     alEffectf(effect, AL_EAXREVERB_DECAY_TIME, reverb->flDecayTime);
 133     alEffectf(effect, AL_EAXREVERB_DECAY_HFRATIO, reverb->flDecayHFRatio);
 134     alEffectf(effect, AL_EAXREVERB_DECAY_LFRATIO, reverb->flDecayLFRatio);
 135     alEffectf(effect, AL_EAXREVERB_REFLECTIONS_GAIN, reverb->flReflectionsGain);
 136     alEffectf(effect, AL_EAXREVERB_REFLECTIONS_DELAY, reverb->flReflectionsDelay);
 137     alEffectfv(effect, AL_EAXREVERB_REFLECTIONS_PAN, reverb->flReflectionsPan);
 138     alEffectf(effect, AL_EAXREVERB_LATE_REVERB_GAIN, reverb->flLateReverbGain);
 139     alEffectf(effect, AL_EAXREVERB_LATE_REVERB_DELAY, reverb->flLateReverbDelay);
 140     alEffectfv(effect, AL_EAXREVERB_LATE_REVERB_PAN, reverb->flLateReverbPan);
 141     alEffectf(effect, AL_EAXREVERB_ECHO_TIME, reverb->flEchoTime);
 142     alEffectf(effect, AL_EAXREVERB_ECHO_DEPTH, reverb->flEchoDepth);
 143     alEffectf(effect, AL_EAXREVERB_MODULATION_TIME, reverb->flModulationTime);
 144     alEffectf(effect, AL_EAXREVERB_MODULATION_DEPTH, reverb->flModulationDepth);
 145     alEffectf(effect, AL_EAXREVERB_AIR_ABSORPTION_GAINHF, reverb->flAirAbsorptionGainHF);
 146     alEffectf(effect, AL_EAXREVERB_HFREFERENCE, reverb->flHFReference);
 147     alEffectf(effect, AL_EAXREVERB_LFREFERENCE, reverb->flLFReference);
 148     alEffectf(effect, AL_EAXREVERB_ROOM_ROLLOFF_FACTOR, reverb->flRoomRolloffFactor);
 149     alEffecti(effect, AL_EAXREVERB_DECAY_HFLIMIT, reverb->iDecayHFLimit);
 150
 151     /* Check if an error occured, and return failure if so. */
 152     if((err=alGetError()) != AL_NO_ERROR)
 153     {
 154         fprintf(stderr, "Error setting up reverb: %s\n", alGetString(err));
 155         return 0;
 156     }
 157
 158     return 1;
 159 }
 160
 161
 162 /* LoadBuffer loads the named audio file into an OpenAL buffer object, and
 163  * returns the new buffer ID.
 164  */
 165 static ALuint LoadSound(const char *filename)
 166 {
 167     ALenum err, format;
 168     ALuint buffer;
 169     SNDFILE *sndfile;
 170     SF_INFO sfinfo;
 171     short *membuf;
 172     sf_count_t num_frames;
 173     ALsizei num_bytes;
 174
 175     /* Open the audio file and check that it's usable. */
 176     sndfile = sf_open(filename, SFM_READ, &sfinfo);
 177     if(!sndfile)
 178     {
 179         fprintf(stderr, "Could not open audio in %s: %s\n", filename, sf_strerror(sndfile));
 180         return 0;
 181     }
 182     if(sfinfo.frames < 1 || sfinfo.frames > (sf_count_t)(INT_MAX/sizeof(short))/sfinfo.channels)
 183     {
 184         fprintf(stderr, "Bad sample count in %s (%" PRId64 ")\n", filename, sfinfo.frames);
 185         sf_close(sndfile);
 186         return 0;
 187     }
 188
 189     /* Get the sound format, and figure out the OpenAL format */
 190     if(sfinfo.channels == 1)
 191         format = AL_FORMAT_MONO16;
 192     else if(sfinfo.channels == 2)
 193         format = AL_FORMAT_STEREO16;
 194     else
 195     {
 196         fprintf(stderr, "Unsupported channel count: %d\n", sfinfo.channels);
 197         sf_close(sndfile);
 198         return 0;
 199     }
 200
 201     /* Decode the whole audio file to a buffer. */
 202     membuf = malloc((size_t)(sfinfo.frames * sfinfo.channels) * sizeof(short));
 203
 204     num_frames = sf_readf_short(sndfile, membuf, sfinfo.frames);
 205     if(num_frames < 1)
 206     {
 207         free(membuf);
 208         sf_close(sndfile);
 209         fprintf(stderr, "Failed to read samples in %s (%" PRId64 ")\n", filename, num_frames);
 210         return 0;
 211     }
 212     num_bytes = (ALsizei)(num_frames * sfinfo.channels) * (ALsizei)sizeof(short);
 213
 214     /* Buffer the audio data into a new buffer object, then free the data and
 215      * close the file.
 216      */
 217     buffer = 0;
 218     alGenBuffers(1, &buffer);
 219     alBufferData(buffer, format, membuf, num_bytes, sfinfo.samplerate);
 220
 221     free(membuf);
 222     sf_close(sndfile);
 223
 224     /* Check if an error occured, and clean up if so. */
 225     err = alGetError();
 226     if(err != AL_NO_ERROR)
 227     {
 228         fprintf(stderr, "OpenAL Error: %s\n", alGetString(err));
 229         if(buffer && alIsBuffer(buffer))
 230             alDeleteBuffers(1, &buffer);
 231         return 0;
 232     }
 233
 234     return buffer;
 235 }
 236
 237
 238 /* Helper to calculate the dot-product of the two given vectors. */
 239 static ALfloat dot_product(const ALfloat vec0[3], const ALfloat vec1[3])
 240 {
 241     return vec0[0]*vec1[0] + vec0[1]*vec1[1] + vec0[2]*vec1[2];
 242 }
 243
 244 /* Helper to normalize a given vector. */
 245 static void normalize(ALfloat vec[3])
 246 {
 247     ALfloat mag = sqrtf(dot_product(vec, vec));
 248     if(mag > 0.00001f)
 249     {
 250         vec[0] /= mag;
 251         vec[1] /= mag;
 252         vec[2] /= mag;
 253     }
 254     else
 255     {
 256         vec[0] = 0.0f;
 257         vec[1] = 0.0f;
 258         vec[2] = 0.0f;
 259     }
 260 }
 261
 262
 263 /* The main update function to update the listener and environment effects. */
 264 static void UpdateListenerAndEffects(float timediff, const ALuint slots[2], const ALuint effects[2], const EFXEAXREVERBPROPERTIES reverbs[2])
 265 {
 266     static const ALfloat listener_move_scale = 10.0f;
 267     /* Individual reverb zones are connected via "portals". Each portal has a
 268      * position (center point of the connecting area), a normal (facing
 269      * direction), and a radius (approximate size of the connecting area).
 270      */
 271     const ALfloat portal_pos[3] = { 0.0f, 0.0f, 0.0f };
 272     const ALfloat portal_norm[3] = { sqrtf(0.5f), 0.0f, -sqrtf(0.5f) };
 273     const ALfloat portal_radius = 2.5f;
 274     ALfloat other_dir[3], this_dir[3];
 275     ALfloat listener_pos[3];
 276     ALfloat local_norm[3];
 277     ALfloat local_dir[3];
 278     ALfloat near_edge[3];
 279     ALfloat far_edge[3];
 280     ALfloat dist, edist;
 281
 282     /* Update the listener position for the amount of time passed. This uses a
 283      * simple triangular LFO to offset the position (moves along the X axis
 284      * between -listener_move_scale and +listener_move_scale for each
 285      * transition).
 286      */
 287     listener_pos[0] = (fabsf(2.0f - timediff/2.0f) - 1.0f) * listener_move_scale;
 288     listener_pos[1] = 0.0f;
 289     listener_pos[2] = 0.0f;
 290     alListenerfv(AL_POSITION, listener_pos);
 291
 292     /* Calculate local_dir, which represents the listener-relative point to the
 293      * adjacent zone (should also include orientation). Because EAX Reverb uses
 294      * left-handed coordinates instead of right-handed like the rest of OpenAL,
 295      * negate Z for the local values.
 296      */
 297     local_dir[0] = portal_pos[0] - listener_pos[0];
 298     local_dir[1] = portal_pos[1] - listener_pos[1];
 299     local_dir[2] = -(portal_pos[2] - listener_pos[2]);
 300     /* A normal application would also rotate the portal's normal given the
 301      * listener orientation, to get the listener-relative normal.
 302      */
 303     local_norm[0] = portal_norm[0];
 304     local_norm[1] = portal_norm[1];
 305     local_norm[2] = -portal_norm[2];
 306
 307     /* Calculate the distance from the listener to the portal, and ensure it's
 308      * far enough away to not suffer severe floating-point precision issues.
 309      */
 310     dist = sqrtf(dot_product(local_dir, local_dir));
 311     if(dist > 0.00001f)
 312     {
 313         const EFXEAXREVERBPROPERTIES *other_reverb, *this_reverb;
 314         ALuint other_effect, this_effect;
 315         ALfloat magnitude, dir_dot_norm;
 316
 317         /* Normalize the direction to the portal. */
 318         local_dir[0] /= dist;
 319         local_dir[1] /= dist;
 320         local_dir[2] /= dist;
 321
 322         /* Calculate the dot product of the portal's local direction and local
 323          * normal, which is used for angular and side checks later on.
 324          */
 325         dir_dot_norm = dot_product(local_dir, local_norm);
 326
 327         /* Figure out which zone we're in. */
 328         if(dir_dot_norm <= 0.0f)
 329         {
 330             /* We're in front of the portal, so we're in Zone 0. */
 331             this_effect = effects[0];
 332             other_effect = effects[1];
 333             this_reverb = &reverbs[0];
 334             other_reverb = &reverbs[1];
 335         }
 336         else
 337         {
 338             /* We're behind the portal, so we're in Zone 1. */
 339             this_effect = effects[1];
 340             other_effect = effects[0];
 341             this_reverb = &reverbs[1];
 342             other_reverb = &reverbs[0];
 343         }
 344
 345         /* Calculate the listener-relative extents of the portal. */
 346         /* First, project the listener-to-portal vector onto the portal's plane
 347          * to get the portal-relative direction along the plane that goes away
 348          * from the listener (toward the farthest edge of the portal).
 349          */
 350         far_edge[0] = local_dir[0] - local_norm[0]*dir_dot_norm;
 351         far_edge[1] = local_dir[1] - local_norm[1]*dir_dot_norm;
 352         far_edge[2] = local_dir[2] - local_norm[2]*dir_dot_norm;
 353
 354         edist = sqrtf(dot_product(far_edge, far_edge));
 355         if(edist > 0.0001f)
 356         {
 357             /* Rescale the portal-relative vector to be at the radius edge. */
 358             ALfloat mag = portal_radius / edist;
 359             far_edge[0] *= mag;
 360             far_edge[1] *= mag;
 361             far_edge[2] *= mag;
 362
 363             /* Calculate the closest edge of the portal by negating the
 364              * farthest, and add an offset to make them both relative to the
 365              * listener.
 366              */
 367             near_edge[0] = local_dir[0]*dist - far_edge[0];
 368             near_edge[1] = local_dir[1]*dist - far_edge[1];
 369             near_edge[2] = local_dir[2]*dist - far_edge[2];
 370             far_edge[0] += local_dir[0]*dist;
 371             far_edge[1] += local_dir[1]*dist;
 372             far_edge[2] += local_dir[2]*dist;
 373
 374             /* Normalize the listener-relative extents of the portal, then
 375              * calculate the panning magnitude for the other zone given the
 376              * apparent size of the opening. The panning magnitude affects the
 377              * envelopment of the environment, with 1 being a point, 0.5 being
 378              * half coverage around the listener, and 0 being full coverage.
 379              */
 380             normalize(far_edge);
 381             normalize(near_edge);
 382             magnitude = 1.0f - acosf(dot_product(far_edge, near_edge))/(float)(M_PI*2.0);
 383
 384             /* Recalculate the panning direction, to be directly between the
 385              * direction of the two extents.
 386              */
 387             local_dir[0] = far_edge[0] + near_edge[0];
 388             local_dir[1] = far_edge[1] + near_edge[1];
 389             local_dir[2] = far_edge[2] + near_edge[2];
 390             normalize(local_dir);
 391         }
 392         else
 393         {
 394             /* If we get here, the listener is directly in front of or behind
 395              * the center of the portal, making all aperture edges effectively
 396              * equidistant. Calculating the panning magnitude is simplified,
 397              * using the arctangent of the radius and distance.
 398              */
 399             magnitude = 1.0f - (atan2f(portal_radius, dist) / (float)M_PI);
 400         }
 401
 402         /* Scale the other zone's panning vector. */
 403         other_dir[0] = local_dir[0] * magnitude;
 404         other_dir[1] = local_dir[1] * magnitude;
 405         other_dir[2] = local_dir[2] * magnitude;
 406         /* Pan the current zone to the opposite direction of the portal, and
 407          * take the remaining percentage of the portal's magnitude.
 408          */
 409         this_dir[0] = local_dir[0] * (magnitude-1.0f);
 410         this_dir[1] = local_dir[1] * (magnitude-1.0f);
 411         this_dir[2] = local_dir[2] * (magnitude-1.0f);
 412
 413         /* Now set the effects' panning vectors and gain. Energy is shared
 414          * between environments, so attenuate according to each zone's
 415          * contribution (note: gain^2 = energy).
 416          */
 417         alEffectf(this_effect, AL_EAXREVERB_REFLECTIONS_GAIN, this_reverb->flReflectionsGain * sqrtf(magnitude));
 418         alEffectf(this_effect, AL_EAXREVERB_LATE_REVERB_GAIN, this_reverb->flLateReverbGain * sqrtf(magnitude));
 419         alEffectfv(this_effect, AL_EAXREVERB_REFLECTIONS_PAN, this_dir);
 420         alEffectfv(this_effect, AL_EAXREVERB_LATE_REVERB_PAN, this_dir);
 421
 422         alEffectf(other_effect, AL_EAXREVERB_REFLECTIONS_GAIN, other_reverb->flReflectionsGain * sqrtf(1.0f-magnitude));
 423         alEffectf(other_effect, AL_EAXREVERB_LATE_REVERB_GAIN, other_reverb->flLateReverbGain * sqrtf(1.0f-magnitude));
 424         alEffectfv(other_effect, AL_EAXREVERB_REFLECTIONS_PAN, other_dir);
 425         alEffectfv(other_effect, AL_EAXREVERB_LATE_REVERB_PAN, other_dir);
 426     }
 427     else
 428     {
 429         /* We're practically in the center of the portal. Give the panning
 430          * vectors a 50/50 split, with Zone 0 covering the half in front of
 431          * the normal, and Zone 1 covering the half behind.
 432          */
 433         this_dir[0] = local_norm[0] / 2.0f;
 434         this_dir[1] = local_norm[1] / 2.0f;
 435         this_dir[2] = local_norm[2] / 2.0f;
 436
 437         other_dir[0] = local_norm[0] / -2.0f;
 438         other_dir[1] = local_norm[1] / -2.0f;
 439         other_dir[2] = local_norm[2] / -2.0f;
 440
 441         alEffectf(effects[0], AL_EAXREVERB_REFLECTIONS_GAIN, reverbs[0].flReflectionsGain * sqrtf(0.5f));
 442         alEffectf(effects[0], AL_EAXREVERB_LATE_REVERB_GAIN, reverbs[0].flLateReverbGain * sqrtf(0.5f));
 443         alEffectfv(effects[0], AL_EAXREVERB_REFLECTIONS_PAN, this_dir);
 444         alEffectfv(effects[0], AL_EAXREVERB_LATE_REVERB_PAN, this_dir);
 445
 446         alEffectf(effects[1], AL_EAXREVERB_REFLECTIONS_GAIN, reverbs[1].flReflectionsGain * sqrtf(0.5f));
 447         alEffectf(effects[1], AL_EAXREVERB_LATE_REVERB_GAIN, reverbs[1].flLateReverbGain * sqrtf(0.5f));
 448         alEffectfv(effects[1], AL_EAXREVERB_REFLECTIONS_PAN, other_dir);
 449         alEffectfv(effects[1], AL_EAXREVERB_LATE_REVERB_PAN, other_dir);
 450     }
 451
 452     /* Finally, update the effect slots with the updated effect parameters. */
 453     alAuxiliaryEffectSloti(slots[0], AL_EFFECTSLOT_EFFECT, (ALint)effects[0]);
 454     alAuxiliaryEffectSloti(slots[1], AL_EFFECTSLOT_EFFECT, (ALint)effects[1]);
 455 }
 456
 457
 458 int main(int argc, char **argv)
 459 {
 460     static const int MaxTransitions = 8;
 461     EFXEAXREVERBPROPERTIES reverbs[2] = {
 462         EFX_REVERB_PRESET_CARPETEDHALLWAY,
 463         EFX_REVERB_PRESET_BATHROOM
 464     };
 465     ALCdevice *device = NULL;
 466     ALCcontext *context = NULL;
 467     ALuint effects[2] = { 0, 0 };
 468     ALuint slots[2] = { 0, 0 };
 469     ALuint direct_filter = 0;
 470     ALuint buffer = 0;
 471     ALuint source = 0;
 472     ALCint num_sends = 0;
 473     ALenum state = AL_INITIAL;
 474     ALfloat direct_gain = 1.0f;
 475     int basetime = 0;
 476     int loops = 0;
 477
 478     /* Print out usage if no arguments were specified */
 479     if(argc < 2)
 480     {
 481         fprintf(stderr, "Usage: %s [-device <name>] [options] <filename>\n\n"
 482         "Options:\n"
 483         "\t-nodirect\tSilence direct path output (easier to hear reverb)\n\n",
 484         argv[0]);
 485         return 1;
 486     }
 487
 488     /* Initialize OpenAL, and check for EFX support with at least 2 auxiliary
 489      * sends (if multiple sends are supported, 2 are provided by default; if
 490      * you want more, you have to request it through alcCreateContext).
 491      */
 492     argv++; argc--;
 493     if(InitAL(&argv, &argc) != 0)
 494         return 1;
 495
 496     while(argc > 0)
 497     {
 498         if(strcmp(argv[0], "-nodirect") == 0)
 499             direct_gain = 0.0f;
 500         else
 501             break;
 502         argv++;
 503         argc--;
 504     }
 505     if(argc < 1)
 506     {
 507         fprintf(stderr, "No filename spacified.\n");
 508         CloseAL();
 509         return 1;
 510     }
 511
 512     context = alcGetCurrentContext();
 513     device = alcGetContextsDevice(context);
 514
 515     if(!alcIsExtensionPresent(device, "ALC_EXT_EFX"))
 516     {
 517         fprintf(stderr, "Error: EFX not supported\n");
 518         CloseAL();
 519         return 1;
 520     }
 521
 522     num_sends = 0;
 523     alcGetIntegerv(device, ALC_MAX_AUXILIARY_SENDS, 1, &num_sends);
 524     if(alcGetError(device) != ALC_NO_ERROR || num_sends < 2)
 525     {
 526         fprintf(stderr, "Error: Device does not support multiple sends (got %d, need 2)\n",
 527                 num_sends);
 528         CloseAL();
 529         return 1;
 530     }
 531
 532     /* Define a macro to help load the function pointers. */
 533 #define LOAD_PROC(T, x)  ((x) = FUNCTION_CAST(T, alGetProcAddress(#x)))
 534     LOAD_PROC(LPALGENFILTERS, alGenFilters);
 535     LOAD_PROC(LPALDELETEFILTERS, alDeleteFilters);
 536     LOAD_PROC(LPALISFILTER, alIsFilter);
 537     LOAD_PROC(LPALFILTERI, alFilteri);
 538     LOAD_PROC(LPALFILTERIV, alFilteriv);
 539     LOAD_PROC(LPALFILTERF, alFilterf);
 540     LOAD_PROC(LPALFILTERFV, alFilterfv);
 541     LOAD_PROC(LPALGETFILTERI, alGetFilteri);
 542     LOAD_PROC(LPALGETFILTERIV, alGetFilteriv);
 543     LOAD_PROC(LPALGETFILTERF, alGetFilterf);
 544     LOAD_PROC(LPALGETFILTERFV, alGetFilterfv);
 545
 546     LOAD_PROC(LPALGENEFFECTS, alGenEffects);
 547     LOAD_PROC(LPALDELETEEFFECTS, alDeleteEffects);
 548     LOAD_PROC(LPALISEFFECT, alIsEffect);
 549     LOAD_PROC(LPALEFFECTI, alEffecti);
 550     LOAD_PROC(LPALEFFECTIV, alEffectiv);
 551     LOAD_PROC(LPALEFFECTF, alEffectf);
 552     LOAD_PROC(LPALEFFECTFV, alEffectfv);
 553     LOAD_PROC(LPALGETEFFECTI, alGetEffecti);
 554     LOAD_PROC(LPALGETEFFECTIV, alGetEffectiv);
 555     LOAD_PROC(LPALGETEFFECTF, alGetEffectf);
 556     LOAD_PROC(LPALGETEFFECTFV, alGetEffectfv);
 557
 558     LOAD_PROC(LPALGENAUXILIARYEFFECTSLOTS, alGenAuxiliaryEffectSlots);
 559     LOAD_PROC(LPALDELETEAUXILIARYEFFECTSLOTS, alDeleteAuxiliaryEffectSlots);
 560     LOAD_PROC(LPALISAUXILIARYEFFECTSLOT, alIsAuxiliaryEffectSlot);
 561     LOAD_PROC(LPALAUXILIARYEFFECTSLOTI, alAuxiliaryEffectSloti);
 562     LOAD_PROC(LPALAUXILIARYEFFECTSLOTIV, alAuxiliaryEffectSlotiv);
 563     LOAD_PROC(LPALAUXILIARYEFFECTSLOTF, alAuxiliaryEffectSlotf);
 564     LOAD_PROC(LPALAUXILIARYEFFECTSLOTFV, alAuxiliaryEffectSlotfv);
 565     LOAD_PROC(LPALGETAUXILIARYEFFECTSLOTI, alGetAuxiliaryEffectSloti);
 566     LOAD_PROC(LPALGETAUXILIARYEFFECTSLOTIV, alGetAuxiliaryEffectSlotiv);
 567     LOAD_PROC(LPALGETAUXILIARYEFFECTSLOTF, alGetAuxiliaryEffectSlotf);
 568     LOAD_PROC(LPALGETAUXILIARYEFFECTSLOTFV, alGetAuxiliaryEffectSlotfv);
 569 #undef LOAD_PROC
 570
 571     /* Load the sound into a buffer. */
 572     buffer = LoadSound(argv[0]);
 573     if(!buffer)
 574     {
 575         CloseAL();
 576         return 1;
 577     }
 578
 579     /* Generate two effects for two "zones", and load a reverb into each one.
 580      * Note that unlike single-zone reverb, where you can store one effect per
 581      * preset, for multi-zone reverb you should have one effect per environment
 582      * instance, or one per audible zone. This is because we'll be changing the
 583      * effects' properties in real-time based on the environment instance
 584      * relative to the listener.
 585      */
 586     alGenEffects(2, effects);
 587     if(!LoadEffect(effects[0], &reverbs[0]) || !LoadEffect(effects[1], &reverbs[1]))
 588     {
 589         alDeleteEffects(2, effects);
 590         alDeleteBuffers(1, &buffer);
 591         CloseAL();
 592         return 1;
 593     }
 594
 595     /* Create the effect slot objects, one for each "active" effect. */
 596     alGenAuxiliaryEffectSlots(2, slots);
 597
 598     /* Tell the effect slots to use the loaded effect objects, with slot 0 for
 599      * Zone 0 and slot 1 for Zone 1. Note that this effectively copies the
 600      * effect properties. Modifying or deleting the effect object afterward
 601      * won't directly affect the effect slot until they're reapplied like this.
 602      */
 603     alAuxiliaryEffectSloti(slots[0], AL_EFFECTSLOT_EFFECT, (ALint)effects[0]);
 604     alAuxiliaryEffectSloti(slots[1], AL_EFFECTSLOT_EFFECT, (ALint)effects[1]);
 605     assert(alGetError()==AL_NO_ERROR && "Failed to set effect slot");
 606
 607     /* For the purposes of this example, prepare a filter that optionally
 608      * silences the direct path which allows us to hear just the reverberation.
 609      * A filter like this is normally used for obstruction, where the path
 610      * directly between the listener and source is blocked (the exact
 611      * properties depending on the type and thickness of the obstructing
 612      * material).
 613      */
 614     alGenFilters(1, &direct_filter);
 615     alFilteri(direct_filter, AL_FILTER_TYPE, AL_FILTER_LOWPASS);
 616     alFilterf(direct_filter, AL_LOWPASS_GAIN, direct_gain);
 617     assert(alGetError()==AL_NO_ERROR && "Failed to set direct filter");
 618
 619     /* Create the source to play the sound with, place it in front of the
 620      * listener's path in the left zone.
 621      */
 622     source = 0;
 623     alGenSources(1, &source);
 624     alSourcei(source, AL_LOOPING, AL_TRUE);
 625     alSource3f(source, AL_POSITION, -5.0f, 0.0f, -2.0f);
 626     alSourcei(source, AL_DIRECT_FILTER, (ALint)direct_filter);
 627     alSourcei(source, AL_BUFFER, (ALint)buffer);
 628
 629     /* Connect the source to the effect slots. Here, we connect source send 0
 630      * to Zone 0's slot, and send 1 to Zone 1's slot. Filters can be specified
 631      * to occlude the source from each zone by varying amounts; for example, a
 632      * source within a particular zone would be unfiltered, while a source that
 633      * can only see a zone through a window or thin wall may be attenuated for
 634      * that zone.
 635      */
 636     alSource3i(source, AL_AUXILIARY_SEND_FILTER, (ALint)slots[0], 0, AL_FILTER_NULL);
 637     alSource3i(source, AL_AUXILIARY_SEND_FILTER, (ALint)slots[1], 1, AL_FILTER_NULL);
 638     assert(alGetError()==AL_NO_ERROR && "Failed to setup sound source");
 639
 640     /* Get the current time as the base for timing in the main loop. */
 641     basetime = altime_get();
 642     loops = 0;
 643     printf("Transition %d of %d...\n", loops+1, MaxTransitions);
 644
 645     /* Play the sound for a while. */
 646     alSourcePlay(source);
 647     do {
 648         int curtime;
 649         ALfloat timediff;
 650
 651         /* Start a batch update, to ensure all changes apply simultaneously. */
 652         alcSuspendContext(context);
 653
 654         /* Get the current time to track the amount of time that passed.
 655          * Convert the difference to seconds.
 656          */
 657         curtime = altime_get();
 658         timediff = (float)(curtime - basetime) / 1000.0f;
 659
 660         /* Avoid negative time deltas, in case of non-monotonic clocks. */
 661         if(timediff < 0.0f)
 662             timediff = 0.0f;
 663         else while(timediff >= 4.0f*(float)((loops&1)+1))
 664         {
 665             /* For this example, each transition occurs over 4 seconds, and
 666              * there's 2 transitions per cycle.
 667              */
 668             if(++loops < MaxTransitions)
 669                 printf("Transition %d of %d...\n", loops+1, MaxTransitions);
 670             if(!(loops&1))
 671             {
 672                 /* Cycle completed. Decrease the delta and increase the base
 673                  * time to start a new cycle.
 674                  */
 675                 timediff -= 8.0f;
 676                 basetime += 8000;
 677             }
 678         }
 679
 680         /* Update the listener and effects, and finish the batch. */
 681         UpdateListenerAndEffects(timediff, slots, effects, reverbs);
 682         alcProcessContext(context);
 683
 684         al_nssleep(10000000);
 685
 686         alGetSourcei(source, AL_SOURCE_STATE, &state);
 687     } while(alGetError() == AL_NO_ERROR && state == AL_PLAYING && loops < MaxTransitions);
 688
 689     /* All done. Delete resources, and close down OpenAL. */
 690     alDeleteSources(1, &source);
 691     alDeleteAuxiliaryEffectSlots(2, slots);
 692     alDeleteEffects(2, effects);
 693     alDeleteFilters(1, &direct_filter);
 694     alDeleteBuffers(1, &buffer);
 695
 696     CloseAL();
 697
 698     return 0;
 699 }