antkeeper
/
superbuild


								/*

								 * OpenAL Multi-Zone Reverb Example

								 *

								 * Copyright (c) 2018 by Chris Robinson <chris.kcat@gmail.com>

								 *

								 * Permission is hereby granted, free of charge, to any person obtaining a copy

								 * of this software and associated documentation files (the "Software"), to deal

								 * in the Software without restriction, including without limitation the rights

								 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

								 * copies of the Software, and to permit persons to whom the Software is

								 * furnished to do so, subject to the following conditions:

								 *

								 * The above copyright notice and this permission notice shall be included in

								 * all copies or substantial portions of the Software.

								 *

								 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

								 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

								 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

								 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

								 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

								 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

								 * THE SOFTWARE.

								 */


								/* This file contains an example for controlling multiple reverb zones to

								 * smoothly transition between reverb environments. The general concept is to

								 * extend single-reverb by also tracking the closest adjacent environment, and

								 * utilize EAX Reverb's panning vectors to position them relative to the

								 * listener.

								 */


								#include <stdio.h>

								#include <assert.h>

								#include <math.h>


								#include <SDL_sound.h>


								#include "AL/al.h"

								#include "AL/alc.h"

								#include "AL/alext.h"

								#include "AL/efx-presets.h"


								#include "common/alhelpers.h"


								#ifndef M_PI

								#define M_PI 3.14159265358979323846

								#endif


								/* Filter object functions */

								static LPALGENFILTERS alGenFilters;

								static LPALDELETEFILTERS alDeleteFilters;

								static LPALISFILTER alIsFilter;

								static LPALFILTERI alFilteri;

								static LPALFILTERIV alFilteriv;

								static LPALFILTERF alFilterf;

								static LPALFILTERFV alFilterfv;

								static LPALGETFILTERI alGetFilteri;

								static LPALGETFILTERIV alGetFilteriv;

								static LPALGETFILTERF alGetFilterf;

								static LPALGETFILTERFV alGetFilterfv;


								/* Effect object functions */

								static LPALGENEFFECTS alGenEffects;

								static LPALDELETEEFFECTS alDeleteEffects;

								static LPALISEFFECT alIsEffect;

								static LPALEFFECTI alEffecti;

								static LPALEFFECTIV alEffectiv;

								static LPALEFFECTF alEffectf;

								static LPALEFFECTFV alEffectfv;

								static LPALGETEFFECTI alGetEffecti;

								static LPALGETEFFECTIV alGetEffectiv;

								static LPALGETEFFECTF alGetEffectf;

								static LPALGETEFFECTFV alGetEffectfv;


								/* Auxiliary Effect Slot object functions */

								static LPALGENAUXILIARYEFFECTSLOTS alGenAuxiliaryEffectSlots;

								static LPALDELETEAUXILIARYEFFECTSLOTS alDeleteAuxiliaryEffectSlots;

								static LPALISAUXILIARYEFFECTSLOT alIsAuxiliaryEffectSlot;

								static LPALAUXILIARYEFFECTSLOTI alAuxiliaryEffectSloti;

								static LPALAUXILIARYEFFECTSLOTIV alAuxiliaryEffectSlotiv;

								static LPALAUXILIARYEFFECTSLOTF alAuxiliaryEffectSlotf;

								static LPALAUXILIARYEFFECTSLOTFV alAuxiliaryEffectSlotfv;

								static LPALGETAUXILIARYEFFECTSLOTI alGetAuxiliaryEffectSloti;

								static LPALGETAUXILIARYEFFECTSLOTIV alGetAuxiliaryEffectSlotiv;

								static LPALGETAUXILIARYEFFECTSLOTF alGetAuxiliaryEffectSlotf;

								static LPALGETAUXILIARYEFFECTSLOTFV alGetAuxiliaryEffectSlotfv;


								/* LoadEffect loads the given initial reverb properties into the given OpenAL

								 * effect object, and returns non-zero on success.

								 */

								static int LoadEffect(ALuint effect, const EFXEAXREVERBPROPERTIES *reverb)

								{

								    ALenum err;


								    alGetError();


								    /* Prepare the effect for EAX Reverb (standard reverb doesn't contain

								     * the needed panning vectors).

								     */

								    alEffecti(effect, AL_EFFECT_TYPE, AL_EFFECT_EAXREVERB);

								    if((err=alGetError()) != AL_NO_ERROR)

								    {

								        fprintf(stderr, "Failed to set EAX Reverb: %s (0x%04x)\n", alGetString(err), err);

								        return 0;

								    }


								    /* Load the reverb properties. */

								    alEffectf(effect, AL_EAXREVERB_DENSITY, reverb->flDensity);

								    alEffectf(effect, AL_EAXREVERB_DIFFUSION, reverb->flDiffusion);

								    alEffectf(effect, AL_EAXREVERB_GAIN, reverb->flGain);

								    alEffectf(effect, AL_EAXREVERB_GAINHF, reverb->flGainHF);

								    alEffectf(effect, AL_EAXREVERB_GAINLF, reverb->flGainLF);

								    alEffectf(effect, AL_EAXREVERB_DECAY_TIME, reverb->flDecayTime);

								    alEffectf(effect, AL_EAXREVERB_DECAY_HFRATIO, reverb->flDecayHFRatio);

								    alEffectf(effect, AL_EAXREVERB_DECAY_LFRATIO, reverb->flDecayLFRatio);

								    alEffectf(effect, AL_EAXREVERB_REFLECTIONS_GAIN, reverb->flReflectionsGain);

								    alEffectf(effect, AL_EAXREVERB_REFLECTIONS_DELAY, reverb->flReflectionsDelay);

								    alEffectfv(effect, AL_EAXREVERB_REFLECTIONS_PAN, reverb->flReflectionsPan);

								    alEffectf(effect, AL_EAXREVERB_LATE_REVERB_GAIN, reverb->flLateReverbGain);

								    alEffectf(effect, AL_EAXREVERB_LATE_REVERB_DELAY, reverb->flLateReverbDelay);

								    alEffectfv(effect, AL_EAXREVERB_LATE_REVERB_PAN, reverb->flLateReverbPan);

								    alEffectf(effect, AL_EAXREVERB_ECHO_TIME, reverb->flEchoTime);

								    alEffectf(effect, AL_EAXREVERB_ECHO_DEPTH, reverb->flEchoDepth);

								    alEffectf(effect, AL_EAXREVERB_MODULATION_TIME, reverb->flModulationTime);

								    alEffectf(effect, AL_EAXREVERB_MODULATION_DEPTH, reverb->flModulationDepth);

								    alEffectf(effect, AL_EAXREVERB_AIR_ABSORPTION_GAINHF, reverb->flAirAbsorptionGainHF);

								    alEffectf(effect, AL_EAXREVERB_HFREFERENCE, reverb->flHFReference);

								    alEffectf(effect, AL_EAXREVERB_LFREFERENCE, reverb->flLFReference);

								    alEffectf(effect, AL_EAXREVERB_ROOM_ROLLOFF_FACTOR, reverb->flRoomRolloffFactor);

								    alEffecti(effect, AL_EAXREVERB_DECAY_HFLIMIT, reverb->iDecayHFLimit);


								    /* Check if an error occured, and return failure if so. */

								    if((err=alGetError()) != AL_NO_ERROR)

								    {

								        fprintf(stderr, "Error setting up reverb: %s\n", alGetString(err));

								        return 0;

								    }


								    return 1;

								}


								/* LoadBuffer loads the named audio file into an OpenAL buffer object, and

								 * returns the new buffer ID.

								 */

								static ALuint LoadSound(const char *filename)

								{

								    Sound_Sample *sample;

								    ALenum err, format;

								    ALuint buffer;

								    Uint32 slen;


								    /* Open the audio file */

								    sample = Sound_NewSampleFromFile(filename, NULL, 65536);

								    if(!sample)

								    {

								        fprintf(stderr, "Could not open audio in %s\n", filename);

								        return 0;

								    }


								    /* Get the sound format, and figure out the OpenAL format */

								    if(sample->actual.channels == 1)

								    {

								        if(sample->actual.format == AUDIO_U8)

								            format = AL_FORMAT_MONO8;

								        else if(sample->actual.format == AUDIO_S16SYS)

								            format = AL_FORMAT_MONO16;

								        else

								        {

								            fprintf(stderr, "Unsupported sample format: 0x%04x\n", sample->actual.format);

								            Sound_FreeSample(sample);

								            return 0;

								        }

								    }

								    else if(sample->actual.channels == 2)

								    {

								        if(sample->actual.format == AUDIO_U8)

								            format = AL_FORMAT_STEREO8;

								        else if(sample->actual.format == AUDIO_S16SYS)

								            format = AL_FORMAT_STEREO16;

								        else

								        {

								            fprintf(stderr, "Unsupported sample format: 0x%04x\n", sample->actual.format);

								            Sound_FreeSample(sample);

								            return 0;

								        }

								    }

								    else

								    {

								        fprintf(stderr, "Unsupported channel count: %d\n", sample->actual.channels);

								        Sound_FreeSample(sample);

								        return 0;

								    }


								    /* Decode the whole audio stream to a buffer. */

								    slen = Sound_DecodeAll(sample);

								    if(!sample->buffer || slen == 0)

								    {

								        fprintf(stderr, "Failed to read audio from %s\n", filename);

								        Sound_FreeSample(sample);

								        return 0;

								    }


								    /* Buffer the audio data into a new buffer object, then free the data and

								     * close the file. */

								    buffer = 0;

								    alGenBuffers(1, &buffer);

								    alBufferData(buffer, format, sample->buffer, slen, sample->actual.rate);

								    Sound_FreeSample(sample);


								    /* Check if an error occured, and clean up if so. */

								    err = alGetError();

								    if(err != AL_NO_ERROR)

								    {

								        fprintf(stderr, "OpenAL Error: %s\n", alGetString(err));

								        if(buffer && alIsBuffer(buffer))

								            alDeleteBuffers(1, &buffer);

								        return 0;

								    }


								    return buffer;

								}


								/* Helper to calculate the dot-product of the two given vectors. */

								static ALfloat dot_product(const ALfloat vec0[3], const ALfloat vec1[3])

								{

								    return vec0[0]*vec1[0] + vec0[1]*vec1[1] + vec0[2]*vec1[2];

								}


								/* Helper to normalize a given vector. */

								static void normalize(ALfloat vec[3])

								{

								    ALfloat mag = sqrtf(dot_product(vec, vec));

								    if(mag > 0.00001f)

								    {

								        vec[0] /= mag;

								        vec[1] /= mag;

								        vec[2] /= mag;

								    }

								    else

								    {

								        vec[0] = 0.0f;

								        vec[1] = 0.0f;

								        vec[2] = 0.0f;

								    }

								}


								/* The main update function to update the listener and environment effects. */

								static void UpdateListenerAndEffects(float timediff, const ALuint slots[2], const ALuint effects[2], const EFXEAXREVERBPROPERTIES reverbs[2])

								{

								    static const ALfloat listener_move_scale = 10.0f;

								    /* Individual reverb zones are connected via "portals". Each portal has a

								     * position (center point of the connecting area), a normal (facing

								     * direction), and a radius (approximate size of the connecting area).

								     */

								    const ALfloat portal_pos[3] = { 0.0f, 0.0f, 0.0f };

								    const ALfloat portal_norm[3] = { sqrtf(0.5f), 0.0f, -sqrtf(0.5f) };

								    const ALfloat portal_radius = 2.5f;

								    ALfloat other_dir[3], this_dir[3];

								    ALfloat listener_pos[3];

								    ALfloat local_norm[3];

								    ALfloat local_dir[3];

								    ALfloat near_edge[3];

								    ALfloat far_edge[3];

								    ALfloat dist, edist;


								    /* Update the listener position for the amount of time passed. This uses a

								     * simple triangular LFO to offset the position (moves along the X axis

								     * between -listener_move_scale and +listener_move_scale for each

								     * transition).

								     */

								    listener_pos[0] = (fabsf(2.0f - timediff/2.0f) - 1.0f) * listener_move_scale;

								    listener_pos[1] = 0.0f;

								    listener_pos[2] = 0.0f;

								    alListenerfv(AL_POSITION, listener_pos);


								    /* Calculate local_dir, which represents the listener-relative point to the

								     * adjacent zone (should also include orientation). Because EAX Reverb uses

								     * left-handed coordinates instead of right-handed like the rest of OpenAL,

								     * negate Z for the local values.

								     */

								    local_dir[0] = portal_pos[0] - listener_pos[0];

								    local_dir[1] = portal_pos[1] - listener_pos[1];

								    local_dir[2] = -(portal_pos[2] - listener_pos[2]);

								    /* A normal application would also rotate the portal's normal given the

								     * listener orientation, to get the listener-relative normal.

								     */

								    local_norm[0] = portal_norm[0];

								    local_norm[1] = portal_norm[1];

								    local_norm[2] = -portal_norm[2];


								    /* Calculate the distance from the listener to the portal, and ensure it's

								     * far enough away to not suffer severe floating-point precision issues.

								     */

								    dist = sqrtf(dot_product(local_dir, local_dir));

								    if(dist > 0.00001f)

								    {

								        const EFXEAXREVERBPROPERTIES *other_reverb, *this_reverb;

								        ALuint other_effect, this_effect;

								        ALfloat magnitude, dir_dot_norm;


								        /* Normalize the direction to the portal. */

								        local_dir[0] /= dist;

								        local_dir[1] /= dist;

								        local_dir[2] /= dist;


								        /* Calculate the dot product of the portal's local direction and local

								         * normal, which is used for angular and side checks later on.

								         */

								        dir_dot_norm = dot_product(local_dir, local_norm);


								        /* Figure out which zone we're in. */

								        if(dir_dot_norm <= 0.0f)

								        {

								            /* We're in front of the portal, so we're in Zone 0. */

								            this_effect = effects[0];

								            other_effect = effects[1];

								            this_reverb = &reverbs[0];

								            other_reverb = &reverbs[1];

								        }

								        else

								        {

								            /* We're behind the portal, so we're in Zone 1. */

								            this_effect = effects[1];

								            other_effect = effects[0];

								            this_reverb = &reverbs[1];

								            other_reverb = &reverbs[0];

								        }


								        /* Calculate the listener-relative extents of the portal. */

								        /* First, project the listener-to-portal vector onto the portal's plane

								         * to get the portal-relative direction along the plane that goes away

								         * from the listener (toward the farthest edge of the portal).

								         */

								        far_edge[0] = local_dir[0] - local_norm[0]*dir_dot_norm;

								        far_edge[1] = local_dir[1] - local_norm[1]*dir_dot_norm;

								        far_edge[2] = local_dir[2] - local_norm[2]*dir_dot_norm;


								        edist = sqrtf(dot_product(far_edge, far_edge));

								        if(edist > 0.0001f)

								        {

								            /* Rescale the portal-relative vector to be at the radius edge. */

								            ALfloat mag = portal_radius / edist;

								            far_edge[0] *= mag;

								            far_edge[1] *= mag;

								            far_edge[2] *= mag;


								            /* Calculate the closest edge of the portal by negating the

								             * farthest, and add an offset to make them both relative to the

								             * listener.

								             */

								            near_edge[0] = local_dir[0]*dist - far_edge[0];

								            near_edge[1] = local_dir[1]*dist - far_edge[1];

								            near_edge[2] = local_dir[2]*dist - far_edge[2];

								            far_edge[0] += local_dir[0]*dist;

								            far_edge[1] += local_dir[1]*dist;

								            far_edge[2] += local_dir[2]*dist;


								            /* Normalize the listener-relative extents of the portal, then

								             * calculate the panning magnitude for the other zone given the

								             * apparent size of the opening. The panning magnitude affects the

								             * envelopment of the environment, with 1 being a point, 0.5 being

								             * half coverage around the listener, and 0 being full coverage.

								             */

								            normalize(far_edge);

								            normalize(near_edge);

								            magnitude = 1.0f - acosf(dot_product(far_edge, near_edge))/(float)(M_PI*2.0);


								            /* Recalculate the panning direction, to be directly between the

								             * direction of the two extents.

								             */

								            local_dir[0] = far_edge[0] + near_edge[0];

								            local_dir[1] = far_edge[1] + near_edge[1];

								            local_dir[2] = far_edge[2] + near_edge[2];

								            normalize(local_dir);

								        }

								        else

								        {

								            /* If we get here, the listener is directly in front of or behind

								             * the center of the portal, making all aperture edges effectively

								             * equidistant. Calculating the panning magnitude is simplified,

								             * using the arctangent of the radius and distance.

								             */

								            magnitude = 1.0f - (atan2f(portal_radius, dist) / (float)M_PI);

								        }


								        /* Scale the other zone's panning vector. */

								        other_dir[0] = local_dir[0] * magnitude;

								        other_dir[1] = local_dir[1] * magnitude;

								        other_dir[2] = local_dir[2] * magnitude;

								        /* Pan the current zone to the opposite direction of the portal, and

								         * take the remaining percentage of the portal's magnitude.

								         */

								        this_dir[0] = local_dir[0] * (magnitude-1.0f);

								        this_dir[1] = local_dir[1] * (magnitude-1.0f);

								        this_dir[2] = local_dir[2] * (magnitude-1.0f);


								        /* Now set the effects' panning vectors and gain. Energy is shared

								         * between environments, so attenuate according to each zone's

								         * contribution (note: gain^2 = energy).

								         */

								        alEffectf(this_effect, AL_EAXREVERB_REFLECTIONS_GAIN, this_reverb->flReflectionsGain * sqrtf(magnitude));

								        alEffectf(this_effect, AL_EAXREVERB_LATE_REVERB_GAIN, this_reverb->flLateReverbGain * sqrtf(magnitude));

								        alEffectfv(this_effect, AL_EAXREVERB_REFLECTIONS_PAN, this_dir);

								        alEffectfv(this_effect, AL_EAXREVERB_LATE_REVERB_PAN, this_dir);


								        alEffectf(other_effect, AL_EAXREVERB_REFLECTIONS_GAIN, other_reverb->flReflectionsGain * sqrtf(1.0f-magnitude));

								        alEffectf(other_effect, AL_EAXREVERB_LATE_REVERB_GAIN, other_reverb->flLateReverbGain * sqrtf(1.0f-magnitude));

								        alEffectfv(other_effect, AL_EAXREVERB_REFLECTIONS_PAN, other_dir);

								        alEffectfv(other_effect, AL_EAXREVERB_LATE_REVERB_PAN, other_dir);

								    }

								    else

								    {

								        /* We're practically in the center of the portal. Give the panning

								         * vectors a 50/50 split, with Zone 0 covering the half in front of

								         * the normal, and Zone 1 covering the half behind.

								         */

								        this_dir[0] = local_norm[0] / 2.0f;

								        this_dir[1] = local_norm[1] / 2.0f;

								        this_dir[2] = local_norm[2] / 2.0f;


								        other_dir[0] = local_norm[0] / -2.0f;

								        other_dir[1] = local_norm[1] / -2.0f;

								        other_dir[2] = local_norm[2] / -2.0f;


								        alEffectf(effects[0], AL_EAXREVERB_REFLECTIONS_GAIN, reverbs[0].flReflectionsGain * sqrtf(0.5f));

								        alEffectf(effects[0], AL_EAXREVERB_LATE_REVERB_GAIN, reverbs[0].flLateReverbGain * sqrtf(0.5f));

								        alEffectfv(effects[0], AL_EAXREVERB_REFLECTIONS_PAN, this_dir);

								        alEffectfv(effects[0], AL_EAXREVERB_LATE_REVERB_PAN, this_dir);


								        alEffectf(effects[1], AL_EAXREVERB_REFLECTIONS_GAIN, reverbs[1].flReflectionsGain * sqrtf(0.5f));

								        alEffectf(effects[1], AL_EAXREVERB_LATE_REVERB_GAIN, reverbs[1].flLateReverbGain * sqrtf(0.5f));

								        alEffectfv(effects[1], AL_EAXREVERB_REFLECTIONS_PAN, other_dir);

								        alEffectfv(effects[1], AL_EAXREVERB_LATE_REVERB_PAN, other_dir);

								    }


								    /* Finally, update the effect slots with the updated effect parameters. */

								    alAuxiliaryEffectSloti(slots[0], AL_EFFECTSLOT_EFFECT, effects[0]);

								    alAuxiliaryEffectSloti(slots[1], AL_EFFECTSLOT_EFFECT, effects[1]);

								}


								int main(int argc, char **argv)

								{

								    static const int MaxTransitions = 8;

								    EFXEAXREVERBPROPERTIES reverbs[2] = {

								        EFX_REVERB_PRESET_CARPETEDHALLWAY,

								        EFX_REVERB_PRESET_BATHROOM

								    };

								    ALCdevice *device = NULL;

								    ALCcontext *context = NULL;

								    ALuint effects[2] = { 0, 0 };

								    ALuint slots[2] = { 0, 0 };

								    ALuint direct_filter = 0;

								    ALuint buffer = 0;

								    ALuint source = 0;

								    ALCint num_sends = 0;

								    ALenum state = AL_INITIAL;

								    ALfloat direct_gain = 1.0f;

								    int basetime = 0;

								    int loops = 0;


								    /* Print out usage if no arguments were specified */

								    if(argc < 2)

								    {

								        fprintf(stderr, "Usage: %s [-device <name>] [options] <filename>\n\n"

								        "Options:\n"

								        "\t-nodirect\tSilence direct path output (easier to hear reverb)\n\n",

								        argv[0]);

								        return 1;

								    }


								    /* Initialize OpenAL, and check for EFX support with at least 2 auxiliary

								     * sends (if multiple sends are supported, 2 are provided by default; if

								     * you want more, you have to request it through alcCreateContext).

								     */

								    argv++; argc--;

								    if(InitAL(&argv, &argc) != 0)

								        return 1;


								    while(argc > 0)

								    {

								        if(strcmp(argv[0], "-nodirect") == 0)

								            direct_gain = 0.0f;

								        else

								            break;

								        argv++;

								        argc--;

								    }

								    if(argc < 1)

								    {

								        fprintf(stderr, "No filename spacified.\n");

								        CloseAL();

								        return 1;

								    }


								    context = alcGetCurrentContext();

								    device = alcGetContextsDevice(context);


								    if(!alcIsExtensionPresent(device, "ALC_EXT_EFX"))

								    {

								        fprintf(stderr, "Error: EFX not supported\n");

								        CloseAL();

								        return 1;

								    }


								    num_sends = 0;

								    alcGetIntegerv(device, ALC_MAX_AUXILIARY_SENDS, 1, &num_sends);

								    if(alcGetError(device) != ALC_NO_ERROR || num_sends < 2)

								    {

								        fprintf(stderr, "Error: Device does not support multiple sends (got %d, need 2)\n",

								                num_sends);

								        CloseAL();

								        return 1;

								    }


								    /* Define a macro to help load the function pointers. */

								#define LOAD_PROC(x)  ((x) = alGetProcAddress(#x))

								    LOAD_PROC(alGenFilters);

								    LOAD_PROC(alDeleteFilters);

								    LOAD_PROC(alIsFilter);

								    LOAD_PROC(alFilteri);

								    LOAD_PROC(alFilteriv);

								    LOAD_PROC(alFilterf);

								    LOAD_PROC(alFilterfv);

								    LOAD_PROC(alGetFilteri);

								    LOAD_PROC(alGetFilteriv);

								    LOAD_PROC(alGetFilterf);

								    LOAD_PROC(alGetFilterfv);


								    LOAD_PROC(alGenEffects);

								    LOAD_PROC(alDeleteEffects);

								    LOAD_PROC(alIsEffect);

								    LOAD_PROC(alEffecti);

								    LOAD_PROC(alEffectiv);

								    LOAD_PROC(alEffectf);

								    LOAD_PROC(alEffectfv);

								    LOAD_PROC(alGetEffecti);

								    LOAD_PROC(alGetEffectiv);

								    LOAD_PROC(alGetEffectf);

								    LOAD_PROC(alGetEffectfv);


								    LOAD_PROC(alGenAuxiliaryEffectSlots);

								    LOAD_PROC(alDeleteAuxiliaryEffectSlots);

								    LOAD_PROC(alIsAuxiliaryEffectSlot);

								    LOAD_PROC(alAuxiliaryEffectSloti);

								    LOAD_PROC(alAuxiliaryEffectSlotiv);

								    LOAD_PROC(alAuxiliaryEffectSlotf);

								    LOAD_PROC(alAuxiliaryEffectSlotfv);

								    LOAD_PROC(alGetAuxiliaryEffectSloti);

								    LOAD_PROC(alGetAuxiliaryEffectSlotiv);

								    LOAD_PROC(alGetAuxiliaryEffectSlotf);

								    LOAD_PROC(alGetAuxiliaryEffectSlotfv);

								#undef LOAD_PROC


								    /* Initialize SDL_sound. */

								    Sound_Init();


								    /* Load the sound into a buffer. */

								    buffer = LoadSound(argv[0]);

								    if(!buffer)

								    {

								        CloseAL();

								        Sound_Quit();

								        return 1;

								    }


								    /* Generate two effects for two "zones", and load a reverb into each one.

								     * Note that unlike single-zone reverb, where you can store one effect per

								     * preset, for multi-zone reverb you should have one effect per environment

								     * instance, or one per audible zone. This is because we'll be changing the

								     * effects' properties in real-time based on the environment instance

								     * relative to the listener.

								     */

								    alGenEffects(2, effects);

								    if(!LoadEffect(effects[0], &reverbs[0]) || !LoadEffect(effects[1], &reverbs[1]))

								    {

								        alDeleteEffects(2, effects);

								        alDeleteBuffers(1, &buffer);

								        Sound_Quit();

								        CloseAL();

								        return 1;

								    }


								    /* Create the effect slot objects, one for each "active" effect. */

								    alGenAuxiliaryEffectSlots(2, slots);


								    /* Tell the effect slots to use the loaded effect objects, with slot 0 for

								     * Zone 0 and slot 1 for Zone 1. Note that this effectively copies the

								     * effect properties. Modifying or deleting the effect object afterward

								     * won't directly affect the effect slot until they're reapplied like this.

								     */

								    alAuxiliaryEffectSloti(slots[0], AL_EFFECTSLOT_EFFECT, effects[0]);

								    alAuxiliaryEffectSloti(slots[1], AL_EFFECTSLOT_EFFECT, effects[1]);

								    assert(alGetError()==AL_NO_ERROR && "Failed to set effect slot");


								    /* For the purposes of this example, prepare a filter that optionally

								     * silences the direct path which allows us to hear just the reverberation.

								     * A filter like this is normally used for obstruction, where the path

								     * directly between the listener and source is blocked (the exact

								     * properties depending on the type and thickness of the obstructing

								     * material).

								     */

								    alGenFilters(1, &direct_filter);

								    alFilteri(direct_filter, AL_FILTER_TYPE, AL_FILTER_LOWPASS);

								    alFilterf(direct_filter, AL_LOWPASS_GAIN, direct_gain);

								    assert(alGetError()==AL_NO_ERROR && "Failed to set direct filter");


								    /* Create the source to play the sound with, place it in front of the

								     * listener's path in the left zone.

								     */

								    source = 0;

								    alGenSources(1, &source);

								    alSourcei(source, AL_LOOPING, AL_TRUE);

								    alSource3f(source, AL_POSITION, -5.0f, 0.0f, -2.0f);

								    alSourcei(source, AL_DIRECT_FILTER, direct_filter);

								    alSourcei(source, AL_BUFFER, buffer);


								    /* Connect the source to the effect slots. Here, we connect source send 0

								     * to Zone 0's slot, and send 1 to Zone 1's slot. Filters can be specified

								     * to occlude the source from each zone by varying amounts; for example, a

								     * source within a particular zone would be unfiltered, while a source that

								     * can only see a zone through a window or thin wall may be attenuated for

								     * that zone.

								     */

								    alSource3i(source, AL_AUXILIARY_SEND_FILTER, slots[0], 0, AL_FILTER_NULL);

								    alSource3i(source, AL_AUXILIARY_SEND_FILTER, slots[1], 1, AL_FILTER_NULL);

								    assert(alGetError()==AL_NO_ERROR && "Failed to setup sound source");


								    /* Get the current time as the base for timing in the main loop. */

								    basetime = altime_get();

								    loops = 0;

								    printf("Transition %d of %d...\n", loops+1, MaxTransitions);


								    /* Play the sound for a while. */

								    alSourcePlay(source);

								    do {

								        int curtime;

								        ALfloat timediff;


								        /* Start a batch update, to ensure all changes apply simultaneously. */

								        alcSuspendContext(context);


								        /* Get the current time to track the amount of time that passed.

								         * Convert the difference to seconds.

								         */

								        curtime = altime_get();

								        timediff = (ALfloat)(curtime - basetime) / 1000.0f;


								        /* Avoid negative time deltas, in case of non-monotonic clocks. */

								        if(timediff < 0.0f)

								            timediff = 0.0f;

								        else while(timediff >= 4.0f*((loops&1)+1))

								        {

								            /* For this example, each transition occurs over 4 seconds, and

								             * there's 2 transitions per cycle.

								             */

								            if(++loops < MaxTransitions)

								                printf("Transition %d of %d...\n", loops+1, MaxTransitions);

								            if(!(loops&1))

								            {

								                /* Cycle completed. Decrease the delta and increase the base

								                 * time to start a new cycle.

								                 */

								                timediff -= 8.0f;

								                basetime += 8000;

								            }

								        }


								        /* Update the listener and effects, and finish the batch. */

								        UpdateListenerAndEffects(timediff, slots, effects, reverbs);

								        alcProcessContext(context);


								        al_nssleep(10000000);


								        alGetSourcei(source, AL_SOURCE_STATE, &state);

								    } while(alGetError() == AL_NO_ERROR && state == AL_PLAYING && loops < MaxTransitions);


								    /* All done. Delete resources, and close down SDL_sound and OpenAL. */

								    alDeleteSources(1, &source);

								    alDeleteAuxiliaryEffectSlots(2, slots);

								    alDeleteEffects(2, effects);

								    alDeleteFilters(1, &direct_filter);

								    alDeleteBuffers(1, &buffer);


								    Sound_Quit();

								    CloseAL();


								    return 0;

								}