#+title: Simulated Sense of Hearing

 #+author: Robert McIntyre

 #+email: rlm@mit.edu

 #+description: Simulating multiple listeners and the sense of hearing in jMonkeyEngine3

 #+keywords: simulated hearing, openal, clojure, jMonkeyEngine3, LWJGL, AI

 #+SETUPFILE: ../../aurellem/org/setup.org

 #+INCLUDE: ../../aurellem/org/level-0.org

 #+BABEL: :exports both :noweb yes :cache no :mkdirp yes

 

 * Hearing

 

 I want to be able to place ears in a similar manner to how I place

 the eyes.  I want to be able to place ears in a unique spatial

 position, and receive as output at every tick the F.F.T. of whatever

 signals are happening at that point.

 

 Hearing is one of the more difficult senses to simulate, because there

 is less support for obtaining the actual sound data that is processed

 by jMonkeyEngine3.

 

 jMonkeyEngine's sound system works as follows:

 

  - jMonkeyEngine uses the =AppSettings= for the particular application

    to determine what sort of =AudioRenderer= should be used.

  - although some support is provided for multiple AudioRendering

    backends, jMonkeyEngine at the time of this writing will either

    pick no AudioRenderer at all, or the =LwjglAudioRenderer=

  - jMonkeyEngine tries to figure out what sort of system you're

    running and extracts the appropriate native libraries.

  - the =LwjglAudioRenderer= uses the [[http://lwjgl.org/][=LWJGL=]] (LightWeight Java Game

    Library) bindings to interface with a C library called [[http://kcat.strangesoft.net/openal.html][=OpenAL=]]

  - =OpenAL= calculates the 3D sound localization and feeds a stream of

    sound to any of various sound output devices with which it knows

    how to communicate.

 

 A consequence of this is that there's no way to access the actual

 sound data produced by =OpenAL=.  Even worse, =OpenAL= only supports

 one /listener/, which normally isn't a problem for games, but becomes

 a problem when trying to make multiple AI creatures that can each hear

 the world from a different perspective.

 

 To make many AI creatures in jMonkeyEngine that can each hear the

 world from their own perspective, it is necessary to go all the way

 back to =OpenAL= and implement support for simulated hearing there.

 

 * Extending =OpenAL=

 ** =OpenAL= Devices

    

 =OpenAL= goes to great lengths to support many different systems, all

 with different sound capabilities and interfaces.  It accomplishes this

 difficult task by providing code for many different sound backends in

 pseudo-objects called /Devices/.  There's a device for the Linux Open

 Sound System and the Advanced Linux Sound Architecture, there's one

 for Direct Sound on Windows, there's even one for Solaris. =OpenAL=

 solves the problem of platform independence by providing all these

 Devices.

 

 Wrapper libraries such as LWJGL are free to examine the system on

 which they are running and then select an appropriate device for that

 system. 

 

 There are also a few "special" devices that don't interface with any

 particular system.  These include the Null Device, which doesn't do

 anything, and the Wave Device, which writes whatever sound it receives

 to a file, if everything has been set up correctly when configuring

 =OpenAL=.

 

 Actual mixing of the sound data happens in the Devices, and they are

 the only point in the sound rendering process where this data is

 available. 

 

 Therefore, in order to support multiple listeners, and get the sound

 data in a form that the AIs can use, it is necessary to create a new

 Device, which supports this features.

 

 ** The Send Device

 Adding a device to OpenAL is rather tricky -- there are five separate

 files in the =OpenAL= source tree that must be modified to do so. I've

 documented this process [[./add-new-device.org][here]] for anyone who is interested.

 

 

 Onward to that actual Device!

 

 again, my objectives are:

 

  - Support Multiple Listeners from jMonkeyEngine3

  - Get access to the rendered sound data for further processing from

    clojure.

 

 ** =send.c=

 

 ** Header

 #+name: send-header

 #+begin_src C

 #include "config.h"

 #include <stdlib.h>

 #include "alMain.h"

 #include "AL/al.h"

 #include "AL/alc.h"

 #include "alSource.h"

 #include <jni.h>

 

 //////////////////// Summary

 

 struct send_data;

 struct context_data;

 

 static void addContext(ALCdevice *, ALCcontext *);

 static void syncContexts(ALCcontext *master, ALCcontext *slave);

 static void syncSources(ALsource *master, ALsource *slave, 

 			ALCcontext *masterCtx, ALCcontext *slaveCtx);

 

 static void syncSourcei(ALuint master, ALuint slave,

 			ALCcontext *masterCtx, ALCcontext *ctx2, ALenum param);

 static void syncSourcef(ALuint master, ALuint slave,

 			ALCcontext *masterCtx, ALCcontext *ctx2, ALenum param);

 static void syncSource3f(ALuint master, ALuint slave,

 			ALCcontext *masterCtx, ALCcontext *ctx2, ALenum param);

 

 static void swapInContext(ALCdevice *, struct context_data *);

 static void saveContext(ALCdevice *, struct context_data *);

 static void limitContext(ALCdevice *, ALCcontext *);

 static void unLimitContext(ALCdevice *);

 

 static void init(ALCdevice *);

 static void renderData(ALCdevice *, int samples);

 

 #define UNUSED(x)  (void)(x)

 #+end_src

 

 The main idea behind the Send device is to take advantage of the fact

 that LWJGL only manages one /context/ when using OpenAL.  A /context/

 is like a container that holds samples and keeps track of where the

 listener is.  In order to support multiple listeners, the Send device

 identifies the LWJGL context as the master context, and creates any

 number of slave contexts to represent additional listeners.  Every

 time the device renders sound, it synchronizes every source from the

 master LWJGL context to the slave contexts.  Then, it renders each

 context separately, using a different listener for each one.  The

 rendered sound is made available via JNI to jMonkeyEngine.

 

 To recap, the process is: 

  - Set the LWJGL context as "master" in the =init()= method.

  - Create any number of additional contexts via =addContext()=

  - At every call to =renderData()= sync the master context with the

    slave contexts with =syncContexts()=

  - =syncContexts()= calls =syncSources()= to sync all the sources

    which are in the master context.

  - =limitContext()= and =unLimitContext()= make it possible to render

    only one context at a time.

 

 ** Necessary State

 #+name: send-state

 #+begin_src C

 ////////////////////  State

 

 typedef struct context_data {

   ALfloat ClickRemoval[MAXCHANNELS];

   ALfloat PendingClicks[MAXCHANNELS];

   ALvoid *renderBuffer;

   ALCcontext *ctx;

 } context_data;

 

 typedef struct send_data {

   ALuint size;

   context_data **contexts;

   ALuint numContexts;

   ALuint maxContexts;

 } send_data;

 #+end_src

 

 Switching between contexts is not the normal operation of a Device,

 and one of the problems with doing so is that a Device normally keeps

 around a few pieces of state such as the =ClickRemoval= array above

 which will become corrupted if the contexts are not done in

 parallel. The solution is to create a copy of this normally global

 device state for each context, and copy it back and forth into and out

 of the actual device state whenever a context is rendered.

 

 ** Synchronization Macros

 #+name: sync-macros

 #+begin_src C

 ////////////////////  Context Creation / Synchronization

 

 #define _MAKE_SYNC(NAME, INIT_EXPR, GET_EXPR, SET_EXPR)	\

   void NAME (ALuint sourceID1, ALuint sourceID2,	\

 	     ALCcontext *ctx1, ALCcontext *ctx2,	\

 	     ALenum param){				\

     INIT_EXPR;						\

     ALCcontext *current = alcGetCurrentContext();	\

     alcMakeContextCurrent(ctx1);			\

     GET_EXPR;						\

     alcMakeContextCurrent(ctx2);			\

     SET_EXPR;						\

     alcMakeContextCurrent(current);			\

   }

   

 #define MAKE_SYNC(NAME, TYPE, GET, SET)			\

   _MAKE_SYNC(NAME,					\

 	     TYPE value,				\

              GET(sourceID1, param, &value),		\

              SET(sourceID2, param, value))

   

 #define MAKE_SYNC3(NAME, TYPE, GET, SET)				\

   _MAKE_SYNC(NAME,							\

 	     TYPE value1; TYPE value2; TYPE value3;,			\

 	     GET(sourceID1, param, &value1, &value2, &value3),		\

 	     SET(sourceID2, param,  value1,  value2,  value3))

 

 MAKE_SYNC( syncSourcei,  ALint,   alGetSourcei,  alSourcei);

 MAKE_SYNC( syncSourcef,  ALfloat, alGetSourcef,  alSourcef);

 MAKE_SYNC3(syncSource3i, ALint,   alGetSource3i, alSource3i);

 MAKE_SYNC3(syncSource3f, ALfloat, alGetSource3f, alSource3f);

   

 #+end_src

 

 Setting the state of an =OpenAL= source is done with the =alSourcei=,

 =alSourcef=, =alSource3i=, and =alSource3f= functions.  In order to

 completely synchronize two sources, it is necessary to use all of

 them. These macros help to condense the otherwise repetitive

 synchronization code involving these similar low-level =OpenAL= functions.

 

 ** Source Synchronization

 #+name: sync-sources

 #+begin_src C

 void syncSources(ALsource *masterSource, ALsource *slaveSource, 

 		 ALCcontext *masterCtx, ALCcontext *slaveCtx){

   ALuint master = masterSource->source;

   ALuint slave = slaveSource->source;

   ALCcontext *current = alcGetCurrentContext();

 

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_PITCH);

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_GAIN);

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_MAX_DISTANCE);

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_ROLLOFF_FACTOR);

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_REFERENCE_DISTANCE);

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_MIN_GAIN);

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_MAX_GAIN);

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_CONE_OUTER_GAIN);

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_CONE_INNER_ANGLE);

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_CONE_OUTER_ANGLE);

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_SEC_OFFSET);

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_SAMPLE_OFFSET);

   syncSourcef(master,slave,masterCtx,slaveCtx,AL_BYTE_OFFSET);

     

   syncSource3f(master,slave,masterCtx,slaveCtx,AL_POSITION);

   syncSource3f(master,slave,masterCtx,slaveCtx,AL_VELOCITY);

   syncSource3f(master,slave,masterCtx,slaveCtx,AL_DIRECTION);

   

   syncSourcei(master,slave,masterCtx,slaveCtx,AL_SOURCE_RELATIVE);

   syncSourcei(master,slave,masterCtx,slaveCtx,AL_LOOPING);

 

   alcMakeContextCurrent(masterCtx);

   ALint source_type;

   alGetSourcei(master, AL_SOURCE_TYPE, &source_type);

 

   // Only static sources are currently synchronized! 

   if (AL_STATIC == source_type){

     ALint master_buffer;

     ALint slave_buffer;

     alGetSourcei(master, AL_BUFFER, &master_buffer);

     alcMakeContextCurrent(slaveCtx);

     alGetSourcei(slave, AL_BUFFER, &slave_buffer);

     if (master_buffer != slave_buffer){

       alSourcei(slave, AL_BUFFER, master_buffer);

     }

   }

   

   // Synchronize the state of the two sources.

   alcMakeContextCurrent(masterCtx);

   ALint masterState;

   ALint slaveState;

 

   alGetSourcei(master, AL_SOURCE_STATE, &masterState);

   alcMakeContextCurrent(slaveCtx);

   alGetSourcei(slave, AL_SOURCE_STATE, &slaveState);

 

   if (masterState != slaveState){

     switch (masterState){

     case AL_INITIAL : alSourceRewind(slave); break;

     case AL_PLAYING : alSourcePlay(slave);   break;

     case AL_PAUSED  : alSourcePause(slave);  break;

     case AL_STOPPED : alSourceStop(slave);   break;

     }

   }

   // Restore whatever context was previously active.

   alcMakeContextCurrent(current);

 }

 #+end_src

 This function is long because it has to exhaustively go through all the

 possible state that a source can have and make sure that it is the

 same between the master and slave sources.  I'd like to take this

 moment to salute the [[http://connect.creativelabs.com/openal/Documentation/Forms/AllItems.aspx][=OpenAL= Reference Manual]], which provides a very

 good description of =OpenAL='s internals.

 

 ** Context Synchronization

 #+name: sync-contexts

 #+begin_src C

 void syncContexts(ALCcontext *master, ALCcontext *slave){

   /* If there aren't sufficient sources in slave to mirror 

      the sources in master, create them. */

   ALCcontext *current = alcGetCurrentContext();

 

   UIntMap *masterSourceMap = &(master->SourceMap);

   UIntMap *slaveSourceMap = &(slave->SourceMap);

   ALuint numMasterSources = masterSourceMap->size;

   ALuint numSlaveSources = slaveSourceMap->size;

 

   alcMakeContextCurrent(slave);

   if (numSlaveSources < numMasterSources){

     ALuint numMissingSources = numMasterSources - numSlaveSources;

     ALuint newSources[numMissingSources];

     alGenSources(numMissingSources, newSources);

   }

 

   /* Now, slave is guaranteed to have at least as many sources

      as master.  Sync each source from master to the corresponding

      source in slave. */

   int i;

   for(i = 0; i < masterSourceMap->size; i++){

     syncSources((ALsource*)masterSourceMap->array[i].value,

 		(ALsource*)slaveSourceMap->array[i].value,

 		master, slave);

   }

   alcMakeContextCurrent(current);

 }

 #+end_src

 

 Most of the hard work in Context Synchronization is done in

 =syncSources()=. The only thing that =syncContexts()= has to worry

 about is automatically creating new sources whenever a slave context

 does not have the same number of sources as the master context.

 

 ** Context Creation

 #+name: context-creation

 #+begin_src C

 static void addContext(ALCdevice *Device, ALCcontext *context){

   send_data *data = (send_data*)Device->ExtraData;

   // expand array if necessary

   if (data->numContexts >= data->maxContexts){

     ALuint newMaxContexts = data->maxContexts*2 + 1;

     data->contexts = realloc(data->contexts, newMaxContexts*sizeof(context_data));

     data->maxContexts = newMaxContexts;

   }

   // create context_data and add it to the main array

   context_data *ctxData;

   ctxData = (context_data*)calloc(1, sizeof(*ctxData));

   ctxData->renderBuffer = 

     malloc(BytesFromDevFmt(Device->FmtType) * 

 	   Device->NumChan * Device->UpdateSize);

   ctxData->ctx = context;

 

   data->contexts[data->numContexts] = ctxData;

   data->numContexts++;

 }

 #+end_src

 

 Here, the slave context is created, and it's data is stored in the

 device-wide =ExtraData= structure.  The =renderBuffer= that is created

 here is where the rendered sound samples for this slave context will

 eventually go.

 

 ** Context Switching

 #+name: context-switching

 #+begin_src C

 ////////////////////  Context Switching 

 

 /* A device brings along with it two pieces of state

  * which have to be swapped in and out with each context.

  */

 static void swapInContext(ALCdevice *Device, context_data *ctxData){

   memcpy(Device->ClickRemoval, ctxData->ClickRemoval, sizeof(ALfloat)*MAXCHANNELS);

   memcpy(Device->PendingClicks, ctxData->PendingClicks, sizeof(ALfloat)*MAXCHANNELS);

 }

 

 static void saveContext(ALCdevice *Device, context_data *ctxData){

   memcpy(ctxData->ClickRemoval, Device->ClickRemoval, sizeof(ALfloat)*MAXCHANNELS);

   memcpy(ctxData->PendingClicks, Device->PendingClicks, sizeof(ALfloat)*MAXCHANNELS);

 }  

 

 static ALCcontext **currentContext;

 static ALuint currentNumContext;

 

 /* By default, all contexts are rendered at once for each call to aluMixData.

  * This function uses the internals of the ALCdevice struct to temporally 

  * cause aluMixData to only render the chosen context.

  */

 static void limitContext(ALCdevice *Device, ALCcontext *ctx){

   currentContext  = Device->Contexts;

   currentNumContext  = Device->NumContexts;

   Device->Contexts = &ctx;

   Device->NumContexts = 1;

 }

 

 static void unLimitContext(ALCdevice *Device){

   Device->Contexts = currentContext;

   Device->NumContexts = currentNumContext;

 }

 #+end_src

 

 =OpenAL= normally renders all Contexts in parallel, outputting the

 whole result to the buffer.  It does this by iterating over the

 Device->Contexts array and rendering each context to the buffer in

 turn.  By temporally setting Device->NumContexts to 1 and adjusting

 the Device's context list to put the desired context-to-be-rendered

 into position 0, we can get trick =OpenAL= into rendering each slave

 context separate from all the others.

 

 ** Main Device Loop

 #+name: main-loop

 #+begin_src C

 ////////////////////   Main Device Loop

 

 /* Establish the LWJGL context as the master context, which will

  * be synchronized to all the slave contexts

  */

 static void init(ALCdevice *Device){

   ALCcontext *masterContext = alcGetCurrentContext();

   addContext(Device, masterContext);

 }

 

 

 static void renderData(ALCdevice *Device, int samples){

   if(!Device->Connected){return;}

   send_data *data = (send_data*)Device->ExtraData;

   ALCcontext *current = alcGetCurrentContext();

 

   ALuint i;

   for (i = 1; i < data->numContexts; i++){

     syncContexts(data->contexts[0]->ctx , data->contexts[i]->ctx);

   }

   

   if ((ALuint) samples > Device->UpdateSize){

     printf("exceeding internal buffer size; dropping samples\n");

     printf("requested %d; available %d\n", samples, Device->UpdateSize);

     samples = (int) Device->UpdateSize;

   }

 

   for (i = 0; i < data->numContexts; i++){

     context_data *ctxData = data->contexts[i];

     ALCcontext *ctx = ctxData->ctx;

     alcMakeContextCurrent(ctx);

     limitContext(Device, ctx);

     swapInContext(Device, ctxData);

     aluMixData(Device, ctxData->renderBuffer, samples);

     saveContext(Device, ctxData);

     unLimitContext(Device);

   }

   alcMakeContextCurrent(current);

 }

 #+end_src

 

 The main loop synchronizes the master LWJGL context with all the slave

 contexts, then walks each context, rendering just that context to it's

 audio-sample storage buffer.

 

 ** JNI Methods

 

 At this point, we have the ability to create multiple listeners by

 using the master/slave context trick, and the rendered audio data is

 waiting patiently in internal buffers, one for each listener.  We need

 a way to transport this information to Java, and also a way to drive

 this device from Java.  The following JNI interface code is inspired

 by the way LWJGL interfaces with =OpenAL=.

 

 *** step

 #+name: jni-step

 #+begin_src C

 ////////////////////   JNI Methods

 

 #include "com_aurellem_send_AudioSend.h"

 

 /*

  * Class:     com_aurellem_send_AudioSend

  * Method:    nstep

  * Signature: (JI)V

  */

 JNIEXPORT void JNICALL Java_com_aurellem_send_AudioSend_nstep

 (JNIEnv *env, jclass clazz, jlong device, jint samples){

   UNUSED(env);UNUSED(clazz);UNUSED(device);

   renderData((ALCdevice*)((intptr_t)device), samples);

 }

 #+end_src

 This device, unlike most of the other devices in =OpenAL=, does not

 render sound unless asked. This enables the system to slow down or

 speed up depending on the needs of the AIs who are using it to

 listen.  If the device tried to render samples in real-time, a

 complicated AI whose mind takes 100 seconds of computer time to

 simulate 1 second of AI-time would miss almost all of the sound in

 its environment.

 

 

 *** getSamples

 #+name: jni-get-samples

 #+begin_src C

 /*

  * Class:     com_aurellem_send_AudioSend

  * Method:    ngetSamples

  * Signature: (JLjava/nio/ByteBuffer;III)V

  */

 JNIEXPORT void JNICALL Java_com_aurellem_send_AudioSend_ngetSamples

 (JNIEnv *env, jclass clazz, jlong device, jobject buffer, jint position, 

  jint samples, jint n){

   UNUSED(clazz);  

 

   ALvoid *buffer_address = 

     ((ALbyte *)(((char*)(*env)->GetDirectBufferAddress(env, buffer)) + position));

   ALCdevice *recorder = (ALCdevice*) ((intptr_t)device);

   send_data *data = (send_data*)recorder->ExtraData;

   if ((ALuint)n > data->numContexts){return;}

   memcpy(buffer_address, data->contexts[n]->renderBuffer, 

 	 BytesFromDevFmt(recorder->FmtType) * recorder->NumChan * samples);

 }

 #+end_src

 

 This is the transport layer between C and Java that will eventually

 allow us to access rendered sound data from clojure.

 

 *** Listener Management

 

 =addListener=, =setNthListenerf=, and =setNthListener3f= are

 necessary to change the properties of any listener other than the

 master one, since only the listener of the current active context is

 affected by the normal =OpenAL= listener calls.

 #+name: listener-manage

 #+begin_src C

 /*

  * Class:     com_aurellem_send_AudioSend

  * Method:    naddListener

  * Signature: (J)V

  */

 JNIEXPORT void JNICALL Java_com_aurellem_send_AudioSend_naddListener

 (JNIEnv *env, jclass clazz, jlong device){

   UNUSED(env); UNUSED(clazz);

   //printf("creating new context via naddListener\n");

   ALCdevice *Device = (ALCdevice*) ((intptr_t)device);

   ALCcontext *new = alcCreateContext(Device, NULL);

   addContext(Device, new);

 }

 

 /*

  * Class:     com_aurellem_send_AudioSend

  * Method:    nsetNthListener3f

  * Signature: (IFFFJI)V

  */

 JNIEXPORT void JNICALL Java_com_aurellem_send_AudioSend_nsetNthListener3f

   (JNIEnv *env, jclass clazz, jint param, 

    jfloat v1, jfloat v2, jfloat v3, jlong device, jint contextNum){

   UNUSED(env);UNUSED(clazz);

 

   ALCdevice *Device = (ALCdevice*) ((intptr_t)device);

   send_data *data = (send_data*)Device->ExtraData;

   

   ALCcontext *current = alcGetCurrentContext();

   if ((ALuint)contextNum > data->numContexts){return;}

   alcMakeContextCurrent(data->contexts[contextNum]->ctx);

   alListener3f(param, v1, v2, v3);

   alcMakeContextCurrent(current);

 }

 

 /*

  * Class:     com_aurellem_send_AudioSend

  * Method:    nsetNthListenerf

  * Signature: (IFJI)V

  */

 JNIEXPORT void JNICALL Java_com_aurellem_send_AudioSend_nsetNthListenerf

 (JNIEnv *env, jclass clazz, jint param, jfloat v1, jlong device, 

  jint contextNum){

 

   UNUSED(env);UNUSED(clazz);

   

   ALCdevice *Device = (ALCdevice*) ((intptr_t)device);

   send_data *data = (send_data*)Device->ExtraData;

   

   ALCcontext *current = alcGetCurrentContext();

   if ((ALuint)contextNum > data->numContexts){return;}

   alcMakeContextCurrent(data->contexts[contextNum]->ctx);

   alListenerf(param, v1);

   alcMakeContextCurrent(current);

 }

 #+end_src

 

 *** Initialization

 =initDevice= is called from the Java side after LWJGL has created its

 context, and before any calls to =addListener=. It establishes the

 LWJGL context as the master context.

 

 =getAudioFormat= is a convenience function that uses JNI to build up a

 =javax.sound.sampled.AudioFormat= object from data in the Device. This

 way, there is no ambiguity about what the bits created by =step= and

 returned by =getSamples= mean.

 #+name: jni-init

 #+begin_src C

 /*

  * Class:     com_aurellem_send_AudioSend

  * Method:    ninitDevice

  * Signature: (J)V

  */                     

 JNIEXPORT void JNICALL Java_com_aurellem_send_AudioSend_ninitDevice

 (JNIEnv *env, jclass clazz, jlong device){

   UNUSED(env);UNUSED(clazz);

   ALCdevice *Device = (ALCdevice*) ((intptr_t)device);

   init(Device);

 }

 

 /*

  * Class:     com_aurellem_send_AudioSend

  * Method:    ngetAudioFormat

  * Signature: (J)Ljavax/sound/sampled/AudioFormat;

  */

 JNIEXPORT jobject JNICALL Java_com_aurellem_send_AudioSend_ngetAudioFormat

 (JNIEnv *env, jclass clazz, jlong device){

   UNUSED(clazz);

   jclass AudioFormatClass = 

     (*env)->FindClass(env, "javax/sound/sampled/AudioFormat");

   jmethodID AudioFormatConstructor = 

     (*env)->GetMethodID(env, AudioFormatClass, "<init>", "(FIIZZ)V");

   

   ALCdevice *Device = (ALCdevice*) ((intptr_t)device);

   int isSigned;

   switch (Device->FmtType)

     {

     case DevFmtUByte: 

     case DevFmtUShort: isSigned = 0; break;  

     default : isSigned = 1;   

     }

   float frequency = Device->Frequency;

   int bitsPerFrame = (8 * BytesFromDevFmt(Device->FmtType));

   int channels = Device->NumChan;

   jobject format = (*env)->

     NewObject(

 	      env,AudioFormatClass,AudioFormatConstructor,

 	      frequency,

 	      bitsPerFrame,

 	      channels,

 	      isSigned,

 	      0);

   return format;

 }

 #+end_src

 

 ** Boring Device management stuff

 This code is more-or-less copied verbatim from the other =OpenAL=

 backends. It's the basis for =OpenAL='s primitive object system.

 #+name: device-init

 #+begin_src C

 ////////////////////   Device Initialization / Management

 

 static const ALCchar sendDevice[] = "Multiple Audio Send";

 

 static ALCboolean send_open_playback(ALCdevice *device, 

  const ALCchar *deviceName)

 {

   send_data *data;

   // stop any buffering for stdout, so that I can 

   // see the printf statements in my terminal immediately

   setbuf(stdout, NULL);

 

   if(!deviceName)

     deviceName = sendDevice;

   else if(strcmp(deviceName, sendDevice) != 0)

     return ALC_FALSE;

   data = (send_data*)calloc(1, sizeof(*data));

   device->szDeviceName = strdup(deviceName);

   device->ExtraData = data;

   return ALC_TRUE;

 }

 

 static void send_close_playback(ALCdevice *device)

 {

   send_data *data = (send_data*)device->ExtraData;

   alcMakeContextCurrent(NULL);

   ALuint i;

   // Destroy all slave contexts. LWJGL will take care of 

   // its own context.

   for (i = 1; i < data->numContexts; i++){

     context_data *ctxData = data->contexts[i];

     alcDestroyContext(ctxData->ctx);

     free(ctxData->renderBuffer);

     free(ctxData);

   }

   free(data);

   device->ExtraData = NULL;

 }

 

 static ALCboolean send_reset_playback(ALCdevice *device)

 {

   SetDefaultWFXChannelOrder(device);

   return ALC_TRUE;

 }

 

 static void send_stop_playback(ALCdevice *Device){

   UNUSED(Device);

 }

 

 static const BackendFuncs send_funcs = {

   send_open_playback,

   send_close_playback,

   send_reset_playback,

   send_stop_playback,

   NULL,

   NULL,  /* These would be filled with functions to    */

   NULL,  /* handle capturing audio if we we into that  */

   NULL,  /* sort of thing...                           */

   NULL,

   NULL

 };

 

 ALCboolean alc_send_init(BackendFuncs *func_list){

   *func_list = send_funcs;

   return ALC_TRUE;

 }

 

 void alc_send_deinit(void){}

 

 void alc_send_probe(enum DevProbe type)

 {

   switch(type)

     {

     case DEVICE_PROBE:

       AppendDeviceList(sendDevice);

       break;

     case ALL_DEVICE_PROBE:

       AppendAllDeviceList(sendDevice);

       break;

     case CAPTURE_DEVICE_PROBE:

       break;

     }

 }

 #+end_src

 

 * The Java interface, =AudioSend=

 

 The Java interface to the Send Device follows naturally from the JNI

 definitions. It is included here for completeness. The only thing here

 of note is the =deviceID=. This is available from LWJGL, but to only

 way to get it is reflection. Unfortunately, there is no other way to

 control the Send device than to obtain a pointer to it.

 

 #+include: "../java/src/com/aurellem/send/AudioSend.java" src java :exports code

 

 * Finally, Ears in clojure! 

 

 Now that the infrastructure is complete (modulo a few patches to

 jMonkeyEngine3 to support accessing this modified version of =OpenAL=

 that are not worth discussing), the clojure ear abstraction is rather

 simple.  Just as there were =SceneProcessors= for vision, there are

 now =SoundProcessors= for hearing.

 

 #+include "../../jmeCapture/src/com/aurellem/capture/audio/SoundProcessor.java" src java 

 

 #+name: ears

 #+begin_src clojure

 (ns cortex.hearing

   "Simulate the sense of hearing in jMonkeyEngine3. Enables multiple

   listeners at different positions in the same world. Passes vectors

   of floats in the range [-1.0 -- 1.0] in PCM format to any arbitrary

   function."

   {:author "Robert McIntyre"}

   (:use (cortex world util))

   (:import java.nio.ByteBuffer)

   (:import org.tritonus.share.sampled.FloatSampleTools)

   (:import com.aurellem.capture.audio.SoundProcessor)

   (:import javax.sound.sampled.AudioFormat))

   

 (defn sound-processor

   "Deals with converting ByteBuffers into Vectors of floats so that

   the continuation functions can be defined in terms of immutable

   stuff."

   [continuation]

   (proxy [SoundProcessor] []

     (cleanup [])

     (process

       [#^ByteBuffer audioSamples numSamples #^AudioFormat audioFormat]

       (let [bytes  (byte-array numSamples)

             num-floats (/ numSamples  (.getFrameSize audioFormat))

             floats (float-array num-floats)]

         (.get audioSamples bytes 0 numSamples)

         (FloatSampleTools/byte2floatInterleaved

          bytes 0 floats 0 num-floats audioFormat)

         (continuation

          (vec floats))))))

 

 (defn add-ear 

   "Add an ear to the world.  The continuation function will be called

   on the FFT or the sounds which the ear hears in the given

   timeframe. Sound is 3D."

   [world listener continuation]

   (let [renderer (.getAudioRenderer world)]

     (.addListener renderer listener)

     (.registerSoundProcessor renderer listener

 			     (sound-processor continuation))

     listener))

 #+end_src

 

 * Example

 

 #+name: test-hearing

 #+begin_src clojure :results silent

 (ns cortex.test.hearing

   (:use (cortex world util hearing))

   (:import (com.jme3.audio AudioNode Listener))

   (:import com.jme3.scene.Node

 	   com.jme3.system.AppSettings))

 

 (defn setup-fn [world]

   (let [listener (Listener.)]

     (add-ear world listener #(println-repl (nth % 0)))))

   

 (defn play-sound [node world value]

   (if (not value)

     (do

       (.playSource (.getAudioRenderer world) node))))

 

 (defn test-basic-hearing []

    (let [node1 (AudioNode. (asset-manager) "Sounds/pure.wav" false false)]

      (world

       (Node.)

       {"key-space" (partial play-sound node1)}

       setup-fn

       no-op)))

 

 (defn test-advanced-hearing

   "Testing hearing:

    You should see a blue sphere flying around several

    cubes.  As the sphere approaches each cube, it turns

    green."

   []

   (doto (com.aurellem.capture.examples.Advanced.)

     (.setSettings

      (doto (AppSettings. true)

        (.setAudioRenderer "Send")))

     (.setShowSettings false)

     (.setPauseOnLostFocus false)))

 

 #+end_src

 

 This extremely basic program prints out the first sample it encounters

 at every time stamp. You can see the rendered sound being printed at

 the REPL.

 

  - As a bonus, this method of capturing audio for AI can also be used

    to capture perfect audio from a jMonkeyEngine application, for use

    in demos and the like.

 

 

 * COMMENT Code Generation

 

 #+begin_src clojure :tangle ../../cortex/src/cortex/hearing.clj

 <<ears>>

 #+end_src

 

 #+begin_src clojure :tangle ../../cortex/src/cortex/test/hearing.clj

 <<test-hearing>>

 #+end_src

 

 #+begin_src C :tangle ../Alc/backends/send.c

 <<send-header>>

 <<send-state>>

 <<sync-macros>>

 <<sync-sources>>

 <<sync-contexts>>

 <<context-creation>>

 <<context-switching>>

 <<main-loop>>

 <<jni-step>>

 <<jni-get-samples>>

 <<listener-manage>>

 <<jni-init>>

 <<device-init>>

 #+end_src