Eseguire un file WAVE mediante le funzioni della libreria libopenal
Da Gambas-it.org - Wikipedia.
La libreria libopenal è la libreria ordinaria delle risorse di OpenAl. Mediante le funzioni di questa libreria è possibile eseguire un file WAV e gestire il suono in 3D.
Per poter fruire delle risorse esterne della libreria standard di OpenAl, bisognerà richiamare l'attuale libreria condivisa: "libopenal.so.1.24.1 ".
Mostriamo di seguito un semplice esempio per eseguire in modo ordinario un file WAV:
Library "libopenal:1.24.1" Private Const AL_BUFFER As Short = 4105 Private Const AL_FALSE As Boolean = False Private Const AL_PLAYING As Short = 4114 Private Const AL_SOURCE_STATE As Short = 4112 ' ALCdevice *alcOpenDevice(const ALCchar *devicename) ' Initialize the OpenAL audio layer. Returns a pointer to the opened device. Private Extern alcOpenDevice(devicename As String) As Pointer ' ALCcontext * alcCreateContext(ALCdevice *device, ALCint* attrlist) ' This function creates a context using a specified device. Private Extern alcCreateContext(dev As Pointer, attrlist As Pointer) As Pointer ' ALCboolean alcMakeContextCurrent(ALCcontext *context) ' This function makes a specified context the current context. Private Extern alcMakeContextCurrent(contexP As Pointer) ' ALenum alGetError(ALvoid) ' This function returns the current error state And Then clears the Error state. Returns an Alenum representing the error state. Private Extern alGetError() As Integer ' void alGenBuffers(ALsizei n, ALuint * sources) ' Create Buffer objects. Private Extern alGenBuffers(n As Integer, buffers As Pointer) ' void alGenSources(Alsizei n, ALuint *sources) ' Create Source objects. Private Extern alGenSources(n As Integer, sources As Pointer) ' void alBufferData(ALuint buffer, ALenum Format, Const ALvoid * data, ALsizei size, ALsizei freq) ' This function fills a buffer with audio data. Private Extern alBufferData(buffer As Integer, formato As Integer, data As Pointer, size As Integer, freq As Integer) ' void alSourcei(Aluint source, ALenum param, ALint value) ' This function sets an integer Property of a source. Private Extern alSourcei(sourcI As Integer, param As Integer, valuInt As Integer) ' void alSourcePlay(ALuint source) ' This function plays a source. The playing source will have its state changed To AL_PLAYING. Private Extern alSourcePlay(sourcI As Integer) ' void alGetSourcei(ALuint source, ALenum pname, ALint * value) ' This function retrieves an integer property of a source. Private Extern alGetSourcei(sourcI As Integer, PNAME As Integer, valP As Pointer) ' void alDeleteSources(ALsizei n, const ALuint * sources) ' Delete Source objects. Private Extern alDeleteSources(n As Integer, sources As Pointer) ' void alDeleteBuffers(ALsizei n, const ALuint * buffers) ' Delete Buffer objects. Private Extern alDeleteBuffers(n As Integer, buffers As Pointer) ' void alcDestroyContext(ALCcontext context) ' Destroy an OpenAl context. Private Extern alcDestroyContext(contexP As Pointer) ' ALCboolean alcCloseDevice (ALCdevice *Device) ' The alcCloseDevice function allows the application (i.e. the client program) to disconnect from a device (i.e. the server). Private Extern alcCloseDevice(dev As Pointer) ' void alutLoadWAVFile (ALbyte *fileName, ALenum *format, void **data, ALsizei *size, ALsizei *frequency) ' Load a WAV file. Private Extern alutLoadWAVFile(a As String, bufferP As Pointer, formatoP As Pointer, dataP As Pointer, sizeP As Pointer, ver As Pointer) In "libalut:0.1.0" Public Sub Main() Dim device, context, data As Pointer Dim err, alSource, alBuffer, source_state as integer Dim frequenza, dime_dati As Integer Dim fileWav As String Dim formatB As Byte Dim alLoop As Boolean Dim tm As Date fileWav = "/percorso/del/file.wav" device = alcOpenDevice("OpenAL Soft") If IsNull(device) = False Then ' Crea un contesto OpenAl: context = alcCreateContext(device, Null) ' Imposta un contesto attivo: alcMakeContextCurrent(context) Endif err = alGetError() If err <> 0 Then Error.Raise("Errore nella inizializzazione della libreria !") ' Genera i buffer e le sorgenti sonore: alGenBuffers(1, VarPtr(alBuffer)) alGenSources(1, VarPtr(alSource)) alLoop = AL_FALSE alutLoadWAVFile(fileWav, VarPtr(formatB), VarPtr(data), VarPtr(dime_dati), VarPtr(frequenza), VarPtr(alLoop)) alBufferData(alBuffer, formatB, data, dime_dati, frequenza) alSourcei(alSource, AL_BUFFER, alBuffer) alSourcePlay(alSource) alGetSourcei(alSource, AL_SOURCE_STATE, VarPtr(source_state)) tm = Now While source_state = AL_PLAYING alGetSourcei(alSource, AL_SOURCE_STATE, VarPtr(source_state)) Write "\r\e[0mTempo trascorso: \e[31m" & Str(Time(0, 0, 0, DateDiff(tm, Now, gb.Millisecond))) Wait 0.01 Wend ' Va in chiusura: libera la memoria e rilascia il contesto ed il dispositivo "OpenAl": alDeleteSources(1, VarPtr(alSource)) ' Elimina il buffer generato: alDeleteBuffers(1, VarPtr(alBuffer)) ' Rilascia i contesti generati: alcDestroyContext(context) ' Chiude in fine il dispositivo "OpenAl": alcCloseDevice(device) End