Differenze tra le versioni di "Eseguire un file WAV con le funzioni esterne del API di LibAo"

Da Gambas-it.org - Wikipedia.
 
(22 versioni intermedie di uno stesso utente non sono mostrate)
Riga 1: Riga 1:
 
'''Libao''' è una libreria multi-piattaforma che permette ai programmi di inviare dati audio PCM ai dispositivi audio nativi su una vasta gamma di piattaforme.
 
'''Libao''' è una libreria multi-piattaforma che permette ai programmi di inviare dati audio PCM ai dispositivi audio nativi su una vasta gamma di piattaforme.
  
−
Per l'uso delle risorse della libreria ''libao'' bisognerà richiamare nel proprio applicativo Gambas la libreria attualmente alla versione: "''libao.so.4.0.0''" .
+
E' necessario avere installata nel sistema e richiamare in Gambas la libreria condivisa: "''libao.so.4.1.1'' "
  
−
Di seguito un possibile codice per eseguire un file audio WAV con le risorse della libreria ''libao'' un'onda sinusoidale. Nell'esempio si supporrà che il file wav abbia una frequenza di campionamento a 44100 hertz, una risoluzione a 16bit e due canali:
+
Possiamo utilizzare almeno due modalità per eseguire un file WAV.
−
  '''Public''' Struct ao_sample_format
+
===1<SUP>a</sup> modalità===
 +
Library "libao:4.1.1"
 +
 +
Public Struct ao_sample_format
 +
  bits As Integer            <FONT color=gray>' ''bits per sample''</font>
 +
  rate As Integer            <FONT color=gray>' ''samples per second (in a single channel)''</font>
 +
  channels As Integer        <FONT color=gray>' ''number of audio channels''</font>
 +
  byte_format As Integer      <FONT color=gray>' ''Byte ordering in sample, see constants below''</font>
 +
  matrix As Pointer          <FONT color=gray>' ''input channel location/ordering''</font>
 +
End Struct
 +
 +
Public Struct ao_info
 +
  type As Integer
 +
  name As Pointer
 +
  short_name As Pointer
 +
  author As Pointer
 +
  comment As Pointer
 +
  preferred_byte_format As Integer
 +
  priority As Integer
 +
  options As Pointer
 +
  option_count As Integer
 +
End Struct
 +
 +
Private Const AO_FMT_LITTLE As Integer = 1
 +
Private Const AO_FMT_BIG As Integer = 2
 +
Private Const AO_FMT_NATIVE As Integer = 4
 +
 +
<FONT color=gray>' ''void ao_initialize(void)''
 +
' ''Library setup.''</font>
 +
Private Extern ao_initialize()
 +
 +
<FONT color=gray>' ''int ao_default_driver_id(void)''
 +
' ''Driver information.''</font>
 +
Private Extern ao_default_driver_id() As Integer
 +
 +
<FONT color=gray>' ''ao_info *ao_driver_info(int driver_id)''
 +
' ''Get information about a particular driver.''</font>
 +
Private Extern ao_driver_info(driver_id As Integer) As Ao_info
 +
 +
<FONT color=gray>' ''ao_device * ao_open_live(int driver_id, ao_sample_format *format, ao_option *option)''
 +
' ''Open a live playback audio device for output.''</font>
 +
Private Extern ao_open_live(driver_id As Integer, ao_format As Ao_sample_format, option As Pointer) As Pointer
 +
 +
<FONT color=gray>' ''int ao_play(ao_device *device, char *output_samples, uint_32 num_bytes)''
 +
' ''Play a block of audio data to an open device.''</font>
 +
Private Extern ao_play(device As Pointer, output_samples As Pointer, num_bytes As Integer) As Integer
 +
 +
<FONT color=gray>' ''void ao_shutdown(void)''
 +
' ''Unloads all of the plugins and deallocates any internal data structures the library has created.''</font>
 +
Private Extern ao_shutdown()
 +
 
 +
 +
Public Sub Main()
 +
 +
  Dim device As Pointer
 +
  Dim ao_sf As New Ao_sample_format
 +
  Dim info As Ao_info
 +
  Dim default_driver, i, err, rbc As Integer
 +
  Dim buffer As Byte[]
 +
  Dim fileWAV, fmt As String
 +
  Dim fl As File
 +
  Dim b As Byte
 +
 +
  fileWAV = "<FONT color=darkgreen>''/percorso/del/file.wav''</font>"
 +
 +
  fl = Open fileWAV For Read
 +
 
 +
<FONT color=gray>' ''Inizializza la libreria 'libao':''</font>
 +
  ao_initialize()
 +
   
 +
<FONT color=gray>' ''Imposta il driver audio come predefinito:''</font>
 +
  default_driver = ao_default_driver_id()
 +
 
 +
<FONT color=gray>' ''Raccoglie alcune informazioni del dipositivo audio di sistema utilizzato:''</font>
 +
  Print "Informazioni sul dispositivo audio utilizzato:"
 +
  info = ao_driver_info(default_driver)
 +
  With info
 +
    Print "Tipo:                  "; IIf(.type = 1, "Live Output", "File output")
 +
    Print "Nome:                  "; String@(.name)
 +
    Print "Abbreviazione:          "; String@(.short_name)
 +
    Print "Realizzatore:          "; String@(.author)
 +
    Print "Commento:              "; String@(.comment)
 +
    Select Case .preferred_byte_format
 +
      Case AO_FMT_LITTLE
 +
        fmt = "little-endian order"
 +
      Case AO_FMT_BIG
 +
        fmt = "big-endian order"
 +
      Case AO_FMT_NATIVE
 +
        fmt = "native ordering of the computer"
 +
    End Select
 +
    Print "Formato byte preferito: "; fmt
 +
    Print "Priorità:              "; .priority
 +
    Print "Opzioni:                ";
 +
    For b = 1 To .option_count
 +
      Print String@(Pointer@(.options + CInt(8 * b))); ", ";
 +
    Next
 +
  End With
 +
  Print "\n____________________________"
 +
 +
<FONT color=gray>' ''Imposta le caratteristiche del file wav caricato, leggendole da esso:''</font>
 +
  With ao_sf
 +
    Seek #fl, 34
 +
    .bits = Read #fl As Short
 +
    Seek #fl, 22
 +
    .channels = Read #fl As Short
 +
    .rate = Read #fl As Integer
 +
    .byte_format = info.preferred_byte_format
 +
<FONT color=gray>' ''Mostra alcune informazioni generali sul file wav caricato:''</font>
 +
  Print "File wav:    "; fileWAV
 +
  Print "Dimensione:  "; Lof(fl); " byte"
 +
  Print "Risoluzione: "; .bits; " bit"
 +
  Print "Canali:      "; .channels
 +
  Print "Frequenza:  "; .rate; " hertz"
 +
  rbc = .rate * .bits * .channels
 +
  Print "Durata:      "; Time(0, 0, 0, ((Lof(fl) * 8) / rbc) * 1000)
 +
  Print
 +
  End With
 +
 +
<FONT color=gray>' ''Apre il driver:''</font>
 +
  device = ao_open_live(default_driver, ao_sf, 0)
 +
  If device == 0 Then Error.Raise("Errore nell'apertura del dispositivo audio !")
 +
   
 +
  buffer = New Byte[Lof(fl)]
 +
     
 +
<FONT color=gray>' ''Ciclo per l'elaborazione dell'audio:''</font>
 +
  For i = 1 To (buffer.Count) / 1024
 +
<FONT color=gray>' ''Carica i dati audio nel vettore di tipo "Byte[]":''</font>
 +
    buffer.Read(fl, 0, 1024)
 +
<FONT color=gray>' ''Esegue i dati audio:''</font>
 +
    err = ao_play(device, buffer.Data, 1024)
 +
    If err < 1 Then Error.Raise("Errore nell'esecuzione dei dati audio !")
 +
    Write #File.out, "\r" & CStr(Time(0, 0, 0, ((Seek(fl) * 8) / rbc) * 1000))
 +
  Next
 +
 
 +
<FONT color=gray>' ''Va in chiusura:''</font>
 +
  fl.Close
 +
  ao_shutdown()
 +
 +
  End
 +
 
 +
 
 +
===2<SUP>a</sup> modalità===
 +
La seconda modalità fa uso sia della libreria principale "''libao.so.4.1.1''", sia della libreria "''libalsa.so''".
 +
Library "libao:4.1.1"
 +
 +
Public Struct ao_sample_format
 
   bits As Integer            <FONT color=gray>' ''bits per sample''</font>
 
   bits As Integer            <FONT color=gray>' ''bits per sample''</font>
 
   rate As Integer            <FONT color=gray>' ''samples per second (in a single channel)''</font>
 
   rate As Integer            <FONT color=gray>' ''samples per second (in a single channel)''</font>
Riga 10: Riga 155:
 
   byte_format As Integer      <FONT color=gray>' ''Byte ordering in sample, see constants below''</font>
 
   byte_format As Integer      <FONT color=gray>' ''Byte ordering in sample, see constants below''</font>
 
   matrix As Pointer          <FONT color=gray>' ''input channel location/ordering''</font>
 
   matrix As Pointer          <FONT color=gray>' ''input channel location/ordering''</font>
−
  '''End''' Struct
+
  End Struct
 
   
 
   
−
  '''Private''' ao_sf As Struct Ao_sample_format
+
  Private Const AO_FMT_LITTLE As Integer = 1
 
   
 
   
 +
<FONT color=gray>' ''void ao_initialize(void)''
 +
' ''Library setup''</font>
 +
Private Extern ao_initialize()
 
   
 
   
−
  Library "libao:4.0.0"
+
  <FONT color=gray>' ''int ao_default_driver_id(void)''
 +
' ''Driver information''</font>
 +
Private Extern ao_default_driver_id() As Integer
 
   
 
   
−
  '''Private''' Const AO_FMT_LITTLE As Integer = 1
+
  <FONT color=gray>' ''ao_device * ao_open_live(int driver_id, ao_sample_format *format, ao_option *option)''
 +
' ''Driver information''</font>
 +
Private Extern ao_open_live(driver_id As Integer, fmt As Ao_sample_format, option As Pointer) As Pointer
 +
 
 +
<FONT color=gray>' ''void ao_shutdown(void)''
 +
' ''Library teardown''</font>
 +
Private Extern ao_shutdown()
 
   
 
   
−
<FONT color=gray>' ''void ao_initialize(void)''</font>
 
−
<FONT color=gray>' ''library setup''</font>
 
−
'''Private''' Extern ao_initialize()
 
 
   
 
   
−
  <FONT color=gray>' ''int ao_default_driver_id(void)''</font>
+
  Library "/usr/lib/x86_64-linux-gnu/ao/plugins-4/libalsa"
−
<FONT color=gray>' ''driver information''</font>
 
−
'''Private''' Extern ao_default_driver_id() As Integer
 
 
   
 
   
−
  <FONT color=gray>' ''ao_device * ao_open_live(int driver_id, ao_sample_format *format, ao_option *option)''</font>
+
  <FONT color=gray>' ''int ao_plugin_test()''
−
  <FONT color=gray>' ''driver information''</font>
+
  ' ''Determine if parameters are requires for this particular plugin.''</font>
−
  '''Private''' Extern ao_open_live(driver_id As Integer, fmt As Ao_sample_format, option As Pointer) As Pointer
+
  Private Extern ao_plugin_test() As Integer
 
   
 
   
−
  <FONT color=gray>' ''int ao_play(ao_device *device, char *output_samples, uint_32 num_bytes)''</font>
+
  <FONT color=gray>' ''int ao_plugin_device_init(ao_device *device)''
−
  <FONT color=gray>' ''Write samples to the device. Channels are interleaved. 1 indicates success.''</font>
+
  ' Initialize internal data structures.''</font>
−
  '''Private''' Extern ao_play(device As Pointer, output_samples As Byte[], num_bytes As Integer) As Integer
+
  Private Extern ao_plugin_device_init(ao_dev As Pointer) As Integer
 
   
 
   
−
  <FONT color=gray>' ''int ao_close(ao_device *device)''</font>
+
  <FONT color=gray>' ''int ao_plugin_open(ao_device *device, ao_sample_format *format)''
−
  <FONT color=gray>' ''Chiude il dispositivo audio''</font>
+
  ' ''Prepare the audio device for playback.''</font>
−
  '''Private''' Extern ao_close(device As Pointer) As Integer
+
  Private Extern ao_plugin_open(ao_dev As Pointer, fmt As Ao_sample_format) As Integer
 
   
 
   
−
  <FONT color=gray>' ''void ao_shutdown(void)''</font>
+
  <FONT color=gray>' ''int ao_plugin_play(ao_device *device, const char *output_samples, uint_32 num_bytes)''
−
  <FONT color=gray>' ''library teardown''</font>
+
  ' ''Play num_bytes of audio data.''</font>
−
  '''Private''' Extern ao_shutdown()
+
  Private Extern ao_plugin_play(ao_dev As Pointer, output_samples As Pointer, num_bytes As Integer) As Integer
 
   
 
   
 +
<FONT color=gray>' ''int ao_plugin_close(ao_device *device)''
 +
' ''Close the audio device.''</font>
 +
Private Extern ao_plugin_close(ao_dev As Pointer) As Integer
 
   
 
   
−
  '''Public''' Sub Main()
+
  <FONT color=gray>' ''void ao_plugin_device_clear(ao_device *device)''
 +
' ''Free the internal data structures.''</font>
 +
Private Extern ao_plugin_device_clear(ao_dev As Pointer)
 
   
 
   
−
  Dim device As Pointer
 
−
  Dim default_driver, buf_size, i, err As Integer
 
−
  Dim buffer As Byte[]
 
−
  Dim fileWAV As String
 
−
  Dim fl As File
 
 
   
 
   
 +
Public Sub Main()
 
   
 
   
−
    fileWAV = "''/percorso/del/file.wav''"
+
  Dim device As Pointer
 +
  Dim ao_sf As New Ao_sample_format
 +
  Dim default_driver, i, err, rbc As Integer
 +
  Dim buffer As Byte[]
 +
  Dim fileWAV As String
 +
  Dim fl As File
 
   
 
   
−
    fl = Open fileWAV For Read
+
  fileWAV = "<FONT color=darkgreen>''/percorso/del/file.wav''</font>"
−
 
 
 
   
 
   
 +
  fl = Open fileWAV For Read
 +
 
 
  <FONT color=gray>' ''Inizializza la libreria 'libao':''</font>
 
  <FONT color=gray>' ''Inizializza la libreria 'libao':''</font>
−
    ao_initialize()
+
  ao_initialize()
 
      
 
      
 
  <FONT color=gray>' ''Imposta il driver audio come predefinito:''</font>
 
  <FONT color=gray>' ''Imposta il driver audio come predefinito:''</font>
−
    default_driver = ao_default_driver_id()
+
  default_driver = ao_default_driver_id()
 
   
 
   
−
  <FONT color=gray>' ''Imposta le caratteristiche del file wav caricato:''</font>
+
  <FONT color=gray>' ''Imposta le caratteristiche del file wav caricato, leggendole da esso:''</font>
−
    With ao_sf
+
  With ao_sf
−
      .bits = 16
+
    Seek #fl, 34
−
      .channels = 2
+
    .bits = Read #fl As Short
−
      .rate = 44100
+
    Seek #fl, 22
−
      .byte_format = AO_FMT_LITTLE
+
    .channels = Read #fl As Short
−
     End With
+
    .rate = Read #fl As Integer
 +
    .byte_format = AO_FMT_LITTLE
 +
<FONT color=gray>' ''Mostra alcune informazioni generali sul file wav caricato:''</font>
 +
     Print "File wav:    "; fileWAV
 +
    Print "Dimensione:  "; Lof(fl); " byte"
 +
    Print "Risoluzione: "; .bits; " bit"
 +
    Print "Canali:      "; .channels
 +
    Print "Frequenza:  "; .rate; " hertz"
 +
    rbc = .rate * .bits * .channels
 +
    Print "Durata:      "; Time(0, 0, 0, ((Lof(fl) * 8) / rbc) * 1000)
 +
    Print
 +
  End With
 
    
 
    
 +
  Wait 0.1
 +
 
  <FONT color=gray>' ''Apre il driver:''</font>
 
  <FONT color=gray>' ''Apre il driver:''</font>
−
    device = ao_open_live(default_driver, VarPtr(ao_sf), Null)
+
  device = ao_open_live(default_driver, ao_sf, 0)
−
    If IsNull(device) Then Error.Raise("Errore nell'apertura del dispositivo audio !")
+
  If device == 0 Then Error.Raise("Errore nell'apertura del dispositivo audio !")
−
   
+
−
    buffer = New Byte[Stat(fileWAV).Size]
+
  err = ao_plugin_test()
 +
  If err == 0 Then Error.Raise("Il driver audio ha bisogno che vengano impostate alcune opzioni !")
 +
 
 +
  ao_plugin_device_init(device)
 +
 
 +
  ao_plugin_open(device, ao_sf)
 +
 +
  buffer = New Byte[Lof(fl)]
 +
 +
<FONT color=gray>' ''Riportiamo il puntatore interno del flusso del file a zero:''</font>
 +
  Seek #fl, 0
 
      
 
      
 
  <FONT color=gray>' ''Ciclo per l'elaborazione dell'audio:''</font>
 
  <FONT color=gray>' ''Ciclo per l'elaborazione dell'audio:''</font>
−
    For i = 1 To (buffer.Count) / 1024
+
  For i = 1 To (buffer.Count) / 1024
−
 
 
  <FONT color=gray>' ''Carica i dati audio nel vettore di tipo "Byte[]":''</font>
 
  <FONT color=gray>' ''Carica i dati audio nel vettore di tipo "Byte[]":''</font>
−
      buffer.Read(fl, 0, 1024)
+
    buffer.Read(fl, 0, 1024)
−
 
 
  <FONT color=gray>' ''Esegue i dati audio:''</font>
 
  <FONT color=gray>' ''Esegue i dati audio:''</font>
−
      err = ao_play(device, buffer, 1024)
+
    err = ao_plugin_play(device, buffer.Data, 1024)
−
      If err < 1 Then Error.Raise("Errore nell'esecuzione dei dati audio !")
+
    If err < 1 Then Error.Raise("Errore nell'esecuzione dei dati audio !")
−
     
+
    Write #File.out, "\r" & CStr(Time(0, 0, 0, ((Seek(fl) * 8) / rbc) * 1000))
−
    Next
+
  Next
 
   
 
   
−
 
 
 
  <FONT color=gray>' ''Va in chiusura:''</font>
 
  <FONT color=gray>' ''Va in chiusura:''</font>
−
    fl.Close
+
  fl.Close
−
    buffer.Clear()
+
  ao_plugin_close(device)
−
    ao_close(device)
+
  ao_plugin_device_clear(device)
−
    ao_shutdown()
+
  ao_shutdown()
 
   
 
   
−
  '''End'''
+
  End
  
  
  
 
=Riferimenti=
 
=Riferimenti=
−
[1] [http://www.xiph.org/ao/doc/ L'API di LibAo]
+
* http://www.xiph.org/ao/doc/
 +
* http://manual.freeshell.org/libao-1.0.0

Versione attuale delle 18:47, 13 gen 2024

Libao è una libreria multi-piattaforma che permette ai programmi di inviare dati audio PCM ai dispositivi audio nativi su una vasta gamma di piattaforme.

E' necessario avere installata nel sistema e richiamare in Gambas la libreria condivisa: "libao.so.4.1.1 "

Possiamo utilizzare almeno due modalità per eseguire un file WAV.

1a modalità

Library "libao:4.1.1"

Public Struct ao_sample_format
  bits As Integer             ' bits per sample
  rate As Integer             ' samples per second (in a single channel)
  channels As Integer         ' number of audio channels
  byte_format As Integer      ' Byte ordering in sample, see constants below
  matrix As Pointer           ' input channel location/ordering
End Struct

Public Struct ao_info
  type As Integer
  name As Pointer
  short_name As Pointer
  author As Pointer
  comment As Pointer
  preferred_byte_format As Integer
  priority As Integer
  options As Pointer
  option_count As Integer
End Struct

Private Const AO_FMT_LITTLE As Integer = 1
Private Const AO_FMT_BIG As Integer = 2
Private Const AO_FMT_NATIVE As Integer = 4

' void ao_initialize(void)
' Library setup.
Private Extern ao_initialize()

' int ao_default_driver_id(void)
' Driver information.
Private Extern ao_default_driver_id() As Integer

' ao_info *ao_driver_info(int driver_id)
' Get information about a particular driver.
Private Extern ao_driver_info(driver_id As Integer) As Ao_info

' ao_device * ao_open_live(int driver_id, ao_sample_format *format, ao_option *option)
' Open a live playback audio device for output.
Private Extern ao_open_live(driver_id As Integer, ao_format As Ao_sample_format, option As Pointer) As Pointer

' int ao_play(ao_device *device, char *output_samples, uint_32 num_bytes)
' Play a block of audio data to an open device.
Private Extern ao_play(device As Pointer, output_samples As Pointer, num_bytes As Integer) As Integer

' void ao_shutdown(void)
' Unloads all of the plugins and deallocates any internal data structures the library has created.
Private Extern ao_shutdown()
 

Public Sub Main()

 Dim device As Pointer
 Dim ao_sf As New Ao_sample_format
 Dim info As Ao_info
 Dim default_driver, i, err, rbc As Integer
 Dim buffer As Byte[]
 Dim fileWAV, fmt As String
 Dim fl As File
 Dim b As Byte

 fileWAV = "/percorso/del/file.wav"

 fl = Open fileWAV For Read
  
' Inizializza la libreria 'libao':
 ao_initialize()
   
' Imposta il driver audio come predefinito:
 default_driver = ao_default_driver_id()
  
' Raccoglie alcune informazioni del dipositivo audio di sistema utilizzato:
 Print "Informazioni sul dispositivo audio utilizzato:"
 info = ao_driver_info(default_driver)
 With info
   Print "Tipo:                   "; IIf(.type = 1, "Live Output", "File output")
   Print "Nome:                   "; String@(.name)
   Print "Abbreviazione:          "; String@(.short_name)
   Print "Realizzatore:           "; String@(.author)
   Print "Commento:               "; String@(.comment)
   Select Case .preferred_byte_format
     Case AO_FMT_LITTLE
       fmt = "little-endian order"
     Case AO_FMT_BIG
       fmt = "big-endian order"
     Case AO_FMT_NATIVE
       fmt = "native ordering of the computer"
   End Select
   Print "Formato byte preferito: "; fmt
   Print "Priorità:               "; .priority
   Print "Opzioni:                ";
   For b = 1 To .option_count
     Print String@(Pointer@(.options + CInt(8 * b))); ", ";
   Next
 End With
 Print "\n____________________________"

' Imposta le caratteristiche del file wav caricato, leggendole da esso:
 With ao_sf
   Seek #fl, 34
   .bits = Read #fl As Short
   Seek #fl, 22
   .channels = Read #fl As Short
   .rate = Read #fl As Integer
   .byte_format = info.preferred_byte_format
' Mostra alcune informazioni generali sul file wav caricato:
  Print "File wav:    "; fileWAV
  Print "Dimensione:  "; Lof(fl); " byte"
  Print "Risoluzione: "; .bits; " bit"
  Print "Canali:      "; .channels
  Print "Frequenza:   "; .rate; " hertz"
  rbc = .rate * .bits * .channels
  Print "Durata:      "; Time(0, 0, 0, ((Lof(fl) * 8) / rbc) * 1000)
  Print
  End With

' Apre il driver:
  device = ao_open_live(default_driver, ao_sf, 0)
  If device == 0 Then Error.Raise("Errore nell'apertura del dispositivo audio !")
   
 buffer = New Byte[Lof(fl)]
      
' Ciclo per l'elaborazione dell'audio:
 For i = 1 To (buffer.Count) / 1024
' Carica i dati audio nel vettore di tipo "Byte[]":
   buffer.Read(fl, 0, 1024)
' Esegue i dati audio:
   err = ao_play(device, buffer.Data, 1024)
   If err < 1 Then Error.Raise("Errore nell'esecuzione dei dati audio !")
   Write #File.out, "\r" & CStr(Time(0, 0, 0, ((Seek(fl) * 8) / rbc) * 1000))
 Next
 
' Va in chiusura:
 fl.Close
 ao_shutdown()

End


2a modalità

La seconda modalità fa uso sia della libreria principale "libao.so.4.1.1", sia della libreria "libalsa.so". 

Library "libao:4.1.1"

Public Struct ao_sample_format
  bits As Integer             ' bits per sample
  rate As Integer             ' samples per second (in a single channel)
  channels As Integer         ' number of audio channels
  byte_format As Integer      ' Byte ordering in sample, see constants below
  matrix As Pointer           ' input channel location/ordering
End Struct

Private Const AO_FMT_LITTLE As Integer = 1

' void ao_initialize(void)
' Library setup
Private Extern ao_initialize()

' int ao_default_driver_id(void)
' Driver information
Private Extern ao_default_driver_id() As Integer

' ao_device * ao_open_live(int driver_id, ao_sample_format *format, ao_option *option)
' Driver information
Private Extern ao_open_live(driver_id As Integer, fmt As Ao_sample_format, option As Pointer) As Pointer
  
' void ao_shutdown(void)
' Library teardown
Private Extern ao_shutdown()


Library "/usr/lib/x86_64-linux-gnu/ao/plugins-4/libalsa"

' int ao_plugin_test()
' Determine if parameters are requires for this particular plugin.
Private Extern ao_plugin_test() As Integer

' int ao_plugin_device_init(ao_device *device)
' Initialize internal data structures.
Private Extern ao_plugin_device_init(ao_dev As Pointer) As Integer

' int ao_plugin_open(ao_device *device, ao_sample_format *format)
' Prepare the audio device for playback.
Private Extern ao_plugin_open(ao_dev As Pointer, fmt As Ao_sample_format) As Integer

' int ao_plugin_play(ao_device *device, const char *output_samples, uint_32 num_bytes)
' Play num_bytes of audio data.
Private Extern ao_plugin_play(ao_dev As Pointer, output_samples As Pointer, num_bytes As Integer) As Integer

' int ao_plugin_close(ao_device *device)
' Close the audio device.
Private Extern ao_plugin_close(ao_dev As Pointer) As Integer

' void ao_plugin_device_clear(ao_device *device)
' Free the internal data structures.
Private Extern ao_plugin_device_clear(ao_dev As Pointer)


Public Sub Main()

 Dim device As Pointer
 Dim ao_sf As New Ao_sample_format
 Dim default_driver, i, err, rbc As Integer
 Dim buffer As Byte[]
 Dim fileWAV As String
 Dim fl As File

 fileWAV = "/percorso/del/file.wav"

 fl = Open fileWAV For Read
  
' Inizializza la libreria 'libao':
 ao_initialize()
   
' Imposta il driver audio come predefinito:
 default_driver = ao_default_driver_id()

' Imposta le caratteristiche del file wav caricato, leggendole da esso:
 With ao_sf
   Seek #fl, 34
   .bits = Read #fl As Short
   Seek #fl, 22
   .channels = Read #fl As Short
   .rate = Read #fl As Integer
   .byte_format = AO_FMT_LITTLE
' Mostra alcune informazioni generali sul file wav caricato:
   Print "File wav:    "; fileWAV
   Print "Dimensione:  "; Lof(fl); " byte"
   Print "Risoluzione: "; .bits; " bit"
   Print "Canali:      "; .channels
   Print "Frequenza:   "; .rate; " hertz"
   rbc = .rate * .bits * .channels
   Print "Durata:      "; Time(0, 0, 0, ((Lof(fl) * 8) / rbc) * 1000)
   Print
 End With
  
 Wait 0.1

' Apre il driver:
 device = ao_open_live(default_driver, ao_sf, 0)
 If device == 0 Then Error.Raise("Errore nell'apertura del dispositivo audio !")

 err = ao_plugin_test()
 If err == 0 Then Error.Raise("Il driver audio ha bisogno che vengano impostate alcune opzioni !")
  
 ao_plugin_device_init(device)
  
 ao_plugin_open(device, ao_sf)

 buffer = New Byte[Lof(fl)]

' Riportiamo il puntatore interno del flusso del file a zero:
 Seek #fl, 0
   
' Ciclo per l'elaborazione dell'audio:
 For i = 1 To (buffer.Count) / 1024
' Carica i dati audio nel vettore di tipo "Byte[]":
   buffer.Read(fl, 0, 1024)
' Esegue i dati audio:
   err = ao_plugin_play(device, buffer.Data, 1024)
   If err < 1 Then Error.Raise("Errore nell'esecuzione dei dati audio !")
   Write #File.out, "\r" & CStr(Time(0, 0, 0, ((Seek(fl) * 8) / rbc) * 1000))
 Next

' Va in chiusura:
 fl.Close
 ao_plugin_close(device)
 ao_plugin_device_clear(device)
 ao_shutdown()

End


Riferimenti

Estratto da "https://www.gambas-it.org/wiki/index.php?title=Eseguire_un_file_WAV_con_le_funzioni_esterne_del_API_di_LibAo&oldid=36217"