Differenze tra le versioni di "Generare un'onda sinusoidale con le funzioni esterne della libreria PortAudio"

Da Gambas-it.org - Wikipedia.
Riga 63: Riga 63:
 
   Dim outputParameters As New PaStreamParameters
 
   Dim outputParameters As New PaStreamParameters
 
   Dim PaStream As Pointer
 
   Dim PaStream As Pointer
−
   Dim err, left_phase, right_phase, i, j, k As Integer
+
   Dim err, fase_sin, fase_des, i, j, k As Integer
−
   Dim buffer As New Single[1024, 2]     ' stereo output buffer
+
   Dim buffer As New Single[1024, 2]                     <FONT color=gray>' ''Buffer per Uscita stereo''</font>
−
   Dim sine As New Single[TABLE_SIZE]           ' sine wavetable
+
   Dim sinus As New Single[TABLE_SIZE]                   <FONT color=gray>' ''Frequenza dell'onda sinusoidale''</font>
−
   Dim left_inc As Integer = 2
+
   Dim inc_sin As Integer = 2
−
   Dim right_inc As Integer = 2
+
   Dim inc_des As Integer = 2
 
    
 
    
 
   
 
   
 
   For i = 0 To TABLE_SIZE - 1
 
   For i = 0 To TABLE_SIZE - 1
−
     sine[i] = CSingle(Sin((CFloat(i) / CFloat(TABLE_SIZE)) * Pi * 2.0))
+
     sinus[i] = CSingle(Sin((CFloat(i) / CFloat(TABLE_SIZE)) * Pi * 2.0))
 
   Next
 
   Next
 
      
 
      
Riga 77: Riga 77:
 
   If err < paNoError Then Error.Raise("Impossibile inizializzare la libreria 'PortAudio': " & Pa_GetErrorText(err))
 
   If err < paNoError Then Error.Raise("Impossibile inizializzare la libreria 'PortAudio': " & Pa_GetErrorText(err))
 
    
 
    
−
   outputParameters.device = Pa_GetDefaultOutputDevice()    ' default output device
+
   outputParameters.device = Pa_GetDefaultOutputDevice()    <FONT color=gray>' ''Dispositivo audio prestabilito''</font>
 
   If outputParameters.device = paNoDevice Then Error.Raise("Nessun dispositvo audio presente nel sistema !")
 
   If outputParameters.device = paNoDevice Then Error.Raise("Nessun dispositvo audio presente nel sistema !")
−
   outputParameters.channelCount = 2                        ' stereo Output
+
   outputParameters.channelCount = 2                        <FONT color=gray>' ''Uscita stereo''</font>
−
   outputParameters.sampleFormat = paFloat32                ' 32 bit floating point Output
+
   outputParameters.sampleFormat = paFloat32                <FONT color=gray>' ''Uscita a 32 bit''</font>
 
   outputParameters.suggestedLatency = 0.050
 
   outputParameters.suggestedLatency = 0.050
 
   outputParameters.hostApiSpecificStreamInfo = Null
 
   outputParameters.hostApiSpecificStreamInfo = Null
Riga 93: Riga 93:
 
   For k = 0 To ((10 * SAMPLE_RATE) / FRAMES_PER_BUFFER) - 1
 
   For k = 0 To ((10 * SAMPLE_RATE) / FRAMES_PER_BUFFER) - 1
 
     For j = 0 To FRAMES_PER_BUFFER - 1
 
     For j = 0 To FRAMES_PER_BUFFER - 1
−
       buffer[j, 1] = sine[left_phase]           ' Canale sinistro
+
       buffer[j, 1] = sinus[fase_sin]         <FONT color=gray>' ''Canale sinistro''</font>
−
       buffer[j, 0] = sine[right_phase]          ' Canale destro
+
       buffer[j, 0] = sinus[fase_des]          <FONT color=gray>' ''Canale destro''</font>
−
       left_phase += left_inc
+
       fase_sin += inc_sin
−
       If left_phase >= TABLE_SIZE Then left_phase -= TABLE_SIZE  
+
       If fase_sin >= TABLE_SIZE Then fase_sin -= TABLE_SIZE  
−
       right_phase += right_inc
+
       fase_des += inc_des
−
       If right_phase >= TABLE_SIZE Then right_phase -= TABLE_SIZE  
+
       If fase_des >= TABLE_SIZE Then fase_des -= TABLE_SIZE  
 
     Next
 
     Next
 
     err = Pa_WriteStream(PaStream, buffer, FRAMES_PER_BUFFER)
 
     err = Pa_WriteStream(PaStream, buffer, FRAMES_PER_BUFFER)

Versione delle 05:22, 14 lug 2014

La libreria PortAudio è una libreria per la gestione in tempo reale dei dati audio in entrata ed in uscita. Essa fa parte di un assortimento di API e librerie create per la musica e per altri media.

E' possibile con alcune funzioni esterne della libreria PortAudio generare un'onda sinusoidale. Sarà necessario avere installata nel proprio sistema la libreria condivisa: libportaudio.so.2.0.0


Mostriamo di seguito un possibile codice: 

Public Struct PaStreamParameters
  device As Integer
  channelCount As Integer
  sampleFormat As Long
  suggestedLatency As Float
  hostApiSpecificStreamInfo As Pointer
End Struct

Private Const SAMPLE_RATE As Integer = 44100
Private Const FRAMES_PER_BUFFER As Integer = 1024
Private Const TABLE_SIZE As Short = 440
Private Const paNoError As Integer = 0
Private Const paNoDevice As Integer = -1
Private Const paFloat32 As Integer = 1
Private Const paClipOff As Integer = 1

 
Library "libportaudio:2.0.0"

' PaError Pa_Initialize(void)
' Library initialization function - call this before using PortAudio.
' This function initializes internal data structures and prepares underlying host APIs for use.
Private Extern Pa_Initialize() As Integer

' PaDeviceIndex Pa_GetDefaultOutputDevice( void )
' Retrieve the index of the default output device.
Private Extern Pa_GetDefaultOutputDevice() As Integer

' PaError Pa_OpenStream( PaStream** stream, const PaStreamParameters *inputParameters, const PaStreamParameters *outputParameters,
' double sampleRate, unsigned long framesPerBuffer, PaStreamFlags streamFlags, PaStreamCallback *streamCallback, void *userData )
' Opens a stream for either input, output or both.
Private Extern Pa_OpenStream(PaStr As Pointer, inPa As PaStreamParameters, outPa As PaStreamParameters, sampleRate As Float, fraPBuf As Long, Flags As Long, Callb As Pointer, Data As Pointer) As Integer

' PaError Pa_StartStream( PaStream *stream )
' Commences audio processing.
Private Extern Pa_StartStream(PaStr As Pointer) As Integer

' PaError Pa_WriteStream( PaStream* stream, const void *buffer, unsigned long frames )
' Write samples to an output stream.
Private Extern Pa_WriteStream(PaStr As Pointer, buff As Single[], frames As Long) As Integer

' PaError Pa_CloseStream( PaStream *stream )
' Closes an audio stream.
Private Extern Pa_CloseStream(PaStr As Pointer) As Integer

' PaError Pa_Terminate( void )
' Library termination function.
Private Extern Pa_Terminate() As Integer

' const char *Pa_GetErrorText(PaError errnum)
' Translates the supplied PortAudio error number into a human readable message.
Private Extern Pa_GetErrorText(errnum As Integer) As String


Public Sub Main()

 Dim outputParameters As New PaStreamParameters
 Dim PaStream As Pointer
 Dim err, fase_sin, fase_des, i, j, k As Integer
 Dim buffer As New Single[1024, 2]                     ' Buffer per Uscita stereo
 Dim sinus As New Single[TABLE_SIZE]                   ' Frequenza dell'onda sinusoidale
 Dim inc_sin As Integer = 2
 Dim inc_des As Integer = 2
 

  For i = 0 To TABLE_SIZE - 1
    sinus[i] = CSingle(Sin((CFloat(i) / CFloat(TABLE_SIZE)) * Pi * 2.0))
  Next
   
  err = Pa_Initialize()
  If err < paNoError Then Error.Raise("Impossibile inizializzare la libreria 'PortAudio': " & Pa_GetErrorText(err))
 
  outputParameters.device = Pa_GetDefaultOutputDevice()     ' Dispositivo audio prestabilito
  If outputParameters.device = paNoDevice Then Error.Raise("Nessun dispositvo audio presente nel sistema !")
  outputParameters.channelCount = 2                         ' Uscita stereo
  outputParameters.sampleFormat = paFloat32                 ' Uscita a 32 bit
  outputParameters.suggestedLatency = 0.050
  outputParameters.hostApiSpecificStreamInfo = Null
   
  err = Pa_OpenStream(VarPtr(PaStream), Null, outputParameters, SAMPLE_RATE, FRAMES_PER_BUFFER, paClipOff, 0, 0)
  If err < paNoError Then Error.Raise("Impossibile aprire un flusso audio: " & Pa_GetErrorText(err))
   
  err = Pa_StartStream(PaStream)
  If err < paNoError Then Error.Raise("Impossibile avviare il processo audio: " & Pa_GetErrorText(err))
   

  For k = 0 To ((10 * SAMPLE_RATE) / FRAMES_PER_BUFFER) - 1
    For j = 0 To FRAMES_PER_BUFFER - 1
      buffer[j, 1] = sinus[fase_sin]          ' Canale sinistro
      buffer[j, 0] = sinus[fase_des]          ' Canale destro
      fase_sin += inc_sin
      If fase_sin >= TABLE_SIZE Then fase_sin -= TABLE_SIZE 
      fase_des += inc_des
      If fase_des >= TABLE_SIZE Then fase_des -= TABLE_SIZE 
    Next
    err = Pa_WriteStream(PaStream, buffer, FRAMES_PER_BUFFER)
    If err < paNoError Then Error.Raise("Impossibile avviare il processo audio: " & Pa_GetErrorText(err))
  Next
   
' Va in chiusura:
  err = Pa_CloseStream(PaStream)
  If err < paNoError Then Error.Raise("Impossibile chiudere il flusso audio: " & Pa_GetErrorText(err))
   
  Pa_Terminate()

End


Riferimenti

Estratto da "https://www.gambas-it.org/wiki/index.php?title=Generare_un%27onda_sinusoidale_con_le_funzioni_esterne_della_libreria_PortAudio&oldid=15746"