Differenze tra le versioni di "Eseguire un file WAV mediante le funzioni esterne del API di libaudiofile e di Alsa"

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Di seguito mostriamo un semplice codice per l'esecuzione di un file audio di formato WAV mediante la libreria ''Libaudiofile'' e la libreria di Alsa:
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Di seguito mostriamo due semplici codici per l'esecuzione di un file audio di formato WAV mediante la libreria ''Libaudiofile'' e la libreria di Alsa.
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====Primo esempio====
 
  Private Const bufferFrames As Short = 4096
 
  Private Const bufferFrames As Short = 4096
 
   
 
   
Riga 122: Riga 124:
 
   
 
   
 
  '''End'''
 
  '''End'''
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====Secondo esempio====
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Library "libaudiofile:1.0.0"
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Private Const AF_DEFAULT_TRACK As Integer = 1001
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Private Const AF_SAMPFMT_TWOSCOMP As Integer = 401      ' linear two's complement
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<FONT color=gray>' ''AFfilehandle afOpenFile (const char *filename, const char *mode, AFfilesetup setup)''
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' ''Opens a specified audio file and creates a file handle structure''</font>
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Private Extern afOpenFile(filename As String, mode As String, setup As Pointer) As Pointer
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<FONT color=gray>' ''AFframecount afGetFrameCount (AFfilehandle file, int track)''
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' ''Get the total sample frame count.''</font>
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Private Extern afGetFrameCount(AFfilehandle As Pointer, track As Integer) As Integer
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<FONT color=gray>' ''float afGetFrameSize (AFfilehandle, int track, int expand3to4)''
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' ''Calculate the frame size in bytes for an audio track.''</font>
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Private Extern afGetFrameSize(AFfilehandle As Pointer, track As Integer, expand3to4 As Integer) As Single
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<FONT color=gray>' ''void afGetSampleFormat (AFfilehandle file, int track, int *sampleFormat, int *sampleWidth)''
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' ''Get the sample format for a specified audio track.''</font>
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Private Extern afGetSampleFormat(AFfilehandle As Pointer, track As Integer, sampleFP As Pointer, sampleWP As Pointer)
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<FONT color=gray>' ''int afGetChannels (AFfilehandle, int track)''
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' ''Gets number of channels.''</font>
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Private Extern afGetChannels(AFfilehandle As Pointer, track As Integer) As Integer
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<FONT color=gray>' ''double afGetRate (AFfilehandle, int track)''
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' ''Gets sampling rate.''</font>
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Private Extern afGetRate(AFfilehandle As Pointer, track As Integer) As Float
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<FONT color=gray>' ''int afSetVirtualSampleFormat (AFfilehandle, int track, int sampleFormat, int sampleWidth)''
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' ''Set the virtual data format for a track in an audio file''</font>
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Private Extern afSetVirtualSampleFormat(AFfilehandle As Pointer, track As Integer, sampleFormat As Integer, sampleWidth As Integer) As Integer
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<FONT color=gray>' ''int afReadFrames (AFfilehandle, int track, void *buffer, int frameCount)''
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' ''reads sample frames from a given audio track in an audio file.''
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' ''Returns the number of frames successfully read from file into the array referred to by samples.''</font>
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Private Extern afReadFrames(AFfilehandle As Pointer, track As Integer, buf As Short[], frameCount As Integer) As Integer
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<FONT color=gray>' ''int afCloseFile (AFfilehandle file)''
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' ''Closes an open audio file.''</font>
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Private Extern afCloseFile(AFfilehandle As Pointer) As Integer
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Library "libasound:2"
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Private Const SND_PCM_STREAM_PLAYBACK As Integer = 0
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Private Const SND_PCM_FORMAT_S16 As Integer = 2
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Private Const SND_PCM_ACCESS_RW_INTERLEAVED As Integer = 3
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<FONT color=gray>' ''int snd_pcm_open (snd_pcm_t **pcm, const char *name, snd_pcm_stream_t stream, int mode)''
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' ''Opens a PCM.''</font>
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Private Extern snd_pcm_open(pcm As Pointer, name As String, streamI As Integer, mode As Integer) As Integer
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<FONT color=gray>' ''int snd_pcm_set_params (snd_pcm_t *pcm, snd_pcm_format_t format, snd_pcm_access_t access, unsigned int channels, unsigned int rate, int soft_resample, unsigned int latency)''
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' ''Set the hardware and software parameters in a simple way.''</font>
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Private Extern snd_pcm_set_params(pcm As Pointer, formatI As Integer, accessI As Integer, channels As Integer, rate As Integer, soft_resample As Integer, latency As Integer) As Integer
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<FONT color=gray>' ''snd_pcm_sframes_t snd_pcm_writei (snd_pcm_t *pcm, const void *buffer, snd_pcm_uframes_t size)''
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' ''Write interleaved frames to a PCM.''</font>
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Private Extern snd_pcm_writei(pcm As Pointer, buf As Short[], size As Integer) As Integer
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<FONT color=gray>' ''int snd_pcm_recover (snd_pcm_t * pcm, int err, int silent)''
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' ''Recover the stream state from an error or suspend.''</font>
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Private Extern snd_pcm_recover(pcm As Pointer, errorI As Integer, silent As Integer) As Integer
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<FONT color=gray>' ''snd_pcm_drain (snd_pcm_t *pcm)''
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' ''Stop a PCM preserving pending frames.''</font>
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Private Extern snd_pcm_drain(pcm As Pointer) As Integer
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<FONT color=gray>' ''int snd_pcm_close (snd_pcm_t *pcm)''
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' ''Close PCM handle''</font>
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Private Extern snd_pcm_close(pcm As Pointer) As Integer
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'''Public''' Sub Main()
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  Dim afOF, sFP, sWP, handle As Pointer
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  Dim percorsoFile As String = "''percorso/del/file.wav''"
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  Dim frameCount, canali, sampleFormat, sampleWidth, frequenza As Integer
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  Dim err, frameLetti, frameScritti As Integer
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  Dim frameSize As Single
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  Dim bufferFrames As Short = 4096
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  Dim buffer As Short[]
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<FONT color=gray>' ''Parte AudioFile:''</font>
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    afOF = afOpenFile(percorsoFile, "r", Null)
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    If IsNull(afOF) Then Error.Raise("Impossibile aprire il file !")
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<FONT color=gray>' ''Estrae informazioni generali sul file audio:''</font>
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    frameCount = afGetFrameCount(afOF, AF_DEFAULT_TRACK)
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    canali = afGetChannels(afOF, AF_DEFAULT_TRACK)
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    sFp = VarPtr(sampleFormat)
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    sWP = VarPtr(sampleWidth)
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    afGetSampleFormat(afOF, AF_DEFAULT_TRACK, sFP, sWP)
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    If (Int@(sWP) <> 16) Or (canali > 2) Then Error.Raise("Il file audio deve essere di formato 16-bit monofonico o stereofonico !")
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    frequenza = afGetRate(afOF, AF_DEFAULT_TRACK)
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    frameSize = afGetFrameSize(afOF, AF_DEFAULT_TRACK, 1)
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    Print "File audio: "; percorsoFile
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    Print "Numero di frame nel file: "; frameCount
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    Print "Canali audio di uscita: "; canali
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    Print "Formato del campionamento: "; Int@(sFP)
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    Print "Risoluzione del campionamento: "; Int@(sWP); "-bit"
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    Print "Frequenza di campionamento: Hz "; frequenza
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    Print "Dimensione dei soli dati audio: "; frameCount * frameSize; " byte"
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    buffer = New Short[](frameCount * frameSize)
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<FONT color=gray>' ''Parte Alsa:''</font>
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    err = snd_pcm_open(VarPtr(handle), "default", SND_PCM_STREAM_PLAYBACK, 0)
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    If err < 0 Then Error.Raise("Impossibile inizializzare la libreria Alsa !")
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    err = snd_pcm_set_params(handle, SND_PCM_FORMAT_S16, SND_PCM_ACCESS_RW_INTERLEAVED, canali, frequenza, 1, 500000)
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    If err < 0 Then Error.Raise("Impossibile impostare i parametri audio alla libreria Alsa !")
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<FONT color=gray>' ''Ciclo per eseguire il file wav:''</font>
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    While True
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      frameLetti = afReadFrames(afOF, AF_DEFAULT_TRACK, buffer, bufferFrames)
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      If frameLetti <= 0 Then Break
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<FONT color=gray>' ''Scrive i dati audio nel sub-sistema PCM di Alsa:''</font>
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      frameScritti = snd_pcm_writei(handle, buffer, bufferFrames)
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      If frameScritti < 0 Then
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        frameScritti = snd_pcm_recover(handle, frameScritti, 0)
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        Error.Raise("Impossibile scrivere dati nel dispositivo di uscita di Alsa !")
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      Endif
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    Wend
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<FONT color=gray>' ''Va in chiusura:''</font>
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    snd_pcm_drain(handle)
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    snd_pcm_close(handle)
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    buffer.Clear()
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    afCloseFile(afOF)
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'''End'''
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Versione delle 04:59, 8 apr 2014

La libreria Libaudiofile consente la lettura e la scrittura di file audio appartenenti ai formati wav, aiff, aifc, snd, au, voc ed altri.


Per poter fruire delle risorse della libreria Libaudiofile è necessario aver installata nel proprio sistema la libreria (nell'attuale versione): libaudiofile.so.1.0.0


Di seguito mostriamo due semplici codici per l'esecuzione di un file audio di formato WAV mediante la libreria Libaudiofile e la libreria di Alsa.

Primo esempio

Private Const bufferFrames As Short = 4096

Library "libaudiofile:1.0.0"

Private Const AF_DEFAULT_TRACK As Integer = 1001
Private Const AF_SAMPFMT_TWOSCOMP As Integer = 401      ' linear two's complement

' AFfilehandle afOpenFile (const char *filename, const char *mode, AFfilesetup setup)
' Opens a specified audio file and creates a file handle structure
Private Extern afOpenFile(filename As String, mode As String, setup As Pointer) As Pointer

' int afGetChannels (AFfilehandle, int track)
' Gets number of channels.
Private Extern afGetChannels(AFfilehandle As Pointer, track As Integer) As Integer

' double afGetRate (AFfilehandle, int track)
' Gets sampling rate.
Private Extern afGetRate(AFfilehandle As Pointer, track As Integer) As Float

' int afSetVirtualSampleFormat (AFfilehandle, int track, int sampleFormat, int sampleWidth)
' Set the virtual data format for a track in an audio file
Private Extern afSetVirtualSampleFormat(AFfilehandle As Pointer, track As Integer, sampleFormat As Integer, sampleWidth As Integer) As Integer

' int afReadFrames (AFfilehandle, int track, void *buffer, int frameCount)
' reads sample frames from a given audio track in an audio file.
' Returns the number of frames successfully read from file into the array referred to by samples.
Private Extern afReadFrames(AFfilehandle As Pointer, track As Integer, buf As Short[], frameCount As Integer) As Integer

' int afCloseFile (AFfilehandle file)
' Closes an open audio file.
Private Extern afCloseFile(AFfilehandle As Pointer) As Integer


Library "libasound:2"

Private Const SND_PCM_STREAM_PLAYBACK As Integer = 0
Private Const SND_PCM_FORMAT_S16 As Integer = 2
Private Const SND_PCM_ACCESS_RW_INTERLEAVED As Integer = 3

' int snd_pcm_open (snd_pcm_t **pcm, const char *name, snd_pcm_stream_t stream, int mode)
' Opens a PCM.
Private Extern snd_pcm_open(pcm As Pointer, name As String, streamI As Integer, mode As Integer) As Integer

' int snd_pcm_set_params (snd_pcm_t *pcm, snd_pcm_format_t format, snd_pcm_access_t access, unsigned int channels, unsigned int rate, int soft_resample, unsigned int latency)
' Set the hardware and software parameters in a simple way.
Private Extern snd_pcm_set_params(pcm As Pointer, formatI As Integer, accessI As Integer, channels As Integer, rate As Integer, soft_resample As Integer, latency As Integer) As Integer

' snd_pcm_sframes_t snd_pcm_writei (snd_pcm_t *pcm, const void *buffer, snd_pcm_uframes_t size)
' Write interleaved frames to a PCM.
Private Extern snd_pcm_writei(pcm As Pointer, buf As Short[], size As Integer) As Integer

' int snd_pcm_recover (snd_pcm_t * pcm, int err, int silent)
' Recover the stream state from an error or suspend.
Private Extern snd_pcm_recover(pcm As Pointer, errorI As Integer, silent As Integer) As Integer

' snd_pcm_drain (snd_pcm_t *pcm)
' Stop a PCM preserving pending frames.
Private Extern snd_pcm_drain(pcm As Pointer) As Integer

' int snd_pcm_close (snd_pcm_t *pcm)
' Close PCM handle
Private Extern snd_pcm_close(pcm As Pointer) As Integer


Public Sub Main()

 Dim afOF, AF_NULL_FILESETUP, handle As Pointer
 Dim percorsoFile As String = "percorso/del/file.wav"
 Dim canali, frequenza, err, frameLetti, frameScritti As Integer
 Dim buffer As Short[]
 
' Parte AudioFile:
   afOF = afOpenFile(percorsoFile, "r", AF_NULL_FILESETUP)
   If IsNull(afOF) Then Error.Raise("Impossibile aprire il file !")
   
' Estrae alcune informazioni generali sul file audio:
   canali = afGetChannels(afOF, AF_DEFAULT_TRACK)
   frequenza = afGetRate(afOF, AF_DEFAULT_TRACK)
   Print "Canali audio di uscita: "; canali
   Print "Frequenza di campionamento: Hz "; frequenza

   afSetVirtualSampleFormat(afOF, AF_DEFAULT_TRACK, AF_SAMPFMT_TWOSCOMP, 16)
   
' Parte Alsa:
   err = snd_pcm_open(VarPtr(handle), "default", SND_PCM_STREAM_PLAYBACK, 0)
   If err < 0 Then Error.Raise("Impossibile inizializzare la libreria Alsa !")
   
   err = snd_pcm_set_params(handle, SND_PCM_FORMAT_S16, SND_PCM_ACCESS_RW_INTERLEAVED, canali, frequenza, 1, 500000)
   If err < 0 Then Error.Raise("Impossibile impostare i parametri audio alla libreria Alsa !")
   
   
   buffer = New Short[](bufferFrames * canali)

' Ciclo per eseguire il file wav:
   While True
     
     frameLetti = afReadFrames(afOF, AF_DEFAULT_TRACK, buffer, bufferFrames)
     If frameLetti <= 0 Then Break
     
' Scrive i dati audio nel sub-sistema PCM di Alsa:
     frameScritti = snd_pcm_writei(handle, buffer, bufferFrames)
     If frameScritti < 0 Then
       frameScritti = snd_pcm_recover(handle, frameScritti, 0)
       Error.Raise("Impossibile scrivere dati nel dispositivo di uscita di Alsa !")
     Endif
     
   Wend
   
   
' Va in chiusura:
   snd_pcm_drain(handle)
   snd_pcm_close(handle)
   buffer.Clear()
   afCloseFile(afOF)

End


Secondo esempio

Library "libaudiofile:1.0.0"

Private Const AF_DEFAULT_TRACK As Integer = 1001
Private Const AF_SAMPFMT_TWOSCOMP As Integer = 401      ' linear two's complement

' AFfilehandle afOpenFile (const char *filename, const char *mode, AFfilesetup setup)
' Opens a specified audio file and creates a file handle structure
Private Extern afOpenFile(filename As String, mode As String, setup As Pointer) As Pointer

' AFframecount afGetFrameCount (AFfilehandle file, int track)
' Get the total sample frame count.
Private Extern afGetFrameCount(AFfilehandle As Pointer, track As Integer) As Integer

' float afGetFrameSize (AFfilehandle, int track, int expand3to4)
' Calculate the frame size in bytes for an audio track.
Private Extern afGetFrameSize(AFfilehandle As Pointer, track As Integer, expand3to4 As Integer) As Single

' void afGetSampleFormat (AFfilehandle file, int track, int *sampleFormat, int *sampleWidth)
' Get the sample format for a specified audio track.
Private Extern afGetSampleFormat(AFfilehandle As Pointer, track As Integer, sampleFP As Pointer, sampleWP As Pointer)

' int afGetChannels (AFfilehandle, int track)
' Gets number of channels.
Private Extern afGetChannels(AFfilehandle As Pointer, track As Integer) As Integer

' double afGetRate (AFfilehandle, int track)
' Gets sampling rate.
Private Extern afGetRate(AFfilehandle As Pointer, track As Integer) As Float

' int afSetVirtualSampleFormat (AFfilehandle, int track, int sampleFormat, int sampleWidth)
' Set the virtual data format for a track in an audio file
Private Extern afSetVirtualSampleFormat(AFfilehandle As Pointer, track As Integer, sampleFormat As Integer, sampleWidth As Integer) As Integer

' int afReadFrames (AFfilehandle, int track, void *buffer, int frameCount)
' reads sample frames from a given audio track in an audio file.
' Returns the number of frames successfully read from file into the array referred to by samples.
Private Extern afReadFrames(AFfilehandle As Pointer, track As Integer, buf As Short[], frameCount As Integer) As Integer

' int afCloseFile (AFfilehandle file)
' Closes an open audio file.
Private Extern afCloseFile(AFfilehandle As Pointer) As Integer


Library "libasound:2"

Private Const SND_PCM_STREAM_PLAYBACK As Integer = 0
Private Const SND_PCM_FORMAT_S16 As Integer = 2
Private Const SND_PCM_ACCESS_RW_INTERLEAVED As Integer = 3

' int snd_pcm_open (snd_pcm_t **pcm, const char *name, snd_pcm_stream_t stream, int mode)
' Opens a PCM.
Private Extern snd_pcm_open(pcm As Pointer, name As String, streamI As Integer, mode As Integer) As Integer

' int snd_pcm_set_params (snd_pcm_t *pcm, snd_pcm_format_t format, snd_pcm_access_t access, unsigned int channels, unsigned int rate, int soft_resample, unsigned int latency)
' Set the hardware and software parameters in a simple way.
Private Extern snd_pcm_set_params(pcm As Pointer, formatI As Integer, accessI As Integer, channels As Integer, rate As Integer, soft_resample As Integer, latency As Integer) As Integer

' snd_pcm_sframes_t snd_pcm_writei (snd_pcm_t *pcm, const void *buffer, snd_pcm_uframes_t size)
' Write interleaved frames to a PCM.
Private Extern snd_pcm_writei(pcm As Pointer, buf As Short[], size As Integer) As Integer

' int snd_pcm_recover (snd_pcm_t * pcm, int err, int silent)
' Recover the stream state from an error or suspend.
Private Extern snd_pcm_recover(pcm As Pointer, errorI As Integer, silent As Integer) As Integer

' snd_pcm_drain (snd_pcm_t *pcm)
' Stop a PCM preserving pending frames.
Private Extern snd_pcm_drain(pcm As Pointer) As Integer

' int snd_pcm_close (snd_pcm_t *pcm)
' Close PCM handle
Private Extern snd_pcm_close(pcm As Pointer) As Integer


Public Sub Main()

 Dim afOF, sFP, sWP, handle As Pointer
 Dim percorsoFile As String = "percorso/del/file.wav"
 Dim frameCount, canali, sampleFormat, sampleWidth, frequenza As Integer
 Dim err, frameLetti, frameScritti As Integer
 Dim frameSize As Single
 Dim bufferFrames As Short = 4096
 Dim buffer As Short[]
 
' Parte AudioFile:
   afOF = afOpenFile(percorsoFile, "r", Null)
   If IsNull(afOF) Then Error.Raise("Impossibile aprire il file !")
   
' Estrae informazioni generali sul file audio:
   frameCount = afGetFrameCount(afOF, AF_DEFAULT_TRACK)
   canali = afGetChannels(afOF, AF_DEFAULT_TRACK)
   sFp = VarPtr(sampleFormat)
   sWP = VarPtr(sampleWidth)
   afGetSampleFormat(afOF, AF_DEFAULT_TRACK, sFP, sWP)
   If (Int@(sWP) <> 16) Or (canali > 2) Then Error.Raise("Il file audio deve essere di formato 16-bit monofonico o stereofonico !")
   frequenza = afGetRate(afOF, AF_DEFAULT_TRACK)
   frameSize = afGetFrameSize(afOF, AF_DEFAULT_TRACK, 1)
   Print "File audio: "; percorsoFile
   Print "Numero di frame nel file: "; frameCount
   Print "Canali audio di uscita: "; canali
   Print "Formato del campionamento: "; Int@(sFP)
   Print "Risoluzione del campionamento: "; Int@(sWP); "-bit"
   Print "Frequenza di campionamento: Hz "; frequenza
   Print "Dimensione dei soli dati audio: "; frameCount * frameSize; " byte"

   buffer = New Short[](frameCount * frameSize)
   
' Parte Alsa:
   err = snd_pcm_open(VarPtr(handle), "default", SND_PCM_STREAM_PLAYBACK, 0)
   If err < 0 Then Error.Raise("Impossibile inizializzare la libreria Alsa !")
   
   err = snd_pcm_set_params(handle, SND_PCM_FORMAT_S16, SND_PCM_ACCESS_RW_INTERLEAVED, canali, frequenza, 1, 500000)
   If err < 0 Then Error.Raise("Impossibile impostare i parametri audio alla libreria Alsa !")

' Ciclo per eseguire il file wav:
   While True
     
     frameLetti = afReadFrames(afOF, AF_DEFAULT_TRACK, buffer, bufferFrames)
     If frameLetti <= 0 Then Break
     
' Scrive i dati audio nel sub-sistema PCM di Alsa:
     frameScritti = snd_pcm_writei(handle, buffer, bufferFrames)
     If frameScritti < 0 Then
       frameScritti = snd_pcm_recover(handle, frameScritti, 0)
       Error.Raise("Impossibile scrivere dati nel dispositivo di uscita di Alsa !")
     Endif
     
   Wend
   
   
' Va in chiusura:
   snd_pcm_drain(handle)
   snd_pcm_close(handle)
   buffer.Clear()
   afCloseFile(afOF)

End



Riferimenti

[1] Audio File Library

[2] fifi.org

Estratto da "https://www.gambas-it.org/wiki/index.php?title=Eseguire_un_file_WAV_mediante_le_funzioni_esterne_del_API_di_libaudiofile_e_di_Alsa&oldid=15242"