Differenze tra le versioni di "Eseguire un file WAV mediante le funzioni esterne del API di libaudiofile e di Alsa"
Da Gambas-it.org - Wikipedia.
| Riga 8: | Riga 8: | ||
====Primo esempio==== | ====Primo esempio==== | ||
| − | |||
Private somma_scritti As Integer | Private somma_scritti As Integer | ||
| Riga 79: | Riga 78: | ||
Dim percorsoFile As String = "''percorso/del/file.wav''" | Dim percorsoFile As String = "''percorso/del/file.wav''" | ||
Dim canali, frequenza, err, frameLetti, frameScritti As Integer | Dim canali, frequenza, err, frameLetti, frameScritti As Integer | ||
| + | Dim bufferFrames As Short = 4096 | ||
Dim buffer As Short[] | Dim buffer As Short[] | ||
Versione delle 18:36, 3 feb 2015
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 somma_scritti As Integer
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 bufferFrames As Short = 4096
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
somma_scritti += frameScritti
Print CStr(Date(0, 0, 0, 0, 0, 0, (somma_scritti / frequenza) * 1000))
Wend
' Va in chiusura:
snd_pcm_drain(handle)
snd_pcm_close(handle)
buffer.Clear()
afCloseFile(afOF)
End
Secondo esempio
Private somma_scritti As Integer
Library "libaudiofile:1.0.0"
Private Const AF_DEFAULT_TRACK As Integer = 1001
' 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 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
somma_scritti += frameScritti
Print CStr(Date(0, 0, 0, 0, 0, 0, (somma_scritti / frequenza) * 1000))
Wend
' Va in chiusura:
snd_pcm_drain(handle)
snd_pcm_close(handle)
buffer.Clear()
afCloseFile(afOF)
End
