Di seguito un semplice codice, che ho scritto, per eseguire una traccia a scelta o l'intero CD audio utilizzando le funzioni esterne del API di
Library "libcdio:13.0.0"
Private Enum DRIVER_UNKNOWN = 0, DRIVER_AIX, DRIVER_BSDI, DRIVER_FREEBSD, DRIVER_NETBSD, DRIVER_LINUX, DRIVER_SOLARIS,
DRIVER_OS2, DRIVER_OSX, DRIVER_WIN32, DRIVER_CDRDAO, DRIVER_BINCUE, DRIVER_NRG, DRIVER_DEVICE
Private Const CDIO_INVALID_LSN As Integer = -45301
Private Const CDIO_CDROM_LEADOUT_TRACK As Integer = &AA
' CdIo_t * cdio_open (const char *psz_source, driver_id_t driver_id)
' Sets up to read from place specified by psz_source and driver_id.
Private Extern cdio_open(psz_source As String, driver_id As Integer) As Pointer
' track_t cdio_get_num_tracks(const CdIo_t * p_cdio)
' Get the number of tracks on the CD.
Private Extern cdio_get_num_tracks(p_cdio As Pointer) As Byte
' lsn_t cdio_get_track_lsn(const CdIo_t * p_cdio, track_t u_track)
' Return the starting LSN for track number i_track in p_cdio.
Private Extern cdio_get_track_lsn(p_cdio As Pointer, u_track As Integer) As Integer
' driver_return_code_t cdio_read_audio_sector (const CdIo_t *p_cdio, void *p_buf, lsn_t i_lsn)
' Read an audio sector.
Private Extern cdio_read_audio_sector(p_cdio As Pointer, p_buf As Byte[], i_lsn As Integer) As Integer
' void cdio_destroy(CdIo_t * p_cdio)
' Free any resources associated with p_cdio.
Private Extern cdio_destroy(p_cdio As Pointer)
Library "libasound:2"
Private Const SND_PCM_STREAM_PLAYBACK As Integer = 0
Private Const SND_PCM_FORMAT_S16_LE 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, nome As String, stream As Integer, mode As Integer) As Integer
' const char * snd_strerror (int errnum)
' Returns the message for an Error code.
Private Extern snd_strerror(errnum As Integer) As String
' int snd_pcm_set_params (snd_pcm_t *pcm, snd_pcm_format_t format, snd_pcm_access_t access, unsigned int canali, 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, buffer As Pointer, uframes As Long) As Integer
' int 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 cd As Pointer
Dim traccia, tracce, n_tr, i As Byte
Dim cbf As Integer
Dim lsn As New Integer[]
Dim s As String
' Il valore della variabile "cbf" è data dal prodotto del numero dei canali per la risoluzione in bit per la frequenza della traccia audio:
' canali bit frequenza
cbf = 2 * 16 * 44100
cd = cdio_open(Null, DRIVER_LINUX)
If cd = 0 Then Error.Raise("Impossibile trovare il driver per il cd-audio !")
tracce = cdio_get_num_tracks(cd)
Print "Tracce del CD-Audio (1 - "; tracce; ")"
Print " #: Durata"
' Individua l'indirizzo del settore logico di ciascuna traccia:
For i = 1 To tracce
lsn.Push(cdio_get_track_lsn(cd, i))
Next
lsn.Push(cdio_get_track_lsn(cd, CDIO_CDROM_LEADOUT_TRACK))
For i = 0 To tracce - 1
If (CDIO_INVALID_LSN <> lsn[i]) Then
Print Format(i + 1, "#0:"), Date(0, 0, 0, 0, 0, 0, ((((lsn[i + 1] - lsn[i]) * 2352) * 8) / cbf) * 1000)
Endif
Next
'''''''''''''''''''
n_tr = 1
' Si sceglie se eseguire una sola traccia e l'intero CD audio:
Print "\nPer eseguire una sola traccia, scrivere in console ed inviare il numero corrispondente."
Print "Per eseguire tutte le tracce del CD audio, premere 'Invio.'\n"
Input s
' Se si è scelto di eseguire solo una traccia, imposta il suo numero:
If IsDigit(s) Then
n_tr = Val(s)
tracce = n_tr
Endif
For traccia = n_tr To tracce
For i = 0 To tracce - 1
If i + 1 = traccia Then
Print "Durata del brano: "; Date(0, 0, 0, 0, 0, 0, ((((lsn[i + 1] - lsn[i]) * 2352) * 8) / cbf) * 1000)
Endif
Next
lsn.Push(cdio_get_track_lsn(cd, CDIO_CDROM_LEADOUT_TRACK))
Esecuzione(cd, lsn, traccia)
Next
' Va in chiusura:
cdio_destroy(cd)
End
Private Procedure Esecuzione(pcd As Pointer, sett As Integer[], tr As Byte)
Dim handle As Pointer
Dim err, i, frames, somma_frames As Integer
Dim buf As Byte[]
err = snd_pcm_open(VarPtr(handle), "default", SND_PCM_STREAM_PLAYBACK, 0)
If err < 0 Then Error.Raise("Errore nell'apertura del subsistema PCM: " & snd_strerror(err))
err = snd_pcm_set_params(handle, SND_PCM_FORMAT_S16_LE, SND_PCM_ACCESS_RW_INTERLEAVED, 2, 44100, 1, 500000)
If err < 0 Then Error.Raise("Errore nell'impostazione dei parametri audio: " & snd_strerror(err))
buf = New Byte[2352]
For i = 0 To (sett[tr] - sett[tr - 1]) - 1
cdio_read_audio_sector(pcd, buf, sett[tr - 1] + i)
frames = snd_pcm_writei(handle, buf.Data, 2352 / 4)
somma_frames += frames
Write #File.Out, "\rTempo trascorso: " & Date(0, 0, 0, 0, 0, 0, (somma_frames / 44100) * 1000)
Sleep 0.01
Next
snd_pcm_drain(handle)
' Alla fine dell'esecuzione chiude il subsistema PCM:
err = snd_pcm_close(handle)
If err = 0 Then Print "\nChiusura dell'interfaccia PCM: regolare."
End
