Conoscere con le funzioni esterne di ALSA i dispositivi audio presenti nel sistema
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Versione del 28 mag 2014 alle 05:58 di Vuott (Discussione | contributi) (Creata pagina con 'Alcune funzioni esterne del API di ALSA consentono di conoscere quali sono le porte di entrata e di uscita dell'audio digitale delle schede audio presenti nel proprio sistema....')
Alcune funzioni esterne del API di ALSA consentono di conoscere quali sono le porte di entrata e di uscita dell'audio digitale delle schede audio presenti nel proprio sistema.
Mostriamo di segtuito qualche esempio:
Private Const SND_PCM_STREAM_PLAYBACK As Byte = 0 ' Playback stream Private Const ENOENT As Byte = 2 Private handlCtl As Pointer Library "libasound:2" ' int snd_card_next(int *card) ' Try to determine the next card. Private Extern snd_card_next(cardI As Pointer) As Integer ' const char* snd_pcm_stream_name(snd_pcm_stream_t stream) ' Get name of PCM stream type Private Extern snd_pcm_stream_name(streamI As Byte) As String ' int snd_ctl_open(snd_ctl_t **ctl, const char *name, int mode) ' Opens a CTL. Private Extern snd_ctl_open(ctlP As Pointer, name As String, mode As Integer) As Integer ' snd_ctl_card_info_malloc(ptr) ' Allocate an invalid snd_ctl_card_info_t using standard malloc Private Extern snd_ctl_card_info_malloc(ptr As Pointer) ' int snd_ctl_card_info(snd_ctl_t *ctl, snd_ctl_card_info_t *info) ' Get card related information. Private Extern snd_ctl_card_info(ctlP As Pointer, infoP As Pointer) As Integer ' void snd_ctl_close(snd_ctl_t *ctl) ' chiude il ctl Private Extern snd_ctl_close(ctlP As Pointer) ' int snd_ctl_pcm_next_device(snd_ctl_t *ctl, int *device) ' Get Next PCM device number. Private Extern snd_ctl_pcm_next_device(ctlP As Pointer, device As Pointer) As Integer ' int snd_pcm_info_malloc(snd_pcm_info_t ** ptr) ' Allocate an invalid snd_pcm_info_t using standard malloc Private Extern snd_pcm_info_malloc(ptr As Pointer) As Integer ' void snd_pcm_info_set_device (snd_pcm_info_t *obj, unsigned int val) ' Set wanted device inside a PCM info container Private Extern snd_pcm_info_set_device(pcminfoP As Pointer, ValI As Integer) ' void snd_pcm_info_set_subdevice(snd_pcm_info_t *obj, unsigned int val) ' Set wanted subdevice inside a PCM info container Private Extern snd_pcm_info_set_subdevice(pcminfoP As Pointer, ValI As Integer) ' void snd_pcm_info_set_stream(snd_pcm_info_t *obj, snd_pcm_stream_t val) ' Set wanted stream inside a PCM info container Private Extern snd_pcm_info_set_stream(pcminfoP As Pointer, valInt As Integer) ' int snd_ctl_pcm_info (snd_ctl_t *ctl, snd_pcm_info_t *info) ' Get info about a PCM device. Private Extern snd_ctl_pcm_info(ctlP As Pointer, pcminfoP As Pointer) As Integer ' const char * snd_ctl_card_info_get_id (const snd_ctl_card_info_t *obj) ' Get card identifier From a CTL card info. Private Extern snd_ctl_card_info_get_id(infoP As Pointer) As String ' const char * snd_ctl_card_info_get_name (const snd_ctl_card_info_t *obj) ' Get card name From a CTL card info. Private Extern snd_ctl_card_info_get_name(infoP As Pointer) As String ' const char* snd_pcm_info_get_id(const snd_pcm_info_t * obj) ' Get id from a PCM info container. Private Extern snd_pcm_info_get_id(pcminfoP As Pointer) As String ' const char* snd_pcm_info_get_name (const snd_pcm_info_t * obj) ' Get name From a PCM info container. Private Extern snd_pcm_info_get_name(pcminfoP As Pointer) As String ' unsigned int snd_pcm_info_get_subdevices_count (const snd_pcm_info_t *obj) ' Get subdevices count From a PCM info container. Private Extern snd_pcm_info_get_subdevices_count(pcminfoP As Pointer) As Integer ' unsigned int snd_pcm_info_get_subdevices_avail (const snd_pcm_info_t *obj) ' Get available subdevices count From a PCM info container. Private Extern snd_pcm_info_get_subdevices_avail(pcminfoP As Pointer) As Integer ' const char * snd_pcm_info_get_subdevice_name (const snd_pcm_info_t *obj) ' Get subdevice name From a PCM info container. Private Extern snd_pcm_info_get_subdevice_name(pcminfoP As Pointer) As String ' const char * snd_strerror (int errnum) ' Returns the message For an Error code. Private Extern snd_strerror(errore As Integer) As String Public Sub Form_Open() Me.show Do Wait 0.1 Loop Until Me.Id <> 0 device_list() End Public Sub device_list() Dim info, pcminfo As Pointer Dim card, dev, count, avail, idx, err As Integer Dim name, card_id, card_name, pcm_id, pcm_name, subdevice_name As String snd_ctl_card_info_malloc(VarPtr(info)) snd_pcm_info_malloc(VarPtr(pcminfo)) card = -1 If (snd_card_next(VarPtr(card)) < 0) Or (card < 0) Then Error.Raise("Nessuna scheda audio trovata !") With ListBox1 .Add("******* LISTA DEI DISPOSITIVI HARDWARE DI RIPRODUZIONE AUDIO *******") End With snd_pcm_stream_name(SND_PCM_STREAM_PLAYBACK) While card >= 0 name = "hw:" & card err = snd_ctl_open(VarPtr(handlCtl), name, 0) If err < 0 Then Error("Errore nell'apertura del Controllo: " & card & ":" & snd_strerror(err)) Goto next_card Endif err = snd_ctl_card_info(handlCtl, info) If err < 0 Then Error("Informazione sull'hardware del controllo: " & card & ":" & snd_strerror(err)) snd_ctl_close(handlCtl) Goto next_card Endif dev = -1 While True If snd_ctl_pcm_next_device(handlCtl, VarPtr(dev)) < 0 Then Error.Raise("Errore alla funzione 'snd_ctl_pcm_next_device' !") If dev < 0 Then Break snd_pcm_info_set_device(pcminfo, dev) snd_pcm_info_set_subdevice(pcminfo, 0) snd_pcm_info_set_stream(pcminfo, SND_PCM_STREAM_PLAYBACK) err = snd_ctl_pcm_info(handlCtl, pcminfo) If err < 0 Then If err <> - ENOENT Then Error.Raise("Informazione sull'audio digitale del controllo: " & card & " " & snd_strerror(err)) Continue Endif '''''''' card_id = snd_ctl_card_info_get_id(info) card_name = snd_ctl_card_info_get_name(info) pcm_id = snd_pcm_info_get_id(pcminfo) pcm_name = snd_pcm_info_get_name(pcminfo) With ListBox1 .Add("_______________________________________________________________________________________") .Add(" ") .Add("DISPOSITIVO AUDIO: " & name & " " & card_id & " [" & card_name & "] Device: " & dev & " " & pcm_id & " [" & pcm_name & "]") .Add(" ") End With count = snd_pcm_info_get_subdevices_count(pcminfo) avail = snd_pcm_info_get_subdevices_avail(pcminfo) With ListBox1 .Add("Subdevices: " & avail & "/" & count) .Add(" ") End With For idx = 0 To count - 1 snd_pcm_info_set_subdevice(pcminfo, idx) err = snd_ctl_pcm_info(handlCtl, pcminfo) If err < 0 Then Error.Raise("Informazione sulla Riproduzione audio digitale del controllo: " & card & " " & snd_strerror(err)) Else subdevice_name = snd_pcm_info_get_subdevice_name(pcminfo) With ListBox1 .Add("Subdevice: #" & idx & ": " & subdevice_name) End With Endif Next Wend snd_ctl_close(handlCtl) next_card: If snd_card_next(VarPtr(card)) < 0 Then Error("Errore in 'next_card' !") Break Endif Wend End
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