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| (10 versioni intermedie di uno stesso utente non sono mostrate) |
| Riga 1: |
Riga 1: |
| − | Mostreremo di seguito il codice di un semplice Client Midi di Alsa capace di ricevere dati Midi (a titolo esemplificativo sono stati individuati i quattro tipi più importanti e frequenti) da un altro Client di Alsa (ad esempio da una tastiera Midi esterna) e di inviarli immediatamente ad un altro Client (ad esempio ad un ''softsynth'' per l'ascolto sonoro).
| + | #REDIRECT [[ALSA_e_Gambas:_Esempio_di_semplice_Client_Midi_di_Alsa_in_ricezione_ed_invio_dati]] |
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| − | Al terzo parametro della funzione ''snd_seq_open()'', necessaria per l'apertura del subsistema ''Seq'' di Alsa, va inserita la costante ''SND_SEQ_OPEN_DUPLEX'' per consentire il flusso di dati sia in Entrata che in Uscita.
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| − | <BR>I dati Midi ricevuti sono assegnati ad una variabile di tipo ''Struttura'' organizzata secondo lo schema tipico di un "''Evento''" Midi Alsa.
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| − | Dopo l'avvio del ''softsynth'' e del seguente applicativo, sarà necessario connettere via Alsa la tastiera Midi ed ''softsynth'' al presente applicativo Midi rispettivamente in entrata ed in uscita.
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| − | Public Struct snd_seq_event_t
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| − | type As Byte <FONT color=gray>' ''byte n° 0''</font>
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| − | flag As Byte
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| − | tag As Byte
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| − | queue As Byte
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| − | timestamp1 As Integer
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| − | timestamp2 As Integer
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| − | source_id As Byte
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| − | source_porta As Byte
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| − | dest_id As Byte
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| − | dest_porta As Byte
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| − | channel As Byte <FONT color=gray>' ''byte n° 16''</font>
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| − | note As Byte
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| − | velocity As Short
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| − | parametro As Integer <FONT color=gray>' ''byte n° 20''</font>
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| − | valore As Integer <FONT color=gray>' ''byte n° 24''</font>
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| − | End Struct
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| − | Private Const POLLIN As Short = 1
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| − | Private Const POLLFD As Byte = 8
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| − | Library "libasound:2.0.0"
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| − | Private Const SND_SEQ_OPEN_DUPLEX As Integer = 3
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| − | Private Const SND_SEQ_PORT_CAP_WRITE As Integer = 2
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| − | Private Const SND_SEQ_PORT_CAP_SUBS_WRITE As Integer = 64
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| − | Private Const SND_SEQ_PORT_CAP_READ As Integer = 1
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| − | Private Const SND_SEQ_PORT_CAP_SUBS_READ As Integer = 32
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| − | Private Const SND_SEQ_PORT_TYPE_APPLICATION As Integer = 1048576
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| − | Private Const SND_SEQ_ADDRESS_UNKNOWN As Byte = 253
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| − | Private Const SND_SEQ_ADDRESS_SUBSCRIBERS As Byte = 254
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| − | Private Const SND_SEQ_EVENT_NOTEON As Byte = 6
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| − | Private Const SND_SEQ_EVENT_NOTEOFF As Byte = 7
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| − | Private Const SND_SEQ_EVENT_CONTROLLER As Byte = 10
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| − | Private Const SND_SEQ_EVENT_PGMCHANGE As Byte = 11
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| − | <FONT color=gray>' ''const char * snd_strerror(int errnum)''
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| − | ' ''Returns the message for an error code.''</font>
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| − | Private Extern snd_strerror(errnum As Integer) As String
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| − | <FONT color=gray>' ''int snd_seq_open (snd_seq_t **handle, const char *name, int streams, int mode)
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| − | ' ''Open the ALSA sequencer.''</font>
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| − | Private Extern snd_seq_open(handle As Pointer, name As String, streams As Integer, mode As Integer) As Integer
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| − | <FONT color=gray>' ''int snd_seq_set_client_name(snd_seq_t* seq, const char* name)''
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| − | ' ''Set client name.''</font>
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| − | Private Extern snd_seq_set_client_name(handle As Pointer, name As String) As Integer
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| − | <FONT color=gray>' ''int snd_seq_client_id (snd_seq_t *seq)''
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| − | ' ''Get the client id.''</font>
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| − | Private Extern snd_seq_client_id(handle As Pointer) As Integer
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| − | <FONT color=gray>' ''int snd_seq_create_simple_port(snd_seq_t *seq, const char *name, unsigned int caps, unsigned int type)''
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| − | ' ''Create a port - simple version.''</font>
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| − | Private Extern snd_seq_create_simple_port(handle As Pointer, name As String, caps As Integer, type As Integer) As Integer
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| − | <FONT color=gray>' ''int snd_seq_poll_descriptors_count(snd_seq_t * seq, short events)''
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| − | ' ''Returns the number of poll descriptors.''</font>
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| − | Private Extern snd_seq_poll_descriptors_count(handle As Pointer, events As Short) As Integer
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| − | <FONT color=gray>' ''int snd_seq_poll_descriptors(snd_seq_t * seq, struct pollfd * pfds, unsigned int space, short events)''
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| − | ' ''Get poll descriptors.''</font>
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| − | Private Extern snd_seq_poll_descriptors(handle As Pointer, pfds As Pointer, spaceI As Integer, events As Short) As Integer
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| − | <FONT color=gray>' ''int snd_seq_event_input(snd_seq_t *handle, snd_seq_event_t **ev)''
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| − | ' ''Retrieve an event from sequencer.''</font>
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| − | Private Extern snd_seq_event_input(handle As Pointer, ev As Snd_seq_event_t) As Integer
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| − | <FONT color=gray>' ''int snd_seq_event_output_direct (snd_seq_t *handle, snd_seq_event_t *ev)''
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| − | ' ''Output an event directly to the sequencer NOT through output buffer.''</font>
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| − | Private Extern snd_seq_event_output_direct(handle As Pointer, ev As Snd_seq_event_t) As Integer
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| − | '''Public''' Sub Main()
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| − | Dim seq As Pointer
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| − | Dim idportaE, idportaU, err, id As Integer
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| − | err = snd_seq_open(VarPtr(seq), "default", SND_SEQ_OPEN_DUPLEX, 0)
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| − | If err < 0 Then Error.Raise("Impossibile inizializzare il subsistema 'seq' di ALSA: " & snd_strerror(err))
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| − | Print "Apertura del dispositivo 'seq' di Alsa: regolare\nNome del dispositivo 'seq': "; "'default'"
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| − | err = snd_seq_set_client_name(seq, "Sequencer dimostrativo di ALSA")
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| − | If err < 0 Then Error.Raise("Impossibile assegnare un nome al Client applicativo di ALSA: " & snd_strerror(err))
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| − | id = snd_seq_client_id(seq)
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| − | Print "Numero identificativo del sequencer dimostrativo: "; id
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| − | idportaE = snd_seq_create_simple_port(seq, "Porta di Entrata del sequencer dimostrativo di ALSA", SND_SEQ_PORT_CAP_WRITE Or SND_SEQ_PORT_CAP_SUBS_WRITE, SND_SEQ_PORT_TYPE_APPLICATION)
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| − | If idportaE < 0 Then Error.Raise("Impossibile creare una porta del Client applicativo di ALSA: " & snd_strerror(err))
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| − | Print "Numero identificativo della porta di Entrata: "; idportaE
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| − | idportaU = snd_seq_create_simple_port(seq, "Porta di Uscita del sequencer dimostrativo di ALSA", SND_SEQ_PORT_CAP_READ Or SND_SEQ_PORT_CAP_SUBS_READ, SND_SEQ_PORT_TYPE_APPLICATION)
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| − | If idportaU < 0 Then Error.Raise("Impossibile creare una porta del Client applicativo di ALSA: " & snd_strerror(err))
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| − | Print "Numero identificativo della porta di Uscita: "; idportaU
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| − | Print
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| − | intercettaMessaggiMidi(seq, id, idportaU)
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| − | '''End'''
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| − | '''Public''' Procedure intercettaMessaggiMidi(seqiM As Pointer, idC As Integer, portEx As Integer)
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| − | Dim npfd As Integer
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| − | Dim pfd, ev As Pointer
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| − | Dim midi@ As Snd_seq_event_t
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| − | npfd = snd_seq_poll_descriptors_count(seqiM, POLLIN)
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| − | pfd = Alloc(npfd * POLLFD)
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| − | snd_seq_poll_descriptors(seqiM, pfd, npfd, POLLIN)
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| − | While True
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| − | snd_seq_event_input(seqiM, VarPtr(ev))
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| − | midi@ = ev
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| − | With midi@
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| − | Select Case midi@.type
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| − | Case SND_SEQ_EVENT_NOTEON
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| − | Print "Evento 'NoteOn' sul canale: "; .channel, .note, .velocity
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| − | Case SND_SEQ_EVENT_NOTEOFF
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| − | Print "Evento 'NoteOff' sul canale: "; .channel, .note, .velocity
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| − | Case SND_SEQ_EVENT_CONTROLLER
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| − | Print "Evento 'Control' sul canale: "; .channel, .parametro, .valore
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| − | Case SND_SEQ_EVENT_PGMCHANGE
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| − | Print "Evento 'Program Change' sul canale: "; .channel, .valore
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| − | End Select
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| − | .source_id = idC
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| − | .source_porta = portEx
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| − | .dest_id = SND_SEQ_ADDRESS_SUBSCRIBERS
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| − | .dest_porta = SND_SEQ_ADDRESS_UNKNOWN
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| − | End With
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| − | snd_seq_event_output_direct(seqiM, midi@)
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| − | Wend
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| − | '''End'''
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