Intercettare ed inviare dati Midi grezzi con le funzioni esterne del API di PortMidi
Da Gambas-it.org - Wikipedia.
Versione del 3 giu 2016 alle 16:17 di Vuott (Discussione | contributi)
La libreria PortMidi è una libreria per la gestione in tempo reale dei dati Midi in entrata ed in uscita. Essa fa parte di un assortimento di API e librerie create per la musica e per altri media.
E' possibile con alcune funzioni esterne della libreria PortMidi intercettare i dati Midi grezzi, provenienti da un dispositivo Midi, ed inviarli ad altri dispositivi Midi.
Sarà necessario avere installata nel proprio sistema e richiamare nel programma Gambas la libreria condivisa: ''libportmidi.so.0.0.0
Mostriamo di seguito un possibile codice che intercetta i dati Midi grezzi provenienti da un dispositivo esterno e li invia ad altro dispositivo Midi:
Private s As String Library "libportmidi:0.0.0" Public Struct PmDeviceInfo structVersion As Integer interf As Pointer name As Pointer inputI As Integer outputI As Integer opened As Integer End Struct Public Struct PmEvent message As Integer timestamp As Integer End Struct Private Const PM_FILT_ACTIVE As Integer = 16384 Private Const PM_FILT_CLOCK As Integer = 256 Private Const PM_FILT_SYSEX As Integer = 1 ' int Pm_CountDevices (void) ' Get devices count, ids range from 0 to Pm_CountDevices()-1. Private Extern Pm_CountDevices() As Integer ' const char *Pm_GetErrorText( PmError errnum ) ' Translate portmidi error number into human readable message. Private Extern Pm_GetErrorText(errnum As Integer) As String ' const PmDeviceInfo* Pm_GetDeviceInfo( PmDeviceID id ) ' Returns a pointer to a PmDeviceInfo structure referring to the device specified by id. Private Extern Pm_GetDeviceInfo(id As Integer) As PmDeviceInfo ' PmError Pm_OpenInput( PortMidiStream** stream, PmDeviceID inputDevice, void *inputDriverInfo, int32_t bufferSize, PmTimeProcPtr time_proc, void *time_info ) ' Open Input device. Private Extern Pm_OpenInput(pstream As Pointer, inputDevice As Integer, inputDriverInfo As Pointer, bufferSize As Integer, time_proc As Pointer, time_info As Pointer) As Integer ' PmError Pm_OpenOutput (PortMidiStream **stream, PmDeviceID outputDevice, void *outputDriverInfo, long bufferSize, PmTimeProcPtr time_proc, void *time_info, long latency) ' Open Output device. Private Extern Pm_OpenOutput(pstream As Pointer, outputDevice As Integer, outputDriverInfo As Pointer, bufferSize As Integer, time_proc As Pointer, latency As Long) As Integer ' PmError Pm_SetFilter( PortMidiStream* stream, int32_t filters ) ' Sets filters on an open input stream to drop selected input types. Private Extern Pm_SetFilter(pstream As Pointer, filters As Integer) As Integer ' PmError Pm_Poll( PortMidiStream *stream) ' Tests whether input is available. Private Extern Pm_Poll(pstream As Pointer) As Boolean ' int Pm_Read( PortMidiStream *stream, PmEvent *buffer, int32_t length ) ' Retrieves midi data into a buffer, and returns the number of events read. Private Extern Pm_Read(pstream As Pointer, buffer As PmEvent, lenght As Integer) As Integer ' PmError Pm_Write( PortMidiStream *stream, PmEvent *buffer, int32_t length ) ' Writes midi data from a buffer. Private Extern Pm_Write(pstream As Pointer, buffer As PmEvent, lenght As Integer) As Integer ' PmError Pm_Close( PortMidiStream* stream ) ' Closes a midi stream, flushing any pending buffers. Private Extern Pm_Close(pstream As Pointer) As Integer ' PmError Pm_Terminate( void ) ' Library termination function. Private Extern Pm_Terminate() As Integer Public Sub Main() Dim def_in, def_out, err, i As Integer Dim info As PmDeviceInfo Dim def As String Dim midi_in, midi_out As Pointer Print "Dispositivi Midi e loro porte disponibili:\n" def_in = Pm_GetDefaultInputDeviceID() def_out = Pm_GetDefaultOutputDeviceID() For i = 0 To Pm_CountDevices() - 1 info = Pm_GetDeviceInfo(i) If info.inputI > 0 Then def = IIf(i = def_in, "default ", Null) Print i; ": "; String@(info.interf); " "; String@(info.name); " ("; def; "input)" def = Null Endif If info.outputI > 0 Then def = IIf(i = def_out, "default ", Null) Print i; ": "; String@(info.interf); " "; String@(info.name); " ("; def; "output)" Endif Next ' Attende che sia inserito il numero del dispositivo Midi, da cui si riceverranno i dati Midi. Print "\nInserire il numero del dispositivo Midi, dal quale si riceveranno i dati Midi..." Input s Print "Porta del dispositivo Midi scelta: "; s err = Pm_OpenInput(VarPtr(midi_in), Val(s), 0, 128, 0, 0) If err Then Print Pm_GetErrorText(err) Chiude() Endif ' Attende che sia inserito il numero del dispositivo Midi, al quale si invieranno i dati Midi. Print "\nInserire il numero del dispositivo Midi, al quale si invieranno i dati Midi..." Input s Print "Porta del dispositivo Midi scelta: "; s err = Pm_OpenOutput(VarPtr(midi_out), Val(s), 0, 512, 0, 0) If err Then Print Pm_GetErrorText(err) Chiude() Endif s = Null ' Filtriamo i dati Midi ricevuti che non ci interessano: Pm_SetFilter(midi_in, PM_FILT_ACTIVE Or PM_FILT_CLOCK Or PM_FILT_SYSEX) Print "\nMidi Monitor pronto...\n" Print "Assicurarsi di aver connesso le porte dei dispositivi Midi coinvolti !" Intercetta_Messaggi(midi_in, midi_out) ' Va in chiusura: Chiude(midi_out) End Private Procedure Intercetta_Messaggi(midIn As Pointer, midEx As Pointer) Dim pe As New PmEvent Dim status, count As Integer Print "\n\nMidi Monitor pronto...\n\nStatus", "nota", "velocità" ' Riceve i dati Midi dal dispositivo Midi, leggendoli dalla sua porta in Uscita: While True status = Pm_Poll(midIn) If status = True Then count = Pm_Read(midIn, pe, 1) If count > 0 Then ' Volendo, possiamo stampare nella console i dati Midi ricevuti: Print (pe.message And &FF) And &f, (pe.message \ CInt(2 ^ 8)) And 255, (pe.message \ CInt(2 ^ 16)) And 255 ' Invia i dati al dispositivo Midi, scrivendoli sulla sua porta in Entrata: Pm_Write(midEx, pe, 1) Else ' Va in chiusura: Chiude(midEx) Error.Raise("Errore nella ricezione dei Messaggi Midi:" & Pm_GetErrorText(count)) Endif Endif Wend End Private Procedure Chiude(midi As Pointer) Pt_Close(midi) Pm_Terminate() Quit End