Versione delle 09:46, 9 giu 2016

Mostriamo di seguito il codice per di un semplice applicativo per la riproduzione di file Midi.

Bisogna avere installato Jackd. Una volta lanciato l'applicativo, aprire Jackd e nella scheda "Audio" connettere il dispositivo "Fluidsynth", presente nella colonna "Clients leggibili/Porte d'uscita", al dispositivo "system" presente nella colonna "Clients scrivibili/Porte d'entrata".

Si dovrà, inoltre, individuare un file soundfont bank con estensione .sf2, da far caricare successivamente dalla funzione esterna "fluid_synth_sfload" per poter ottenere i suoni.

Private settings As Pointer
Private synth As Pointer
Private adriver As Pointer
Private player As Pointer
Private fileMidi As String
Private Const ALL_SOUND_OFF As Integer = 120
Private Const ALL_NOTES_OFF As Integer = 123


Library "libfluidsynth:1.5.2"

' fluid_settings_t* new_fluid_settings(void)
' Create a new settings object. 
Private Extern new_fluid_settings() As Pointer

' fluid_synth_t * new_fluid_synth (fluid_settings_t *settings)
' Create new FluidSynth instance.
Private Extern new_fluid_synth(settP As Pointer) As Pointer

' fluid_player_t* new_fluid_player(fluid_synth_t * synth)
' Create a new MIDI player.
Private Extern new_fluid_player(synth As Pointer) As Pointer

' int fluid_settings_setint(fluid_settings_t *settings, const char *name, int val)
' Set an integer value for a setting.
Private Extern fluid_settings_setint(settP As Pointer, name As String, valI As Integer) As Integer

' fluid_audio_driver_t* new_fluid_audio_driver(fluid_settings_t * settings, fluid_synth_t * synth)
' Create a new audio driver.
Private Extern new_fluid_audio_driver(settings As Pointer, synth As Pointer) As Pointer 

' int fluid_is_soundfont(const char * filename)
' Check if a file is a SoundFont file.
Private Extern fluid_is_soundfont(filename As String) As Integer

' int fluid_synth_sfload(fluid_synth_t * synth, const char * filename, nt reset_presets)
' Load a SoundFont file (filename is interpreted by SoundFont loaders).
Private Extern fluid_synth_sfload(synth As Pointer, filename As String, reset_presets As Integer) As Integer

' int fluid_is_midifile(const char * filename)
' Check if a file is a MIDI file.
Private Extern fluid_is_midifile(filename As String) As Integer

' int fluid_player_add(fluid_player_t * player, Const char * midifile)
' Add a MIDI file to a player queue.
Private Extern fluid_player_add(player As Pointer, $fileMidi As String) As Integer

' int fluid_player_play(fluid_player_t * player)
' Activates play mode for a MIDI player if not already playing.
Private Extern fluid_player_play(player As Pointer) As Integer

' int fluid_player_stop(fluid_player_t * player)
' Stops a MIDI player.
Private Extern fluid_player_stop(player As Pointer) As Integer

' int fluid_player_get_status(fluid_player_t * player)
' Get MIDI player status.
Private Extern fluid_player_get_status(player As Pointer) As Integer

' int fluid_synth_cc (fluid_synth_t *synth, int chan, int ctrl, int val)
' Send a MIDI controller event on a MIDI channel.
Private Extern fluid_synth_cc(synth As Pointer, chan As Integer, ctrl As integer, ival As Integer) As Integer
 
' void delete_fluid_audio_driver(fluid_audio_driver_t * driver)
' Deletes an audio driver instance.
Private Extern delete_fluid_audio_driver(driver As Pointer)

' int delete_fluid_player(fluid_player_t * player)
' Delete a MIDI player instance.
Private Extern delete_fluid_player(player As Pointer) As Integer

' int delete_fluid_synth(fluid_synth_t * synth)
' Delete a FluidSynth instance.
Private Extern delete_fluid_synth(synth As Pointer) As Integer

' void delete_fluid_settings(fluid_settings_t * settings)
' Delete the provided settings object.
Private Extern delete_fluid_settings(settings As Pointer)


Public Sub Form_Open()

 Dim i As Integer
 Dim filesbk As String

  filesbk = "/percorso/del/file/soundfont.sf2"
  
  settings = new_fluid_settings()
  
  synth = new_fluid_synth(settings)
  
  player = new_fluid_player(synth)
  
  i = fluid_settings_setint(settings, "audio.jack.autoconnect", 1)
  If i = 0 Then Error.Raise("Errore alla funzione 'fluid_settings_setint()' !")
  
  adriver = new_fluid_audio_driver(settings, synth)
  If IsNull(adriver) Then Error.Raise("Impossibile creare un driver audio !")
  
  i = fluid_is_soundfont(filesbk)
  If CBool(i) = False then Error.Raise("Il file non è un soundfont bank !")
    
  i = fluid_synth_sfload(synth, filesbk, 1)
  If i < 0 Then Error.Raise("Errore alla funzione 'fluid_synth_sfload()' !")
  
End


Public Sub Button1_Click()

 Dim i As Integer
   
  i = fluid_player_add(player, fileMidi)
 If i < 0 Then Error.Raise("Errore alla funzione 'fluid_player_add()' !")
  
' Avvia l'esecuzione del file Midi:
  i = fluid_player_play(player)
  If i < 0 Then Error.Raise("Errore alla funzione 'fluid_player_play()' !")
 
  Do
    Wait 0.01
  Loop Until fluid_player_get_status(player) <> 1
 
  i = delete_fluid_player(player)
  If i < 0 Then Error.Raise("Errore alla funzione 'delete_fluid_player()' !")

  player = new_fluid_player(synth)
  
End


Public Sub Button2_Click()

 Dim i As Integer
 Dim b As Byte

' Arresta l'esecuzione del file Midi:
  i = fluid_player_stop(player)
  If i < 0 Then Error.Raise("Errore alla funzione 'fluid_player_stop()' !")
  
  For b = 0 To 15
    i = fluid_synth_cc(synth, b, ALL_NOTES_OFF, 0)
    If i < 0 Then Error.Raise("Errore alla funzione 'fluid_synth_cc()' !")
    i = fluid_synth_cc(synth, b, ALL_SOUND_OFF, 0)
    If i < 0 Then Error.Raise("Errore alla funzione 'fluid_synth_cc()' !")
  Next
   
End


Public Sub Form_Close()

  delete_fluid_audio_driver(adriver)

  delete_fluid_player(player)
 
  delete_fluid_synth(synth)
 
  delete_fluid_settings(settings)
 
End


Public Sub MenuApri_Click()

 Dim i As Integer

  With Dialog
    .Title = "Apri file Midi..."
    .Filter = ["*.mid", "File Midi"]
    If .OpenFile() Then Return
    fileMidi = .Path
  End With

  i = fluid_is_midifile(fileMidi)
  If CBool(i) = False Then Error.Raise("Il file caricato non è un file Midi standard !")
 
End

Riferimenti

• http://www.fluidsynth.org/
• http://fluidsynth.sourceforge.net/api/