Versione delle 14:17, 9 feb 2015

La libreria LibVLC consente di eseguire anche file MIDI, purché si abbiano installati nel sistema anche:

• vlc-plugin-fluidsynth - le risorse dei plugin di FluidSynth per VLC;
• fluid-soundfont-gm - Fluid (R3) General MIDI SoundFont (GM);
• ovviamente lo stesso FluidSynth.

E' possibile eseguire dati Midi anche direttamente da internet.

Per creare in Gambas un'applicazione con la presente risorsa, si dovrà installare e richiamare la libreria dinamica e condivisa libvlc.so.5.4.0.

Esempio con applicazione grafica

Mostriamo di seguito un semplice esempio, nel quale si potrà avviare, arrestare, porre in pausa e riprendere l'esecuzione del file Midi:

Private inst As Pointer
Private mp As Pointer
 

Library "libvlc:5.4.0"

Private Enum libvlc_NothingSpecial = 0,
        libvlc_Opening,
        libvlc_Buffering,
        libvlc_Playing,
        libvlc_Paused,
        libvlc_Stopped,
        libvlc_Ended,
        libvlc_Error

' libvlc_instance_t * libvlc_new (int argc, const char *const *argv)
' Create And initialize a libvlc instance.
Private Extern libvlc_new(argc As Integer, argv As String) As Pointer

' libvlc_media_t * libvlc_media_new_path (libvlc_instance_t *p_instance, const char *path)
' Create a media for a certain file path.
Private Extern libvlc_media_new_path(p_instance As Pointer, path As String) As Pointer

' libvlc_media_player_t * libvlc_media_player_new_from_media (libvlc_media_t *p_md)
' Create a Media Player object from a Media.
Private Extern libvlc_media_player_new_from_media(p_md As Pointer) As Pointer

' int libvlc_media_player_play (libvlc_media_player_t * p_mi)
' Play the audio file.
Private Extern libvlc_media_player_play(p_mi As Pointer) As Integer

' void libvlc_media_player_stop (libvlc_media_player_t * p_mi)
' Stop the audio file.
Private Extern libvlc_media_player_stop(p_mi As Pointer)

' libvlc_time_t libvlc_media_player_get_length(libvlc_media_player_t *, libvlc_exception_t *)
' Get the current movie length (in ms).
Private Extern libvlc_media_player_get_length(p_mi As Pointer, l_ex As Pointer) As Integer

' libvlc_time_t libvlc_media_player_get_time(libvlc_media_player_t * p_mi)
' Get the current movie time (in ms).
Private Extern libvlc_media_player_get_time(p_mi As Pointer) As Integer

' libvlc_state_t libvlc_media_player_get_state(libvlc_media_player_t *p_mi)
' Get current movie state.
Private Extern libvlc_media_player_get_state(p_mi As Pointer) As Integer

' void   libvlc_media_player_pause (libvlc_media_player_t *p_mi)
' Toggle pause.
Private Extern libvlc_media_player_pause(p_mi As Pointer)

' void libvlc_media_player_release (libvlc_media_player_t * p_mi)
' Release a media_player after use Decrement the reference count of a media player object.
Private Extern libvlc_media_player_release(p_mi As Pointer)
 

Public Sub Button1_Click()

 Dim m As Pointer
 
   
' Inizializza la libreria VLC:
  inst = libvlc_new(0, Null)
   
' Crea un nuovo oggetto multimedia:
  m = libvlc_media_new_path(inst, "/percorso/del/file.mid")
   
' Crea un media player:
  mp = libvlc_media_player_new_from_media(m)
   
 ' Avvia l'esecuzione del file Midi da parte del media player:
  libvlc_media_player_play(mp)

  Do
    TextLabel1.Text = "Durata: " & Str(Date(0, 0, 0, 0, 0, 0, libvlc_media_player_get_length(mp, 0)))
    TextLabel2.Text = "<FONT Color=red>" & Str(Date(0, 0, 0, 0, 0, 0, libvlc_media_player_get_time(mp)))
    Wait 0.01
  Loop Until libvlc_media_player_get_state(mp) > libvlc_Paused

  Chiude()

End


Public Sub Button2_Click()

  Chiude()

End


Private Procedure Chiude()

' Arresta l'esecuzione del file Midi:
  libvlc_media_player_stop(mp)

' Rilascia e chiude il media player:
  libvlc_media_player_release(mp)
 
  ToggleButton1.Value = False

End


Public Sub ToggleButton1_Click()

' Pone in pausa o riprende (se già in pausa) l'esecuzione del file Midi:
  libvlc_media_player_pause(mp)

End

Esempio con applicazione a riga di comando

Library "libvlc:5.4.0"

Enum libvlc_NothingSpecial = 0,
     libvlc_Opening,
     libvlc_Buffering,
     libvlc_Playing,
     libvlc_Paused,
     libvlc_Stopped,
     libvlc_Ended,
     libvlc_Error

' libvlc_instance_t * libvlc_new (int argc, const char *const *argv)
' Create And initialize a libvlc instance.
Private Extern libvlc_new(argc As Integer, argv As String) As Pointer

' libvlc_media_t * libvlc_media_new_path (libvlc_instance_t *p_instance, const char *path)
' Create a media for a certain Midi file path.
Private Extern libvlc_media_new_path(p_instance As Pointer, path As String) As Pointer

' libvlc_media_player_t * libvlc_media_player_new_from_media (libvlc_media_t *p_md)
' Create a Media Player object from a Media.
Private Extern libvlc_media_player_new_from_media(p_md As Pointer) As Pointer

' int libvlc_media_player_play (libvlc_media_player_t * p_mi)
' Play the Midi file.
Private Extern libvlc_media_player_play(p_mi As Pointer) As Integer

' libvlc_time_t libvlc_media_player_get_time(libvlc_media_player_t * p_mi)
' Get the current movie time (in ms).
Private Extern libvlc_media_player_get_time(p_mi As Pointer) As Integer

' libvlc_state_t libvlc_media_player_get_state(libvlc_media_player_t *p_mi)
' Get current movie state.
Private Extern libvlc_media_player_get_state(p_mi As Pointer) As Integer
 
' void libvlc_media_player_release (libvlc_media_player_t * p_mi)
' Release a media_player after use Decrement the reference count of a media player object.
Private Extern libvlc_media_player_release(p_mi As Pointer)

' libvlc_release (libvlc_instance_t * p_instance)
' Decrement the reference count of a libvlc instance, and destroy it if it reaches zero.
Private Extern libvlc_release(p_instance As Pointer)


Public Sub Main()

 Dim m As Pointer
 Dim inst As Pointer
 Dim mp As Pointer
  
   
' Inizializza la libreria VLC:
   inst = libvlc_new(0, Null)
   
' Crea un nuovo oggetto multimedia:
   m = libvlc_media_new_path(inst, "/percorso/del/file/Midi")
   
' Crea un media player:
   mp = libvlc_media_player_new_from_media(m)
   
 ' Avvia l'esecuzione del file Midi da parte del media player:
   libvlc_media_player_play(mp)

  While libvlc_media_player_get_state(mp) < libvlc_Stopped
    Write #File.Out, Str(Date(0, 0, 0, 0, 0, 0, libvlc_media_player_get_time(mp))) & "\r"
  Wend


' Va in chiusura:

' Rilascia e chiude il media player:
   libvlc_media_player_release(mp)
    
' Chiude la libreria VLC:
   libvlc_release(inst)

End

Riferimenti

• Il sito del API di LibVLC.
• Videolan Wiki - Midi