Versione attuale delle 06:52, 27 dic 2023

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 condivisa "libvlc.so.5.6.1 ".

Indice

1 Esempio con applicazione grafica
- 1.1 Esempio con effetto video
2 Esempio con applicazione a riga di comando
3 Esecuzione on-line di un file Midi da una pagina web
4 Riferimenti

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
Private m As Pointer


Library "libvlc:5.6.1"

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)

' void libvlc_media_release (libvlc_media_t *p_md)
' Decrement the reference count of a media descriptor object.
Private Extern libvlc_media_release(p_md 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)


Library "libSDL2-2.0:0.2800.5"

Private Const SDL_INIT_AUDIO As Integer = 16

' int SDL_Init(Uint32 flags)
' Initialize the SDL library.
Private Extern SDL_Init(flags As Integer) As Integer

' void SDL_Quit(void)
' Clean up all initialized subsystems.
Private Extern SDL_Quit()


Public Sub Button1_Click()
 
 SDL_Init(SDL_INIT_AUDIO)
   
' 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)

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

 Chiude()

End


Public Sub Button2_Click()

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

End


Private Procedure Chiude()

' Chiude le librerie VLC e SDL:
 libvlc_media_player_release(mp)
 libvlc_media_release(m)
 libvlc_release(inst)
 SDL_Quit()
 
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 effetto video

In quest'altro esempio mostreremo un effetto video (Spectrum analyzer) di VLC, che rappresenta un "Analizzatore di spettro", all'interno di una DrawingArea

Private inst As Pointer
Private mp As Pointer
 

Library "libvlc:5.6.1"

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

' void libvlc_media_player_set_xwindow (libvlc_media_player_t *p_mi, uint32_t drawable)
' Set an X Window System drawable where the media player should render its video output.
Private Extern libvlc_media_player_set_xwindow(p_mi As Pointer, drawable As Integer)

' 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)

' 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)

' void libvlc_media_release (libvlc_media_t *p_md)
' Decrement the reference count of a media descriptor object.
Private Extern libvlc_media_release(p_md 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)


Library "libSDL2-2.0:0.2800.5"

Private Const SDL_INIT_AUDIO As Integer = 16

' int SDL_Init(Uint32 flags)
' Initialize the SDL library.
Private Extern SDL_Init(flags As Integer) As Integer

' void SDL_Quit(void)
' Clean up all initialized subsystems.
Private Extern SDL_Quit()


Public Sub Button1_Click()

 Dim ss As String[]
 Dim m As Pointer
 Dim id As Integer
 
 SDL_Init(SDL_INIT_AUDIO)
  
 ss = ["--audio-visual=visual", "--effect-list=spectrum"]
  
' Inizializza la libreria VLC:
 inst = libvlc_new(ss.Count, ss)
   
' 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)
  
' Per far mostrare l'effetto video "Analizzatore di spettro" nella "DrawingArea", ricaviamo il suo identificativo:
 id = DrawingArea1.Id
  
' Passiamo l'identificativo della finestra, nella quale dovrà essere mostrato l'effetto "Spectrum analyzer":
 libvlc_media_player_set_xwindow(mp, id)
   
 ' Avvia l'esecuzione del file Midi da parte del media player:
 libvlc_media_player_play(mp)
 
 Repeat
   TextLabel1.Text = "Durata: " & Str(Time(0, 0, 0, libvlc_media_player_get_length(mp, 0)))
   TextLabel2.Text = "<FONT Color=red>" & Str(Time(0, 0, 0, libvlc_media_player_get_time(mp)))
   Wait 0.01
 Until libvlc_media_player_get_state(mp) > libvlc_Paused
 
 Chiude()

End


Public Sub Button2_Click()

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

End


Private Procedure Chiude()
   
' Chiude le librerie VLC e SDL:
 libvlc_media_player_release(mp)
 libvlc_media_release(m)
 libvlc_release(inst)
 SDL_Quit()
   
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:5.6.1"

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_get_duration(libvlc_media_t *p_md)
' Get duration (in ms) of media descriptor object item.
Private Extern libvlc_media_get_duration(p_md As Pointer) As Long

' 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)

' void libvlc_media_release (libvlc_media_t *p_md)
' Decrement the reference count of a media descriptor object.
Private Extern libvlc_media_release(p_md 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)


Library "libSDL2-2.0:0.2800.5"

Private Const SDL_INIT_AUDIO As Integer = 16

' int SDL_Init(Uint32 flags)
' Initialize the SDL library.
Private Extern SDL_Init(flags As Integer) As Integer

' void SDL_Quit(void)
' Clean up all initialized subsystems.
Private Extern SDL_Quit()


Public Sub Main()

 Dim m, inst, mp As Pointer
 Dim l As Long
 
 SDL_Init(SDL_INIT_AUDIO)
      
' 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)
 
 Repeat 
   l = libvlc_media_get_duration(m)
 Until l > 0
 Print "Durata: "; Time(0, 0, 0, l)
 
 While libvlc_media_player_get_state(mp) < libvlc_Stopped
   Write "\r   \e[31m" & Str(Time(0, 0, 0, libvlc_media_player_get_time(mp)))
   Wait 0.01
 Wend
  
' Chiude la libreria VLC:
 libvlc_media_player_release(mp)
 libvlc_media_release(m)
 libvlc_release(inst)
 SDL_Quit()
  
End

Esecuzione on-line di un file Midi da una pagina web

Per eseguire on-line un file Midi dal collegamento presente in una pagina web, bisognerà:
1) assicurarsi che l'indirizzo web, ove è ospitato il file Midi da eseguire, inizi con l'acronimo del protocollo "http" e non con "https";
2) utilizzare la funzione "libvlc_media_new_location( )" al posto della funzione "libvlc_media_new_path( )".

Esempio:

media = libvlc_media_new_location(instance, "http://www.indirizzo/web/del/file.mid")

@@ Riga 6: / Riga 6: @@
 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.5.6.0''".
+Per creare in Gambas un'applicazione con la presente risorsa, si dovrà installare e richiamare la libreria condivisa "''libvlc.so.5.6.1'' ".
 ===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:
@@ Riga 16: / Riga 14: @@
-  Library "libvlc:5.6.0"
+  Library "<FONT Color=blue>libvlc:5.6.1</font>"
   Private Enum libvlc_NothingSpecial = 0,
@@ Riga 76: / Riga 74: @@
-  Library "libSDL2-2.0:0.10.0"
+  Library "<FONT Color=red>libSDL2-2.0:0.2800.5</font>"
   Private Const SDL_INIT_AUDIO As Integer = 16
@@ Riga 89: / Riga 87: @@
-  '''Public''' Sub Button1_Click()
+  Public Sub Button1_Click()
    SDL_Init(SDL_INIT_AUDIO)
@@ Riga 97: / Riga 95: @@
   <FONT color=gray>' ''Crea un nuovo oggetto multimedia:''</font>
-   m = libvlc_media_new_path(inst, "<FONT color=gray>''/percorso/del/file.mid''</font>")
+   m = libvlc_media_new_path(inst, "<FONT color=darkgreen>''/percorso/del/file.mid''</font>")
   <FONT color=gray>' ''Crea un media player:''</font>
@@ Riga 106: / Riga 104: @@
    Repeat
-     TextLabel1.Text = "Durata: " & Str(Date(0, 0, 0, 0, 0, 0, libvlc_media_player_get_length(mp, 0)))
+    TextLabel1.Text = "Durata: " & Str(Time(0, 0, 0, libvlc_media_player_get_length(mp, 0)))
-     TextLabel2.Text = "&lt;FONT Color=red>" & Str(Date(0, 0, 0, 0, 0, 0, libvlc_media_player_get_time(mp)))
+    TextLabel2.Text = "&lt;FONT Color=red>" & Str(Time(0, 0, 0, libvlc_media_player_get_time(mp)))
-     Wait 0.01
+    Wait 0.01
    Until libvlc_media_player_get_state(mp) > libvlc_Paused
    Chiude()
-  '''End'''
+  End
-  '''Public''' Sub Button2_Click()
+  Public Sub Button2_Click()
   <FONT color=gray>' ''Arresta l'esecuzione del file Midi:''</font>
    libvlc_media_player_stop(mp)
-  '''End'''
+  End
-  '''Private''' Procedure Chiude()
+  Private Procedure Chiude()
   <FONT color=gray>' ''Chiude le librerie VLC e SDL:''</font>
@@ Riga 132: / Riga 130: @@
    SDL_Quit()
-  '''End'''
+  End
-  '''Public''' Sub ToggleButton1_Click()
+  Public Sub ToggleButton1_Click()
   <FONT color=gray>' ''Pone in pausa o riprende (se già in pausa) l'esecuzione del file Midi:''</font>
    libvlc_media_player_pause(mp)
-  '''End'''
+  End
+====Esempio con effetto video====
 In quest'altro esempio mostreremo un effetto video (''Spectrum analyzer'') di VLC, che rappresenta un "Analizzatore di spettro", all'interno di una ''DrawingArea''
   Private inst As Pointer
@@ Riga 148: / Riga 146: @@
-  Library "libvlc:5.6.0"
+  Library "<FONT color=blue>libvlc:5.6.1</font>"
   Private Enum libvlc_NothingSpecial = 0,
@@ Riga 216: / Riga 214: @@
-  Library "libSDL2-2.0:0.10.0"
+  Library "<FONT color=red>libSDL2-2.0:0.2800.5</font>"
   Private Const SDL_INIT_AUDIO As Integer = 16
@@ Riga 229: / Riga 227: @@
-  '''Public''' Sub Button1_Click()
+  Public Sub Button1_Click()
    Dim ss As String[]
@@ Riga 243: / Riga 241: @@
   <FONT color=gray>' ''Crea un nuovo oggetto multimedia:''</font>
-   m = libvlc_media_new_path(inst, "<FONT color=gray>''/percorso/del/file.mid''</font>")
+   m = libvlc_media_new_path(inst, "<FONT color=darkgreen>''/percorso/del/file.mid''</font>")
   <FONT color=gray>' ''Crea un media player:''</font>
@@ Riga 258: / Riga 256: @@
    Repeat
-     TextLabel1.Text = "Durata: " & Str(Date(0, 0, 0, 0, 0, 0, libvlc_media_player_get_length(mp, 0)))
+     TextLabel1.Text = "Durata: " & Str(Time(0, 0, 0, libvlc_media_player_get_length(mp, 0)))
-     TextLabel2.Text = "&lt;FONT Color=red>" & Str(Date(0, 0, 0, 0, 0, 0, libvlc_media_player_get_time(mp)))
+     TextLabel2.Text = "&lt;FONT Color=red>" & Str(Time(0, 0, 0, libvlc_media_player_get_time(mp)))
      Wait 0.01
    Until libvlc_media_player_get_state(mp) > libvlc_Paused
@@ Riga 265: / Riga 263: @@
    Chiude()
-  '''End'''
+  End
-  '''Public''' Sub Button2_Click()
+  Public Sub Button2_Click()
   <FONT color=gray>' ''Arresta l'esecuzione del file Midi:''</font>
    libvlc_media_player_stop(mp)
-  '''End'''
+  End
-  '''Private''' Procedure Chiude()
+  Private Procedure Chiude()
   <FONT color=gray>' ''Chiude le librerie VLC e SDL:''</font>
@@ Riga 284: / Riga 282: @@
    SDL_Quit()
-  '''End'''
+  End
-  '''Public''' Sub ToggleButton1_Click()
+  Public Sub ToggleButton1_Click()
   <FONT color=gray>' ''Pone in pausa o riprende (se già in pausa) l'esecuzione del file Midi:''</font>
    libvlc_media_player_pause(mp)
-  '''End'''
+  End
 ===Esempio con applicazione ''a riga di comando''===
-  Library "libvlc:5.6.0"
+  Library "<FONT color=blue>libvlc:5.6.1</font>"
   Enum libvlc_NothingSpecial = 0,
@@ Riga 323: / Riga 320: @@
   ' ''Play the Midi file.''</font>
   Private Extern libvlc_media_player_play(p_mi As Pointer) As Integer
+ <FONT color=gray>' ''libvlc_time_t libvlc_media_get_duration(libvlc_media_t *p_md)''
+ ' ''Get duration (in ms) of media descriptor object item.''</font>
+ Private Extern libvlc_media_get_duration(p_md As Pointer) As Long
   <FONT color=gray>' ''libvlc_time_t libvlc_media_player_get_time(libvlc_media_player_t * p_mi)''
@@ Riga 345: / Riga 346: @@
-  Library "libSDL2-2.0:0.10.0"
+  Library "<FONT color=red>libSDL2-2.0:0.2800.5</font>"
   Private Const SDL_INIT_AUDIO As Integer = 16
@@ Riga 358: / Riga 359: @@
-  '''Public''' Sub Main()
+  Public Sub Main()
    Dim m, inst, mp As Pointer
+  Dim l As Long
    SDL_Init(SDL_INIT_AUDIO)
@@ Riga 368: / Riga 370: @@
   <FONT color=gray>' ''Crea un nuovo oggetto multimedia:''</font>
-   m = libvlc_media_new_path(inst, "<FONT color=gray>''/percorso/del/file.mid''</font>")
+   m = libvlc_media_new_path(inst, "<FONT color=darkgreen>''/percorso/del/file.mid''</font>")
   <FONT color=gray>' ''Crea un media player:''</font>
@@ Riga 375: / Riga 377: @@
    <FONT color=gray>' ''Avvia l'esecuzione del file Midi da parte del media player:''</font>
    libvlc_media_player_play(mp)
+  Repeat
+    l = libvlc_media_get_duration(m)
+  Until l > 0
+  Print "Durata: "; Time(0, 0, 0, l)
    While libvlc_media_player_get_state(mp) < libvlc_Stopped
-     Write "\r\e[31m" & Str(Date(0, 0, 0, 0, 0, 0, libvlc_media_player_get_time(mp)))
+     Write "\r   \e[31m" & Str(Time(0, 0, 0, libvlc_media_player_get_time(mp)))
+    Wait 0.01
    Wend
@@ Riga 386: / Riga 394: @@
    SDL_Quit()
-  '''End'''
+  End
@@ Riga 395: / Riga 403: @@
 Esempio:
-  media = libvlc_media_new_location(instance, "<FONT color=gray>''http&#058;//www.indirizzo/web/del/file.mid''</font>")
+  media = libvlc_media_new_location(instance, "<FONT color=darkgreen>''http&#058;//www.indirizzo/web/del/file.mid''</font>")

Differenze tra le versioni di "Eseguire un file Midi mediante le funzioni esterne del API di VLC"

Versione attuale delle 06:52, 27 dic 2023

Indice

Esempio con applicazione grafica

Esempio con effetto video

Esempio con applicazione a riga di comando

Esecuzione on-line di un file Midi da una pagina web

Riferimenti

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