Visualizza wikitesto di Registrare in tempo reale in un file l'audio di una radio WEB con le funzioni esterne del API di VLC

Con le riorse di '''VLC''' è possibile ascoltare e contemporaneamente registrare in un file audio in tempo reale i dati audio trasmessi da una radio WEB.

Mostriamo il seguente esempio partico in ambiente grafico:
 Private bo As Boolean
 
 
 Library "libvlc:5.6.1"
 
 <FONT Color=gray>' ''libvlc_instance_t * libvlc_new (int argc, const char *const *argv)''
 ' ''Create And initialize a libvlc instance.''</font>
 Private Extern libvlc_new(argc As Integer, argv As String[]) As Pointer
 
 <FONT Color=gray>' ''libvlc_media_t *libvlc_media_new_location(libvlc_instance_t *p_instance, const char * psz_mrl)''
 ' ''Create a media with a certain given media resource location, for instance a valid URL.''</font>
 Private Extern libvlc_media_new_location(p_instance As Pointer, path As String) As Pointer

 <FONT Color=gray>' ''void libvlc_media_add_option (libvlc_media_t *p_md, const char *psz_options)
 ' ''Add an option to the media.''</font>
 Private Extern libvlc_media_add_option(p_mi As Pointer, psz_options As String)

 <FONT Color=gray>' ''libvlc_media_player_t * libvlc_media_player_new(libvlc_instance_t *p_libvlc_instance)
 ' ''Create an empty Media Player object.''</font>
 Private Extern libvlc_media_player_new(p_libvlc_instance As Pointer) As Pointer

 <FONT Color=gray>' ''void libvlc_media_player_set_media(libvlc_media_player_t *p_mi, libvlc_media_t *p_md)
 ' ''Set the media that will be used by the media_player.''</font>
 Private Extern libvlc_media_player_set_media(p_md As Pointer, mp As Pointer)

 <FONT Color=gray>' ''int libvlc_media_player_play (libvlc_media_player_t * p_mi)
 ' ''Play the video file.''</font>
 Private Extern libvlc_media_player_play(p_mi As Pointer) As Integer

 <FONT Color=gray>' ''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.''</font>
 Private Extern libvlc_media_player_release(p_mi As Pointer)

 <FONT Color=gray>' ''void libvlc_media_release (libvlc_media_t *p_md)
 ' ''Decrement the reference count of a media descriptor object.''</font>
 Private Extern libvlc_media_release(p_md As Pointer)

 <FONT Color=gray>' ''libvlc_release (libvlc_instance_t * p_instance)
 ' ''Decrement the reference count of a libvlc instance, and destroy it if it reaches zero.''</font>
 Private Extern libvlc_release(p_instance As Pointer)
 
 
 Public Sub ToggleButton1_Click()
 
  Dim inst, mp, m As Pointer
  Dim tm As Date

  If ToggleButton1.Value Then

 <FONT Color=gray>' ''Inizializza la libreria VLC:''</font>
    inst = libvlc_new(0, Null)

 <FONT Color=gray>' ''Crea un nuovo oggetto multimedia.
 ' Nel secondo argomento della funzione va specificato l'indirizzo del flusso di dati audio trasmessi dalla radio web:''</font>
    m = libvlc_media_new_location(inst, "https://stream.rockantenne.de/70er-rock/stream/mp3?aw_0_1st.playerid=radio.de")

 <FONT Color=gray>' ''Imposta i parametri per il formato audio e per creare il file audio:''</font>
    libvlc_media_add_option(m, ":sout=#transcode{acodec=mp3,ab=128,samplerate=44100,channels=2}:duplicate{dst=display,dst=std{access=file,mux=raw,dst=/tmp/audio.mp3}}")

 <FONT Color=gray>' ''Crea il media player:''</font>
    mp = libvlc_media_player_new(inst)

    libvlc_media_player_set_media(mp, m)

    libvlc_media_release(m)

 <FONT Color=gray>' ''Avvia la registrazione audio da parte del media player:''</font>
    libvlc_media_player_play(mp)

    tm = Now

    While bo = False
      Me.Title = Str(Time(0, 0, 0, DateDiff(tm, Now, gb.Millisecond)))
 <FONT Color=gray>' ''Il Wait consente di agire su altri oggetti posti sul Form:''</font>
      Wait 0.01
    Wend

 <FONT Color=gray>' ''Chiude la libreria VLC ed il programma:''</font>
    libvlc_media_player_release(mp)
    libvlc_release(inst)
    Me.Close
  Else
 <FONT Color=gray>' ''Causa l'arresto della registrazione, la chiusura della libreria VLC e del programma:''</font>
    bo = True
  Endif
 
 End