Visualizza wikitesto di Registrare in un file audio una fonte sonora esterna usando una linea di pipeline con la funzione 'gst parse launch()'

La funzione esterna "gst_parse_launch()" della libreria ''GStreamer'' consente di costruire e gestire in modo semplice una pipeline ''GStreamer''. La riga della pipeline gestita dalla funzione esterna "gst_parse_launch()" è un insieme di elementi separati da punti esclamativi (!). Le proprietà possono essere aggiunte agli elementi, sotto forma di: ''proprietà = valore''.

Mediante tale funzione esterna ed un'apposita pipeline di elementi ''GStreamer'' è possibile registrare una fonte audio esterna e salvare, quanto registrato, in un file audio.

Sarà necessario avere installata nel sistema e richiamare nell'applicazione Gambas la libreria condivisa: "''libgstreamer-1.0'' ".

=Registrare una fonte audio esterna in un file audio di formato WAV=
Mostriamo un esempio pratico per registrare in WAV una fonte sonora esterna:
 Private audio As Pointer
 Private bo As Boolean
 
 
 Library "libgstreamer-1.0"
 
 Private Enum GST_STATE_VOID_PENDING = 0, GST_STATE_NULL, GST_STATE_READY, GST_STATE_PAUSED, GST_STATE_PLAYING
 Private Const GST_FORMAT_TIME As Integer = 3
 
 <FONT Color=gray>' ''gst_init (int *argc, char **argv[])''
 ' ''Initializes the GStreamer library, setting up internal path lists, registering built-in elements, and loading standard plugins.''</font>
 Private Extern gst_init(argc As Pointer, argv As Pointer)
 
 <FONT Color=gray>' ''GstElement * gst_parse_launch (const gchar *pipeline_description, GError **error)''
 ' ''Create a new pipeline based on command line syntax.''</font>
 Private Extern gst_parse_launch(description As String, GError As Pointer) As Pointer
 
 <FONT Color=gray>' ''GstStateChangeReturn gst_element_set_state(GstElement *element, GstState state)''
 ' ''Sets the state of the element.''</font>
 Private Extern gst_element_set_state(gstelement As Pointer, state As Integer) As Integer
  
 <FONT Color=gray>' ''gboolean gst_element_query_position (GstElement *element, GstFormat format, gint64 *cur)''
 ' ''Queries an element for the stream position in nanoseconds.''</font>
 Private Extern gst_element_query_position(gstelement As Pointer, gstformat As Pointer, cur As Pointer) As Boolean
 
 <FONT Color=gray>' ''void gst_object_unref(gpointer object)''
 ' ''Decrements the reference count on object.''</font>
 Private Extern gst_object_unref(gobject As Pointer)
 
 
 Public Sub Main()
  
  Dim tempus As Long
      
  gst_init(0, 0)
   
 <FONT Color=gray>' ''Salviamo, quanto registrato, in un file WAV 44100 hertz, 16-bit, 2 canali:''</font>
  audio = gst_parse_launch("alsasrc ! audio/x-raw,rate=<FONT Color=#B22222>44100</font>,depth=<FONT Color=#B22222>16</font>,channels=<FONT Color=#B22222>2</font>,width=16,signed=true ! volume volume=2.0 ! wavenc ! filesink location=<FONT Color=darkgreen>''/percorso/del/file.wav''</font>", 0)
        
 <FONT Color=gray>' ''Avviamo la registrazione audio:''</font>
  gst_element_set_state(audio, GST_STATE_PLAYING)
   
  While Not bo
    gst_element_query_position(audio, GST_FORMAT_TIME, VarPtr(tempus))
    Write "\rTempo trascorso: " & Str(Time(0, 0, 0, tempus / 1000000))
    Flush
    Wait 0.1
  Wend
 
 <FONT Color=gray>' ''Arresta la registrazione del file WAV:''</font>
  gst_element_set_state(audio, GST_STATE_NULL)
  gst_object_unref(audio)
  Print "\nRegistrazione terminata."
  Quit
 
 End
 
 
 Public Sub Application_Read()
 
  bo = True
 
 End

=Registrare una fonte audio esterna in un file audio di formato MP3=
Mostriamo un esempio pratico per registrare in MP3 una fonte sonora esterna:
 Private bo As Boolean
 
 
 Library "libgstreamer-1.0"
 
 Private Enum GST_STATE_VOID_PENDING = 0, GST_STATE_NULL, GST_STATE_READY, GST_STATE_PAUSED, GST_STATE_PLAYING
 Private Const GST_FORMAT_TIME As Integer = 3
 
 <FONT Color=gray>' ''gst_init (int *argc, char **argv[])''
 ' ''Initializes the GStreamer library, setting up internal path lists, registering built-in elements, and loading standard plugins.''</font>
 Private Extern gst_init(argc As Pointer, argv As Pointer)
 
 <FONT Color=gray>' ''GstElement * gst_parse_launch (const gchar *pipeline_description, GError **error)''
 ' ''Create a new pipeline based on command line syntax.''</font>
 Private Extern gst_parse_launch(description As String, GError As Pointer) As Pointer
 
 <FONT Color=gray>' ''GstStateChangeReturn gst_element_set_state(GstElement *element, GstState state)''
 ' ''Sets the state of the element.''</font>
 Private Extern gst_element_set_state(gstelement As Pointer, state As Integer) As Integer
  
 <FONT Color=gray>' ''gboolean gst_element_query_position (GstElement *element, GstFormat format, gint64 *cur)''
 ' ''Queries an element for the stream position in nanoseconds.''</font>
 Private Extern gst_element_query_position(gstelement As Pointer, gstformat As Pointer, cur As Pointer) As Boolean
 
 <FONT Color=gray>' ''void gst_object_unref(gpointer object)''
 ' ''Decrements the reference count on object.''</font>
 Private Extern gst_object_unref(gobject As Pointer)
 
 
 Public Sub Main()
  
  Dim audio As Pointer
  Dim tempus As Long
      
  gst_init(0, 0)
   
 <FONT Color=gray>' ''Questa pipeline consente di registrare in un file audio MP3:''</font>
  audio = gst_parse_launch("alsasrc ! audioconvert ! lamemp3enc ! filesink location=<FONT Color=darkgreen>''/percorso/del/file.mp3''</font>", 0)
        
 <FONT Color=gray>' ''Avvia la registrazione audio:''</font>
  gst_element_set_state(audio, GST_STATE_PLAYING)
   
  While Not bo
    gst_element_query_position(audio, GST_FORMAT_TIME, VarPtr(tempus))
    Write "\rTempo trascorso: " & Str(Time(0, 0, 0, tempus / 1000000))
    Flush
    Wait 0.1
  Wend
 
 <FONT Color=gray>' ''Arresta la registrazione del file MP3:''</font>
  gst_element_set_state(audio, GST_STATE_NULL)
  gst_object_unref(audio)
  Print "\nRegistrazione terminata."
  Quit
 
 End
 
 
 Public Sub Application_Read()
 
  bo = True
 
 End

=Registrare una fonte audio esterna in un file audio di formato OGG=
Mostriamo un esempio pratico per registrare in OGG una fonte sonora esterna:
 Private audio As Pointer
 Private bo As Boolean
 
 
 Library "libgstreamer-1.0"
 
 Private Enum GST_STATE_VOID_PENDING = 0, GST_STATE_NULL, GST_STATE_READY, GST_STATE_PAUSED, GST_STATE_PLAYING
 Private Const GST_FORMAT_TIME As Integer = 3
 
 <FONT Color=gray>' ''gst_init (int *argc, char **argv[])''
 ' ''Initializes the GStreamer library, setting up internal path lists, registering built-in elements, and loading standard plugins.''</font>
 Private Extern gst_init(argc As Pointer, argv As Pointer)
 
 <FONT Color=gray>' ''GstElement * gst_parse_launch (const gchar *pipeline_description, GError **error)''
 ' ''Create a new pipeline based on command line syntax.''</font>
 Private Extern gst_parse_launch(description As String, GError As Pointer) As Pointer
 
 <FONT Color=gray>' ''GstStateChangeReturn gst_element_set_state(GstElement *element, GstState state)''
 ' ''Sets the state of the element.''</font>
 Private Extern gst_element_set_state(gstelement As Pointer, state As Integer) As Integer
  
 <FONT Color=gray>' ''gboolean gst_element_query_position (GstElement *element, GstFormat format, gint64 *cur)''
 ' ''Queries an element for the stream position in nanoseconds.''</font>
 Private Extern gst_element_query_position(gstelement As Pointer, gstformat As Pointer, cur As Pointer) As Boolean
 
 <FONT Color=gray>' ''void gst_object_unref(gpointer object)''
 ' ''Decrements the reference count on object.''</font>
 Private Extern gst_object_unref(gobject As Pointer)
 
 
 Public Sub Main()
  
  Dim tempus As Long
      
  gst_init(0, 0)
   
 <FONT Color=gray>' ''Questa pipeline consente di registrare in un file audio OGG:''</font>
  audio = gst_parse_launch("alsasrc ! audioconvert ! vorbisenc ! oggmux ! filesink location=<FONT Color=darkgreen>''/percorso/del/file.ogg''</font>", 0)
        
 <FONT Color=gray>' ''Avviamo la registrazione audio:''</font>
  gst_element_set_state(audio, GST_STATE_PLAYING)
   
  While Not bo
    gst_element_query_position(audio, GST_FORMAT_TIME, VarPtr(tempus))
    Write "\rTempo trascorso: " & Str(Time(0, 0, 0, tempus / 1000000))
    Flush
    Wait 0.1
  Wend
 
 <FONT Color=gray>' ''Arresta la registrazione del file OGG:''</font>
   gst_element_set_state(audio, GST_STATE_NULL)
   gst_object_unref(audio)
   Print "\nRegistrazione terminata."
   Quit
 
 End
 
 
 Public Sub Application_Read()
 
  bo = True
 
 End

=Registrare una fonte audio esterna in un file audio di formato AAC=
Mostriamo un esempio pratico per registrare in AAC una fonte sonora esterna:
 Private audio As Pointer
 Private bo As Boolean
 
 
 Library "libgstreamer-1.0"
 
 Private Enum GST_STATE_VOID_PENDING = 0, GST_STATE_NULL, GST_STATE_READY, GST_STATE_PAUSED, GST_STATE_PLAYING
 Private Const GST_FORMAT_TIME As Integer = 3
 
 <FONT Color=gray>' ''gst_init (int *argc, char **argv[])''
 ' ''Initializes the GStreamer library, setting up internal path lists, registering built-in elements, and loading standard plugins.''</font>
 Private Extern gst_init(argc As Pointer, argv As Pointer)
 
 <FONT Color=gray>' ''GstElement * gst_parse_launch (const gchar *pipeline_description, GError **error)''
 ' ''Create a new pipeline based on command line syntax.''</font>
 Private Extern gst_parse_launch(description As String, GError As Pointer) As Pointer
 
 <FONT Color=gray>' ''GstStateChangeReturn gst_element_set_state(GstElement *element, GstState state)''
 ' ''Sets the state of the element.''</font>
 Private Extern gst_element_set_state(gstelement As Pointer, state As Integer) As Integer
  
 <FONT Color=gray>' ''gboolean gst_element_query_position (GstElement *element, GstFormat format, gint64 *cur)''
 ' ''Queries an element for the stream position in nanoseconds.''</font>
 Private Extern gst_element_query_position(gstelement As Pointer, gstformat As Pointer, cur As Pointer) As Boolean
 
 <FONT Color=gray>' ''void gst_object_unref(gpointer object)''
 ' ''Decrements the reference count on object.''</font>
 Private Extern gst_object_unref(gobject As Pointer)
 
 
 Public Sub Main()
  
  Dim tempus As Long
      
  gst_init(0, 0)
   
 <FONT Color=gray>' ''Questa pipeline consente di registrare in un file audio AAC:''</font>
  audio = gst_parse_launch("alsasrc ! audioconvert ! faac ! audio/mpeg,stream-format=adts,channels=2,rate=44100 ! filesink location=<FONT Color=darkgreen>''/percorso/del/file.aac''</font>", 0)
        
 <FONT Color=gray>' ''Avviamo la registrazione audio:''</font>
  gst_element_set_state(audio, GST_STATE_PLAYING)
   
  While Not bo
    gst_element_query_position(audio, GST_FORMAT_TIME, VarPtr(tempus))
    Write "\rTempo trascorso: " & Str(Time(0, 0, 0, tempus / 1000000))
    Flush
    Wait 0.1
  Wend
 
 <FONT Color=gray>' ''Arresta la registrazione del file AAC:''</font>
   gst_element_set_state(audio, GST_STATE_NULL)
   gst_object_unref(audio)
   Print "\nRegistrazione terminata."
   Quit
 
 End
 
 
 Public Sub Application_Read()
 
  bo = True
 
 End