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

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

' gst_init (int *argc, char **argv[])
' Initializes the GStreamer library, setting up internal path lists, registering built-in elements, and loading standard plugins.
Private Extern gst_init(argc As Pointer, argv As Pointer)

' GstElement * gst_parse_launch (const gchar *pipeline_description, GError **error)
' Create a new pipeline based on command line syntax.
Private Extern gst_parse_launch(description As String, GError As Pointer) As Pointer

' GstStateChangeReturn gst_element_set_state(GstElement *element, GstState state)
' Sets the state of the element.
Private Extern gst_element_set_state(gstelement As Pointer, state As Integer) As Integer
 
' gboolean gst_element_query_position (GstElement *element, GstFormat format, gint64 *cur)
' Queries an element for the stream position in nanoseconds.
Private Extern gst_element_query_position(gstelement As Pointer, gstformat As Pointer, cur As Pointer) As Boolean

' void gst_object_unref(gpointer object)
' Decrements the reference count on object.
Private Extern gst_object_unref(gobject As Pointer)


Public Sub Main()
 
 Dim tempus As Long
     
 gst_init(0, 0)
  
' Salviamo, quanto registrato, in un file WAV 44100 hertz, 16-bit, 2 canali:
 audio = gst_parse_launch("alsasrc ! audio/x-raw,rate=44100,depth=16,channels=2,width=16,signed=true ! volume volume=2.0 ! wavenc ! filesink location=/percorso/del/file.wav", 0)
       
' Avviamo la registrazione audio:
 gst_element_set_state(audio, GST_STATE_PLAYING)
  
 While Not bo
   gst_element_query_position(audio, GST_FORMAT_TIME, VarPtr(tempus))
   Write "\rTempo trascorso: " & Write "\rTempo trascorso: " & Str(Time(0, 0, 0, tempus / 1000000))
   Flush
   Wait 0.1
 Wend

' Arresta la registrazione del file MP3:
 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 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

' gst_init (int *argc, char **argv[])
' Initializes the GStreamer library, setting up internal path lists, registering built-in elements, and loading standard plugins.
Private Extern gst_init(argc As Pointer, argv As Pointer)

' GstElement * gst_parse_launch (const gchar *pipeline_description, GError **error)
' Create a new pipeline based on command line syntax.
Private Extern gst_parse_launch(description As String, GError As Pointer) As Pointer

' GstStateChangeReturn gst_element_set_state(GstElement *element, GstState state)
' Sets the state of the element.
Private Extern gst_element_set_state(gstelement As Pointer, state As Integer) As Integer
 
' gboolean gst_element_query_position (GstElement *element, GstFormat format, gint64 *cur)
' Queries an element for the stream position in nanoseconds.
Private Extern gst_element_query_position(gstelement As Pointer, gstformat As Pointer, cur As Pointer) As Boolean

' void gst_object_unref(gpointer object)
' Decrements the reference count on object.
Private Extern gst_object_unref(gobject As Pointer)


Public Sub Main()
 
 Dim tempus As Long
     
 gst_init(0, 0)
  
' Questa pipeline consente di registrare in un file audio MP3:
 audio = gst_parse_launch("alsasrc ! audioconvert ! lamemp3enc ! filesink location=/percorso/del/file.mp3", 0)
       
' Avviamo la registrazione audio:
 gst_element_set_state(audio, GST_STATE_PLAYING)
  
 While Not bo
   gst_element_query_position(audio, GST_FORMAT_TIME, VarPtr(tempus))
   Write "\rTempo trascorso: " & Write "\rTempo trascorso: " & Str(Time(0, 0, 0, tempus / 1000000))
   Flush
   Wait 0.1
 Wend

' Arresta la registrazione del file MP3:
 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

' gst_init (int *argc, char **argv[])
' Initializes the GStreamer library, setting up internal path lists, registering built-in elements, and loading standard plugins.
Private Extern gst_init(argc As Pointer, argv As Pointer)

' GstElement * gst_parse_launch (const gchar *pipeline_description, GError **error)
' Create a new pipeline based on command line syntax.
Private Extern gst_parse_launch(description As String, GError As Pointer) As Pointer

' GstStateChangeReturn gst_element_set_state(GstElement *element, GstState state)
' Sets the state of the element.
Private Extern gst_element_set_state(gstelement As Pointer, state As Integer) As Integer
 
' gboolean gst_element_query_position (GstElement *element, GstFormat format, gint64 *cur)
' Queries an element for the stream position in nanoseconds.
Private Extern gst_element_query_position(gstelement As Pointer, gstformat As Pointer, cur As Pointer) As Boolean

' void gst_object_unref(gpointer object)
' Decrements the reference count on object.
Private Extern gst_object_unref(gobject As Pointer)


Public Sub Main()
 
 Dim tempus As Long
     
 gst_init(0, 0)
  
' Questa pipeline consente di registrare in un file audio OGG:
 audio = gst_parse_launch("alsasrc ! audioconvert ! vorbisenc ! oggmux ! filesink location=/percorso/del/file.ogg", 0)
       
' Avviamo la registrazione audio:
 gst_element_set_state(audio, GST_STATE_PLAYING)
  
 While Not bo
   gst_element_query_position(audio, GST_FORMAT_TIME, VarPtr(tempus))
   Write "\rTempo trascorso: " & Write "\rTempo trascorso: " & Str(Time(0, 0, 0, tempus / 1000000))
   Flush
   Wait 0.1
 Wend

' Arresta la registrazione del file OGG:
  gst_element_set_state(audio, GST_STATE_NULL)
  gst_object_unref(audio)
  Print "\nRegistrazione terminata."
  Quit

End


Public Sub Application_Read()

 bo = True

End