Convertire un file WAV in un file OGG usando una linea di pipeline con la funzione 'gst parse launch()'
Da Gambas-it.org - Wikipedia.
Versione del 5 mar 2016 alle 20:24 di Vuott (Discussione | contributi)
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.
Sarà necessario avere installata nel sistema e richiamare nell'applicazione Gambas la libreria dinamica condivisa: "libgstreamer-1.0"
Mostriamo un esempio pratico di conversione di un file audio di formato WAV in un file audio di formato OGG:
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_duration(GstElement *element, GstFormat format, gint64 *duration)
' Queries an element for the total stream duration in nanoseconds.
Private Extern gst_element_query_duration(gselement As Pointer, formatI As Integer, duration As Pointer) As Boolean
' 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 audio As Pointer
Dim pos, dur As Long
gst_init(0, 0)
audio = gst_parse_launch("filesrc location=/percorso/del/file/audio.wav ! wavparse ! audioconvert ! vorbisenc ! oggmux ! filesink location=/percorso/del/file/audio.ogg", 0)
' Avviamo la conversione audio:
gst_element_set_state(audio, GST_STATE_PLAYING)
While True
gst_element_query_position(audio, GST_FORMAT_TIME, VarPtr(pos))
gst_element_query_duration(audio, GST_FORMAT_TIME, VarPtr(dur))
If (pos > 0) And (pos >= dur) Then Break
Write #File.Out, "\rTempo: " & Date(0, 0, 0, 0, 0, 0, pos / 1000000)
Wend
gst_object_unref(audio)
End
