Differenze tra le versioni di "Modificare ad un file WAV la frequenza di campionamento e il numero di canali usando una linea di pipeline con la funzione 'gst parse launch()'"
Da Gambas-it.org - Wikipedia.
| Riga 35: | Riga 35: | ||
| − | + | Public Sub Main() | |
Dim audio As Pointer | Dim audio As Pointer | ||
| − | Dim | + | Dim durata, pos As Long |
| − | + | gst_init(0, 0) | |
| − | + | audio = gst_parse_launch("uridecodebin uri=file://<FONT Color=darkgreen>''/percorso/del/file/audio.wav''</font> ! audioresample ! audioconvert ! audio/x-raw, <FONT Color=#B22222>rate=8000</font>, <FONT Color=#B22222>channels=1</font> ! wavenc ! filesink location=<FONT Color=gray>''/percorso/del/nuovo/file.wav''</font>", 0) | |
| − | + | ||
<FONT Color=gray>' ''Avviamo la conversione audio:''</font> | <FONT Color=gray>' ''Avviamo la conversione audio:''</font> | ||
| − | + | gst_element_set_state(audio, GST_STATE_PLAYING) | |
| − | + | ||
| − | + | Repeat | |
| − | + | gst_element_query_duration(audio, GST_FORMAT_TIME, VarPtr(durata)) | |
| − | + | Wait 0.01 | |
| − | + | Until durata > -1 | |
| − | + | ||
| − | + | Repeat | |
| − | + | gst_element_query_position(audio, GST_FORMAT_TIME, VarPtr(pos)) | |
| − | + | Write "\r\e[0mDurata: " & Time(0, 0, 0, durata / 1000000) & " Pos. \e[31m" & Time(0, 0, 0, pos / 1000000) | |
| + | Wait 0.001 | ||
| + | Until pos >= durata | ||
| + | |||
| + | gst_object_unref(audio) | ||
| − | + | Quit | |
| − | + | End | |
| − | |||
Versione delle 04:49, 12 dic 2023
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, nel quale ad un file WAV la frequenza di campionamento verrà ridotta a 8000 hertz ed il numero dei canali ad 1 (mono):
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 durata, pos As Long
gst_init(0, 0)
audio = gst_parse_launch("uridecodebin uri=file:///percorso/del/file/audio.wav ! audioresample ! audioconvert ! audio/x-raw, rate=8000, channels=1 ! wavenc ! filesink location=/percorso/del/nuovo/file.wav", 0)
' Avviamo la conversione audio:
gst_element_set_state(audio, GST_STATE_PLAYING)
Repeat
gst_element_query_duration(audio, GST_FORMAT_TIME, VarPtr(durata))
Wait 0.01
Until durata > -1
Repeat
gst_element_query_position(audio, GST_FORMAT_TIME, VarPtr(pos))
Write "\r\e[0mDurata: " & Time(0, 0, 0, durata / 1000000) & " Pos. \e[31m" & Time(0, 0, 0, pos / 1000000)
Wait 0.001
Until pos >= durata
gst_object_unref(audio)
Quit
End
