Differenze tra le versioni di "Visualizzare un oscilloscopio di GStreamer mediante la funzione 'gst parse launch()' durante l'esecuzione di un file audio"
Da Gambas-it.org - Wikipedia.
| Riga 49: | Riga 49: | ||
audio = gst_parse_launch("filesrc location=<FONT Color=gray>''/percorso/del/file/audio''</font> ! decodebin ! tee name=t " & | audio = gst_parse_launch("filesrc location=<FONT Color=gray>''/percorso/del/file/audio''</font> ! decodebin ! tee name=t " & | ||
| − | + | "! queue ! audioconvert ! wavescope style=3 ! video/x-raw, width=1000 ! videoconvert ! ximagesink t. " & | |
| − | + | "! queue ! audioconvert ! m. t. ! queue ! autoaudiosink", 0) | |
<FONT Color=gray>' ''Avviamo l'esecuzione del file audio:''</font> | <FONT Color=gray>' ''Avviamo l'esecuzione del file audio:''</font> | ||
Versione delle 07:05, 28 lug 2020
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"
Usando i plugin "wavescope" o "monoscope" unitamente a "autoaudiosink" all'interno della riga della pipeline della funzione gst_parse_launch(), è possibile scegliere la visualizzazione di due tipi diversi di oscilloscopio attivo durante l'esecuzione di un file audio di formato wav, mp3 ed .ogg.
Uso del plugin wavescope
Mostriamo un esempio pratico usando i plugin "wavescope" e "autoaudiosink" all'interno della riga della pipeline della funzione gst_parse_launch():
Private audio As Pointer
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 pos, dur As Long
Dim po, du As Date
gst_init(0, 0)
audio = gst_parse_launch("filesrc location=/percorso/del/file/audio ! decodebin ! tee name=t " &
"! queue ! audioconvert ! wavescope style=3 ! video/x-raw, width=1000 ! videoconvert ! ximagesink t. " &
"! queue ! audioconvert ! m. t. ! queue ! autoaudiosink", 0)
' Avviamo l'esecuzione del file 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))
po = Date(0, 0, 0, 0, 0, 0, pos / 1000000)
du = Date(0, 0, 0, 0, 0, 0, dur / 1000000)
If (pos > 0) And (CStr(po) >= CStr(du)) Then Break
Write #File.Out, "\rDurata: " & du & " " & "Tempo trascorso: " & po
Wend
Termina()
End
Public Sub Application_Read()
Dim s As String
Input #File.In, s
Select Case s
Case "p"
' Pone in pausa la riproduzione del file mediale:
gst_element_set_state(audio, GST_STATE_PAUSED)
Case "r"
' Riprende la riproduzione del file mediale:
gst_element_set_state(audio, GST_STATE_PLAYING)
Case "s"
' Arresta la riproduzione del file mediale:
gst_element_set_state(audio, GST_STATE_NULL)
Termina()
End Select
End
Private Procedure Termina()
gst_object_unref(audio)
Print "\nEsecuzione terminata."
Quit
End
Uso del plugin monoscope
Mostriamo un esempio pratico usando i plugin "monoscope" e "autoaudiosink" all'interno della riga della pipeline della funzione gst_parse_launch():
Private audio As Pointer
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 pos, dur As Long
Dim po, du As Date
gst_init(0, 0)
audio = gst_parse_launch("filesrc location=/percorso/del/file/audio ! decodebin ! tee name=t " &
"! queue ! audioconvert ! monoscope ! ximagesink ! queue ! m. t. ! queue ! autoaudiosink", 0)
' Avviamo l'esecuzione del file 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))
po = Date(0, 0, 0, 0, 0, 0, pos / 1000000)
du = Date(0, 0, 0, 0, 0, 0, dur / 1000000)
If (pos > 0) And (CStr(po) >= CStr(du)) Then Break
Write #File.Out, "\rDurata: " & du & " " & "Tempo trascorso: " & po
Wend
Termina()
End
Public Sub Application_Read()
Dim s As String
Input #File.In, s
Select Case s
Case "p"
' Pone in pausa la riproduzione del file mediale:
gst_element_set_state(audio, GST_STATE_PAUSED)
Case "r"
' Riprende la riproduzione del file mediale:
gst_element_set_state(audio, GST_STATE_PLAYING)
Case "s"
' Arresta la riproduzione del file mediale:
gst_element_set_state(audio, GST_STATE_NULL)
Termina()
End Select
End
Private Procedure Termina()
gst_object_unref(audio)
Print "\nEsecuzione terminata."
Quit
End
Riferimenti
- http://docs.gstreamer.com/display/GstSDK/gst-launch
- https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-bad-plugins/html/gst-plugins-bad-plugins-wavescope.html
- https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-good-plugins/html/gst-plugins-good-plugins-monoscope.html
- http://gstreamer.freedesktop.org/
- http://gstreamer.com/
