Ottenere un file WAV da un file Midi con la funzione esterna ''gst parse launch()'' del API di GStreamer
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Versione del 22 set 2016 alle 08:18 di Vuott (Discussione | contributi)
E' possibile ottenere un file audio formato WAV da un file Midi mediante una linea di pipeline gestita dalla funzione gst parse launch() del API di GStreamer.
Mostriamo un esempio pratico:
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
Private stato As Integer = GST_STATE_PLAYING
' 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 midi As Pointer
Dim posizione, durata As Long
Dim dur, pos As Date
gst_init(0, 0)
midi = gst_parse_launch("filesrc location=/percorso/del/file.mid ! decodebin ! audioconvert ! audioresample ! volume volume=7.0 ! wavenc ! filesink location =/tmp/file.wav", 0)
' Avviamo la riproduzione del file Midi per la creazione del file audio WAV:
gst_element_set_state(midi, GST_STATE_PLAYING)
While stato = GST_STATE_PLAYING
gst_element_query_duration(midi, GST_FORMAT_TIME, VarPtr(durata))
gst_element_query_position(midi, GST_FORMAT_TIME, VarPtr(posizione))
dur = Date(0, 0, 0, 0, 0, 0, durata / 1000000)
pos = Date(0, 0, 0, 0, 0, 0, posizione / 1000000)
If (posizione > 0) And (pos >= dur) Then Break
Write #File.Out, "\rDurata: " & Date(0, 0, 0, 0, 0, 0, durata / 1000000) & " Pos. " & Date(0, 0, 0, 0, 0, 0, posizione / 1000000)
Wait 0.01
Wend
gst_object_unref(midi)
Print "\nCreazione del file audio WAV terminata."
Quit
End
