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 13 dic 2020 alle 13:09 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
' 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
' 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 volume As Float
Dim durata As Long
Dim dur, tempus As Date
Dim dd As Integer
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)
Repeat
gst_element_query_duration(midi, GST_FORMAT_TIME, VarPtr(durata))
dur = Date(0, 0, 0, 0, 0, 0, durata / 1000000)
Until dur > 0
tempus = Now
Repeat
dd = DateDiff(tempus, Now, gb.Millisecond)
Write "\r\e[0mDurata: " & dur & " Pos. \e[31m" & CStr(Date(0, 0, 0, 0, 0, 0, dd))
Wait 0.001
Until dd > (durata / 1000000)
gst_object_unref(midi)
Print "\nCreazione del file audio WAV terminata."
End
Uso dei plugin specifici di GStreamer per il Midi
Si potrà anche far uso dei plugin specifici di GStreamer per il Midi, che sono:
- midiparse
- fluiddec
In tal caso la stringa della pipeline dei plugin del codice, sopra esposto, sarà la seguente:
midi = gst_parse_launch("filesrc location=/percorso/del/file.mid ! midiparse ! fluiddec ! audioconvert ! audioresample ! volume volume=7.0 ! wavenc ! filesink location =/tmp/file.wav", 0)
