set properties of plugin upon construction of object
Weipeng He
heweipeng at gmail.com
Mon Oct 6 12:21:33 PDT 2014
Hi all,
I am pretty new to programming gstreamer plugin and using gobject.
I have a question about how the properties are set during the
construction phase.
Let's say, I have a plugin name myfilter with property wsize. I can set
the the value of wsize using
gst-launch-1.0 alsasrc ! audioconvert ! myfilter wsize=256 ! fakesink
However, the value of wsize is set after the construction of the object,
namely the function gst_my_filter_init(GstMyFilter*). More precisely,
gst_my_filter_set_property is called after gst_my_filter_init and then
the wsize is set to 256.
What I want is to know the value of wsize when constructing, so that I
can know how much buffer space i should allocate for the object instance
GstMyFilter.
Besides, I also want to specify that wsize can only be set upon
construction. I used G_PARAM_CONSTRUCT_ONLY for the parameter
specification. However, using this flag will make wsize always the
default value.
Please find my code in the attachment.
Thank you so much!
Best,
Weipeng
-------------- next part --------------
/*
* GStreamer
* Copyright (C) 2005 Thomas Vander Stichele <thomas at apestaart.org>
* Copyright (C) 2005 Ronald S. Bultje <rbultje at ronald.bitfreak.net>
* Copyright (C) 2014 Weipeng He <2he at informatik.uni-hamburg.de>
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*
* Alternatively, the contents of this file may be used under the
* GNU Lesser General Public License Version 2.1 (the "LGPL"), in
* which case the following provisions apply instead of the ones
* mentioned above:
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#ifndef __GST_MYFILTER_H__
#define __GST_MYFILTER_H__
#include <gst/gst.h>
G_BEGIN_DECLS
/* #defines don't like whitespacey bits */
#define GST_TYPE_MYFILTER \
(gst_my_filter_get_type())
#define GST_MYFILTER(obj) \
(G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_MYFILTER,GstMyFilter))
#define GST_MYFILTER_CLASS(klass) \
(G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_MYFILTER,GstMyFilterClass))
#define GST_IS_MYFILTER(obj) \
(G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_MYFILTER))
#define GST_IS_MYFILTER_CLASS(klass) \
(G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_MYFILTER))
typedef struct _GstMyFilter GstMyFilter;
typedef struct _GstMyFilterClass GstMyFilterClass;
struct _GstMyFilter
{
GstElement element;
GstPad *sinkpad, *srcpad;
gboolean silent;
guint wsize;
};
struct _GstMyFilterClass
{
GstElementClass parent_class;
};
GType gst_my_filter_get_type (void);
G_END_DECLS
#endif /* __GST_MYFILTER_H__ */
-------------- next part --------------
/*
* GStreamer
* Copyright (C) 2014 Weipeng He <2he at informatik.uni-hamburg.de>
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*
* Alternatively, the contents of this file may be used under the
* GNU Lesser General Public License Version 2.1 (the "LGPL"), in
* which case the following provisions apply instead of the ones
* mentioned above:
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/**
* SECTION:element-myfilter
*
* FIXME:Describe myfilter here.
*
* <refsect2>
* <title>Example launch line</title>
* |[
* gst-launch -v -m fakesrc ! myfilter ! fakesink silent=TRUE
* ]|
* </refsect2>
*/
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <gst/gst.h>
#include "gstmyfilter.h"
GST_DEBUG_CATEGORY_STATIC (gst_my_filter_debug);
#define GST_CAT_DEFAULT gst_my_filter_debug
/* Filter signals and args */
enum
{
/* FILL ME */
LAST_SIGNAL
};
enum
{
PROP_0,
PROP_SILENT,
PROP_WSIZE
};
/* the capabilities of the inputs and outputs.
*
* describe the real formats here.
*/
static GstStaticPadTemplate sink_factory = GST_STATIC_PAD_TEMPLATE ("sink",
GST_PAD_SINK,
GST_PAD_ALWAYS,
GST_STATIC_CAPS (
"audio/x-raw, "
"format = (string) F64LE, "
"channels = (int) {1, 2}, "
"rate = (int) [8000, 96000]"
)
);
static GstStaticPadTemplate src_factory = GST_STATIC_PAD_TEMPLATE ("src",
GST_PAD_SRC,
GST_PAD_ALWAYS,
GST_STATIC_CAPS ("ANY")
);
#define gst_my_filter_parent_class parent_class
G_DEFINE_TYPE (GstMyFilter, gst_my_filter, GST_TYPE_ELEMENT);
static void gst_my_filter_set_property (GObject * object, guint prop_id,
const GValue * value, GParamSpec * pspec);
static void gst_my_filter_get_property (GObject * object, guint prop_id,
GValue * value, GParamSpec * pspec);
static gboolean gst_my_filter_sink_event (GstPad * pad, GstObject * parent, GstEvent * event);
static GstFlowReturn gst_my_filter_chain (GstPad * pad, GstObject * parent, GstBuffer * buf);
/* GObject vmethod implementations */
/* initialize the myfilter's class */
static void
gst_my_filter_class_init (GstMyFilterClass * klass)
{
GObjectClass *gobject_class;
GstElementClass *gstelement_class;
gobject_class = (GObjectClass *) klass;
gstelement_class = (GstElementClass *) klass;
gobject_class->set_property = gst_my_filter_set_property;
gobject_class->get_property = gst_my_filter_get_property;
g_object_class_install_property (gobject_class, PROP_SILENT,
g_param_spec_boolean ("silent", "Silent", "Produce verbose output ?",
FALSE, G_PARAM_READWRITE));
g_object_class_install_property (gobject_class, PROP_WSIZE,
g_param_spec_uint("wsize", "Window Size", "Window Size of the FFT",
4, 16384, 1024, G_PARAM_READWRITE | G_PARAM_CONSTRUCT));
gst_element_class_set_details_simple(gstelement_class,
"myfilter",
"Example/hwp",
"Hello World!",
"Weipeng He <2he at informatik.uni-hamburg.de>");
gst_element_class_add_pad_template (gstelement_class,
gst_static_pad_template_get (&src_factory));
gst_element_class_add_pad_template (gstelement_class,
gst_static_pad_template_get (&sink_factory));
}
/* initialize the new element
* instantiate pads and add them to element
* set pad calback functions
* initialize instance structure
*/
static void
gst_my_filter_init (GstMyFilter * filter)
{
filter->sinkpad = gst_pad_new_from_static_template (&sink_factory, "sink");
gst_pad_set_event_function (filter->sinkpad,
GST_DEBUG_FUNCPTR(gst_my_filter_sink_event));
gst_pad_set_chain_function (filter->sinkpad,
GST_DEBUG_FUNCPTR(gst_my_filter_chain));
GST_PAD_SET_PROXY_CAPS (filter->sinkpad);
gst_element_add_pad (GST_ELEMENT (filter), filter->sinkpad);
filter->srcpad = gst_pad_new_from_static_template (&src_factory, "src");
GST_PAD_SET_PROXY_CAPS (filter->srcpad);
gst_element_add_pad (GST_ELEMENT (filter), filter->srcpad);
filter->silent = FALSE;
filter->wsize = 1024;
}
static void
gst_my_filter_set_property (GObject * object, guint prop_id,
const GValue * value, GParamSpec * pspec)
{
GstMyFilter *filter = GST_MYFILTER (object);
switch (prop_id) {
case PROP_SILENT:
filter->silent = g_value_get_boolean (value);
break;
case PROP_WSIZE:
filter->wsize = g_value_get_uint(value);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
}
}
static void
gst_my_filter_get_property (GObject * object, guint prop_id,
GValue * value, GParamSpec * pspec)
{
GstMyFilter *filter = GST_MYFILTER (object);
switch (prop_id) {
case PROP_SILENT:
g_value_set_boolean (value, filter->silent);
break;
case PROP_WSIZE:
g_value_set_uint(value, filter->wsize);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
}
}
/* GstElement vmethod implementations */
/* this function handles sink events */
static gboolean
gst_my_filter_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
{
gboolean ret;
// GstMyFilter* filter = GST_MYFILTER (parent);
switch (GST_EVENT_TYPE (event)) {
case GST_EVENT_CAPS:
{
GstCaps * caps;
gst_event_parse_caps (event, &caps);
/* do something with the caps */
/* and forward */
ret = gst_pad_event_default (pad, parent, event);
break;
}
default:
ret = gst_pad_event_default (pad, parent, event);
break;
}
return ret;
}
/* Functions below print the Capabilities in a human-friendly format */
static gboolean print_field (GQuark field, const GValue * value, gpointer pfx) {
gchar *str = gst_value_serialize (value);
g_print ("%s %15s: %s\n", (gchar *) pfx, g_quark_to_string (field), str);
g_free (str);
return TRUE;
}
static void print_caps (const GstCaps * caps, const gchar * pfx) {
guint i;
g_return_if_fail (caps != NULL);
if (gst_caps_is_any (caps)) {
g_print ("%sANY\n", pfx);
return;
}
if (gst_caps_is_empty (caps)) {
g_print ("%sEMPTY\n", pfx);
return;
}
for (i = 0; i < gst_caps_get_size (caps); i++) {
GstStructure *structure = gst_caps_get_structure (caps, i);
g_print ("%s%s\n", pfx, gst_structure_get_name (structure));
gst_structure_foreach (structure, print_field, (gpointer) pfx);
}
}
/* chain function
* this function does the actual processing
*/
static GstFlowReturn
gst_my_filter_chain (GstPad * pad, GstObject * parent, GstBuffer * buf)
{
GstMyFilter *filter;
filter = GST_MYFILTER (parent);
if (!filter->silent) {
g_print ("Have data of size %" G_GSIZE_FORMAT" bytes! wsize=%" G_GUINT32_FORMAT"\n",
gst_buffer_get_size(buf), filter->wsize);
/*
gchar* padname = gst_pad_get_name(pad);
g_print("Pad Name: %s\n", padname);
g_free(padname);
GstCaps* caps = gst_pad_get_current_caps(pad);
print_caps(caps, "");
gst_caps_unref(caps);
caps = gst_pad_get_allowed_caps(pad);
print_caps(caps, "");
gst_caps_unref(caps);
*/
}
/* just push out the incoming buffer without touching it */
return gst_pad_push (filter->srcpad, buf);
}
/* entry point to initialize the plug-in
* initialize the plug-in itself
* register the element factories and other features
*/
static gboolean myfilter_init (GstPlugin * myfilter) {
/* debug category for fltering log messages
*
* exchange the string 'Template myfilter' with your description
*/
GST_DEBUG_CATEGORY_INIT (gst_my_filter_debug, "myfilter",
0, "Template myfilter");
return gst_element_register (myfilter, "myfilter", GST_RANK_NONE,
GST_TYPE_MYFILTER);
}
/* PACKAGE: this is usually set by autotools depending on some _INIT macro
* in configure.ac and then written into and defined in config.h, but we can
* just set it ourselves here in case someone doesn't use autotools to
* compile this code. GST_PLUGIN_DEFINE needs PACKAGE to be defined.
*/
#ifndef PACKAGE
#define PACKAGE "myfirstmyfilter"
#endif
/* gstreamer looks for this structure to register myfilters
*
* exchange the string 'Template myfilter' with your myfilter description
*/
GST_PLUGIN_DEFINE (
GST_VERSION_MAJOR,
GST_VERSION_MINOR,
myfilter,
"Template myfilter",
myfilter_init,
VERSION,
"LGPL",
"GStreamer",
"http://gstreamer.net/"
)
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