String parameter in an element

Sat Apr 14 22:36:51 PDT 2012

Hello,

I am having problems with a simple chain element I have created. I'm trying
to add a new argument to my code. It is a string type. The code compiles and
runs, but I give it a value to the argument, and when I try to use the
value, it appears as blank. Any suggestions? Thanks.

I run it as:
gst-launch -v -m videotestsrc pattern=snow ! template line_color="blue" !
autovideosink

Heres is my header file:

#ifndef __GST_TEMPLATE__
#define __GST_TEMPLATE__

#include "gstreamer-0.10/gst/gst.h"

G_BEGIN_DECLS

/* #defines don't like whitespacey bits */
#define GST_TYPE_TEMPLATE \
  (gst_template_get_type())
#define GST_TEMPLATE(obj) \
  (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_TEMPLATE,GstTemplate))
#define GST_TEMPLATE_CLASS(klass) \
  (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_TEMPLATE,GstTemplateClass))
#define GST_IS_TEMPLATE(obj) \
  (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_TEMPLATE))
#define GST_IS_TEMPLATE_CLASS(klass) \
  (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_TEMPLATE))

typedef struct _GstTemplate      GstTemplate;
typedef struct _GstTemplateClass GstTemplateClass;

struct _GstTemplate
{
  GstElement element;

  GstPad *sinkpad, *srcpad;

  gboolean silent;

  char *line_color;
};

struct _GstTemplateClass 
{
  GstElementClass parent_class;
};

GType gst_template_get_type (void);

G_END_DECLS

#endif /* __GST_TEMPLATE__ */

------------------------------------Here is my source
file----------------------------------

#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#include <gst/gst.h>
#include "gst_template.h"

GST_DEBUG_CATEGORY_STATIC (gst_template_debug);
#define GST_CAT_DEFAULT gst_template_debug

enum
{
  PROP_0,
  PROP_SILENT,
  LINE_COLOR
};

static GstStaticPadTemplate sink_factory = GST_STATIC_PAD_TEMPLATE ("sink",
    GST_PAD_SINK,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("ANY")
    );

static GstStaticPadTemplate src_factory = GST_STATIC_PAD_TEMPLATE ("src",
    GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("ANY")
    );

GST_BOILERPLATE (GstTemplate, gst_template, GstElement,
    GST_TYPE_ELEMENT);

static void gst_template_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec);
static void gst_template_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec);

static gboolean gst_template_set_caps (GstPad * pad, GstCaps * caps);
static GstFlowReturn gst_template_chain (GstPad * pad, GstBuffer * buf);

static GType
gst_tempalte_color_get_type (void)
{
  static GType template_color_type = 0;
  static const GEnumValue template_color[] = {
    {GST_COLOR_RED, "The color red", "red"},
    {GST_COLOR_BLUE, "The color blue", "blue"},
    {0, NULL, NULL}
  };

  if (!template_color_type) {
    template_color_type =
        g_enum_register_static ("Temlate", template_color);
  }
  return template_color_type;
}

static void
gst_template_base_init (gpointer gclass)
{
  GstElementClass *element_class = GST_ELEMENT_CLASS (gclass);

  gst_element_class_set_details_simple(element_class,
    "Plugin Template",
    "Template",
    "Generic Chain Element",
    "name email");

  gst_element_class_add_pad_template (element_class,
      gst_static_pad_template_get (&src_factory));
  gst_element_class_add_pad_template (element_class,
      gst_static_pad_template_get (&sink_factory));
}

static void
gst_template_class_init (GstTemplateClass * klass)
{
  GObjectClass *gobject_class;
  GstElementClass *gstelement_class;

  gobject_class = (GObjectClass *) klass;
  gstelement_class = (GstElementClass *) klass;

  gobject_class->set_property = gst_template_set_property;
  gobject_class->get_property = gst_template_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, LINE_COLOR, 
	  g_param_spec_string ("line_color", "Line_color", "Chenge the color of the
line", "red", G_PARAM_READWRITE));
}

static void
gst_template_init (GstTemplate * filter,
    GstTemplateClass * gclass)
{
  filter->sinkpad = gst_pad_new_from_static_template (&sink_factory,
"sink");
  gst_pad_set_setcaps_function (filter->sinkpad,
                                GST_DEBUG_FUNCPTR(gst_template_set_caps));
  gst_pad_set_getcaps_function (filter->sinkpad,
                                GST_DEBUG_FUNCPTR(gst_pad_proxy_getcaps));

  gst_pad_set_chain_function (filter->sinkpad,
                              GST_DEBUG_FUNCPTR(gst_template_chain));

  filter->srcpad = gst_pad_new_from_static_template (&src_factory, "src");
  gst_pad_set_getcaps_function (filter->srcpad,
                                GST_DEBUG_FUNCPTR(gst_pad_proxy_getcaps));

  gst_element_add_pad (GST_ELEMENT (filter), filter->sinkpad);
  gst_element_add_pad (GST_ELEMENT (filter), filter->srcpad);
  filter->silent = FALSE;

}

static void
gst_template_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstTemplate *filter = GST_TEMPLATE (object);

  switch (prop_id) {
    case PROP_SILENT:
      filter->silent = g_value_get_boolean (value);
      break;
    case LINE_COLOR:
      filter->line_color = g_value_get_string (value);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_template_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec)
{
  GstTemplate *filter = GST_TEMPLATE (object);

  switch (prop_id) {
    case PROP_SILENT:
      g_value_set_boolean (value, filter->silent);
      break;
    case LINE_COLOR:
      g_value_set_string (value, filter->line_color);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }

}

static gboolean
gst_template_set_caps (GstPad * pad, GstCaps * caps)
{
  GstStructure *structure = gst_caps_get_structure(caps,0);
  GstTemplate *filter;
  GstPad *otherpad;

  filter = GST_TEMPLATE (gst_pad_get_parent (pad));

  gst_structure_get_int (structure, "rate", &filter->srcpad);
  otherpad = (pad == filter->srcpad) ? filter->sinkpad : filter->srcpad;
  gst_object_unref (filter);

  return gst_pad_set_caps (otherpad, caps);
}

static GstBuffer *
gst_template_convert (GstPad * pad, GstBuffer *in)
{
  GstBuffer *tempbuf;
  char *color;
  GstTemplate *filter;

  filter = GST_TEMPLATE (GST_OBJECT_PARENT (pad));

  color = filter->line_color;

  g_print(" \n\nTHE COLOR IS %s\n\n",color);

  tempbuf = in;

  return tempbuf;
}

static GstFlowReturn
gst_template_chain (GstPad * pad, GstBuffer * buf)
{
  GstTemplate *filter;
  GstBuffer *outbuf;

  filter = GST_TEMPLATE (GST_OBJECT_PARENT (pad));

  outbuf = gst_template_convert (pad, buf);

  return gst_pad_push (filter->srcpad, outbuf);
}

static gboolean
plugin_init (GstPlugin * plugin)
{
  GST_DEBUG_CATEGORY_INIT (gst_template_debug, "template",
      0, "Template plugin");

  return gst_element_register (plugin, "template", GST_RANK_NONE,
      GST_TYPE_TEMPLATE);
}

#ifndef PACKAGE
#define PACKAGE "plugintemplate"
#endif

/* gstreamer looks for this structure to register plugins
 *
 * exchange the string 'Template plugin' with your plugin description
 */
GST_PLUGIN_DEFINE (
    GST_VERSION_MAJOR,
    GST_VERSION_MINOR,
    "template",
    "Template Example",
    plugin_init,
    "0.10.28",
    "GPL",
    "GStreamer",
    "http://gstreamer.net/"
)

--
View this message in context: http://gstreamer-devel.966125.n4.nabble.com/String-parameter-in-an-element-tp4558627p4558627.html
Sent from the GStreamer-devel mailing list archive at Nabble.com.