How to parse current capabilities of a pad in a plugin?

[ssshukla26]

Hi,

I want to get capabilities set on my sink pad in a pipe !

Let suppose my pipe is as follows

gst-launch-1.0 -e filesrc location=rawvideo_yuv420.yuv blocksize=460800 !
*video/x-raw,format=I420,width=640,height=480,framerate=30/1* !
myh264encoder silent=true ! decodebin ! autovideosink 

My gstreamer plugin is *myh264encoder*. 

Now how can I get width as 640 and height as 480 and framerate as 30 from
the caps "*video/x-raw,format=I420,width=640,height=480,framerate=30/1*"
inside my gstreamer plugin's init function ?

I tried the following but it didn't worked

1) This give me width=[ 16, 2147483647 ]

GstPad *pad = gst_pad_new_from_static_template (&sink_factory,"sink");
*GstCaps *caps = gst_pad_get_pad_template_caps (pad);*
GstStructure *structure = gst_caps_get_structure (caps, 0); 
gchar *str = gst_value_serialize
(gst_structure_get_value(structure,"width"));
g_print("width = %s\n",str);
g_free(str);

2) This give me width=(null)

GstPad *pad = gst_pad_new_from_static_template (&sink_factory,"sink");
*GstCaps *caps = gst_pad_get_current_caps (pad);*
GstStructure *structure = gst_caps_get_structure (caps, 0); 
gchar *str = gst_value_serialize
(gst_structure_get_value(structure,"width"));
g_print("width = %s\n",str);
g_free(str);

3) I used *gst_pad_set_event_function* technique, but am not sure that am
implementing it correctly

- /*Under init function of my plugin I do as below*/

filter->sinkpad = gst_pad_new_from_static_template (&sink_factory, "sink");
gst_pad_set_event_function
(filter->sinkpad,GST_DEBUG_FUNCPTR(g*st_myencoder_sink_event*));
gst_element_add_pad (GST_ELEMENT (filter), filter->sinkpad);

- /*Implementing the sink event function as below*/

static gboolean *gst_myencoder_sink_event* (GstPad * pad, GstObject *
parent, GstEvent * event)
{
    gboolean ret;
    GstMyEncoder *filter = GST_MYENCODER (parent);

    switch (GST_EVENT_TYPE (event)) {
        case GST_EVENT_CAPS:
            {
                GstCaps * caps;

                gst_event_parse_caps (event, &caps);
                /* do something with the caps */
                GstStructure *structure = gst_caps_get_structure (caps, 0);
                gchar *str = gst_value_serialize
(gst_structure_get_value(structure,"width"));
                g_print("width = %s\n",str);
                g_free(str);

                /* and forward */
                ret = gst_pad_event_default (pad, parent, event);
                break;
            }
        default:
            ret = gst_pad_event_default (pad, parent, event);
            break;
    }
    return ret;
}


Please let me know, as my requirement is to parse the caps and initialize
the encoder resply to the caps. 




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