GstCaps
Capabilities of pads
GstCaps is used to attach capabilities to a pad. Capabilities are made of
a mime-type and a set of properties. GstCaps can be named and chained into
a list, which is then a GstCaps on its own.
GstCaps are created with gst_caps_new(), which takes a name, a mime type and
a pointer to a #GstProps. A convenience macro with a cleaner syntax is
available to create a caps with GST_CAPS_NEW(). The following example shows how
to create a GstCaps.
GstCaps *caps;
caps = gst_caps_new (
"my_caps", /* capability name */
"audio/raw", /* mime type */
gst_props_new ( /* properties */
"format", GST_PROPS_STRING ("float"),
"channels", GST_PROPS_INT (5),
NULL));
The following code example is equivalent to the above example:
GstCaps *caps;
caps = GST_CAPS_NEW (
"my_caps", /* capability name */
"audio/raw", /* mime type */
"format", GST_PROPS_STRING ("float"),
"channels", GST_PROPS_INT (5)
);
GstCaps are refcounted with gst_caps_ref() and gst_caps_unref().
GstCaps can be chained with the gst_caps_append(), gst_caps_prepend() and
gst_caps_chain() functions. Use gst_caps_get_by_name() to get a named caps
structure from a chained list.
To get the properties of a caps structure the functions
gst_caps_get_boolean(), gst_caps_get_fourcc_int(), gst_caps_get_int(),
gst_caps_get_string(), gst_caps_get_float(), which all take a property name as an argument.
The properties of the caps structure can be modified with gst_caps_set, which
takes a list of key value pairs in the #GstProps syntax as shown by this example:
GstCaps *caps;
....
gst_caps_set (caps, "format", GST_PROPS_STRING ("int"), NULL);
gst_caps_set (caps, "channels", GST_PROPS_INT (20), NULL);
before modifying a GstCaps, it is a good idea to make a copy if it first with
gst_caps_copy_on_write(). This will copy the GstCaps if the refcount is >1.
If you need a unique instance of a GstCaps you can use the convenient
GST_CAPS_FACTORY() macro as shown below.
GST_CAPS_FACTORY (my_caps,
GST_CAPS_NEW (
"caps1",
"audio/raw",
"format", GST_PROPS_STRING ("float"),
"channels", GST_PROPS_INT (5)
),
GST_CAPS_NEW (
"caps2",
"audio/raw",
"format", GST_PROPS_STRING ("int"),
"channels", GST_PROPS_INT (5)
)
)
void
some_function (void)
{
GstCaps *caps = GST_CAPS_GET (my_caps);
...
}
If you want to check if a link between source and destination caps
is always possible, use gst_caps_is_always_compatible(), which returns
a boolean.
If you want to check if a link between source and destination caps
might be possible, use gst_caps_intersect(), which returns an intersection
of the capabilities.
#GstProps, #GstPad
The GType of the caps boxed type, for use in GValues.
The gstcaps structure
@type:
@flags:
@structs:
@caps:
@Returns:
@caps:
@Returns:
@caps1:
@caps2:
@caps:
@capstoadd:
@Returns:
@caps:
@newcaps:
@oldcaps:
@caps1:
@caps2:
@Returns:
@fromcaps:
@tocaps:
@caps:
@Returns:
@caps1:
@caps2:
@Returns:
@caps:
@parent:
@Returns:
@parent:
@Returns:
@caps1:
@caps2:
@Returns: