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GstCaps — Capabilities of pads
#include <gst/gst.h> #define GST_TYPE_CAPS struct GstCaps; GstCaps* gst_caps_copy (const GstCaps *caps); GstCaps* gst_caps_copy_1 (const GstCaps *caps); void gst_caps_append (GstCaps *caps1, GstCaps *caps2); void gst_caps_replace (GstCaps **caps, GstCaps *newcaps); gboolean gst_caps_is_always_compatible (const GstCaps *caps1, const GstCaps *caps2); GstCaps* gst_caps_normalize (const GstCaps *caps); GstCaps* gst_caps_intersect (const GstCaps *caps1, const GstCaps *caps2); xmlNodePtr gst_caps_save_thyself (const GstCaps *caps, xmlNodePtr parent); GstCaps* gst_caps_load_thyself (xmlNodePtr parent); GstCaps* gst_caps_union (const GstCaps *caps1, const GstCaps *caps2);
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_simpl(), which takes a mime type and a list of arguments in sets of 3, terminated with NULL. Each set of 3 arguments is the name of a field, the GType of the field, and the value of the field. The following example shows how to create a GstCaps.
GstCaps *caps; caps = gst_caps_new ( "audio/x-raw-int", /* mime type */ "channels", G_TYPE_INT, 5, NULL);
The following code example is equivalent to the above example:
GstCaps *caps; caps = gst_caps_from_string ("audio/x-raw-int, channels = (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 fields of the caps structure can be modified with gst_caps_set_simple, which takes the caps structure to be modified, a list of arguments in sets of 3, terminated by NULL. The format of these arguments is the same as above.
GstCaps *caps; .... gst_caps_set_simple (caps, "channels", G_TYPE_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.
GstStaticCaps my_caps = GST_STATIC_CAPS ( "audio/x-raw-float, " "channels = (int) 5; " "audio/x-raw-int, " "channels = (int) 5" ) ) void some_function (void) { GstCaps *caps = gst_caps_copy (gst_static_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.
#define GST_TYPE_CAPS gst_caps_get_type()
The GType of the caps boxed type, for use in GValues.
struct GstCaps { GType type; guint16 flags; GPtrArray *structs; gpointer _gst_reserved[GST_PADDING]; };
The gstcaps structure
GstCaps* gst_caps_copy (const GstCaps *caps);
Deeply copies a GstCaps, including all structures and all the structures' values.
GstCaps* gst_caps_copy_1 (const GstCaps *caps);
Creates a new GstCaps and appends a copy of the first structure contained in caps.
caps : | the GstCaps to copy |
Returns : | the new GstCaps |
void gst_caps_append (GstCaps *caps1, GstCaps *caps2);
Appends the structures contained in caps2 to caps1. The structures in caps2 are not copied -- they are transferred to caps1, and then caps2 is freed.
void gst_caps_replace (GstCaps **caps, GstCaps *newcaps);
Replaces *caps with newcaps. Frees the GstCaps in the location pointed to by caps, if applicable, then modifies caps to point to newcaps.
gboolean gst_caps_is_always_compatible (const GstCaps *caps1, const GstCaps *caps2);
GstCaps* gst_caps_normalize (const GstCaps *caps);
Creates a new GstCaps that represents the same set of formats as caps, but contains no lists. Each list is expanded into separate GstStructures.
GstCaps* gst_caps_intersect (const GstCaps *caps1, const GstCaps *caps2);
Creates a new GstCaps that contains all the formats that are common to both caps1 and caps2.
xmlNodePtr gst_caps_save_thyself (const GstCaps *caps, xmlNodePtr parent);
caps : | |
parent : | |
Returns : |
GstStructure, GstPad
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