struct GstCaps

struct GstCaps {
  GstMiniObject mini_object;
};

Object describing media types.

struct GstStaticCaps

struct GstStaticCaps {
  GstCaps *caps;
  const char *string;
};

Datastructure to initialize GstCaps from a string description usually used in conjunction with GST_STATIC_CAPS() and gst_static_caps_get() to instantiate a GstCaps.

enum GstCapsIntersectMode

typedef enum {
  GST_CAPS_INTERSECT_ZIG_ZAG            =  0,
  GST_CAPS_INTERSECT_FIRST              =  1
} GstCapsIntersectMode;

Modes of caps intersection

GST_CAPS_INTERSECT_ZIG_ZAG tries to preserve overall order of both caps by iterating on the caps' structures as the following matrix shows:

1
2
3
4
5

caps1
      +-------------
      | 1  2  4  7
caps2 | 3  5  8 10
      | 6  9 11 12

Used when there is no explicit precedence of one caps over the other. e.g. tee's sink pad getcaps function, it will probe its src pad peers' for their caps and intersect them with this mode.

GST_CAPS_INTERSECT_FIRST is useful when an element wants to preserve another element's caps priority order when intersecting with its own caps. Example: If caps1 is [A, B, C] and caps2 is [E, B, D, A], the result would be [A, B], maintaining the first caps priority on the intersection.

enum GstCapsFlags

typedef enum {
  GST_CAPS_FLAG_ANY = (GST_MINI_OBJECT_FLAG_LAST << 0)
} GstCapsFlags;

Extra flags for a caps.

GST_CAPS_ANY

#define GST_CAPS_ANY              _gst_caps_any

Means that the element/pad can output 'anything'. Useful for elements that output unknown media, such as filesrc. This macro returns a singleton and should not be unreffed.

GST_CAPS_NONE

#define GST_CAPS_NONE             _gst_caps_none

The opposite of GST_CAPS_ANY: it means that the pad/element outputs an undefined media type that can not be detected. This macro returns a singleton and should not be unreffed.

GST_CAPS_REFCOUNT()

#define GST_CAPS_REFCOUNT(caps)                 GST_MINI_OBJECT_REFCOUNT(caps)

Get access to the reference count field of the caps

GST_CAPS_REFCOUNT_VALUE()

#define GST_CAPS_REFCOUNT_VALUE(caps)           GST_MINI_OBJECT_REFCOUNT_VALUE(caps)

Get the reference count value of the caps.

GST_STATIC_CAPS_ANY

#define GST_STATIC_CAPS_ANY       GST_STATIC_CAPS("ANY")

Creates a new GstCaps static caps that matches anything. This can be used in pad templates.

GST_STATIC_CAPS_NONE

#define GST_STATIC_CAPS_NONE      GST_STATIC_CAPS("NONE")

Creates a new GstCaps static caps that matches nothing. This can be used in pad templates.

GST_CAPS_IS_SIMPLE()

#define GST_CAPS_IS_SIMPLE(caps) (gst_caps_get_size(caps) == 1)

Convenience macro that checks if the number of structures in the given caps is exactly one.

GST_STATIC_CAPS()

#define             GST_STATIC_CAPS(string)

Creates a new GstCaps static caps from an input string. This can be used in pad templates.

GST_CAPS_FLAGS()

#define GST_CAPS_FLAGS(caps)                    GST_MINI_OBJECT_FLAGS(caps)

A flags word containing GstCapsFlags flags set on this caps.

GST_CAPS_FLAG_IS_SET()

#define GST_CAPS_FLAG_IS_SET(caps,flag)        GST_MINI_OBJECT_FLAG_IS_SET (caps, flag)

Gives the status of a specific flag on a caps.

GST_CAPS_FLAG_SET()

#define GST_CAPS_FLAG_SET(caps,flag)           GST_MINI_OBJECT_FLAG_SET (caps, flag)

Sets a caps flag on a caps.

GST_CAPS_FLAG_UNSET()

#define GST_CAPS_FLAG_UNSET(caps,flag)         GST_MINI_OBJECT_FLAG_UNSET (caps, flag)

Clears a caps flag.

gst_caps_new_empty ()

GstCaps *           gst_caps_new_empty                  (void);

Creates a new GstCaps that is empty. That is, the returned GstCaps contains no media formats. The GstCaps is guaranteed to be writable. Caller is responsible for unreffing the returned caps.

gst_caps_new_empty_simple ()

GstCaps *           gst_caps_new_empty_simple           (const char *media_type);

Creates a new GstCaps that contains one GstStructure with name media_type. Caller is responsible for unreffing the returned caps.

gst_caps_new_any ()

GstCaps *           gst_caps_new_any                    (void);

Creates a new GstCaps that indicates that it is compatible with any media format.

gst_caps_new_simple ()

GstCaps *           gst_caps_new_simple                 (const char *media_type,
                                                         const char *fieldname,
                                                         ...);

Creates a new GstCaps that contains one GstStructure. The structure is defined by the arguments, which have the same format as gst_structure_new(). Caller is responsible for unreffing the returned caps.

gst_caps_new_full ()

GstCaps *           gst_caps_new_full                   (GstStructure *struct1,
                                                         ...);

Creates a new GstCaps and adds all the structures listed as arguments. The list must be NULL-terminated. The structures are not copied; the returned GstCaps owns the structures.

gst_caps_new_full_valist ()

GstCaps *           gst_caps_new_full_valist            (GstStructure *structure,
                                                         va_list var_args);

Creates a new GstCaps and adds all the structures listed as arguments. The list must be NULL-terminated. The structures are not copied; the returned GstCaps owns the structures.

gst_caps_is_writable()

#define         gst_caps_is_writable(caps)     gst_mini_object_is_writable (GST_MINI_OBJECT_CAST (caps))

Tests if you can safely modify caps. It is only safe to modify caps when there is only one owner of the caps - ie, the object is writable.

gst_caps_copy ()

GstCaps *           gst_caps_copy                       (const GstCaps *caps);

Creates a new GstCaps as a copy of the old caps. The new caps will have a refcount of 1, owned by the caller. The structures are copied as well.

Note that this function is the semantic equivalent of a gst_caps_ref() followed by a gst_caps_make_writable(). If you only want to hold on to a reference to the data, you should use gst_caps_ref().

When you are finished with the caps, call gst_caps_unref() on it.

gst_caps_copy_nth ()

GstCaps *           gst_caps_copy_nth                   (const GstCaps *caps,
                                                         guint nth);

Creates a new GstCaps and appends a copy of the nth structure contained in caps.

gst_static_caps_get ()

GstCaps *           gst_static_caps_get                 (GstStaticCaps *static_caps);

Converts a GstStaticCaps to a GstCaps.

gst_static_caps_cleanup ()

void                gst_static_caps_cleanup             (GstStaticCaps *static_caps);

Clean up the cached caps contained in static_caps.

gst_caps_append ()

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. If either caps is ANY, the resulting caps will be ANY.

gst_caps_merge ()

GstCaps *           gst_caps_merge                      (GstCaps *caps1,
                                                         GstCaps *caps2);

Appends the structures contained in caps2 to caps1 if they are not yet expressed by caps1. The structures in caps2 are not copied -- they are transferred to a writable copy of caps1, and then caps2 is freed. If either caps is ANY, the resulting caps will be ANY.

gst_caps_append_structure ()

void                gst_caps_append_structure           (GstCaps *caps,
                                                         GstStructure *structure);

Appends structure to caps. The structure is not copied; caps becomes the owner of structure.

gst_caps_remove_structure ()

void                gst_caps_remove_structure           (GstCaps *caps,
                                                         guint idx);

removes the stucture with the given index from the list of structures contained in caps.

gst_caps_steal_structure ()

GstStructure *      gst_caps_steal_structure            (GstCaps *caps,
                                                         guint index);

Retrieves the structure with the given index from the list of structures contained in caps. The caller becomes the owner of the returned structure.

gst_caps_merge_structure ()

GstCaps *           gst_caps_merge_structure            (GstCaps *caps,
                                                         GstStructure *structure);

Appends structure to caps if its not already expressed by caps.

gst_caps_get_size ()

guint               gst_caps_get_size                   (const GstCaps *caps);

Gets the number of structures contained in caps.

gst_caps_get_structure ()

GstStructure *      gst_caps_get_structure              (const GstCaps *caps,
                                                         guint index);

Finds the structure in caps that has the index index, and returns it.

WARNING: This function takes a const GstCaps *, but returns a non-const GstStructure *. This is for programming convenience -- the caller should be aware that structures inside a constant GstCaps should not be modified. However, if you know the caps are writable, either because you have just copied them or made them writable with gst_caps_make_writable(), you may modify the structure returned in the usual way, e.g. with functions like gst_structure_set().

You do not need to free or unref the structure returned, it belongs to the GstCaps.

gst_caps_set_value ()

void                gst_caps_set_value                  (GstCaps *caps,
                                                         const char *field,
                                                         const GValue *value);

Sets the given field on all structures of caps to the given value. This is a convenience function for calling gst_structure_set_value() on all structures of caps.

gst_caps_set_simple ()

void                gst_caps_set_simple                 (GstCaps *caps,
                                                         const char *field,
                                                         ...);

Sets fields in a GstCaps. The arguments must be passed in the same manner as gst_structure_set(), and be NULL-terminated.

gst_caps_set_simple_valist ()

void                gst_caps_set_simple_valist          (GstCaps *caps,
                                                         const char *field,
                                                         va_list varargs);

Sets fields in a GstCaps. The arguments must be passed in the same manner as gst_structure_set(), and be NULL-terminated.

gst_caps_is_any ()

gboolean            gst_caps_is_any                     (const GstCaps *caps);

Determines if caps represents any media format.

gst_caps_is_empty ()

gboolean            gst_caps_is_empty                   (const GstCaps *caps);

Determines if caps represents no media formats.

gst_caps_is_fixed ()

gboolean            gst_caps_is_fixed                   (const GstCaps *caps);

Fixed GstCaps describe exactly one format, that is, they have exactly one structure, and each field in the structure describes a fixed type. Examples of non-fixed types are GST_TYPE_INT_RANGE and GST_TYPE_LIST.

gst_caps_is_equal ()

gboolean            gst_caps_is_equal                   (const GstCaps *caps1,
                                                         const GstCaps *caps2);

Checks if the given caps represent the same set of caps.

gst_caps_is_equal_fixed ()

gboolean            gst_caps_is_equal_fixed             (const GstCaps *caps1,
                                                         const GstCaps *caps2);

Tests if two GstCaps are equal. This function only works on fixed GstCaps.

gst_caps_is_strictly_equal ()

gboolean            gst_caps_is_strictly_equal          (const GstCaps *caps1,
                                                         const GstCaps *caps2);

Checks if the given caps are exactly the same set of caps.

gst_caps_is_always_compatible ()

gboolean            gst_caps_is_always_compatible       (const GstCaps *caps1,
                                                         const GstCaps *caps2);

A given GstCaps structure is always compatible with another if every media format that is in the first is also contained in the second. That is, caps1 is a subset of caps2.

gst_caps_is_subset ()

gboolean            gst_caps_is_subset                  (const GstCaps *subset,
                                                         const GstCaps *superset);

Checks if all caps represented by subset are also represented by superset.

gst_caps_is_subset_structure ()

gboolean            gst_caps_is_subset_structure        (const GstCaps *caps,
                                                         const GstStructure *structure);

Checks if structure is a subset of caps. See gst_caps_is_subset() for more information.

gst_caps_can_intersect ()

gboolean            gst_caps_can_intersect              (const GstCaps *caps1,
                                                         const GstCaps *caps2);

Tries intersecting caps1 and caps2 and reports whether the result would not be empty

gst_caps_intersect ()

GstCaps *           gst_caps_intersect                  (GstCaps *caps1,
                                                         GstCaps *caps2);

Creates a new GstCaps that contains all the formats that are common to both caps1 and caps2. Defaults to GST_CAPS_INTERSECT_ZIG_ZAG mode.

gst_caps_intersect_full ()

GstCaps *           gst_caps_intersect_full             (GstCaps *caps1,
                                                         GstCaps *caps2,
                                                         GstCapsIntersectMode mode);

Creates a new GstCaps that contains all the formats that are common to both caps1 and caps2, the order is defined by the GstCapsIntersectMode used.

gst_caps_normalize ()

GstCaps *           gst_caps_normalize                  (GstCaps *caps);

Returns a GstCaps that represents the same set of formats as caps, but contains no lists. Each list is expanded into separate GstStructures.

This function takes ownership of caps.

gst_caps_simplify ()

GstCaps *           gst_caps_simplify                   (GstCaps *caps);

Converts the given caps into a representation that represents the same set of formats, but in a simpler form. Component structures that are identical are merged. Component structures that have values that can be merged are also merged.

This method does not preserve the original order of caps.

gst_caps_replace ()

gboolean            gst_caps_replace                    (GstCaps **old_caps,
                                                         GstCaps *new_caps);

Modifies a pointer to a GstCaps to point to a different GstCaps. The modification is done atomically (so this is useful for ensuring thread safety in some cases), and the reference counts are updated appropriately (the old caps is unreffed, the new is reffed).

Either ncaps or the GstCaps pointed to by ocaps may be NULL.

gst_caps_take ()

gboolean            gst_caps_take                       (GstCaps **old_caps,
                                                         GstCaps *new_caps);

Modifies a pointer to a GstCaps to point to a different GstCaps. This function is similar to gst_caps_replace() except that it takes ownership of new_caps.

gst_caps_to_string ()

gchar *             gst_caps_to_string                  (const GstCaps *caps);

Converts caps to a string representation. This string representation can be converted back to a GstCaps by gst_caps_from_string().

For debugging purposes its easier to do something like this:

1

GST_LOG ("caps are %" GST_PTR_FORMAT, caps);

This prints the caps in human readable form.

gst_caps_from_string ()

GstCaps *           gst_caps_from_string                (const gchar *string);

Converts caps from a string representation.

gst_caps_subtract ()

GstCaps *           gst_caps_subtract                   (GstCaps *minuend,
                                                         GstCaps *subtrahend);

Subtracts the subtrahend from the minuend.

gst_caps_make_writable()

#define         gst_caps_make_writable(caps)   GST_CAPS_CAST (gst_mini_object_make_writable (GST_MINI_OBJECT_CAST (caps)))

Returns a writable copy of caps.

If there is only one reference count on caps, the caller must be the owner, and so this function will return the caps object unchanged. If on the other hand there is more than one reference on the object, a new caps object will be returned. The caller's reference on caps will be removed, and instead the caller will own a reference to the returned object.

In short, this function unrefs the caps in the argument and refs the caps that it returns. Don't access the argument after calling this function. See also: gst_caps_ref().

gst_caps_truncate ()

GstCaps *           gst_caps_truncate                   (GstCaps *caps);

Discard all but the first structure from caps. Useful when fixating.

gst_caps_fixate ()

GstCaps *           gst_caps_fixate                     (GstCaps *caps);

Modifies the given caps into a representation with only fixed values. First the caps will be truncated and then the first structure will be fixated with gst_structure_fixate().

gst_caps_ref ()

GstCaps *           gst_caps_ref                        (GstCaps *caps);

Add a reference to a GstCaps object.

From this point on, until the caller calls gst_caps_unref() or gst_caps_make_writable(), it is guaranteed that the caps object will not change. This means its structures won't change, etc. To use a GstCaps object, you must always have a refcount on it -- either the one made implicitly by e.g. gst_caps_new_simple(), or via taking one explicitly with this function.

gst_caps_unref ()

void                gst_caps_unref                      (GstCaps *caps);

Unref a GstCaps and and free all its structures and the structures' values when the refcount reaches 0.