GstCaps

GstCaps — Structure describing sets of media formats

Functions

#define GST_CAPS_REFCOUNT()
#define GST_CAPS_REFCOUNT_VALUE()
#define GST_CAPS_IS_SIMPLE()
#define GST_STATIC_CAPS()
#define GST_CAPS_FLAGS()
#define GST_CAPS_FLAG_IS_SET()
#define GST_CAPS_FLAG_SET()
#define GST_CAPS_FLAG_UNSET()
GstCaps * gst_caps_new_empty ()
GstCaps * gst_caps_new_empty_simple ()
GstCaps * gst_caps_new_any ()
GstCaps * gst_caps_new_simple ()
GstCaps * gst_caps_new_full ()
GstCaps * gst_caps_new_full_valist ()
#define gst_caps_is_writable()
GstCaps * gst_caps_copy ()
GstCaps * gst_caps_copy_nth ()
GstCaps * gst_static_caps_get ()
void gst_static_caps_cleanup ()
void gst_caps_append ()
GstCaps * gst_caps_merge ()
void gst_caps_append_structure ()
void gst_caps_append_structure_full ()
void gst_caps_remove_structure ()
GstStructure * gst_caps_steal_structure ()
GstCaps * gst_caps_merge_structure ()
GstCaps * gst_caps_merge_structure_full ()
guint gst_caps_get_size ()
GstStructure * gst_caps_get_structure ()
GstCapsFeatures * gst_caps_get_features ()
void gst_caps_set_features ()
void gst_caps_set_value ()
void gst_caps_set_simple ()
void gst_caps_set_simple_valist ()
gboolean gst_caps_is_any ()
gboolean gst_caps_is_empty ()
gboolean gst_caps_is_fixed ()
gboolean gst_caps_is_equal ()
gboolean gst_caps_is_equal_fixed ()
gboolean gst_caps_is_strictly_equal ()
gboolean gst_caps_is_always_compatible ()
gboolean gst_caps_is_subset ()
gboolean gst_caps_is_subset_structure ()
gboolean gst_caps_is_subset_structure_full ()
gboolean gst_caps_can_intersect ()
GstCaps * gst_caps_intersect ()
GstCaps * gst_caps_intersect_full ()
GstCaps * gst_caps_normalize ()
GstCaps * gst_caps_simplify ()
gboolean gst_caps_replace ()
gboolean gst_caps_take ()
gchar * gst_caps_to_string ()
GstCaps * gst_caps_from_string ()
GstCaps * gst_caps_subtract ()
#define gst_caps_make_writable()
GstCaps * gst_caps_truncate ()
GstCaps * gst_caps_fixate ()
GstCaps * gst_caps_ref ()
void gst_caps_unref ()

Types and Values

Object Hierarchy


Includes

#include <gst/gst.h>

Description

Caps (capabilities) are lightweight refcounted objects describing media types. They are composed of an array of GstStructure.

Caps are exposed on GstPadTemplate to describe all possible types a given pad can handle. They are also stored in the GstRegistry along with a description of the GstElement.

Caps are exposed on the element pads using the gst_pad_query_caps() pad function. This function describes the possible types that the pad can handle or produce at runtime.

A GstCaps can be constructed with the following code fragment:

Example 4. Creating caps

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GstCaps *caps;
caps = gst_caps_new_simple ("video/x-raw",
     "format", G_TYPE_STRING, "I420",
     "framerate", GST_TYPE_FRACTION, 25, 1,
     "pixel-aspect-ratio", GST_TYPE_FRACTION, 1, 1,
     "width", G_TYPE_INT, 320,
     "height", G_TYPE_INT, 240,
     NULL);

A GstCaps is fixed when it has no properties with ranges or lists. Use gst_caps_is_fixed() to test for fixed caps. Fixed caps can be used in a caps event to notify downstream elements of the current media type.

Various methods exist to work with the media types such as subtracting or intersecting.

Last reviewed on 2011-03-28 (0.11.3)

Functions

GST_CAPS_REFCOUNT()

#define GST_CAPS_REFCOUNT(caps)                 GST_MINI_OBJECT_REFCOUNT(caps)

Get access to the reference count field of the caps

Parameters

caps

a GstCaps

 

GST_CAPS_REFCOUNT_VALUE()

#define GST_CAPS_REFCOUNT_VALUE(caps)           GST_MINI_OBJECT_REFCOUNT_VALUE(caps)

Get the reference count value of the caps.

Parameters

caps

a GstCaps

 

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.

Parameters

caps

the GstCaps instance to check

 

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.

Parameters

string

the string describing the caps

 

GST_CAPS_FLAGS()

#define GST_CAPS_FLAGS(caps)                    GST_MINI_OBJECT_FLAGS(caps)

A flags word containing GstCapsFlags flags set on this caps.

Parameters

caps

a GstCaps.

 

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.

Parameters

caps

a GstCaps.

 

flag

the GstCapsFlags to check.

 

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.

Parameters

caps

a GstCaps.

 

flag

the GstCapsFlags to set.

 

GST_CAPS_FLAG_UNSET()

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

Clears a caps flag.

Parameters

caps

a GstCaps.

 

flag

the GstCapsFlags to clear.

 

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.

Returns

the new GstCaps.

[transfer full]


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.

Parameters

media_type

the media type of the structure

 

Returns

the new GstCaps.

[transfer full]


gst_caps_new_any ()

GstCaps *
gst_caps_new_any (void);

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

Returns

the new GstCaps.

[transfer full]


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.

Parameters

media_type

the media type of the structure

 

fieldname

first field to set

 

...

additional arguments

 

Returns

the new GstCaps.

[transfer full]


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.

Parameters

struct1

the first structure to add

 

...

additional structures to add

 

Returns

the new GstCaps.

[transfer full]


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.

Parameters

structure

the first structure to add

 

var_args

additional structures to add

 

Returns

the new GstCaps.

[transfer full]


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.

Parameters

caps

a GstCaps

 

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.

Parameters

caps

a GstCaps.

 

Returns

the new GstCaps


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 .

Parameters

caps

the GstCaps to copy

 

nth

the nth structure to copy

 

Returns

the new GstCaps.

[transfer full]


gst_static_caps_get ()

GstCaps *
gst_static_caps_get (GstStaticCaps *static_caps);

Converts a GstStaticCaps to a GstCaps.

Parameters

static_caps

the GstStaticCaps to convert

 

Returns

a pointer to the GstCaps. Unref after usage. Since the core holds an additional ref to the returned caps, use gst_caps_make_writable() on the returned caps to modify it.

[transfer full]


gst_static_caps_cleanup ()

void
gst_static_caps_cleanup (GstStaticCaps *static_caps);

Clean up the cached caps contained in static_caps .

Parameters

static_caps

the GstStaticCaps to clean

 

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.

Parameters

caps1

the GstCaps that will be appended to

 

caps2

the GstCaps to append.

[transfer full]

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.

Parameters

caps1

the GstCaps that will take the new entries.

[transfer full]

caps2

the GstCaps to merge in.

[transfer full]

Returns

the merged caps.

[transfer full]


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 .

Parameters

caps

the GstCaps that will be appended to

 

structure

the GstStructure to append.

[transfer full]

gst_caps_append_structure_full ()

void
gst_caps_append_structure_full (GstCaps *caps,
                                GstStructure *structure,
                                GstCapsFeatures *features);

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

Parameters

caps

the GstCaps that will be appended to

 

structure

the GstStructure to append.

[transfer full]

features

the GstCapsFeatures to append.

[transfer full][allow-none]

Since 1.2


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 .

Parameters

caps

the GstCaps to remove from

 

idx

Index of the structure to remove

 

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.

Parameters

caps

the GstCaps to retrieve from

 

index

Index of the structure to retrieve

 

Returns

a pointer to the GstStructure corresponding to index .

[transfer full]


gst_caps_merge_structure ()

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

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

Parameters

caps

the GstCaps to merge into.

[transfer full]

structure

the GstStructure to merge.

[transfer full]

Returns

the merged caps.

[transfer full]


gst_caps_merge_structure_full ()

GstCaps *
gst_caps_merge_structure_full (GstCaps *caps,
                               GstStructure *structure,
                               GstCapsFeatures *features);

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

Parameters

caps

the GstCaps to merge into.

[transfer full]

structure

the GstStructure to merge.

[transfer full]

features

the GstCapsFeatures to merge.

[transfer full][allow-none]

Returns

the merged caps.

[transfer full]

Since 1.2


gst_caps_get_size ()

guint
gst_caps_get_size (const GstCaps *caps);

Gets the number of structures contained in caps .

Parameters

caps

a GstCaps

 

Returns

the number of structures that caps contains


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.

Parameters

caps

a GstCaps

 

index

the index of the structure

 

Returns

a pointer to the GstStructure corresponding to index .

[transfer none]


gst_caps_get_features ()

GstCapsFeatures *
gst_caps_get_features (const GstCaps *caps,
                       guint index);

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

WARNING: This function takes a const GstCaps *, but returns a non-const GstCapsFeatures *. 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 features returned in the usual way, e.g. with functions like gst_caps_features_add().

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

Parameters

caps

a GstCaps

 

index

the index of the structure

 

Returns

a pointer to the GstCapsFeatures corresponding to index .

[transfer none]

Since 1.2


gst_caps_set_features ()

void
gst_caps_set_features (GstCaps *caps,
                       guint index,
                       GstCapsFeatures *features);

Sets the GstCapsFeatures features for the structure at index .

Parameters

caps

a GstCaps

 

index

the index of the structure

 

features

the GstFeatures to set.

[allow-none][transfer full]

Since 1.2


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 .

Parameters

caps

a writable caps

 

field

name of the field to set

 

value

value to set the field to

 

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.

Parameters

caps

the GstCaps to set

 

field

first field to set

 

...

additional parameters

 

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.

Parameters

caps

the GstCaps to set

 

field

first field to set

 

varargs

additional parameters

 

gst_caps_is_any ()

gboolean
gst_caps_is_any (const GstCaps *caps);

Determines if caps represents any media format.

Parameters

caps

the GstCaps to test

 

Returns

TRUE if caps represents any format.


gst_caps_is_empty ()

gboolean
gst_caps_is_empty (const GstCaps *caps);

Determines if caps represents no media formats.

Parameters

caps

the GstCaps to test

 

Returns

TRUE if caps represents no 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.

Parameters

caps

the GstCaps to test

 

Returns

TRUE if caps is fixed


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.

Parameters

caps1

a GstCaps

 

caps2

another GstCaps

 

Returns

TRUE if both caps are equal.


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.

Parameters

caps1

the GstCaps to test

 

caps2

the GstCaps to test

 

Returns

TRUE if the arguments represent the same format


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.

Parameters

caps1

a GstCaps

 

caps2

another GstCaps

 

Returns

TRUE if both caps are strictly equal.


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 .

Parameters

caps1

the GstCaps to test

 

caps2

the GstCaps to test

 

Returns

TRUE if 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 .

Parameters

subset

a GstCaps

 

superset

a potentially greater GstCaps

 

Returns

TRUE if subset is a subset of 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.

Parameters

caps

a GstCaps

 

structure

a potential GstStructure subset of caps

 

Returns

TRUE if structure is a subset of caps


gst_caps_is_subset_structure_full ()

gboolean
gst_caps_is_subset_structure_full (const GstCaps *caps,
                                   const GstStructure *structure,
                                   const GstCapsFeatures *features);

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

Parameters

caps

a GstCaps

 

structure

a potential GstStructure subset of caps

 

features

a GstCapsFeatures for structure .

[allow-none]

Returns

TRUE if structure is a subset of caps

Since 1.2


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

Parameters

caps1

a GstCaps to intersect

 

caps2

a GstCaps to intersect

 

Returns

TRUE if intersection would be not 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.

Parameters

caps1

a GstCaps to intersect

 

caps2

a GstCaps to intersect

 

Returns

the new GstCaps


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.

Parameters

caps1

a GstCaps to intersect

 

caps2

a GstCaps to intersect

 

mode

The intersection algorithm/mode to use

 

Returns

the new GstCaps


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 .

Parameters

caps

a GstCaps to normalize.

[transfer full]

Returns

the normalized GstCaps.

[transfer full]


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 .

Parameters

caps

a GstCaps to simplify.

[transfer full]

Returns

The simplified 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.

Parameters

old_caps

pointer to a pointer to a GstCaps to be replaced.

[inout][transfer full]

new_caps

pointer to a GstCaps that will replace the caps pointed to by ocaps .

[transfer none][allow-none]

Returns

TRUE if new_caps was different from old_caps


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 .

Parameters

old_caps

pointer to a pointer to a GstCaps to be replaced.

[inout][transfer full]

new_caps

pointer to a GstCaps that will replace the caps pointed to by ocaps .

[transfer full][allow-none]

Returns

TRUE if new_caps was different from old_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.

Parameters

caps

a GstCaps

 

Returns

a newly allocated string representing caps .

[transfer full]


gst_caps_from_string ()

GstCaps *
gst_caps_from_string (const gchar *string);

Converts caps from a string representation.

Parameters

string

a string to convert to GstCaps

 

Returns

a newly allocated GstCaps.

[transfer full]


gst_caps_subtract ()

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

Subtracts the subtrahend from the minuend .

This function does not work reliably if optional properties for caps are included on one caps and omitted on the other.

Parameters

minuend

GstCaps to subtract from

 

subtrahend

GstCaps to subtract

 

Returns

the resulting caps


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().

Parameters

caps

a GstCaps.

[transfer full]

Returns

a writable caps which may or may not be the same as caps .

[transfer full]


gst_caps_truncate ()

GstCaps *
gst_caps_truncate (GstCaps *caps);

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

Parameters

caps

the GstCaps to truncate.

[transfer full]

Returns

truncated caps.

[transfer full]


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().

Parameters

caps

a GstCaps to fixate.

[transfer full]

Returns

the fixated caps.

[transfer full]


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.

Parameters

caps

the GstCaps to reference

 

Returns

the same GstCaps object.


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.

Parameters

caps

a GstCaps.

 

Types and Values

struct GstCaps

struct GstCaps {
  GstMiniObject mini_object;
};

Object describing media types.

Members

GstMiniObject mini_object;

the parent type

 

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.

Members

GstCaps *caps;

the cached GstCaps

 

const char *string;

a string describing a caps

 

enum 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.

Members

GST_CAPS_INTERSECT_ZIG_ZAG

Zig-zags over both caps.

 

GST_CAPS_INTERSECT_FIRST

Keeps the first caps order.

 

enum GstCapsFlags

Extra flags for a caps.

Members

GST_CAPS_FLAG_ANY

Caps has no specific content, but can contain anything.

 

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_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.

See Also

GstStructure, GstMiniObject