GStreamer 1.0 Core Reference Manual: GstCaps

## 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

struct | GstCaps
struct | GstStaticCaps
enum | GstCapsIntersectMode
enum | GstCapsFlags
#define | GST_CAPS_ANY
#define | GST_CAPS_NONE
#define | GST_STATIC_CAPS_ANY
#define | GST_STATIC_CAPS_NONE

## Object Hierarchy

        GBoxed
        ╰── GstCaps

## 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:

    1
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    GstCaps *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.

Be aware that the current GstCaps / GstStructure serialization into string has limited support for nested GstCaps / GstStructure fields. It can only support one level of nesting. Using more levels will lead to unexpected behavior when using serialization features, such as `gst_caps_to_string()` or `gst_value_serialize()` and their counterparts.

## 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 structure 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 GstCapsFeatures 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 `new_caps` or the GstCaps pointed to by `old_caps` may be `NULL`.

#### Parameters

old_caps | pointer to a pointer to a GstCaps to be replaced. | [inout][transfer full][nullable]
new_caps | pointer to a GstCaps that will replace the caps pointed to by `old_caps` . | [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 `old_caps` . | [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.

The current implementation of serialization will lead to unexpected results when there are nested GstCaps / GstStructure deeper than one level.

#### 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.

The current implementation of serialization will lead to unexpected results when there are nested GstCaps / GstStructure deeper than one level.

#### 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