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GStreamer 0.9 Core Reference Manual | ![]() |
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GstCapsGstCaps — Structure describing sets of media formats |
#include <gst/gst.h> GstCaps; GstStaticCaps; #define GST_CAPS_FLAGS_ANY #define GST_CAPS_ANY #define GST_CAPS_NONE #define GST_CAPS_REFCOUNT (caps) #define GST_CAPS_REFCOUNT_VALUE (caps) #define GST_STATIC_CAPS_ANY #define GST_STATIC_CAPS_NONE #define GST_CAPS_IS_SIMPLE (caps) #define GST_DEBUG_CAPS (string, caps) #define GST_STATIC_CAPS (string) GstCaps* gst_caps_new_empty (void); GstCaps* gst_caps_new_any (void); GstCaps* gst_caps_new_simple (const char *media_type, const char *fieldname, ...); GstCaps* gst_caps_new_full (GstStructure *struct1, ...); GstCaps* gst_caps_new_full_valist (GstStructure *structure, va_list var_args); GstCaps* gst_caps_copy (const GstCaps *caps); GstCaps* gst_caps_copy_nth (const GstCaps *caps, gint nth); GstCaps* gst_static_caps_get (GstStaticCaps *static_caps); void gst_caps_append (GstCaps *caps1, GstCaps *caps2); void gst_caps_append_structure (GstCaps *caps, GstStructure *structure); int gst_caps_get_size (const GstCaps *caps); GstStructure* gst_caps_get_structure (const GstCaps *caps, int index); void gst_caps_set_simple (GstCaps *caps, char *field, ...); void gst_caps_set_simple_valist (GstCaps *caps, char *field, va_list varargs); gboolean gst_caps_is_any (const GstCaps *caps); gboolean gst_caps_is_empty (const GstCaps *caps); gboolean gst_caps_is_fixed (const GstCaps *caps); gboolean gst_caps_is_equal (const GstCaps *caps1, const GstCaps *caps2); gboolean gst_caps_is_equal_fixed (const GstCaps *caps1, const GstCaps *caps2); gboolean gst_caps_is_always_compatible (const GstCaps *caps1, const GstCaps *caps2); gboolean gst_caps_is_subset (const GstCaps *subset, const GstCaps *superset); GstCaps* gst_caps_intersect (const GstCaps *caps1, const GstCaps *caps2); GstCaps* gst_caps_union (const GstCaps *caps1, const GstCaps *caps2); GstCaps* gst_caps_normalize (const GstCaps *caps); gboolean gst_caps_do_simplify (GstCaps *caps); xmlNodePtr gst_caps_save_thyself (const GstCaps *caps, xmlNodePtr parent); GstCaps* gst_caps_load_thyself (xmlNodePtr parent); void gst_caps_replace (GstCaps **caps, GstCaps *newcaps); gchar* gst_caps_to_string (const GstCaps *caps); GstCaps* gst_caps_from_string (const gchar *string); GstCaps* gst_caps_subtract (const GstCaps *minuend, const GstCaps *subtrahend); GstCaps* gst_caps_make_writable (GstCaps *caps); GstCaps* gst_caps_ref (GstCaps *caps); gboolean gst_caps_structure_fixate_field_boolean (GstStructure *structure, const char *field_name, gboolean target); void gst_caps_truncate (GstCaps *caps); void gst_caps_unref (GstCaps *caps);
typedef struct { GType type; /* refcounting */ gint refcount; guint16 flags; GPtrArray *structs; } GstCaps;
#define GST_CAPS_FLAGS_ANY (1 << 0)
Flags that this caps has no specific content, but can contain anything.
#define GST_CAPS_ANY gst_caps_new_any()
Means that the element/pad can output 'anything'. Useful for elements that output unknown media, such as filesrc.
#define GST_CAPS_NONE gst_caps_new_empty()
The opposite of GST_CAPS_ANY
: it means that the pad/element outputs an
undefined media type that can not be detected.
#define GST_CAPS_REFCOUNT_VALUE(caps) (g_atomic_int_get (&(GST_CAPS(caps))->refcount))
caps : |
#define GST_STATIC_CAPS_ANY GST_STATIC_CAPS("ANY")
Creates a static caps that matches anything. This can be used in pad templates.
#define GST_STATIC_CAPS_NONE GST_STATIC_CAPS("NONE")
Creates a static caps that matches nothing. This can be used in pad templates.
#define GST_CAPS_IS_SIMPLE(caps) (gst_caps_get_size(caps) == 1)
Convinience macro that checks if the number of structures in the gives caps is exactly one.
caps : |
the GstCaps instance to check |
#define GST_DEBUG_CAPS(string, caps)
GST_DEBUG_CAPS
is deprecated and should not be used in newly-written code. do not use anymore
Convinience macro for prining out the contents of caps with GST_DEBUG()
.
string : |
a string the should be prepend to the caps data. |
caps : |
the GstCaps instance to print |
#define GST_STATIC_CAPS(string)
Creates a static caps from an input string. This can be used in pad templates.
string : |
GstCaps* gst_caps_new_empty (void);
Creates a new GstCaps that is empty. That is, the returned GstCaps contains no media formats.
Returns : | the new GstCaps |
GstCaps* gst_caps_new_any (void);
Creates a new GstCaps that indicates that it is compatible with any media format.
Returns : | the new GstCaps |
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()
.
media_type : |
the media type of the structure |
fieldname : |
first field to set |
... : |
additional arguments |
Returns : | the new GstCaps |
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.
struct1 : |
the first structure to add |
... : |
additional structures to add |
Returns : | the new GstCaps |
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.
structure : |
the first structure to add |
var_args : |
additional structures to add |
Returns : | the new GstCaps |
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.
GstCaps* gst_caps_copy_nth (const GstCaps *caps, gint nth);
Creates a new GstCaps
and appends a copy of the nth structure
contained in caps
.
caps : |
the GstCaps to copy
|
nth : |
the nth structure to copy |
Returns : | the new GstCaps
|
GstCaps* gst_static_caps_get (GstStaticCaps *static_caps);
Converts a GstStaticCaps to a GstCaps.
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.
|
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.
void gst_caps_append_structure (GstCaps *caps, GstStructure *structure);
Appends structure
to caps
. The structure is not copied; caps
becomes the owner of structure
.
caps : |
the GstCaps that will be appended to |
structure : |
the GstStructure to append |
int gst_caps_get_size (const GstCaps *caps);
Gets the number of structures contained in caps
.
caps : |
a GstCaps |
Returns : | the number of structures that caps contains
|
GstStructure* gst_caps_get_structure (const GstCaps *caps, int 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.
caps : |
a GstCaps |
index : |
the index of the structure |
Returns : | a pointer to the GstStructure corresponding to index
|
void gst_caps_set_simple (GstCaps *caps, char *field, ...);
Sets fields in a simple GstCaps. A simple GstCaps is one that
only has one structure. The arguments must be passed in the same
manner as @gst_structure_set()
, and be NULL-terminated.
caps : |
the GstCaps to set
|
field : |
first field to set |
... : |
additional parameters |
void gst_caps_set_simple_valist (GstCaps *caps, char *field, va_list varargs);
Sets fields in a simple GstCaps. A simple GstCaps is one that
only has one structure. The arguments must be passed in the same
manner as @gst_structure_set()
, and be NULL-terminated.
caps : |
the GstCaps to copy
|
field : |
first field to set |
varargs : |
additional parameters |
gboolean gst_caps_is_any (const GstCaps *caps);
Determines if caps
represents any media format.
caps : |
the GstCaps to test
|
Returns : | TRUE if caps represents any format.
|
gboolean gst_caps_is_empty (const GstCaps *caps);
Determines if caps
represents no media formats.
caps : |
the GstCaps to test
|
Returns : | TRUE if caps represents no formats.
|
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.
caps : |
the GstCaps to test
|
Returns : | TRUE if caps is fixed
|
gboolean gst_caps_is_equal (const GstCaps *caps1, const GstCaps *caps2);
Checks if the given caps represent the same set of caps.
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.
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
.
gboolean gst_caps_is_subset (const GstCaps *subset, const GstCaps *superset);
Checks if all caps represented by subset
are also represented by superset
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
.
GstCaps* gst_caps_union (const GstCaps *caps1, const GstCaps *caps2);
Creates a new GstCaps that contains all the formats that are in
either caps1
and 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
.
gboolean gst_caps_do_simplify (GstCaps *caps);
Modifies the given caps
inplace 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.
caps : |
a GstCaps to simplify |
Returns : | TRUE, if the caps could be simplified |
xmlNodePtr gst_caps_save_thyself (const GstCaps *caps, xmlNodePtr parent);
Serializes a GstCaps to XML and adds it as a child node of parent
.
caps : |
a GstCaps structure |
parent : |
a XML parent node |
Returns : | a XML node pointer |
GstCaps* gst_caps_load_thyself (xmlNodePtr parent);
Creates a GstCaps from its XML serialization.
parent : |
a XML node |
Returns : | a new GstCaps structure |
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
.
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.
caps : |
a GstCaps |
Returns : | a newly allocated string representing caps .
|
GstCaps* gst_caps_from_string (const gchar *string);
Converts caps
from a string representation.
GstCaps* gst_caps_subtract (const GstCaps *minuend, const GstCaps *subtrahend);
Subtracts the subtrahend
from the minuend
.
GstCaps* gst_caps_make_writable (GstCaps *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()
.
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 gst_caps_new()
, or via taking one explicitly with this
function.
gboolean gst_caps_structure_fixate_field_boolean (GstStructure *structure, const char *field_name, gboolean target);
Fixates a GstStructure by changing the given field_name
field to the given
target
boolean if that field is not fixed yet.
structure : |
a GstStructure |
field_name : |
a field in structure
|
target : |
the target value of the fixation |
Returns : | TRUE if the structure could be fixated |
void gst_caps_truncate (GstCaps *caps);
Destructively discard all but the first structure from caps
. Useful when
fixating. caps
must be writable.
caps : |
the GstCaps to truncate
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