GStreamer 0.8 Core Reference Manual |
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GstValue — GValue implementations specific to GStreamer
#include <gst/gst.h> #define GST_MAKE_FOURCC (a,b,c,d) #define GST_STR_FOURCC (f) #define GST_FOURCC_FORMAT #define GST_FOURCC_ARGS (fourcc) #define GST_VALUE_HOLDS_FOURCC (x) #define GST_VALUE_HOLDS_INT_RANGE (x) #define GST_VALUE_HOLDS_DOUBLE_RANGE (x) #define GST_VALUE_HOLDS_LIST (x) #define GST_VALUE_HOLDS_FIXED_LIST (x) #define GST_VALUE_HOLDS_CAPS (x) #define GST_VALUE_HOLDS_FRACTION (x) #define GST_VALUE_LESS_THAN #define GST_VALUE_EQUAL #define GST_VALUE_GREATER_THAN #define GST_VALUE_UNORDERED int (*GstValueCompareFunc) (const GValue *value1, const GValue *value2); char* (*GstValueSerializeFunc) (const GValue *value1); gboolean (*GstValueDeserializeFunc) (GValue *dest, const char *s); int (*GstValueUnionFunc) (GValue *dest, const GValue *value1, const GValue *value2); int (*GstValueIntersectFunc) (GValue *dest, const GValue *value1, const GValue *value2); int (*GstValueSubtractFunc) (GValue *dest, const GValue *minuend, const GValue *subtrahend); struct GstValueTable; gboolean gst_type_is_fixed (GType type); gboolean gst_value_is_fixed (const GValue *value); void gst_value_register (const GstValueTable *table); void gst_value_init_and_copy (GValue *dest, const GValue *src); gchar* gst_value_serialize (const GValue *value); gboolean gst_value_deserialize (GValue *dest, const gchar *src); void gst_value_list_append_value (GValue *value, const GValue *append_value); void gst_value_list_prepend_value (GValue *value, const GValue *prepend_value); void gst_value_list_concat (GValue *dest, const GValue *value1, const GValue *value2); guint gst_value_list_get_size (const GValue *value); G_CONST_RETURN GValue* gst_value_list_get_value (const GValue *value, guint index); void gst_value_set_fourcc (GValue *value, guint32 fourcc); guint32 gst_value_get_fourcc (const GValue *value); void gst_value_set_int_range (GValue *value, int start, int end); int gst_value_get_int_range_min (const GValue *value); int gst_value_get_int_range_max (const GValue *value); void gst_value_set_double_range (GValue *value, double start, double end); double gst_value_get_double_range_min (const GValue *value); double gst_value_get_double_range_max (const GValue *value); G_CONST_RETURN GstCaps* gst_value_get_caps (const GValue *value); void gst_value_set_caps (GValue *value, const GstCaps *caps); int gst_value_get_fraction_numerator (const GValue *value); int gst_value_get_fraction_denominator (const GValue *value); void gst_value_set_fraction (GValue *value, int numerator, int denominator); gboolean gst_value_fraction_multiply (GValue *product, const GValue *factor1, const GValue *factor2); int gst_value_compare (const GValue *value1, const GValue *value2); gboolean gst_value_can_compare (const GValue *value1, const GValue *value2); gboolean gst_value_union (GValue *dest, const GValue *value1, const GValue *value2); gboolean gst_value_can_union (const GValue *value1, const GValue *value2); void gst_value_register_union_func (GType type1, GType type2, GstValueUnionFunc func); gboolean gst_value_subtract (GValue *dest, const GValue *minuend, const GValue *subtrahend); gboolean gst_value_can_subtract (const GValue *minuend, const GValue *subtrahend); void gst_value_register_subtract_func (GType minuend_type, GType subtrahend_type, GstValueSubtractFunc func); gboolean gst_value_intersect (GValue *dest, const GValue *value1, const GValue *value2); gboolean gst_value_can_intersect (const GValue *value1, const GValue *value2); void gst_value_register_intersect_func (GType type1, GType type2, GstValueIntersectFunc func);
#define GST_MAKE_FOURCC(a,b,c,d) (guint32)((a)|(b)<<8|(c)<<16|(d)<<24)
will transform four characters into a host-endiannness guint32 fourcc:
guint32 fourcc = GST_MAKE_FOURCC ('M','J','P','G');
a : | the first component |
b : | the second component |
c : | the third component |
d : | the fourth component |
#define GST_STR_FOURCC(f) (guint32)(((f)[0])|((f)[1]<<8)|((f)[2]<<16)|((f)[3]<<24))
Creates a fourcc from an input string. The input string should consisnt of at least four characters (this is not checked for!).
guint32 fourcc = GST_STR_FOURCC("MJPG");
f : | a string with four characters |
#define GST_FOURCC_FORMAT "%c%c%c%c"
Can be used to properly output a fourcc (a guint32) value in a printf()-style text message.
printf ("fourcc: %" GST_FOURCC_FORMAT "\n", GST_FOURCC_ARGS (fcc));
#define GST_FOURCC_ARGS(fourcc)
Can be used to properly output a fourcc (a guint32) value in a printf()-style text message.
printf ("fourcc: %" GST_FOURCC_FORMAT "\n", GST_FOURCC_ARGS (fcc));
fourcc : | the fourcc value to print |
#define GST_VALUE_HOLDS_FOURCC(x) (G_VALUE_HOLDS(x, gst_type_fourcc))
Checks if the give GValue contains a FOURCC value.
x : | the GValue to check |
#define GST_VALUE_HOLDS_INT_RANGE(x) (G_VALUE_HOLDS(x, gst_type_int_range))
Checks if the give GValue contains a INT_RANGE value.
x : | the GValue to check |
#define GST_VALUE_HOLDS_DOUBLE_RANGE(x) (G_VALUE_HOLDS(x, gst_type_double_range))
Checks if the give GValue contains a DOUBLE_RANGE value.
x : | the GValue to check |
#define GST_VALUE_HOLDS_LIST(x) (G_VALUE_HOLDS(x, gst_type_list))
Checks if the give GValue contains a LIST value.
x : | the GValue to check |
#define GST_VALUE_HOLDS_FIXED_LIST(x) (G_VALUE_HOLDS(x, gst_type_fixed_list))
Checks if the give GValue contains a FIXED_LIST value.
x : | the GValue to check |
#define GST_VALUE_HOLDS_CAPS(x) (G_VALUE_HOLDS(x, GST_TYPE_CAPS))
Checks if the give GValue contains a CAPS value.
x : | the GValue to check |
#define GST_VALUE_HOLDS_FRACTION(x) (G_VALUE_HOLDS(x, gst_type_fraction))
Checks if the give GValue contains a FRACTION value.
x : | the GValue to check |
#define GST_VALUE_LESS_THAN (-1)
Indicates that the first value provided to a comparison function (gst_value_compare()) is lesser than the second one.
#define GST_VALUE_EQUAL 0
Indicates that the first value provided to a comparison function (gst_value_compare()) is equal to the second one.
#define GST_VALUE_GREATER_THAN 1
Indicates that the first value provided to a comparison function (gst_value_compare()) is greater than the second one.
#define GST_VALUE_UNORDERED 2
Indicates that the comparison function (gst_value_compare()) can not determine a order for the two provided values.
int (*GstValueCompareFunc) (const GValue *value1, const GValue *value2);
value1 : | |
value2 : | |
Returns : | one of GST_VALUE_LESS_THAN, GST_VALUE_EQUAL, GST_VALUE_GREATER_THAN or GST_VALUE_UNORDERED |
gboolean (*GstValueDeserializeFunc) (GValue *dest, const char *s);
dest : | |
s : | |
Returns : |
int (*GstValueUnionFunc) (GValue *dest, const GValue *value1, const GValue *value2);
dest : | |
value1 : | |
value2 : | |
Returns : |
int (*GstValueIntersectFunc) (GValue *dest, const GValue *value1, const GValue *value2);
Functions having this type calculate the intersection of value1 and value2. If the intersection is non-empty, the result is placed in dest and TRUE is returned. If the intersection is empty, dest is unmodified and FALSE is returned.
dest : | a uninitialized GValue that will hold the calculated intersection value |
value1 : | a value to intersect |
value2 : | another value to intersect |
Returns : | TRUE if the intersection is non-empty, FALSE otherwise |
int (*GstValueSubtractFunc) (GValue *dest, const GValue *minuend, const GValue *subtrahend);
dest : | |
minuend : | |
subtrahend : | |
Returns : |
struct GstValueTable { GType type; GstValueCompareFunc compare; GstValueSerializeFunc serialize; GstValueDeserializeFunc deserialize; };
GType type | GType that the functions operate on. |
GstValueCompareFunc compare | A function that compares two values of this type. |
GstValueSerializeFunc serialize | A function that transforms a value of this type to a string. Strings created by this function must be unique and should be human readable. |
GstValueDeserializeFunc deserialize | A function that transforms a string to a value of this type. This function must transform strings created by the serialize function back to the original value. This function may optionally transform other strings into values. |
gboolean gst_type_is_fixed (GType type);
Tests if the given GType, if available in a GstStructure (or any other container) will contain a "fixed" (which means: one possible value) or an "unfixed" (which means: multiple possible values, such as data lists or data ranges) value.
type : | the GType to check |
Returns : | true if the type is "fixed". |
gboolean gst_value_is_fixed (const GValue *value);
Tests if the given GValue, if available in a GstStructure (or any other container) contains a "fixed" (which means: one value) or an "unfixed" (which means: multiple possible values, such as data lists or data ranges) value.
value : | the GValue to check |
Returns : | true if the value is "fixed". |
void gst_value_register (const GstValueTable *table);
Registers functions to perform calculations on GValues of a given type.
table : | structure containing functions to register |
void gst_value_init_and_copy (GValue *dest, const GValue *src);
Initialises the target value to be of the same type as source and then copies the contents from source to target.
dest : | the target value |
src : | the source value |
gchar* gst_value_serialize (const GValue *value);
tries to transform the given value into a string representation that allows getting back this string later on using gst_value_deserialize().
value : | a GValue to serialize |
Returns : | the serialization for value or NULL if none exists |
gboolean gst_value_deserialize (GValue *dest, const gchar *src);
Tries to deserialize a string into the type specified by the given GValue. If the operation succeeds, TRUE is returned, FALSE otherwise.
dest : | GValue to fill with contents of deserialization |
src : | string to deserialize |
Returns : | TRUE on success |
void gst_value_list_append_value (GValue *value, const GValue *append_value);
Appends append_value to the GstValueList in value.
value : | a GstValueList to append a value to |
append_value : | the value to append |
void gst_value_list_prepend_value (GValue *value, const GValue *prepend_value);
Prepends prepend_value to the GstValueList in value.
value : | a GstValueList to prepend a value to |
prepend_value : | the value to prepend |
void gst_value_list_concat (GValue *dest, const GValue *value1, const GValue *value2);
Concatenates copies of value1 and value2 into a list. The value dest is initialized to the type GST_TYPE_LIST.
dest : | an uninitialized GValue to take the result |
value1 : | first value to put into the union |
value2 : | second value to put into the union |
guint gst_value_list_get_size (const GValue *value);
Gets the number of values contained in value.
value : | a GstValueList |
Returns : | the number of values |
G_CONST_RETURN GValue* gst_value_list_get_value (const GValue *value, guint index);
Gets the value that is a member of the list contained in value and has the index index.
value : | a GstValueList |
index : | index of value to get from the list |
Returns : | the value at the given index |
void gst_value_set_fourcc (GValue *value, guint32 fourcc);
Sets value to fourcc.
value : | a GValue initialized to GST_TYPE_FOURCC |
fourcc : | the fourcc to set |
guint32 gst_value_get_fourcc (const GValue *value);
Gets the fourcc contained in value.
value : | a GValue initialized to GST_TYPE_FOURCC |
Returns : | the fourcc contained in value. |
void gst_value_set_int_range (GValue *value, int start, int end);
Sets value to the range specified by start and end.
value : | a GValue initialized to GST_TYPE_INT_RANGE |
start : | the start of the range |
end : | the end of the range |
int gst_value_get_int_range_min (const GValue *value);
Gets the minimum of the range specified by value.
value : | a GValue initialized to GST_TYPE_INT_RANGE |
Returns : | the minimum of the range |
int gst_value_get_int_range_max (const GValue *value);
Gets the maximum of the range specified by value.
value : | a GValue initialized to GST_TYPE_INT_RANGE |
Returns : | the maxumum of the range |
void gst_value_set_double_range (GValue *value, double start, double end);
Sets value to the range specified by start and end.
value : | a GValue initialized to GST_TYPE_DOUBLE_RANGE |
start : | the start of the range |
end : | the end of the range |
double gst_value_get_double_range_min (const GValue *value);
Gets the minimum of the range specified by value.
value : | a GValue initialized to GST_TYPE_DOUBLE_RANGE |
Returns : | the minumum of the range |
double gst_value_get_double_range_max (const GValue *value);
Gets the maximum of the range specified by value.
value : | a GValue initialized to GST_TYPE_DOUBLE_RANGE |
Returns : | the maxumum of the range |
G_CONST_RETURN GstCaps* gst_value_get_caps (const GValue *value);
Gets the contents of value.
value : | a GValue initialized to GST_TYPE_CAPS |
Returns : | the contents of value |
void gst_value_set_caps (GValue *value, const GstCaps *caps);
Sets the contents of value to coorespond to caps. The actual GstCaps structure is copied before it is used.
value : | a GValue initialized to GST_TYPE_CAPS |
caps : | the caps to set the value to |
int gst_value_get_fraction_numerator (const GValue *value);
Gets the numerator of the fraction specified by value.
value : | a GValue initialized to GST_TYPE_FRACTION |
Returns : | the numerator of the fraction. |
int gst_value_get_fraction_denominator (const GValue *value);
Gets the denominator of the fraction specified by value.
value : | a GValue initialized to GST_TYPE_FRACTION |
Returns : | the denominator of the fraction. |
void gst_value_set_fraction (GValue *value, int numerator, int denominator);
Sets value to the fraction specified by numerator over denominator. The fraction gets reduced to the smallest numerator and denominator, and if necessary the sign is moved to the numerator.
value : | a GValue initialized to GST_TYPE_FRACTION |
numerator : | the numerator of the fraction |
denominator : | the denominator of the fraction |
gboolean gst_value_fraction_multiply (GValue *product, const GValue *factor1, const GValue *factor2);
Multiplies the two GValues containing a GstFraction and sets product to the product of the two fractions.
product : | a GValue initialized to GST_TYPE_FRACTION |
factor1 : | a GValue initialized to GST_TYPE_FRACTION |
factor2 : | a GValue initialized to GST_TYPE_FRACTION |
Returns : | FALSE in case of an error (like integer overflow), TRUE otherwise. |
int gst_value_compare (const GValue *value1, const GValue *value2);
Compares value1 and value2. If value1 and value2 cannot be compared, the function returns GST_VALUE_UNORDERED. Otherwise, if value1 is greater than value2, GST_VALUE_GREATER is returned. If value1 is less than value2, GST_VALUE_LESSER is returned. If the values are equal, GST_VALUE_EQUAL is returned.
value1 : | a value to compare |
value2 : | another value to compare |
Returns : | A GstValueCompareType value |
gboolean gst_value_can_compare (const GValue *value1, const GValue *value2);
Determines if value1 and value2 can be compared.
value1 : | a value to compare |
value2 : | another value to compare |
Returns : | TRUE if the values can be compared |
gboolean gst_value_union (GValue *dest, const GValue *value1, const GValue *value2);
Creates a GValue cooresponding to the union of value1 and value2.
dest : | the destination value |
value1 : | a value to union |
value2 : | another value to union |
Returns : | TRUE if the values could be unioned |
gboolean gst_value_can_union (const GValue *value1, const GValue *value2);
Determines if value1 and value2 can be non-trivially unioned. Any two values can be trivially unioned by adding both of them to a GstValueList. However, certain types have the possibility to be unioned in a simpler way. For example, an integer range and an integer can be unioned if the integer is a subset of the integer range. If there is the possibility that two values can be unioned, this function returns TRUE.
value1 : | a value to union |
value2 : | another value to union |
Returns : | TRUE if there is a function allowing the two values to be unioned. |
void gst_value_register_union_func (GType type1, GType type2, GstValueUnionFunc func);
Registers a union function that can create a union between GValues of the type type1 and type2.
type1 : | a type to union |
type2 : | another type to union |
func : | a function that implments creating a union between the two types |
gboolean gst_value_subtract (GValue *dest, const GValue *minuend, const GValue *subtrahend);
Subtracts subtrahend from minuend and stores the result in dest. Note that this means subtraction as in sets, not as in mathematics.
dest : | the destination value for the result if the subtraction is not empty |
minuend : | the value to subtract from |
subtrahend : | the value to subtract |
Returns : | TRUE if the subtraction is not empty |
gboolean gst_value_can_subtract (const GValue *minuend, const GValue *subtrahend);
Checks if it's possible to subtract subtrahend from minuend.
minuend : | the value to subtract from |
subtrahend : | the value to subtract |
Returns : | TRUE if a subtraction is possible |
void gst_value_register_subtract_func (GType minuend_type, GType subtrahend_type, GstValueSubtractFunc func);
Registers func as a function capable of subtracting the values of subtrahend_type from values of minuend_type.
minuend_type : | type of the minuend |
subtrahend_type : | type of the subtrahend |
func : | function to use |
gboolean gst_value_intersect (GValue *dest, const GValue *value1, const GValue *value2);
Calculates the intersection of two values. If the values have a non-empty intersection, the value representing the intersection is placed in dest. If the intersection is non-empty, dest is not modified.
dest : | a uninitialized GValue that will hold the calculated intersection value |
value1 : | a value to intersect |
value2 : | another value to intersect |
Returns : | TRUE if the intersection is non-empty |
gboolean gst_value_can_intersect (const GValue *value1, const GValue *value2);
Determines if intersecting two values will produce a valid result. Two values will produce a valid intersection if they have the same type, or if there is a method (registered by gst_value_register_intersection_func) to calculate the intersection.
value1 : | a value to intersect |
value2 : | another value to intersect |
Returns : | TRUE if the values can intersect |
void gst_value_register_intersect_func (GType type1, GType type2, GstValueIntersectFunc func);
type1 : | |
type2 : | |
func : |
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