Gjsify LogoGjsify Logo

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:

  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 fields 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 until 1.20 the #GstCaps / #GstStructure serialization into string had limited support for nested #GstCaps / #GstStructure fields. It could only support one level of nesting. Using more levels would lead to unexpected behavior when using serialization features, such as gst_caps_to_string() or gst_value_serialize() and their counterparts.

record

Hierarchy

  • Caps

Index

Constructors

Properties

miniObject: Gst.MiniObject

the parent type

field
name: string

Methods

  • 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

    • caps2: Gst.Caps

      the #GstCaps to append

    Returns void

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

    Parameters

    Returns void

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

    Parameters

    Returns void

  • canIntersect(caps2: Gst.Caps): boolean
  • Tries intersecting caps1 and caps2 and reports whether the result would not be empty

    Parameters

    • caps2: Gst.Caps

      a #GstCaps to intersect

    Returns boolean

  • 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().

    Returns Gst.Caps

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

    Parameters

    • nth: number

      the nth structure to copy

    Returns Gst.Caps

  • Calls the provided function once for each structure and caps feature in the #GstCaps. In contrast to gst_caps_foreach(), the function may modify the structure and features. In contrast to gst_caps_filter_and_map_in_place(), the structure and features are removed from the caps if %FALSE is returned from the function. The caps must be mutable.

    Parameters

    Returns void

  • 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().

    This function takes ownership of caps and will call gst_caps_make_writable() on it so you must not use caps afterwards unless you keep an additional reference to it with gst_caps_ref().

    Note that it is not guaranteed that the returned caps have exactly one structure. If caps are empty caps then the returned caps will be the empty too and contain no structure at all.

    Calling this function with ANY caps is not allowed.

    Returns Gst.Caps

  • Calls the provided function once for each structure and caps feature in the #GstCaps. The function must not modify the fields. Also see gst_caps_map_in_place() and gst_caps_filter_and_map_in_place().

    Parameters

    Returns boolean

  • Finds the features in caps at 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 features 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().

    Parameters

    • index: number

      the index of the structure

    Returns CapsFeatures

  • getSize(): number
  • Gets the number of structures contained in caps.

    Returns number

  • Finds the structure in caps at 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().

    Parameters

    • index: number

      the index of the structure

    Returns Gst.Structure

  • 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

    • caps2: Gst.Caps

      a #GstCaps to intersect

    Returns Gst.Caps

  • 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

    Returns Gst.Caps

  • isAlwaysCompatible(caps2: Gst.Caps): boolean
  • 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

    • caps2: Gst.Caps

      the #GstCaps to test

    Returns boolean

  • isAny(): boolean
  • Determines if caps represents any media format.

    Returns boolean

  • isEmpty(): boolean
  • Determines if caps represents no media formats.

    Returns boolean

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

    Parameters

    Returns boolean

  • isEqualFixed(caps2: Gst.Caps): boolean
  • Tests if two #GstCaps are equal. This function only works on fixed #GstCaps.

    Parameters

    • caps2: Gst.Caps

      the #GstCaps to test

    Returns boolean

  • isFixed(): boolean
  • 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.

    Returns boolean

  • isStrictlyEqual(caps2: Gst.Caps): boolean
  • Checks if the given caps are exactly the same set of caps.

    Parameters

    Returns boolean

  • isSubset(superset: Gst.Caps): boolean
  • Checks if all caps represented by subset are also represented by superset.

    Parameters

    • superset: Gst.Caps

      a potentially greater #GstCaps

    Returns boolean

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

    Parameters

    • structure: Gst.Structure

      a potential #GstStructure subset of caps

    Returns boolean

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

    Parameters

    • structure: Gst.Structure

      a potential #GstStructure subset of caps

    • features: CapsFeatures

      a #GstCapsFeatures for structure

    Returns boolean

  • Calls the provided function once for each structure and caps feature in the #GstCaps. In contrast to gst_caps_foreach(), the function may modify but not delete the structures and features. The caps must be mutable.

    Parameters

    Returns boolean

  • 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

    • caps2: Gst.Caps

      the #GstCaps to merge in

    Returns Gst.Caps

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

    This function takes ownership of caps and will call gst_caps_make_writable() on it so you must not use caps afterwards unless you keep an additional reference to it with gst_caps_ref().

    Returns Gst.Caps

  • removeStructure(idx: number): void
  • Removes the structure with the given index from the list of structures contained in caps.

    Parameters

    • idx: number

      Index of the structure to remove

    Returns void

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

    This prints the caps in human readable form.

    This version of the caps serialization function introduces support for nested structures and caps but the resulting strings won't be parsable with GStreamer prior to 1.20 unless #GST_SERIALIZE_FLAG_BACKWARD_COMPAT is passed as flag.

    Parameters

    Returns string

  • Sets the features for the structure at index.

    Parameters

    • index: number

      the index of the structure

    • features: CapsFeatures

      the #GstCapsFeatures to set

    Returns void

  • Sets the features for all the structures of caps.

    Parameters

    Returns void

  • setValue(field: string, value: any): void
  • 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

    • field: string

      name of the field to set

    • value: any

      value to set the field to

    Returns void

  • 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 function takes ownership of caps and will call gst_caps_make_writable() on it if necessary, so you must not use caps afterwards unless you keep an additional reference to it with gst_caps_ref().

    This method does not preserve the original order of caps.

    Returns Gst.Caps

  • 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

    • index: number

      Index of the structure to retrieve

    Returns Gst.Structure

  • 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

    • subtrahend: Gst.Caps

      #GstCaps to subtract

    Returns Gst.Caps

  • toString(): string
  • 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:

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

    This prints the caps in human readable form.

    The implementation of serialization up to 1.20 would lead to unexpected results when there were nested #GstCaps / #GstStructure deeper than one level.

    Returns string

  • Discards all but the first structure from caps. Useful when fixating.

    This function takes ownership of caps and will call gst_caps_make_writable() on it if necessary, so you must not use caps afterwards unless you keep an additional reference to it with gst_caps_ref().

    Note that it is not guaranteed that the returned caps have exactly one structure. If caps is any or empty caps then the returned caps will be the same and contain no structure at all.

    Returns Gst.Caps

  • fromString(string: string): Gst.Caps
  • Converts caps from a string representation.

    The implementation of serialization up to 1.20 would lead to unexpected results when there were nested #GstCaps / #GstStructure deeper than one level.

    Parameters

    • string: string

      a string to convert to #GstCaps

    Returns Gst.Caps

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

    Returns Gst.Caps

  • Creates a new #GstCaps that is empty. That is, the returned #GstCaps contains no media formats. The #GstCaps is guaranteed to be writable.

    Returns Gst.Caps

  • newEmptySimple(mediaType: string): Gst.Caps
  • Creates a new #GstCaps that contains one #GstStructure with name media_type.

    Parameters

    • mediaType: string

      the media type of the structure

    Returns Gst.Caps

Legend

  • Module
  • Object literal
  • Variable
  • Function
  • Function with type parameter
  • Index signature
  • Type alias
  • Type alias with type parameter
  • Enumeration
  • Enumeration member
  • Property
  • Method
  • Interface
  • Interface with type parameter
  • Constructor
  • Property
  • Method
  • Index signature
  • Class
  • Class with type parameter
  • Constructor
  • Property
  • Method
  • Accessor
  • Index signature
  • Inherited constructor
  • Inherited property
  • Inherited method
  • Inherited accessor
  • Protected property
  • Protected method
  • Protected accessor
  • Private property
  • Private method
  • Private accessor
  • Static property
  • Static method