gstreamer/docs/gst/tmpl/gstpad.sgml

<!-- ##### SECTION Title ##### -->
GstPad

<!-- ##### SECTION Short_Description ##### -->
The link between Elements

<!-- ##### SECTION Long_Description ##### -->
<para>
A #GstElement is linked to other elements via "pads", which are extremely 
light-weight generic link points. 
After two pads are retrieved from an element with gst_element_get_pad(), 
the pads can be link with gst_pad_link(). (For quick links,
you can also use gst_element_link(), which will make the obvious
link for you if it's straightforward.)
</para>
<para>
Pads are typically created from a #GstPadTemplate with 
gst_pad_new_from_template().
</para>
<para>
Pads have #GstCaps attached to it to describe the media type they
are capable of dealing with. 
gst_pad_get_caps() and gst_pad_try_set_caps() are used to
manipulate the caps of the pads. 
Pads created from a pad template cannot set capabilities that are 
incompatible with the pad template capabilities.
</para>
<para>
Pads without pad templates can be created with gst_pad_new(),
which takes a direction and a name as an argument.  If the name is NULL,
then a guaranteed unique name will be assigned to it.
</para>
<para>
gst_pad_get_parent() will retrieve the #GstElement that owns the pad.
</para>
<para>
A #GstElement creating a pad will typically use the various 
gst_pad_set_*_function() calls to register callbacks for various events 
on the pads.
</para>
<para>
GstElements will use gst_pad_push() and gst_pad_pull() to push out 
or pull in a buffer. 
gst_pad_select() and gst_pad_selectv() are used by plugins to wait for the
first incoming buffer or event on any of the given set of pads.
</para>
<para>
To send a #GstEvent on a pad, use gst_pad_send_event().
</para>

<para>
Last reviewed on December 13th, 2002 (0.5.0.1)
</para>

<!-- ##### SECTION See_Also ##### -->
<para>
#GstPadTemplate, #GstElement, #GstEvent
</para>

<!-- ##### MACRO GST_PAD_NAME ##### -->
<para>
Gets the name of the pad.
</para>

@pad: a #GstPad to get the name of.
@Returns: the pad's name.


<!-- ##### MACRO GST_PAD_ELEMENT_PRIVATE ##### -->
<para>
Gets the private data set by the element that owns the pad.
</para>

@pad: a #GstPad to get the private data of.
#Returns: a gpointer to the private data.


<!-- ##### MACRO GST_PAD_PARENT ##### -->
<para>
Gets the parent element of this pad.
</para>

@pad: a #GstPad to get the parent of.
@Returns: the parent #GstElement of this pad.


<!-- ##### MACRO GST_PAD_PAD_TEMPLATE ##### -->
<para>
Gets the pad template that was used to create this pad.
</para>

@pad: a #GstPad to get the pad template of.
#Returns: the #GstPadTemplate used to create the pad, or NULL if none was
used.


<!-- ##### MACRO GST_PAD_REALIZE ##### -->
<para>
Returns the real pad of this pad.
</para>

@pad: a #GstPad to realize.
@Returns: the actual #GstPad.


<!-- ##### MACRO GST_PAD_DIRECTION ##### -->
<para>
Gets the pad's direction.
</para>

@pad: a #GstPad to get the direction of.
@Returns: the #GstPadDirection of the pad.


<!-- ##### MACRO GST_PAD_CAPS ##### -->
<para>
Gets the capabilities of a pad.
</para>

@pad: a #GstPad to get the capabilities of.
@Returns: the #GstCaps of the pad.


<!-- ##### MACRO GST_PAD_PEER ##### -->
<para>
Gets the peer pad of this pad.  The peer pad is the pad on to which the parent
element is linked through this pad.
</para>

@pad: a #GstPad to get the peer pad of.
@Returns: the peer #GstPad.


<!-- ##### MACRO GST_PAD_CAN_PULL ##### -->
<para>
Checks if buffers can be pulled from this buffer.
</para>

@pad: a #GstPad to check on if a buffer can be pulled from it.


<!-- ##### MACRO GST_PAD_IS_SINK ##### -->
<para>
Checks if the pad is a sink pad.
</para>

@pad: a #GstPad to check.


<!-- ##### MACRO GST_PAD_IS_SRC ##### -->
<para>
Checks if the pad is a source pad.
</para>

@pad: a #GstPad to check.


<!-- ##### MACRO GST_PAD_IS_LINKED ##### -->
<para>
Checks if the pad is linked.
</para>

@pad: a #GstPad to check.


<!-- ##### MACRO GST_PAD_IS_ACTIVE ##### -->
<para>
Checks if the pad is active.
</para>

@pad: a #GstPad to check


<!-- ##### MACRO GST_PAD_IS_USABLE ##### -->
<para>
Checks if a pad is usable. A usable pad is both linked and active.
</para>

@pad: a #GstPad to check


<!-- ##### STRUCT GstPad ##### -->
<para>
The GstPad object
</para>


<!-- ##### USER_FUNCTION GstPadChainFunction ##### -->
<para>
A function that will be called when chaining buffers.
</para>

@pad: the #GstPad that performed the chain.
@data: 
<!-- # Unused Parameters # -->
@buf: the #GstBuffer that is chained.


<!-- ##### USER_FUNCTION GstPadGetFunction ##### -->
<para>
A function that will be called when pulling a buffer.
</para>

@pad: the #GstPad to get a buffer from.
@Returns: the #GstBuffer pulled.


<!-- ##### USER_FUNCTION GstPadGetCapsFunction ##### -->
<para>
Returns the capabilities of the specified pad. By default this function
will return the pad template capabilities, but can optionally be overridden.
</para>

@pad: the #GstPad to get the capabilities of.
@Returns: the #GstCaps of the pad.
<!-- # Unused Parameters # -->
@caps: the peer's #GstCaps, can be used to filter the capabilities.


<!-- ##### USER_FUNCTION GstPadEventFunction ##### -->
<para>
Function signature to handle an event for the pad.
</para>

@pad: the #GstPad to handle the event.
@event: the #GstEvent to handle.
@Returns: TRUE if the pad could handle the event.


<!-- ##### USER_FUNCTION GstPadLinkFunction ##### -->
<para>
Function signature to handle a new link on the pad.
</para>

@pad: the #GstPad that is linked.
@caps: the peer's #GstCaps.
@Returns: the result of the link with the specified caps.


<!-- ##### ENUM GstPadLinkReturn ##### -->
<para>
The result of a pad link.
</para>

@GST_PAD_LINK_REFUSED: the link was refused.
@GST_PAD_LINK_DELAYED: the link was delayed, probably because the
                       element needs more specific pad capabilitiess.
@GST_PAD_LINK_OK:      the link succeeded.
@GST_PAD_LINK_DONE:    the link succeeded, 
                       any more attempts are not needed.

<!-- ##### USER_FUNCTION GstPadConvertFunction ##### -->
<para>
The signature of a convert function. 
</para>

@pad: the #GstPad to perform the convert on.
@src_format: the source #GstFormat of the conversion.
@src_value: the source value of the conversion.
@dest_format: a pointer to the destination #GstFormat.
@dest_value: a pointer to the destination value.
@Returns: TRUE if the conversion could be performed.


<!-- ##### USER_FUNCTION GstPadDispatcherFunction ##### -->
<para>
A dispatcher function is called for all internally linked pads, see 
gst_pad_dispatcher().
</para>

@pad: the #GstPad that is dispatched.
@data: the gpointer to optional user data.
@Returns: TRUE if the dispatching procedure has to be stopped.


<!-- ##### USER_FUNCTION GstPadIntLinkFunction ##### -->
<para>
The signature of the internal pad link function.
</para>

@pad: The #GstPad to query.
@Returns: a newly allocated #GList of pads that are linked to 
          the given pad on the inside of the parent element.  
          The caller must call g_list_free() on it after use.


<!-- ##### USER_FUNCTION GstPadQueryFunction ##### -->
<para>
The signature of the query function.
</para>

@pad: the #GstPad to query.
@type: the #GstPadQueryType.
@format: a pointer to the target #GstFormat.
@value: a pointer to the target value.
@Returns: TRUE if the query could be performed.


<!-- ##### USER_FUNCTION GstPadEventMaskFunction ##### -->
<para>
The signature of the eventmask function.
</para>

@pad: the #GstPad to query
@Returns: an array of event masks


<!-- ##### USER_FUNCTION GstPadFormatsFunction ##### -->
<para>
The signature of the formats function.
</para>

@pad: a #GstPad to query
@Returns: an array of formats


<!-- ##### USER_FUNCTION GstPadQueryTypeFunction ##### -->
<para>
The signature of the query types function.
</para>

@pad: a #GstPad to query
@Returns: an array of query types


<!-- ##### MACRO GST_PAD_QUERY_TYPE_FUNCTION ##### -->
<para>
A convenience macro to construct query type functions
</para>

@functionname: the name of the function
@...: query types, 0 to mark the last element


<!-- ##### MACRO GST_PAD_FORMATS_FUNCTION ##### -->
<para>
Convenience function to define an array of formats that can be used
as #GstPadGetFormatsFunction.
</para>

@functionname: The name of the function
@...: comma separated list of formats, 0 to mark the end


<!-- ##### MACRO GST_PAD_EVENT_MASK_FUNCTION ##### -->
<para>
Convenience function to define an array of event masks that can be used
as #GstPadGetEventMaskFunction.
</para>

@functionname: The name of the function
@...: comma separated list of event maks, { 0, } to mark the end


<!-- ##### ENUM GstPadDirection ##### -->
<para>
The direction of a pad.
</para>

@GST_PAD_UNKNOWN: direction is unknown.
@GST_PAD_SRC: the pad is a source pad.
@GST_PAD_SINK: the pad is a sink pad.

<!-- ##### ENUM GstPadFlags ##### -->
<para>
Flags for the pad.
</para>

@GST_PAD_DISABLED: the pad is disabled.
@GST_PAD_NEGOTIATING: 
@GST_PAD_FLAG_LAST: subclasses can use this number to enumerate their flags.

<!-- ##### FUNCTION gst_pad_new ##### -->
<para>

</para>

@name: 
@direction: 
@Returns: 


<!-- ##### FUNCTION gst_pad_custom_new ##### -->
<para>

</para>

@type: 
@name: 
@direction: 
@Returns: 


<!-- ##### FUNCTION gst_pad_custom_new_from_template ##### -->
<para>

</para>

@type: 
@templ: 
@name: 
@Returns: 


<!-- ##### FUNCTION gst_pad_new_from_template ##### -->
<para>

</para>

@templ: 
@name: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_direction ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_set_chain_function ##### -->
<para>

</para>

@pad: 
@chain: 


<!-- ##### FUNCTION gst_pad_set_get_function ##### -->
<para>

</para>

@pad: 
@get: 


<!-- ##### FUNCTION gst_pad_set_link_function ##### -->
<para>

</para>

@pad: 
@link: 


<!-- ##### FUNCTION gst_pad_set_getcaps_function ##### -->
<para>

</para>

@pad: 
@getcaps: 


<!-- ##### FUNCTION gst_pad_try_set_caps ##### -->
<para>

</para>

@pad: 
@caps: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_caps ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_check_compatibility ##### -->
<para>

</para>

@srcpad: 
@sinkpad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_set_name ##### -->
<para>

</para>

@pad: 
@name: 


<!-- ##### FUNCTION gst_pad_get_name ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_set_element_private ##### -->
<para>

</para>

@pad: 
@priv: 


<!-- ##### FUNCTION gst_pad_get_element_private ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_set_parent ##### -->
<para>

</para>

@pad: 
@parent: 


<!-- ##### FUNCTION gst_pad_get_parent ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_real_parent ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_add_ghost_pad ##### -->
<para>

</para>

@pad: 
@ghostpad: 


<!-- ##### FUNCTION gst_pad_remove_ghost_pad ##### -->
<para>

</para>

@pad: 
@ghostpad: 


<!-- ##### FUNCTION gst_pad_get_ghost_pad_list ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_peer ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_link ##### -->
<para>

</para>

@srcpad: 
@sinkpad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_link_filtered ##### -->
<para>

</para>

@srcpad: 
@sinkpad: 
@filtercaps: 
@Returns: 


<!-- ##### FUNCTION gst_pad_relink_filtered ##### -->
<para>

</para>

@srcpad: 
@sinkpad: 
@filtercaps: 
@Returns: 


<!-- ##### FUNCTION gst_pad_try_relink_filtered ##### -->
<para>

</para>

@srcpad: 
@sinkpad: 
@filtercaps: 
@Returns: 


<!-- ##### FUNCTION gst_pad_unlink ##### -->
<para>

</para>

@srcpad: 
@sinkpad: 


<!-- ##### FUNCTION gst_pad_can_link ##### -->
<para>

</para>

@srcpad: 
@sinkpad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_can_link_filtered ##### -->
<para>

</para>

@srcpad: 
@sinkpad: 
@filtercaps: 
@Returns: 


<!-- ##### FUNCTION gst_pad_push ##### -->
<para>

</para>

@pad: 
@data: 
<!-- # Unused Parameters # -->
@buf: 


<!-- ##### FUNCTION gst_pad_pull ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_load_and_link ##### -->
<para>

</para>

@self: 
@parent: 


<!-- ##### FUNCTION gst_pad_proxy_link ##### -->
<para>

</para>

@pad: 
@caps: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_pad_template ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_pad_template_caps ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_allowed_caps ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_perform_negotiate ##### -->
<para>

</para>

@srcpad: 
@sinkpad: 
@Returns: 


<!-- ##### FUNCTION gst_ghost_pad_save_thyself ##### -->
<para>

</para>

@pad: 
@parent: 
@Returns: 


<!-- ##### FUNCTION gst_pad_select ##### -->
<para>

</para>

@pad: 
@Varargs: 
@Returns: 
<!-- # Unused Parameters # -->
@padlist: 


<!-- ##### FUNCTION gst_pad_selectv ##### -->
<para>

</para>

@padlist: 
@Returns: 
<!-- # Unused Parameters # -->
@pad: 
@Varargs: 


<!-- ##### FUNCTION gst_pad_dispatcher ##### -->
<para>

</para>

@pad: 
@dispatch: 
@data: 
@Returns: 


<!-- ##### FUNCTION gst_pad_send_event ##### -->
<para>

</para>

@pad: 
@event: 
@Returns: 


<!-- ##### FUNCTION gst_pad_event_default ##### -->
<para>

</para>

@pad: 
@event: 
@Returns: 


<!-- ##### FUNCTION gst_pad_set_event_function ##### -->
<para>

</para>

@pad: 
@event: 


<!-- ##### FUNCTION gst_pad_get_event_masks ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_event_masks_default ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_set_event_mask_function ##### -->
<para>

</para>

@pad: 
@mask_func: 


<!-- ##### FUNCTION gst_pad_set_convert_function ##### -->
<para>

</para>

@pad: 
@convert: 


<!-- ##### FUNCTION gst_pad_convert ##### -->
<para>

</para>

@pad: 
@src_format: 
@src_value: 
@dest_format: 
@dest_value: 
@Returns: 


<!-- ##### FUNCTION gst_pad_convert_default ##### -->
<para>

</para>

@pad: 
@src_format: 
@src_value: 
@dest_format: 
@dest_value: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_formats ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_formats_default ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_set_formats_function ##### -->
<para>

</para>

@pad: 
@formats: 


<!-- ##### FUNCTION gst_pad_get_internal_links ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_internal_links_default ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_set_internal_link_function ##### -->
<para>

</para>

@pad: 
@intlink: 


<!-- ##### FUNCTION gst_pad_set_query_function ##### -->
<para>

</para>

@pad: 
@query: 


<!-- ##### FUNCTION gst_pad_query ##### -->
<para>

</para>

@pad: 
@type: 
@format: 
@value: 
@Returns: 


<!-- ##### FUNCTION gst_pad_query_default ##### -->
<para>

</para>

@pad: 
@type: 
@format: 
@value: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_query_types ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_get_query_types_default ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_set_query_type_function ##### -->
<para>

</para>

@pad: 
@type_func: 


<!-- ##### MACRO gst_pad_add_probe ##### -->
<para>
Adds the probe to the given pad
</para>

@pad: The pad to add the probe to
@probe: The probe to add to the pad


<!-- ##### MACRO gst_pad_remove_probe ##### -->
<para>
Remove the probe from the pad
</para>

@pad: The pad to remove the probe of
@probe: The probe to remove


<!-- ##### FUNCTION gst_pad_is_active ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### FUNCTION gst_pad_set_active ##### -->
<para>

</para>

@pad: 
@active: 


<!-- ##### FUNCTION gst_pad_get_scheduler ##### -->
<para>

</para>

@pad: 
@Returns: 


<!-- ##### STRUCT GstRealPad ##### -->
<para>
The realpad object
</para>


<!-- ##### MACRO GST_RPAD_DIRECTION ##### -->
<para>
Get the direction of the real pad.
</para>

@pad: the realpad to query.


<!-- ##### MACRO GST_RPAD_CAPS ##### -->
<para>
Get the caps of the real pad.
</para>

@pad: the real pad to query.


<!-- ##### MACRO GST_RPAD_PEER ##### -->
<para>
Get the peer element of the real pad.
</para>

@pad: the real pad to query.


<!-- ##### MACRO GST_RPAD_CHAINFUNC ##### -->
<para>
Get the chain function of the real pad.
</para>

@pad: the real pad to query.


<!-- ##### MACRO GST_RPAD_APPFILTER ##### -->
<para>
Get the application filter for this pad
</para>

@pad: the pad to query


<!-- ##### MACRO GST_RPAD_GETFUNC ##### -->
<para>
Get get getfunction of the real pad.
</para>

@pad: the real pad to query.


<!-- ##### MACRO GST_RPAD_CHAINHANDLER ##### -->
<para>
Get the eventhandler function from the real pad.
</para>

@pad: the real pad to query.


<!-- ##### MACRO GST_RPAD_EVENTFUNC ##### -->
<para>
Get the event function of this real pad.
</para>

@pad: the real pad to query.


<!-- ##### MACRO GST_RPAD_EVENTHANDLER ##### -->
<para>
Get the eventhandler function of this real pad.
</para>

@pad: the real pad to query.


<!-- ##### MACRO GST_RPAD_GETHANDLER ##### -->
<para>
Get the gethandler function of this real pad.
</para>

@pad: the real pad to query.


<!-- ##### MACRO GST_RPAD_LINKFUNC ##### -->
<para>
Get the link function of the pad
</para>

@pad: the pad to query


<!-- ##### MACRO GST_RPAD_GETCAPSFUNC ##### -->
<para>
Get the getcaps function of this pad
</para>

@pad: the pad to query


<!-- ##### MACRO GST_RPAD_CONVERTFUNC ##### -->
<para>
Get the convert function of this pad
</para>

@pad: the pad to query


<!-- ##### MACRO GST_RPAD_INTLINKFUNC ##### -->
<para>
Get the internal link function of this pad
</para>

@pad: the pad to query


<!-- ##### MACRO GST_RPAD_QUERYFUNC ##### -->
<para>
Get the query function of this pad
</para>

@pad: the pad to query


<!-- ##### MACRO GST_RPAD_EVENTMASKFUNC ##### -->
<para>
Get the event mask function of this pad
</para>

@pad: the pad to query


<!-- ##### MACRO GST_RPAD_FORMATSFUNC ##### -->
<para>
Get the formats function of this pad
</para>

@pad: the pad to query


<!-- ##### MACRO GST_RPAD_QUERYTYPEFUNC ##### -->
<para>
Get the query types function of this pad
</para>

@pad: the pad to query


<!-- ##### MACRO GST_GPAD_REALPAD ##### -->
<para>
Get the real pad of this ghost pad.
</para>

@pad: the real pad to query.


<!-- ##### STRUCT GstGhostPad ##### -->
<para>
The Ghostpad object
</para>


<!-- ##### FUNCTION gst_ghost_pad_new ##### -->
<para>

</para>

@name: 
@pad: 
@Returns: