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GStreamer 0.10 Core Reference Manual | ![]() |
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#include <gst/gst.h> GstBin; GstBinClass; GstElement* gst_bin_new (const gchar *name); gboolean gst_bin_add (GstBin *bin, GstElement *element); gboolean gst_bin_remove (GstBin *bin, GstElement *element); GstElement* gst_bin_get_by_name (GstBin *bin, const gchar *name); GstElement* gst_bin_get_by_name_recurse_up (GstBin *bin, const gchar *name); GstElement* gst_bin_get_by_interface (GstBin *bin, GType iface); GstIterator* gst_bin_iterate_elements (GstBin *bin); GstIterator* gst_bin_iterate_recurse (GstBin *bin); GstIterator* gst_bin_iterate_sinks (GstBin *bin); GstIterator* gst_bin_iterate_sorted (GstBin *bin); GstIterator* gst_bin_iterate_sources (GstBin *bin); GstIterator* gst_bin_iterate_all_by_interface (GstBin *bin, GType iface); void gst_bin_add_many (GstBin *bin, GstElement *element_1, ...); void gst_bin_remove_many (GstBin *bin, GstElement *element_1, ...); GstPad* gst_bin_find_unconnected_pad (GstBin *bin, GstPadDirection direction); enum GstBinFlags; #define GST_BIN_CHILDREN (bin) #define GST_BIN_CHILDREN_COOKIE (bin) #define GST_BIN_NUMCHILDREN (bin)
GstBin is an element that can contain other GstElement, allowing them to be managed as a group. Pads from the child elements can be ghosted to the bin, see GstGhostPad. This makes the bin look like any other elements and enables creation of higher-level abstraction elements.
A new GstBin is created with gst_bin_new(). Use a GstPipeline instead if you want to create a toplevel bin because a normal bin doesn't have a bus or handle clock distribution of its own.
After the bin has been created you will typically add elements to it with gst_bin_add(). You can remove elements with gst_bin_remove().
An element can be retrieved from a bin with gst_bin_get_by_name(), using the elements name. gst_bin_get_by_name_recurse_up() is mainly used for internal purposes and will query the parent bins when the element is not found in the current bin.
An iterator of elements in a bin can be retrieved with gst_bin_iterate_elements(). Various other iterators exist to retrieve the elements in a bin.
gst_object_unref() is used to drop your reference to the bin.
The element-added signal is fired whenever a new element is added to the bin. Likewise the element-removed signal is fired whenever an element is removed from the bin.
A GstBin internally intercepts every GstMessage posted by its children and implements the following default behaviour for each of them:
GST_MESSAGE_EOS | This message is only posted by sinks in the PLAYING state. If all sinks posted the EOS message, this bin will post and EOS message upwards. |
GST_MESSAGE_SEGMENT_START | just collected and never forwarded upwards. The messages are used to decide when all elements have completed playback of their segment. |
GST_MESSAGE_SEGMENT_DONE | Is posted by GstBin when all elements that posted a SEGMENT_START have posted a SEGMENT_DONE. |
GST_MESSAGE_DURATION | Is posted by an element that detected a change in the stream duration. The default bin behaviour is to clear any cached duration values so that the next duration query will perform a full duration recalculation. The duration change is posted to the application so that it can refetch the new duration with a duration query. |
GST_MESSAGE_CLOCK_LOST | This message is posted by an element when it can no longer provide a clock. The default bin behaviour is to check if the lost clock was the one provided by the bin. If so and the bin is currently in the PLAYING state, the message is forwarded to the bin parent. This message is also generated when a clock provider is removed from the bin. If this message is received by the application, it should PAUSE the pipeline and set it back to PLAYING to force a new clock distribution. |
GST_MESSAGE_CLOCK_PROVIDE | This message is generated when an element can provide a clock. This mostly happens when a new clock provider is added to the bin. The default behaviour of the bin is to mark the currently selected clock as dirty, which will perform a clock recalculation the next time the bin is asked to provide a clock. This message is never sent tot the application but is forwarded to the parent of the bin. |
OTHERS | posted upwards. |
A GstBin implements the following default behaviour for answering to a GstQuery:
GST_QUERY_DURATION | If the query has been asked before with the same format and the bin is a toplevel bin (ie. has no parent), use the cached previous value. If no previous value was cached, the query is sent to all sink elements in the bin and the MAXIMUM of all values is returned. If the bin is a toplevel bin the value is cached. If no sinks are available in the bin, the query fails. |
GST_QUERY_POSITION | The query is sent to all sink elements in the bin and the MAXIMUM of all values is returned. If no sinks are available in the bin, the query fails. |
OTHERS | the query is forwarded to all sink elements, the result of the first sink that answers the query successfully is returned. If no sink is in the bin, the query fails. |
A GstBin will by default forward any event sent to it to all sink elements. If all the sinks return TRUE, the bin will also return TRUE, else FALSE is returned. If no sinks are in the bin, the event handler will return TRUE.
Last reviewed on 2006-04-28 (0.10.6)
typedef struct { /* our children, subclass are supposed to update these * fields to reflect their state with _iterate_*() */ gint numchildren; GList *children; guint32 children_cookie; GstBus *child_bus; GList *messages; gboolean polling; gboolean state_dirty; gboolean clock_dirty; GstClock *provided_clock; GstElement *clock_provider; } GstBin;
The GstBin base class. Subclasses can access these fields provided the LOCK is taken.
gint numchildren; | the number of children in this bin |
GList *children; | the list of children in this bin |
guint32 children_cookie; | updated whenever children changes |
GstBus *child_bus; | internal bus for handling child messages |
GList *messages; | queued and cached messages |
gboolean polling; | the bin is currently calculating its state |
gboolean state_dirty; | the bin needs to recalculate its state |
gboolean clock_dirty; | the bin needs to select a new clock |
GstClock *provided_clock; | the last clock selected |
GstElement *clock_provider; | the element that provided provided_clock |
typedef struct { GstElementClass parent_class; /* virtual methods for subclasses */ gboolean (*add_element) (GstBin *bin, GstElement *element); gboolean (*remove_element) (GstBin *bin, GstElement *element); void (*handle_message) (GstBin *bin, GstMessage *message); } GstBinClass;
Subclasses can override the add_element and remove_element to update the list of children in the bin.
The handle_message method can be overriden to implement custom message handling.
GstElementClass parent_class; | bin parent class |
add_element () | method to add an element to a bin |
remove_element () | method to remove an element from a bin |
handle_message () | method to handle a message from the children |
GstElement* gst_bin_new (const gchar *name);
Creates a new bin with the given name.
name : | the name of the new bin |
Returns : | a new GstBin |
gboolean gst_bin_add (GstBin *bin, GstElement *element);
Adds the given element to the bin. Sets the element's parent, and thus takes ownership of the element. An element can only be added to one bin.
If the element's pads are linked to other pads, the pads will be unlinked before the element is added to the bin.
MT safe.
bin : | a GstBin |
element : | the GstElement to add |
Returns : | TRUE if the element could be added, FALSE if the bin does not want to accept the element. |
gboolean gst_bin_remove (GstBin *bin, GstElement *element);
Removes the element from the bin, unparenting it as well. Unparenting the element means that the element will be dereferenced, so if the bin holds the only reference to the element, the element will be freed in the process of removing it from the bin. If you want the element to still exist after removing, you need to call gst_object_ref() before removing it from the bin.
If the element's pads are linked to other pads, the pads will be unlinked before the element is removed from the bin.
MT safe.
bin : | a GstBin |
element : | the GstElement to remove |
Returns : | TRUE if the element could be removed, FALSE if the bin does not want to remove the element. |
GstElement* gst_bin_get_by_name (GstBin *bin, const gchar *name);
Gets the element with the given name from a bin. This function recurses into child bins.
Returns NULL if no element with the given name is found in the bin.
MT safe. Caller owns returned reference.
bin : | a GstBin |
name : | the element name to search for |
Returns : | the GstElement with the given name, or NULL |
GstElement* gst_bin_get_by_name_recurse_up (GstBin *bin, const gchar *name);
Gets the element with the given name from this bin. If the element is not found, a recursion is performed on the parent bin.
Returns NULL if: - no element with the given name is found in the bin
MT safe. Caller owns returned reference.
bin : | a GstBin |
name : | the element name to search for |
Returns : | the GstElement with the given name, or NULL |
GstElement* gst_bin_get_by_interface (GstBin *bin, GType iface);
Looks for an element inside the bin that implements the given interface. If such an element is found, it returns the element. You can cast this element to the given interface afterwards. If you want all elements that implement the interface, use gst_bin_iterate_all_by_interface(). This function recurses into child bins.
MT safe. Caller owns returned reference.
bin : | a GstBin |
iface : | the GType of an interface |
Returns : | A GstElement inside the bin implementing the interface |
GstIterator* gst_bin_iterate_elements (GstBin *bin);
Gets an iterator for the elements in this bin.
Each element yielded by the iterator will have its refcount increased, so unref after use.
MT safe. Caller owns returned value.
bin : | a GstBin |
Returns : | a GstIterator of GstElement, or NULL |
GstIterator* gst_bin_iterate_recurse (GstBin *bin);
Gets an iterator for the elements in this bin. This iterator recurses into GstBin children.
Each element yielded by the iterator will have its refcount increased, so unref after use.
MT safe. Caller owns returned value.
bin : | a GstBin |
Returns : | a GstIterator of GstElement, or NULL |
GstIterator* gst_bin_iterate_sinks (GstBin *bin);
Gets an iterator for all elements in the bin that have the GST_ELEMENT_IS_SINK flag set.
Each element yielded by the iterator will have its refcount increased, so unref after use.
MT safe. Caller owns returned value.
bin : | a GstBin |
Returns : | a GstIterator of GstElement, or NULL |
GstIterator* gst_bin_iterate_sorted (GstBin *bin);
Gets an iterator for the elements in this bin in topologically sorted order. This means that the elements are returned from the most downstream elements (sinks) to the sources.
This function is used internally to perform the state changes of the bin elements.
Each element yielded by the iterator will have its refcount increased, so unref after use.
MT safe. Caller owns returned value.
bin : | a GstBin |
Returns : | a GstIterator of GstElement, or NULL |
GstIterator* gst_bin_iterate_sources (GstBin *bin);
Gets an iterator for all elements in the bin that have no sinkpads and have the GST_ELEMENT_IS_SINK flag unset.
Each element yielded by the iterator will have its refcount increased, so unref after use.
MT safe. Caller owns returned value.
bin : | a GstBin |
Returns : | a GstIterator of GstElement, or NULL |
GstIterator* gst_bin_iterate_all_by_interface (GstBin *bin, GType iface);
Looks for all elements inside the bin that implements the given interface. You can safely cast all returned elements to the given interface. The function recurses inside child bins. The iterator will yield a series of GstElement that should be unreffed after use.
Each element yielded by the iterator will have its refcount increased, so unref after use.
MT safe. Caller owns returned value.
bin : | a GstBin |
iface : | the GType of an interface |
Returns : | a GstIterator of GstElement for all elements in the bin implementing the given interface, or NULL |
void gst_bin_add_many (GstBin *bin, GstElement *element_1, ...);
Adds a NULL-terminated list of elements to a bin. This function is equivalent to calling gst_bin_add() for each member of the list.
bin : | a GstBin |
element_1 : | the GstElement element to add to the bin |
... : | additional elements to add to the bin |
void gst_bin_remove_many (GstBin *bin, GstElement *element_1, ...);
Remove a list of elements from a bin. This function is equivalent to calling gst_bin_remove() with each member of the list.
bin : | a GstBin |
element_1 : | the first GstElement to remove from the bin |
... : | NULL-terminated list of elements to remove from the bin |
GstPad* gst_bin_find_unconnected_pad (GstBin *bin, GstPadDirection direction);
Recursively looks for elements with an unconnected pad of the given direction within the specified bin and returns an unconnected pad if one is found, or NULL otherwise. If a pad is found, the caller owns a reference to it and should use gst_object_unref() on the pad when it is not needed any longer.
bin : | bin in which to look for elements with unconnected pads |
direction : | whether to look for an unconnected source or sink pad |
Returns : | unconnected pad of the given direction, or NULL. |
Since 0.10.3
typedef enum { /* padding */ GST_BIN_FLAG_LAST = (GST_ELEMENT_FLAG_LAST << 5) } GstBinFlags;
GstBinFlags are a set of flags specific to bins. Most are set/used internally. They can be checked using the GST_OBJECT_FLAG_IS_SET() macro, and (un)set using GST_OBJECT_FLAG_SET() and GST_OBJECT_FLAG_UNSET().
#define GST_BIN_CHILDREN(bin) (GST_BIN_CAST(bin)->children)
Gets the list with children in a bin.
bin : | a GstBin |
#define GST_BIN_CHILDREN_COOKIE(bin) (GST_BIN_CAST(bin)->children_cookie)
Gets the children cookie that watches the children list.
bin : | a GstBin |
#define GST_BIN_NUMCHILDREN(bin) (GST_BIN_CAST(bin)->numchildren)
Gets the number of children in a bin.
bin : | a GstBin |
void user_function (GstBin *bin, GstElement *element, gpointer user_data) : Run First
Will be emitted after the element was added to the bin.
bin : | the GstBin |
element : | the GstElement that was added to the bin |
user_data : | user data set when the signal handler was connected. |
void user_function (GstBin *bin, GstElement *element, gpointer user_data) : Run First
Will be emitted after the element was removed from the bin.
bin : | the GstBin |
element : | the GstElement that was removed from the bin |
user_data : | user data set when the signal handler was connected. |