Element

GstElement is the abstract base class needed to construct an element that can be used in a GStreamer pipeline. Please refer to the plugin writers guide for more information on creating #GstElement subclasses.

The name of a #GstElement can be get with gst_element_get_name() and set with gst_element_set_name(). For speed, GST_ELEMENT_NAME() can be used in the core when using the appropriate locking. Do not use this in plug-ins or applications in order to retain ABI compatibility.

Elements can have pads (of the type #GstPad). These pads link to pads on other elements. #GstBuffer flow between these linked pads. A #GstElement has a #GList of #GstPad structures for all their input (or sink) and output (or source) pads. Core and plug-in writers can add and remove pads with gst_element_add_pad() and gst_element_remove_pad().

An existing pad of an element can be retrieved by name with gst_element_get_static_pad(). A new dynamic pad can be created using gst_element_request_pad() with a #GstPadTemplate. An iterator of all pads can be retrieved with gst_element_iterate_pads().

Elements can be linked through their pads. If the link is straightforward, use the gst_element_link() convenience function to link two elements, or gst_element_link_many() for more elements in a row. Use gst_element_link_filtered() to link two elements constrained by a specified set of #GstCaps. For finer control, use gst_element_link_pads() and gst_element_link_pads_filtered() to specify the pads to link on each element by name.

Each element has a state (see #GstState). You can get and set the state of an element with gst_element_get_state() and gst_element_set_state(). Setting a state triggers a #GstStateChange. To get a string representation of a #GstState, use gst_element_state_get_name().

You can get and set a #GstClock on an element using gst_element_get_clock() and gst_element_set_clock(). Some elements can provide a clock for the pipeline if the #GST_ELEMENT_FLAG_PROVIDE_CLOCK flag is set. With the gst_element_provide_clock() method one can retrieve the clock provided by such an element. Not all elements require a clock to operate correctly. If the #GST_ELEMENT_FLAG_REQUIRE_CLOCK() flag is set, a clock should be set on the element with gst_element_set_clock().

Note that clock selection and distribution is normally handled by the toplevel #GstPipeline so the clock functions are only to be used in very specific situations.

class Element : ObjectGst {

GstElement* gstElement;

GstElement* getElementStruct(bool transferOwnership);

void* getStruct();

this(GstElement* gstElement, bool ownedRef);

long queryPosition();

long queryDuration();

void location(string set);

void caps(Caps cp);

int seek(long time_nanoseconds);

Pad[] pads();

static GType getType();

static Element makeFromUri(GstURIType type, string uri, string elementname);

static bool register(Plugin plugin, string name, uint rank, GType type);

static string stateChangeReturnGetName(GstStateChangeReturn stateRet);

static string stateGetName(GstState state);

void abortState();

bool addPad(Pad pad);

gulong addPropertyDeepNotifyWatch(string propertyName, bool includeValue);

gulong addPropertyNotifyWatch(string propertyName, bool includeValue);

void callAsync(GstElementCallAsyncFunc func, void* userData, GDestroyNotify destroyNotify);

GstStateChangeReturn changeState(GstStateChange transition);

GstStateChangeReturn continueState(GstStateChangeReturn ret);

void createAllPads();

bool foreachPad(GstElementForeachPadFunc func, void* userData);

bool foreachSinkPad(GstElementForeachPadFunc func, void* userData);

bool foreachSrcPad(GstElementForeachPadFunc func, void* userData);

GstClockTime getBaseTime();

Bus getBus();

Clock getClock();

Pad getCompatiblePad(Pad pad, Caps caps);

PadTemplate getCompatiblePadTemplate(PadTemplate compattempl);

Context getContext(string contextType);

Context getContextUnlocked(string contextType);

ListG getContexts();

ElementFactory getFactory();

string getMetadata(string key);

PadTemplate getPadTemplate(string name);

ListG getPadTemplateList();

Pad getRequestPad(string name);

GstClockTime getStartTime();

GstStateChangeReturn getState(GstState state, GstState pending, GstClockTime timeout);

Pad getStaticPad(string name);

bool isLockedState();

Iterator iteratePads();

Iterator iterateSinkPads();

Iterator iterateSrcPads();

bool link(Element dest);

bool linkFiltered(Element dest, Caps filter);

bool linkPads(string srcpadname, Element dest, string destpadname);

bool linkPadsFiltered(string srcpadname, Element dest, string destpadname, Caps filter);

bool linkPadsFull(string srcpadname, Element dest, string destpadname, GstPadLinkCheck flags);

void lostState();

void messageFull(GstMessageType type, GQuark domain, int code, string text, string dbg, string file, string funct, int line);

void messageFullWithDetails(GstMessageType type, GQuark domain, int code, string text, string dbg, string file, string funct, int line, Structure structure);

void noMorePads();

bool postMessage(Message message);

Clock provideClock();

bool query(Query query);

bool queryConvert(GstFormat srcFormat, long srcVal, GstFormat destFormat, long destVal);

bool queryDuration(GstFormat format, long duration);

bool queryPosition(GstFormat format, long cur);

void releaseRequestPad(Pad pad);

bool removePad(Pad pad);

void removePropertyNotifyWatch(gulong watchId);

Pad requestPad(PadTemplate templ, string name, Caps caps);

bool seek(double rate, GstFormat format, GstSeekFlags flags, GstSeekType startType, long start, GstSeekType stopType, long stop);

bool seekSimple(GstFormat format, GstSeekFlags seekFlags, long seekPos);

bool sendEvent(Event event);

void setBaseTime(GstClockTime time);

void setBus(Bus bus);

bool setClock(Clock clock);

void setContext(Context context);

bool setLockedState(bool lockedState);

void setStartTime(GstClockTime time);

GstStateChangeReturn setState(GstState state);

bool syncStateWithParent();

void unlink(Element dest);

void unlinkPads(string srcpadname, Element dest, string destpadname);

gulong addOnNoMorePads(void delegate(Element) dlg, ConnectFlags connectFlags);

gulong addOnPadAdded(void delegate(Pad, Element) dlg, ConnectFlags connectFlags);

gulong addOnPadRemoved(void delegate(Pad, Element) dlg, ConnectFlags connectFlags);

}

Constructors

this this(GstElement* gstElement, bool ownedRef): Sets our main struct and passes it to the parent class.

Members

Functions

abortState void abortState(): Abort the state change of the element. This function is used by elements that do asynchronous state changes and find out something is wrong.
addOnNoMorePads gulong addOnNoMorePads(void delegate(Element) dlg, ConnectFlags connectFlags): This signals that the element will not generate more dynamic pads. Note that this signal will usually be emitted from the context of the streaming thread.
addOnPadAdded gulong addOnPadAdded(void delegate(Pad, Element) dlg, ConnectFlags connectFlags): a new #GstPad has been added to the element. Note that this signal will usually be emitted from the context of the streaming thread. Also keep in mind that if you add new elements to the pipeline in the signal handler you will need to set them to the desired target state with gst_element_set_state() or gst_element_sync_state_with_parent().
addOnPadRemoved gulong addOnPadRemoved(void delegate(Pad, Element) dlg, ConnectFlags connectFlags): a #GstPad has been removed from the element
addPad bool addPad(Pad pad): Adds a pad (link point) to @element. @pad's parent will be set to @element; see gst_object_set_parent() for refcounting information.
addPropertyDeepNotifyWatch gulong addPropertyDeepNotifyWatch(string propertyName, bool includeValue)
addPropertyNotifyWatch gulong addPropertyNotifyWatch(string propertyName, bool includeValue)
callAsync void callAsync(GstElementCallAsyncFunc func, void* userData, GDestroyNotify destroyNotify): Calls @func from another thread and passes @user_data to it. This is to be used for cases when a state change has to be performed from a streaming thread, directly via gst_element_set_state() or indirectly e.g. via SEEK events.
caps void caps(Caps cp): Set the caps property of an Element.
changeState GstStateChangeReturn changeState(GstStateChange transition): Perform @transition on @element.
continueState GstStateChangeReturn continueState(GstStateChangeReturn ret): Commit the state change of the element and proceed to the next pending state if any. This function is used by elements that do asynchronous state changes. The core will normally call this method automatically when an element returned %GST_STATE_CHANGE_SUCCESS from the state change function.
createAllPads void createAllPads(): Creates a pad for each pad template that is always available. This function is only useful during object initialization of subclasses of #GstElement.
foreachPad bool foreachPad(GstElementForeachPadFunc func, void* userData): Call @func with @user_data for each of @element's pads. @func will be called exactly once for each pad that exists at the time of this call, unless one of the calls to @func returns %FALSE in which case we will stop iterating pads and return early. If new pads are added or pads are removed while pads are being iterated, this will not be taken into account until next time this function is used.
foreachSinkPad bool foreachSinkPad(GstElementForeachPadFunc func, void* userData): Call @func with @user_data for each of @element's sink pads. @func will be called exactly once for each sink pad that exists at the time of this call, unless one of the calls to @func returns %FALSE in which case we will stop iterating pads and return early. If new sink pads are added or sink pads are removed while the sink pads are being iterated, this will not be taken into account until next time this function is used.
foreachSrcPad bool foreachSrcPad(GstElementForeachPadFunc func, void* userData): Call @func with @user_data for each of @element's source pads. @func will be called exactly once for each source pad that exists at the time of this call, unless one of the calls to @func returns %FALSE in which case we will stop iterating pads and return early. If new source pads are added or source pads are removed while the source pads are being iterated, this will not be taken into account until next time this function is used.
getBaseTime GstClockTime getBaseTime(): Returns the base time of the element. The base time is the absolute time of the clock when this element was last put to PLAYING. Subtracting the base time from the clock time gives the running time of the element.
getBus Bus getBus(): Returns the bus of the element. Note that only a #GstPipeline will provide a bus for the application.
getClock Clock getClock(): Gets the currently configured clock of the element. This is the clock as was last set with gst_element_set_clock().
getCompatiblePad Pad getCompatiblePad(Pad pad, Caps caps): Looks for an unlinked pad to which the given pad can link. It is not guaranteed that linking the pads will work, though it should work in most cases.
getCompatiblePadTemplate PadTemplate getCompatiblePadTemplate(PadTemplate compattempl): Retrieves a pad template from @element that is compatible with @compattempl. Pads from compatible templates can be linked together.
getContext Context getContext(string contextType): Gets the context with @context_type set on the element or NULL.
getContextUnlocked Context getContextUnlocked(string contextType): Gets the context with @context_type set on the element or NULL.
getContexts ListG getContexts(): Gets the contexts set on the element.
getElementStruct GstElement* getElementStruct(bool transferOwnership): Get the main Gtk struct
getFactory ElementFactory getFactory(): Retrieves the factory that was used to create this element.
getMetadata string getMetadata(string key): Get metadata with @key in @klass.
getPadTemplate PadTemplate getPadTemplate(string name): Retrieves a padtemplate from @element with the given name.
getPadTemplateList ListG getPadTemplateList(): Retrieves a list of the pad templates associated with @element. The list must not be modified by the calling code.
getRequestPad Pad getRequestPad(string name): Retrieves a pad from the element by name (e.g. "src_\%d"). This version only retrieves request pads. The pad should be released with gst_element_release_request_pad().
getStartTime GstClockTime getStartTime(): Returns the start time of the element. The start time is the running time of the clock when this element was last put to PAUSED.
getState GstStateChangeReturn getState(GstState state, GstState pending, GstClockTime timeout): Gets the state of the element.
getStaticPad Pad getStaticPad(string name): Retrieves a pad from @element by name. This version only retrieves already-existing (i.e. 'static') pads.
getStruct void* getStruct(): the main Gtk struct as a void*
isLockedState bool isLockedState(): Checks if the state of an element is locked. If the state of an element is locked, state changes of the parent don't affect the element. This way you can leave currently unused elements inside bins. Just lock their state before changing the state from #GST_STATE_NULL.
iteratePads Iterator iteratePads(): Retrieves an iterator of @element's pads. The iterator should be freed after usage. Also more specialized iterators exists such as gst_element_iterate_src_pads() or gst_element_iterate_sink_pads().
iterateSinkPads Iterator iterateSinkPads(): Retrieves an iterator of @element's sink pads.
iterateSrcPads Iterator iterateSrcPads(): Retrieves an iterator of @element's source pads.
link bool link(Element dest): Links @src to @dest. The link must be from source to destination; the other direction will not be tried. The function looks for existing pads that aren't linked yet. It will request new pads if necessary. Such pads need to be released manually when unlinking. If multiple links are possible, only one is established.
linkFiltered bool linkFiltered(Element dest, Caps filter): Links @src to @dest using the given caps as filtercaps. The link must be from source to destination; the other direction will not be tried. The function looks for existing pads that aren't linked yet. It will request new pads if necessary. If multiple links are possible, only one is established.
linkPads bool linkPads(string srcpadname, Element dest, string destpadname): Links the two named pads of the source and destination elements. Side effect is that if one of the pads has no parent, it becomes a child of the parent of the other element. If they have different parents, the link fails.
linkPadsFiltered bool linkPadsFiltered(string srcpadname, Element dest, string destpadname, Caps filter): Links the two named pads of the source and destination elements. Side effect is that if one of the pads has no parent, it becomes a child of the parent of the other element. If they have different parents, the link fails. If @caps is not %NULL, makes sure that the caps of the link is a subset of @caps.
linkPadsFull bool linkPadsFull(string srcpadname, Element dest, string destpadname, GstPadLinkCheck flags): Links the two named pads of the source and destination elements. Side effect is that if one of the pads has no parent, it becomes a child of the parent of the other element. If they have different parents, the link fails.
location void location(string set): This set's the filename for a filesrc element.
lostState void lostState(): Brings the element to the lost state. The current state of the element is copied to the pending state so that any call to gst_element_get_state() will return %GST_STATE_CHANGE_ASYNC.
messageFull void messageFull(GstMessageType type, GQuark domain, int code, string text, string dbg, string file, string funct, int line): Post an error, warning or info message on the bus from inside an element.
messageFullWithDetails void messageFullWithDetails(GstMessageType type, GQuark domain, int code, string text, string dbg, string file, string funct, int line, Structure structure): Post an error, warning or info message on the bus from inside an element.
noMorePads void noMorePads(): Use this function to signal that the element does not expect any more pads to show up in the current pipeline. This function should be called whenever pads have been added by the element itself. Elements with #GST_PAD_SOMETIMES pad templates use this in combination with autopluggers to figure out that the element is done initializing its pads.
pads Pad[] pads(): Get's all the pads from an element in a Pad[].
postMessage bool postMessage(Message message): Post a message on the element's #GstBus. This function takes ownership of the message; if you want to access the message after this call, you should add an additional reference before calling.
provideClock Clock provideClock(): Get the clock provided by the given element. > An element is only required to provide a clock in the PAUSED > state. Some elements can provide a clock in other states.
query bool query(Query query): Performs a query on the given element.
queryConvert bool queryConvert(GstFormat srcFormat, long srcVal, GstFormat destFormat, long destVal): Queries an element to convert @src_val in @src_format to @dest_format.
queryDuration long queryDuration(): Queries an element for the stream duration. This is a convenience function for gstreamerD.
queryDuration bool queryDuration(GstFormat format, long duration): Queries an element (usually top-level pipeline or playbin element) for the total stream duration in nanoseconds. This query will only work once the pipeline is prerolled (i.e. reached PAUSED or PLAYING state). The application will receive an ASYNC_DONE message on the pipeline bus when that is the case.
queryPosition long queryPosition(): Queries an element for the stream position. This is a convenience function for gstreamerD.
queryPosition bool queryPosition(GstFormat format, long cur): Queries an element (usually top-level pipeline or playbin element) for the stream position in nanoseconds. This will be a value between 0 and the stream duration (if the stream duration is known). This query will usually only work once the pipeline is prerolled (i.e. reached PAUSED or PLAYING state). The application will receive an ASYNC_DONE message on the pipeline bus when that is the case.
releaseRequestPad void releaseRequestPad(Pad pad): Makes the element free the previously requested pad as obtained with gst_element_request_pad().
removePad bool removePad(Pad pad): Removes @pad from @element. @pad will be destroyed if it has not been referenced elsewhere using gst_object_unparent().
removePropertyNotifyWatch void removePropertyNotifyWatch(gulong watchId)
requestPad Pad requestPad(PadTemplate templ, string name, Caps caps): Retrieves a request pad from the element according to the provided template. Pad templates can be looked up using gst_element_factory_get_static_pad_templates().
seek int seek(long time_nanoseconds): For your convenience in gstreamerD: you can seek to the position of the pipeline measured in time_nanoseconds.
seek bool seek(double rate, GstFormat format, GstSeekFlags flags, GstSeekType startType, long start, GstSeekType stopType, long stop): Sends a seek event to an element. See gst_event_new_seek() for the details of the parameters. The seek event is sent to the element using gst_element_send_event().
seekSimple bool seekSimple(GstFormat format, GstSeekFlags seekFlags, long seekPos): Simple API to perform a seek on the given element, meaning it just seeks to the given position relative to the start of the stream. For more complex operations like segment seeks (e.g. for looping) or changing the playback rate or seeking relative to the last configured playback segment you should use gst_element_seek().
sendEvent bool sendEvent(Event event): Sends an event to an element. If the element doesn't implement an event handler, the event will be pushed on a random linked sink pad for downstream events or a random linked source pad for upstream events.
setBaseTime void setBaseTime(GstClockTime time): Set the base time of an element. See gst_element_get_base_time().
setBus void setBus(Bus bus): Sets the bus of the element. Increases the refcount on the bus. For internal use only, unless you're testing elements.
setClock bool setClock(Clock clock): Sets the clock for the element. This function increases the refcount on the clock. Any previously set clock on the object is unreffed.
setContext void setContext(Context context): Sets the context of the element. Increases the refcount of the context.
setLockedState bool setLockedState(bool lockedState): Locks the state of an element, so state changes of the parent don't affect this element anymore.
setStartTime void setStartTime(GstClockTime time): Set the start time of an element. The start time of the element is the running time of the element when it last went to the PAUSED state. In READY or after a flushing seek, it is set to 0.
setState GstStateChangeReturn setState(GstState state): Sets the state of the element. This function will try to set the requested state by going through all the intermediary states and calling the class's state change function for each.
syncStateWithParent bool syncStateWithParent(): Tries to change the state of the element to the same as its parent. If this function returns %FALSE, the state of element is undefined.
unlink void unlink(Element dest): Unlinks all source pads of the source element with all sink pads of the sink element to which they are linked.
unlinkPads void unlinkPads(string srcpadname, Element dest, string destpadname): Unlinks the two named pads of the source and destination elements.

Static functions

getType GType getType()
makeFromUri Element makeFromUri(GstURIType type, string uri, string elementname): Creates an element for handling the given URI.
register bool register(Plugin plugin, string name, uint rank, GType type): Create a new elementfactory capable of instantiating objects of the @type and add the factory to @plugin.
stateChangeReturnGetName string stateChangeReturnGetName(GstStateChangeReturn stateRet): Gets a string representing the given state change result.
stateGetName string stateGetName(GstState state): Gets a string representing the given state.

Variables

gstElement GstElement* gstElement;: the main Gtk struct

Inherited Members

From ObjectGst

gstObject GstObject* gstObject;: the main Gtk struct
getObjectGstStruct GstObject* getObjectGstStruct(bool transferOwnership): Get the main Gtk struct
getStruct void* getStruct(): the main Gtk struct as a void*
getType GType getType()
checkUniqueness bool checkUniqueness(ListG list, string name): Checks to see if there is any object named @name in @list. This function does not do any locking of any kind. You might want to protect the provided list with the lock of the owner of the list. This function will lock each #GstObject in the list to compare the name, so be careful when passing a list with a locked object.
defaultDeepNotify void defaultDeepNotify(ObjectG object, ObjectGst orig, ParamSpec pspec, string[] excludedProps): A default deep_notify signal callback for an object. The user data should contain a pointer to an array of strings that should be excluded from the notify. The default handler will print the new value of the property using g_print.
refSink void* refSink(void* object): Increase the reference count of @object, and possibly remove the floating reference, if @object has a floating reference.
replace bool replace(ObjectGst oldobj, ObjectGst newobj): Atomically modifies a pointer to point to a new object. The reference count of @oldobj is decreased and the reference count of @newobj is increased.
addControlBinding bool addControlBinding(ControlBinding binding): Attach the #GstControlBinding to the object. If there already was a #GstControlBinding for this property it will be replaced.
defaultError void defaultError(ErrorG error, string dbg): A default error function that uses g_printerr() to display the error message and the optional debug sting..
getControlBinding ControlBinding getControlBinding(string propertyName): Gets the corresponding #GstControlBinding for the property. This should be unreferenced again after use.
getControlRate GstClockTime getControlRate(): Obtain the control-rate for this @object. Audio processing #GstElement objects will use this rate to sub-divide their processing loop and call gst_object_sync_values() inbetween. The length of the processing segment should be up to @control-rate nanoseconds.
getGValueArray bool getGValueArray(string propertyName, GstClockTime timestamp, GstClockTime interval, Value[] values): Gets a number of #GValues for the given controlled property starting at the requested time. The array @values need to hold enough space for @n_values of #GValue.
getName string getName(): Returns a copy of the name of @object. Caller should g_free() the return value after usage. For a nameless object, this returns %NULL, which you can safely g_free() as well.
getParent ObjectGst getParent(): Returns the parent of @object. This function increases the refcount of the parent object so you should gst_object_unref() it after usage.
getPathString string getPathString(): Generates a string describing the path of @object in the object hierarchy. Only useful (or used) for debugging.
getValue Value getValue(string propertyName, GstClockTime timestamp): Gets the value for the given controlled property at the requested time.
getValueArray bool getValueArray(string propertyName, GstClockTime timestamp, GstClockTime interval, uint nValues, void* values): Gets a number of values for the given controlled property starting at the requested time. The array @values need to hold enough space for @n_values of the same type as the objects property's type.
hasActiveControlBindings bool hasActiveControlBindings(): Check if the @object has active controlled properties.
hasAncestor bool hasAncestor(ObjectGst ancestor): Check if @object has an ancestor @ancestor somewhere up in the hierarchy. One can e.g. check if a #GstElement is inside a #GstPipeline.
hasAsAncestor bool hasAsAncestor(ObjectGst ancestor): Check if @object has an ancestor @ancestor somewhere up in the hierarchy. One can e.g. check if a #GstElement is inside a #GstPipeline.
hasAsParent bool hasAsParent(ObjectGst parent): Check if @parent is the parent of @object. E.g. a #GstElement can check if it owns a given #GstPad.
doref ObjectGst doref(): Increments the reference count on @object. This function does not take the lock on @object because it relies on atomic refcounting.
removeControlBinding bool removeControlBinding(ControlBinding binding): Removes the corresponding #GstControlBinding. If it was the last ref of the binding, it will be disposed.
setControlBindingDisabled void setControlBindingDisabled(string propertyName, bool disabled): This function is used to disable the control bindings on a property for some time, i.e. gst_object_sync_values() will do nothing for the property.
setControlBindingsDisabled void setControlBindingsDisabled(bool disabled): This function is used to disable all controlled properties of the @object for some time, i.e. gst_object_sync_values() will do nothing.
setControlRate void setControlRate(GstClockTime controlRate): Change the control-rate for this @object. Audio processing #GstElement objects will use this rate to sub-divide their processing loop and call gst_object_sync_values() inbetween. The length of the processing segment should be up to @control-rate nanoseconds.
setName bool setName(string name): Sets the name of @object, or gives @object a guaranteed unique name (if @name is %NULL). This function makes a copy of the provided name, so the caller retains ownership of the name it sent.
setParent bool setParent(ObjectGst parent): Sets the parent of @object to @parent. The object's reference count will be incremented, and any floating reference will be removed (see gst_object_ref_sink()).
suggestNextSync GstClockTime suggestNextSync(): Returns a suggestion for timestamps where buffers should be split to get best controller results.
syncValues bool syncValues(GstClockTime timestamp): Sets the properties of the object, according to the #GstControlSources that (maybe) handle them and for the given timestamp.
unparent void unparent(): Clear the parent of @object, removing the associated reference. This function decreases the refcount of @object.
unref void unref(): Decrements the reference count on @object. If reference count hits zero, destroy @object. This function does not take the lock on @object as it relies on atomic refcounting.
addOnDeepNotify gulong addOnDeepNotify(void delegate(ObjectGst, ParamSpec, ObjectGst) dlg, ConnectFlags connectFlags): The deep notify signal is used to be notified of property changes. It is typically attached to the toplevel bin to receive notifications from all the elements contained in that bin.

Meta

Source

See Implementation

gstreamer Element classes

Element