Portability	portable (depends on GHC)
Stability	alpha
Maintainer	gtk2hs-devel@lists.sourceforge.net
Safe Haskell	Safe-Infered

Media.Streaming.GStreamer.Core.Element

Contents

Detail
Types
Element Operations

Description

Abstract class of pipeline elements.

Synopsis

Detail

Element is the abstract base class needed to construct an element that can be used in a GStreamer pipeline.

All elements have pads (of the type Pad). These pads link to pads on other elements. Buffers flow between these linked pads. An Element has a Pad for each input (or sink) and output (or source).

An element's pad can be retrieved by name with elementGetStaticPad or elementGetRequestPad. An Iterator over all an element's pads can be retrieved with elementIteratePads.

Elements can be linked through their pads. If the link is straightforward, use the elementLink convenience function to link two elements. Use elementLinkFiltered to link two elements constrained by a specified set of Caps. For finer control, use elementLinkPads and elementLinkPadsFiltered to specify the pads to link on each element by name.

Each element has a State. You can get and set the state of an element with elementGetState and elementSetState. To get a string representation of a State, use elementStateGetName.

You can get and set a Clock on an element using elementGetClock and elementSetClock. Some elements can provide a clock for the pipeline if elementProvidesClock returns True. With the elementProvideClock method one can retrieve the clock provided by such an element. Not all elements require a clock to operate correctly. If elementRequiresClock returns True, a clock should be set on the element with elementSetClock.

Note that clock slection and distribution is normally handled by the toplevel Pipeline so the clock functions should only be used in very specific situations.

Types

data Element Source

Instances

Eq Element
Ord Element
GObjectClass Element
ElementClass Element
ObjectClass Element
Iterable Element

castToElement :: GObjectClass obj => obj -> Element Source

gTypeElement :: GType Source

data ElementFlags Source

The flags that an Element may have.

Constructors

ElementLockedState	parent state changes are ignored
ElementIsSink	the element is a sink
ElementUnparenting	child is being removed from the parent bin

Instances

Bounded ElementFlags
Enum ElementFlags
Eq ElementFlags
Show ElementFlags
Flags ElementFlags

data State Source

Constructors

StateVoidPending
StateNull
StateReady
StatePaused
StatePlaying

Instances

Enum State
Eq State
Show State

data StateChange Source

The different state changes that are passed to the state change functions of Elements.

Constructors

StateChangeNullToReady	state change from `StateNull` to `StateReady`
StateChangeReadyToPaused	state change from `StateReady` to `StatePaused`
StateChangePausedToPlaying	state change from `StatePaused` to `StatePlaying`
StateChangePlayingToPaused	state change from `StatePlaying` to `StatePaused`
StateChangePausedToReady	state change from `StatePaused` to `StateReady`
StateChangeReadyToNull	state change from `StateReady` to `StateNull`

Instances

Enum StateChange
Eq StateChange
Show StateChange

data StateChangeReturn Source

Constructors

StateChangeFailure
StateChangeSuccess
StateChangeAsync
StateChangeNoPreroll

Instances

Enum StateChangeReturn
Eq StateChangeReturn
Show StateChangeReturn

Element Operations

elementAddPad Source

Arguments

:: (ElementClass elementT, PadClass padT)
=> elementT	`element` - an element
-> padT	`pad` -
-> IO Bool

Add a pad (link point) to an element. The pad's parent will be set to element.

Pads are not automatically activated so elements should perform the needed steps to activate the pad in case this pad is added in the StatePaused or StatePlaying state. See padSetActive for more information about activating pads.

This function will emit the elementPadAdded signal on the element.

elementGetCompatiblePad Source

Arguments

:: (ElementClass elementT, PadClass padT)
=> elementT	`element` - an element
-> padT	`pad` - a pad
-> Caps	`caps` - the `Caps` to use as a filter
-> IO (Maybe Pad)	a `Pad` that is compatible with `pad`, or `Nothing` if none was found

Look for an unlinked pad to which the pad can link. It is not guaranteed that linking the pads will work, though it should work in most cases.

elementGetCompatiblePadTemplate Source

Arguments

:: (ElementClass elementT, PadTemplateClass padTemplateT)
=> elementT	`element` - an element
-> padTemplateT	`padTemplate` - a pad template
-> IO (Maybe PadTemplate)	the compatible `PadTemplate`, or `Nothing` if none was found

Retrieve a pad template from element that is compatible with padTemplate. Pads from compatible templates can be linked together.

elementGetRequestPad Source

Arguments

:: ElementClass elementT
=> elementT	`element` - an element
-> String	`name` -
-> IO (Maybe Pad)	the requested `Pad` if found, otherwise `Nothing`.

Retrieve a pad from the element by name. This version only retrieves request pads. The pad should be released with elementReleaseRequestPad.

elementGetStaticPad Source

Arguments

:: ElementClass elementT
=> elementT	`element` - an element
-> String	`name` -
-> IO (Maybe Pad)	the requested `Pad` if found, otherwise `Nothing`.

Retreive a pad from element by name. This version only retrieves already-existing (i.e. static) pads.

elementReleaseRequestPad Source

Arguments

:: (ElementClass elementT, PadClass padT)
=> elementT	`element` -
-> padT	`pad` -
-> IO ()

Release a request pad that was previously obtained with elementGetRequestPad.

elementRemovePad Source

Arguments

:: (ElementClass elementT, PadClass padT)
=> elementT	`element` -
-> padT	`pad` -
-> IO Bool	`True` if the pad was succcessfully removed, otherwise `False`

Remove pad from element.

This function is used by plugin developers and should not be used by applications. Pads that were dynamically requested from elements with elementGetRequestPad should be released with the elementReleaseRequestPad function instead.

Pads are not automatically deactivated so elements should perform the needed steps to deactivate the pad in case this pad is removed in the PAUSED or PLAYING state. See padSetActive for more information about deactivating pads.

The pad and the element should be unlocked when calling this function.

This function will emit the padRemoved signal on the element.

Returns: True if the pad could be removed. Can return False if the pad does not belong to the provided element.

elementIteratePads Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> IO (Iterator Pad)	an iterator over the element's pads.

Retrieve an Iterator over element's pads.

elementIterateSinkPads :: ElementClass elementT => elementT -> IO (Iterator Pad)Source

Retrieve an Iterator over element's sink pads.

elementIterateSrcPads :: ElementClass elementT => elementT -> IO (Iterator Pad)Source

Retrieve an Iterator over element's src pads.

elementLink Source

Arguments

:: (ElementClass srcT, ElementClass sinkT)
=> srcT	`src` -
-> sinkT	`sink` -
-> IO Bool	`True` if the pads could be linked, otherwise `False`

Link src to sink. The link must be from source to sink; 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 must be released manually (with elementReleaseRequestPad) when unlinking. If multiple links are possible, only one is established.

Make sure you have added your elements to a Bin or Pipeline with binAdd before trying to link them.

elementUnlink :: (ElementClass srcT, ElementClass sinkT) => srcT -> sinkT -> IO ()Source

Unlink all source pads of the src from all sink pads of the sink.

elementLinkPads Source

Arguments

:: (ElementClass srcT, ElementClass sinkT)
=> srcT	`src` - the element containing the source pad
-> Maybe String	`srcPadName` - the name of the source pad, or `Nothing` for any pad
-> sinkT	`sink` - the element containing the sink pad
-> Maybe String	`sinkPadName` - the name of the sink pad, or `Nothing` for any pad
-> IO Bool	`True` if the pads could be linked, otherwise `False`

Link the named pads of src and sink.

elementUnlinkPads Source

Arguments

:: (ElementClass srcT, ElementClass sinkT)
=> srcT	`src` -
-> String	`srcPadName` -
-> sinkT	`sink` -
-> String	`sinkPadName` -
-> IO ()

Unlink the named pads of src and sink.

elementLinkPadsFiltered Source

Arguments

:: (ElementClass srcT, ElementClass sinkT)
=> srcT	`src` -
-> Maybe String	`srcPadName` -
-> sinkT	`sink` -
-> Maybe String	`sinkPadName` -
-> Caps	`caps` -
-> IO Bool	`True` if the pads could be linked, otherwise `False`

Link the named pads of src and sink. A 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 will fail. If caps is not Nothing, make sure that the Caps of the link is a subset of caps.

elementLinkFiltered Source

Arguments

:: (ElementClass srcT, ElementClass sinkT)
=> srcT	`src` -
-> sinkT	`sink` -
-> Maybe Caps	`caps` -
-> IO Bool	`True` if the pads could be linked, otherwise `False`

Link src to dest using the given Caps as a filter. The link must be from source to sink; the other direction will not be tried. The function looks for existing pads that aren't linked yet. If will request new pads if necessary. If multiple links are possible, only one is established.

Make sure you have added your elements to a Bin or Pipeline with binAdd before trying to link them.

elementSetBaseTime Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> ClockTimeDiff	`time` -
-> IO ()

Set the base time of element. See elementGetBaseTime for more information.

elementGetBaseTime Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> IO ClockTimeDiff	the base time of the element

Return the base time of element. The base time is the absolute time of the clock when this element was last set to StatePlaying. Subtract the base time from the clock time to get the stream time of the element.

elementSetBus Source

Arguments

:: (ElementClass elementT, BusClass busT)
=> elementT	`element` -
-> busT	`bus` -
-> IO ()

Set the Bus used by element. For internal use only, unless you're testing elements.

elementGetBus Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> IO Bus	the bus used by the element

Get the bus of element. Not that only a Pipeline will provide a bus for the application.

elementGetFactory Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> IO ElementFactory	the factory that created `element`

Get the factory used to create element.

elementSetIndex Source

Arguments

:: (ElementClass elementT, IndexClass indexT)
=> elementT	`element` -
-> indexT	`index` -
-> IO ()

Set the Index used by element.

elementIsIndexable Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> IO Bool	`True` if the element can be indexed

Determine whether element can be indexed.

elementRequiresClock Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> IO Bool	`True` if the element requires a clock

Determine whether element requires a clock.

elementSetClock Source

Arguments

:: (ElementClass elementT, ClockClass clockT)
=> elementT	`element` -
-> clockT	`clock` -
-> IO Bool	`True` if the element accepted the clock

Set the Clock used by element.

elementGetClock Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> IO (Maybe Clock)	the clock, or `Nothing` if `element` has none

Get the Clock used by element.

elementProvidesClock Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> IO Bool	`True` if the element provides a clock

Determine whether element provides a clock. A Clock provided by an element can be used as the global clock for a pipeline. An element that can provide a clock is only required to do so in the StatePaused state, meaning that it is fully negotiated and has allocated the resources needed to operate the clock.

elementProvideClock Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> IO (Maybe Clock)	a `Clock`, or `Nothing` if none could be provided

Get the Clock provided by element.

Note that an element is only required to provide a clock in the StatePaused state. Some elements can provide a clock in other states.

elementSetState Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> State	`state` -
-> IO StateChangeReturn	the result of the state change

Set the state of element to state. 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.

This function can return StateChangeAsync, in which case the element will perform the remainder of the state change asynchronously in another thread. An application can use elementGetState to wait for the completion of the state change or it can wait for a state change message on the bus.

elementGetState Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> ClockTime	`timeout` -
-> IO (StateChangeReturn, Maybe State, Maybe State)	the result of the state change, the current state, and the pending state

Get the state of element.

For elements that performed an asynchronous state change, as reported by elementSetState, this function will block up to the specified timeout value for the state change to complete. If the element completes the state change or goes into an error, this function returns immediately with a return value of StateChangeSuccess or StateChangeFailure, respectively.

This function returns StateChangeNoPreroll if the element successfully changed its state but is not able to provide data yet. This mostly happens for live sources that not only produce data in the StatePlaying state. While the state change return is equivalent to StateChangeSuccess, it is returned to the application to signal that some sink elements might not be able to somplete their state change because an element is not producing data to complete the preroll. When setting the element to playing, the preroll will complete and playback will start.

elementSetLockedState Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> Bool	`lockedState` - `True` for locked, `False` for unlocked
-> IO Bool	`True` if the state was changed, `False` if bad parameters were given or no change was needed

Lock the state of element, so state changes in the parent don't affect this element any longer.

elementIsLockedState Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> IO Bool	`True` if `element`'s state is locked, `False` otherwise

Determine whether element's state is locked.

elementAbortState Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> IO ()

Abort element's state change. This function is used by elements that do asynchronous state changes and find out something is wrong.

This function should be called with the state lock held.

elementStateGetName Source

Arguments

:: State	`state` -
-> String	the name of `state`

Get a string representation of state.

elementStateChangeReturnGetName Source

Arguments

:: StateChangeReturn	`stateRet` -
-> String	the name of `stateRet`

Get a string representation of stateRet.

Since 0.10.11.

elementSyncStateWithParent Source

Arguments

:: ElementClass elementT
=> elementT	`element` -
-> IO Bool	`True` if the element's state could be synced with its parent's state

Try to change the state of element to the same as its parent. If this function returns False, the state of the element is undefined.

elementGetQueryTypes :: ElementClass element => element -> IO [QueryType]Source

elementQuery Source

Arguments

:: (ElementClass element, QueryClass query)
=> element	`element` -
-> query	`query` -
-> IO Bool	`True` if the query could be performed

Perform a query on the given element.

For elements that don't implement a query handler, this function forwards the query to a random srcpad or to the peer of a random linked sinkpad of this element.

elementQueryConvert Source

Arguments

:: ElementClass element
=> element	`element` - the element to query
-> Format	`srcFormat` - the format to convert from
-> Int64	`srcVal` - the value to convert
-> Format	`destFormat` - the format to convert to
-> IO (Maybe (Format, Word64))	the resulting format and value

Query an element for the convertion of a value from one format to another.

elementQueryPosition Source

Arguments

:: ElementClass element
=> element	`element` - the element to query
-> Format	`format` - the format requested
-> IO (Maybe (Format, Word64))	the resulting format and value

Query an element for its stream position.

elementQueryDuration Source

Arguments

:: ElementClass element
=> element	`element` - the element to query
-> Format	`format` - the format requested
-> IO (Maybe (Format, Word64))	the resulting format and value

Query an element for its stream duration.

elementSendEvent Source

Arguments

:: (ElementClass element, EventClass event)
=> element	`element` - the element to send the event to
-> event	`event` - the event to send
-> IO Bool	`True` if the event was handled

Send an event to an element.

If the element doesn't implement an event handler, the event will be pushed to a random linked sink pad for upstream events or a random linked source pad for downstream events.

elementSeekSimple Source

Arguments

:: ElementClass element
=> element	`element` - the element to seek on
-> Format	`format` - the `Format` to evecute the seek in, such as `FormatTime`
-> [SeekFlags]	`seekFlags` - seek options; playback applications will usually want to use `[SeekFlagFlush,SeekFlagKeyUnit]`
-> Int64	`seekPos` - the position to seek to, relative to start; if you are doing a seek in `FormatTime` this value is in nanoseconds; see `second`, `msecond`, `usecond`, & `nsecond`
-> IO Bool	`True` if the seek operation succeeded

Perform a seek on the given element. This function only supports seeking to a position relative to the start of the stream. For more complex operations like segment seeks (such as for looping), or changing the playback rate, or seeking relative to the last configured playback segment you should use elementSeek.

In a completely prerolled pipeline in the StatePaused or StatePlaying states, seeking is always guaranteed to return True on a seekable media type, or False when the media type is certainly not seekable (such as a live stream).

Some elements allow for seeking in the StateReady state, in which case they will store the seek event and execute it when they are put into the StatePaused state. If the element supports seek in StateReady, it will always return True when it recieves the event in the StateReady state.

elementSeek Source

Arguments

:: ElementClass element
=> element	`element` - the element to seek on
-> Double	`rate` - the new playback rate
-> Format	`format` - the format of the seek values
-> [SeekFlags]	`seekFlags` - the options to use
-> SeekType	`curType` - type and flags for the new current position
-> Int64	`cur` - the value of the new current position
-> SeekType	`stopType` - type and flags for the new stop position
-> Int64	`stop` - the value of the new stop position
-> IO Bool	`True` if the event was handled

Send a seek event to an element. See eventNewSeek for the details of the parameters. The seek event is sent to the element using elementSendEvent.

elementNoMorePads :: ElementClass element => Signal element (IO ())Source

The signal emitted when an element will not generate more dynamic pads.

elementPadAdded :: ElementClass element => Signal element (Pad -> IO ())Source

The signal emitted when a new Pad has been added to the element.

elementPadRemoved :: ElementClass element => Signal element (Pad -> IO ())Source

The signal emitted when a Pad has been removed from the element.

ElementClass BaseTransform
ElementClass BaseSink
ElementClass PushSrc
ElementClass BaseSrc
ElementClass TagSetter
ElementClass ImplementsInterface
ElementClass Pipeline
ElementClass Bin
ElementClass Element