[][src]Struct gstreamer_base::BaseSrc

pub struct BaseSrc(_, _);

This is a generic base class for source elements. The following types of sources are supported:

The source can be configured to operate in any gst::Format with the BaseSrcExt::set_format method. The currently set format determines the format of the internal gst::Segment and any gst::EventType::Segment events. The default format for BaseSrc is gst::Format::Bytes.

BaseSrc always supports push mode scheduling. If the following conditions are met, it also supports pull mode scheduling:

If all the conditions are met for operating in pull mode, BaseSrc is automatically seekable in push mode as well. The following conditions must be met to make the element seekable in push mode when the format is not gst::Format::Bytes:

When the element does not meet the requirements to operate in pull mode, the offset and length in the BaseSrcClass.create() method should be ignored. It is recommended to subclass PushSrc instead, in this situation. If the element can operate in pull mode but only with specific offsets and lengths, it is allowed to generate an error when the wrong values are passed to the BaseSrcClass.create() function.

BaseSrc has support for live sources. Live sources are sources that when paused discard data, such as audio or video capture devices. A typical live source also produces data at a fixed rate and thus provides a clock to publish this rate. Use BaseSrcExt::set_live to activate the live source mode.

A live source does not produce data in the PAUSED state. This means that the BaseSrcClass.create() method will not be called in PAUSED but only in PLAYING. To signal the pipeline that the element will not produce data, the return value from the READY to PAUSED state will be gst::StateChangeReturn::NoPreroll.

A typical live source will timestamp the buffers it creates with the current running time of the pipeline. This is one reason why a live source can only produce data in the PLAYING state, when the clock is actually distributed and running.

Live sources that synchronize and block on the clock (an audio source, for example) can use BaseSrc::wait_playing when the BaseSrcClass.create() function was interrupted by a state change to PAUSED.

The BaseSrcClass.get_times() method can be used to implement pseudo-live sources. It only makes sense to implement the BaseSrcClass.get_times() function if the source is a live source. The BaseSrcClass.get_times() function should return timestamps starting from 0, as if it were a non-live source. The base class will make sure that the timestamps are transformed into the current running_time. The base source will then wait for the calculated running_time before pushing out the buffer.

For live sources, the base class will by default report a latency of 0. For pseudo live sources, the base class will by default measure the difference between the first buffer timestamp and the start time of get_times and will report this value as the latency. Subclasses should override the query function when this behaviour is not acceptable.

There is only support in BaseSrc for exactly one source pad, which should be named "src". A source implementation (subclass of BaseSrc) should install a pad template in its class_init function, like so:

static void
my_element_class_init (GstMyElementClass *klass)
{
  GstElementClass *gstelement_class = GST_ELEMENT_CLASS (klass);
  // srctemplate should be a #GstStaticPadTemplate with direction
  // %GST_PAD_SRC and name "src"
  gst_element_class_add_static_pad_template (gstelement_class, &srctemplate);

  gst_element_class_set_static_metadata (gstelement_class,
     "Source name",
     "Source",
     "My Source element",
     "The author <my.sink@my.email>");
}

Controlled shutdown of live sources in applications

Applications that record from a live source may want to stop recording in a controlled way, so that the recording is stopped, but the data already in the pipeline is processed to the end (remember that many live sources would go on recording forever otherwise). For that to happen the application needs to make the source stop recording and send an EOS event down the pipeline. The application would then wait for an EOS message posted on the pipeline's bus to know when all data has been processed and the pipeline can safely be stopped.

An application may send an EOS event to a source element to make it perform the EOS logic (send EOS event downstream or post a gst::MessageType::SegmentDone on the bus). This can typically be done with the gst::ElementExt::send_event function on the element or its parent bin.

After the EOS has been sent to the element, the application should wait for an EOS message to be posted on the pipeline's bus. Once this EOS message is received, it may safely shut down the entire pipeline.

Implements

BaseSrcExt, gst::ElementExt, gst::ObjectExt, glib::object::ObjectExt, BaseSrcExtManual

Trait Implementations

impl Clone for BaseSrc[src]

impl Debug for BaseSrc[src]

impl Eq for BaseSrc[src]

impl Hash for BaseSrc[src]

impl IsA<BaseSrc> for PushSrc[src]

impl IsA<Element> for BaseSrc[src]

impl IsA<Object> for BaseSrc[src]

impl Ord for BaseSrc[src]

impl<T: ObjectType> PartialEq<T> for BaseSrc[src]

impl<T: ObjectType> PartialOrd<T> for BaseSrc[src]

impl Send for BaseSrc[src]

impl StaticType for BaseSrc[src]

impl Sync for BaseSrc[src]

Auto Trait Implementations

impl RefUnwindSafe for BaseSrc

impl Unpin for BaseSrc

impl UnwindSafe for BaseSrc

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized
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impl<T> Borrow<T> for T where
    T: ?Sized
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impl<T> BorrowMut<T> for T where
    T: ?Sized
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impl<Super, Sub> CanDowncast<Sub> for Super where
    Sub: IsA<Super>,
    Super: IsA<Super>, 
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impl<T> Cast for T where
    T: ObjectType
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impl<O> ElementExt for O where
    O: IsA<Element>, 
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impl<O> ElementExtManual for O where
    O: IsA<Element>, 
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impl<T> From<T> for T[src]

impl<O> GObjectExtManualGst for O where
    O: IsA<Object>, 
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impl<O> GstObjectExt for O where
    O: IsA<Object>, 
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impl<O> GstObjectExtManual for O where
    O: IsA<Object>, 
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impl<T, U> Into<U> for T where
    U: From<T>, 
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impl<T> ObjectExt for T where
    T: ObjectType
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impl<'a, T> ToGlibContainerFromSlice<'a, *const GList> for T where
    T: GlibPtrDefault + ToGlibPtr<'a, <T as GlibPtrDefault>::GlibType>, 
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impl<'a, T> ToGlibContainerFromSlice<'a, *const GPtrArray> for T where
    T: GlibPtrDefault + ToGlibPtr<'a, <T as GlibPtrDefault>::GlibType>, 
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impl<'a, T> ToGlibContainerFromSlice<'a, *mut GArray> for T where
    T: GlibPtrDefault + ToGlibPtr<'a, <T as GlibPtrDefault>::GlibType>, 
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impl<'a, T> ToGlibContainerFromSlice<'a, *mut GList> for T where
    T: GlibPtrDefault + ToGlibPtr<'a, <T as GlibPtrDefault>::GlibType>, 
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impl<'a, T> ToGlibContainerFromSlice<'a, *mut GPtrArray> for T where
    T: GlibPtrDefault + ToGlibPtr<'a, <T as GlibPtrDefault>::GlibType>, 
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impl<T> ToOwned for T where
    T: Clone
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type Owned = T

The resulting type after obtaining ownership.

impl<T> ToSendValue for T where
    T: ToValue + SetValue + Send + ?Sized
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impl<T> ToValue for T where
    T: SetValue + ?Sized
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impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
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type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.