Struct gstreamer_base::BaseSink

pub struct BaseSink { /* private fields */ }

BaseSink is the base class for sink elements in GStreamer, such as xvimagesink or filesink. It is a layer on top of gst::Element that provides a simplified interface to plugin writers. BaseSink handles many details for you, for example: preroll, clock synchronization, state changes, activation in push or pull mode, and queries.

In most cases, when writing sink elements, there is no need to implement class methods from gst::Element or to set functions on pads, because the BaseSink infrastructure should be sufficient.

BaseSink provides support for exactly one sink pad, which should be named “sink”. A sink implementation (subclass of BaseSink) should install a pad template in its class_init function, like so:

⚠️ The following code is in C ⚠️

static void
my_element_class_init (GstMyElementClass *klass)
{
  GstElementClass *gstelement_class = GST_ELEMENT_CLASS (klass);

  // sinktemplate should be a #GstStaticPadTemplate with direction
  // %GST_PAD_SINK and name "sink"
  gst_element_class_add_static_pad_template (gstelement_class, &sinktemplate);

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

BaseSink will handle the prerolling correctly. This means that it will return gst::StateChangeReturn::Async from a state change to PAUSED until the first buffer arrives in this element. The base class will call the GstBaseSinkClass::preroll vmethod with this preroll buffer and will then commit the state change to the next asynchronously pending state.

When the element is set to PLAYING, BaseSink will synchronise on the clock using the times returned from GstBaseSinkClass::get_times. If this function returns GST_CLOCK_TIME_NONE for the start time, no synchronisation will be done. Synchronisation can be disabled entirely by setting the object sync property to false.

After synchronisation the virtual method GstBaseSinkClass::render will be called. Subclasses should minimally implement this method.

Subclasses that synchronise on the clock in the GstBaseSinkClass::render method are supported as well. These classes typically receive a buffer in the render method and can then potentially block on the clock while rendering. A typical example is an audiosink. These subclasses can use BaseSinkExt::wait_preroll() to perform the blocking wait.

Upon receiving the EOS event in the PLAYING state, BaseSink will wait for the clock to reach the time indicated by the stop time of the last GstBaseSinkClass::get_times call before posting an EOS message. When the element receives EOS in PAUSED, preroll completes, the event is queued and an EOS message is posted when going to PLAYING.

BaseSink will internally use the gst::EventType::Segment events to schedule synchronisation and clipping of buffers. Buffers that fall completely outside of the current segment are dropped. Buffers that fall partially in the segment are rendered (and prerolled). Subclasses should do any subbuffer clipping themselves when needed.

BaseSink will by default report the current playback position in gst::Format::Time based on the current clock time and segment information. If no clock has been set on the element, the query will be forwarded upstream.

The GstBaseSinkClass::set_caps function will be called when the subclass should configure itself to process a specific media type.

The GstBaseSinkClass::start and GstBaseSinkClass::stop virtual methods will be called when resources should be allocated. Any GstBaseSinkClass::preroll, GstBaseSinkClass::render and GstBaseSinkClass::set_caps function will be called between the GstBaseSinkClass::start and GstBaseSinkClass::stop calls.

The GstBaseSinkClass::event virtual method will be called when an event is received by BaseSink. Normally this method should only be overridden by very specific elements (such as file sinks) which need to handle the newsegment event specially.

The GstBaseSinkClass::unlock method is called when the elements should unblock any blocking operations they perform in the GstBaseSinkClass::render method. This is mostly useful when the GstBaseSinkClass::render method performs a blocking write on a file descriptor, for example.

The max-lateness property affects how the sink deals with buffers that arrive too late in the sink. A buffer arrives too late in the sink when the presentation time (as a combination of the last segment, buffer timestamp and element base_time) plus the duration is before the current time of the clock. If the frame is later than max-lateness, the sink will drop the buffer without calling the render method. This feature is disabled if sync is disabled, the GstBaseSinkClass::get_times method does not return a valid start time or max-lateness is set to -1 (the default). Subclasses can use BaseSinkExt::set_max_lateness() to configure the max-lateness value.

The qos property will enable the quality-of-service features of the basesink which gather statistics about the real-time performance of the clock synchronisation. For each buffer received in the sink, statistics are gathered and a QOS event is sent upstream with these numbers. This information can then be used by upstream elements to reduce their processing rate, for example.

The async property can be used to instruct the sink to never perform an ASYNC state change. This feature is mostly usable when dealing with non-synchronized streams or sparse streams.

This is an Abstract Base Class, you cannot instantiate it.

Properties

async

If set to true, the basesink will perform asynchronous state changes. When set to false, the sink will not signal the parent when it prerolls. Use this option when dealing with sparse streams or when synchronisation is not required.

Readable | Writeable

blocksize

The amount of bytes to pull when operating in pull mode.

Readable | Writeable

enable-last-sample

Enable the last-sample property. If false, basesink doesn’t keep a reference to the last buffer arrived and the last-sample property is always set to None. This can be useful if you need buffers to be released as soon as possible, eg. if you’re using a buffer pool.

Readable | Writeable

last-sample

The last buffer that arrived in the sink and was used for preroll or for rendering. This property can be used to generate thumbnails. This property can be None when the sink has not yet received a buffer.

Readable

max-bitrate

Control the maximum amount of bits that will be rendered per second. Setting this property to a value bigger than 0 will make the sink delay rendering of the buffers when it would exceed to max-bitrate.

Readable | Writeable

max-lateness

Readable | Writeable

processing-deadline

Maximum amount of time (in nanoseconds) that the pipeline can take for processing the buffer. This is added to the latency of live pipelines.

Readable | Writeable

qos

Readable | Writeable

render-delay

The additional delay between synchronisation and actual rendering of the media. This property will add additional latency to the device in order to make other sinks compensate for the delay.

Readable | Writeable

stats

Various BaseSink statistics. This property returns a gst::Structure with name application/x-gst-base-sink-stats with the following fields:

• “average-rate” G_TYPE_DOUBLE average frame rate
• “dropped” G_TYPE_UINT64 Number of dropped frames
• “rendered” G_TYPE_UINT64 Number of rendered frames

Readable

sync

Readable | Writeable

throttle-time

The time to insert between buffers. This property can be used to control the maximum amount of buffers per second to render. Setting this property to a value bigger than 0 will make the sink create THROTTLE QoS events.

Readable | Writeable

ts-offset

Controls the final synchronisation, a negative value will render the buffer earlier while a positive value delays playback. This property can be used to fix synchronisation in bad files.

Readable | Writeable

Object

name

Readable | Writeable | Construct

parent

The parent of the object. Please note, that when changing the ‘parent’ property, we don’t emit notify and deep-notify signals due to locking issues. In some cases one can use GstBin::element-added or GstBin::element-removed signals on the parent to achieve a similar effect.

Readable | Writeable

Implements

BaseSinkExt, gst::prelude::ElementExt, gst::prelude::ObjectExt, [trait@glib::ObjectExt], BaseSinkExtManual

Implementations

impl BaseSink

pub const NONE: Option<&'static BaseSink> = None

Trait Implementations

impl Clone for BaseSink

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for BaseSink

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl HasParamSpec for BaseSink

type ParamSpec = ParamSpecObject

type SetValue = BaseSink

Preferred value to be used as setter for the associated ParamSpec.

type BuilderFn = fn(_: &str) -> ParamSpecObjectBuilder<'_, BaseSink>

fn param_spec_builder() -> Self::BuilderFn

impl Hash for BaseSink

fn hash<H>(&self, state: &mut H)

where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T: BaseSinkImpl> IsSubclassable<T> for BaseSink

fn class_init(klass: &mut Class<Self>)

Override the virtual methods of this class for the given subclass and do other class initialization.

fn instance_init(instance: &mut InitializingObject<T>)

Instance specific initialization.

impl Ord for BaseSink

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized + PartialOrd,

Restrict a value to a certain interval.

impl ParentClassIs for BaseSink

type Parent = Element

impl<OT: ObjectType> PartialEq<OT> for BaseSink

fn eq(&self, other: &OT) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<OT: ObjectType> PartialOrd<OT> for BaseSink

fn partial_cmp(&self, other: &OT) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl StaticType for BaseSink

fn static_type() -> Type

Returns the type identifier of Self.

impl Eq for BaseSink

impl IsA<Element> for BaseSink

impl IsA<Object> for BaseSink

impl Send for BaseSink

impl Sync for BaseSink