Class BaseSink

java.lang.Object
org.javagi.base.ProxyInstance
org.gnome.gobject.TypeInstance
org.gnome.gobject.GObject
org.gnome.gobject.InitiallyUnowned
org.freedesktop.gstreamer.gst.GstObject
org.freedesktop.gstreamer.gst.Element
org.freedesktop.gstreamer.base.BaseSink
All Implemented Interfaces:
Proxy
Direct Known Subclasses:
AppSink, AudioBaseSink, BaseSink.BaseSink$Impl, VideoSink
@Generated("org.javagi.JavaGI") public abstract class BaseSink extends Element

GstBaseSink is the base class for sink elements in GStreamer, such as xvimagesink or filesink. It is a layer on top of GstElement that provides a simplified interface to plugin writers. GstBaseSink 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 GstElement or to set functions on pads, because the GstBaseSink infrastructure should be sufficient.

GstBaseSink provides support for exactly one sink pad, which should be named "sink". A sink implementation (subclass of GstBaseSink) 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);

  // 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>");
}

GstBaseSink will handle the prerolling correctly. This means that it will return 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, GstBaseSink 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 GstBaseSink: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 gst_base_sink_wait_preroll() to perform the blocking wait.

Upon receiving the EOS event in the PLAYING state, GstBaseSink 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.

GstBaseSink will internally use the 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.

GstBaseSink will by default report the current playback position in 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 GstBaseSink. 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 GstBaseSink: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 gst_base_sink_set_max_lateness() to configure the max-lateness value.

The GstBaseSink: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 GstBaseSink: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.

  • Constructor Details

    • BaseSink

      public BaseSink(MemorySegment address)
      Create a BaseSink instance for the provided memory address.
      Parameters:
      address - the memory address of the native object

    • BaseSink

      public BaseSink()
      Create a new BaseSink.

  • Method Details

    • getType

      public static @Nullable Type getType()
      Get the GType of the BaseSink class.
      Returns:
      the GType

    • getMemoryLayout

      public static MemoryLayout getMemoryLayout()
      The memory layout of the native struct.
      Returns:
      the memory layout

    • asParent

      protected BaseSink asParent()
      Return this instance as if it were its parent type. Comparable to the Java super keyword, but ensures the parent typeclass is also used in native code.
      Overrides:
      asParent in class Element
      Returns:
      the instance as if it were its parent type

    • doPreroll

      public FlowReturn doPreroll(MiniObject obj)

      If the this BaseSink spawns its own thread for pulling buffers from upstream it should call this method after it has pulled a buffer. If the element needed to preroll, this function will perform the preroll and will then block until the element state is changed.

      This function should be called with the PREROLL_LOCK held.

      Parameters:
      obj - the mini object that caused the preroll
      Returns:
      FlowReturn.OK if the preroll completed and processing can continue. Any other return value should be returned from the render vmethod.

    • getBlocksize

      public int getBlocksize()
      Get the number of bytes that the sink will pull when it is operating in pull mode.
      Returns:
      the number of bytes this BaseSink will pull in pull mode.

    • getDropOutOfSegment

      public boolean getDropOutOfSegment()
      Checks if this BaseSink is currently configured to drop buffers which are outside the current segment
      Returns:
      true if the sink is configured to drop buffers outside the current segment.
      Since:
      1.12

    • getLastSample

      public @Nullable Sample getLastSample()

      Get the last sample that arrived in the sink and was used for preroll or for rendering. This property can be used to generate thumbnails.

      The GstCaps on the sample can be used to determine the type of the buffer.

      Free-function: gst_sample_unref

      Returns:
      a GstSample. gst_sample_unref() after usage. This function returns null when no buffer has arrived in the sink yet or when the sink is not in PAUSED or PLAYING.

    • getLatency

      public ClockTime getLatency()
      Get the currently configured latency.
      Returns:
      The configured latency.

    • getMaxBitrate

      public long getMaxBitrate()
      Get the maximum amount of bits per second that the sink will render.
      Returns:
      the maximum number of bits per second this BaseSink will render.
      Since:
      1.2

    • getMaxLateness

      public long getMaxLateness()
      Gets the max lateness value. See gst_base_sink_set_max_lateness() for more details.
      Returns:
      The maximum time in nanoseconds that a buffer can be late before it is dropped and not rendered. A value of -1 means an unlimited time.

    • getProcessingDeadline

      public ClockTime getProcessingDeadline()
      Get the processing deadline of sink. see gst_base_sink_set_processing_deadline() for more information about the processing deadline.
      Returns:
      the processing deadline
      Since:
      1.16

    • getRenderDelay

      public ClockTime getRenderDelay()
      Get the render delay of sink. see gst_base_sink_set_render_delay() for more information about the render delay.
      Returns:
      the render delay of sink.

    • getStats

      public Structure getStats()

      Return various GstBaseSink statistics. This function returns a GstStructure 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
      Returns:
      pointer to GstStructure
      Since:
      1.18

    • getSync

      public boolean getSync()
      Checks if this BaseSink is currently configured to synchronize against the clock.
      Returns:
      true if the sink is configured to synchronize against the clock.

    • getThrottleTime

      public long getThrottleTime()
      Get the time that will be inserted between frames to control the maximum buffers per second.
      Returns:
      the number of nanoseconds this BaseSink will put between frames.

    • getTsOffset

      public ClockTimeDiff getTsOffset()
      Get the synchronisation offset of sink.
      Returns:
      The synchronisation offset.

    • isAsyncEnabled

      public boolean isAsyncEnabled()
      Checks if this BaseSink is currently configured to perform asynchronous state changes to PAUSED.
      Returns:
      true if the sink is configured to perform asynchronous state changes.

    • isLastSampleEnabled

      public boolean isLastSampleEnabled()
      Checks if this BaseSink is currently configured to store the last received sample in the last-sample property.
      Returns:
      true if the sink is configured to store the last received sample.

    • isQosEnabled

      public boolean isQosEnabled()
      Checks if this BaseSink is currently configured to send Quality-of-Service events upstream.
      Returns:
      true if the sink is configured to perform Quality-of-Service.

    • queryLatency

      public boolean queryLatency(@Nullable Out<Boolean> live, @Nullable Out<Boolean> upstreamLive, @Nullable ClockTime minLatency, @Nullable ClockTime maxLatency)

      Query the sink for the latency parameters. The latency will be queried from the upstream elements. live will be true if this BaseSink is configured to synchronize against the clock. upstreamLive will be true if an upstream element is live.

      If both live and upstreamLive are true, the sink will want to compensate for the latency introduced by the upstream elements by setting the minLatency to a strictly positive value.

      This function is mostly used by subclasses.

      Parameters:
      live - if the sink is live
      upstreamLive - if an upstream element is live
      minLatency - the min latency of the upstream elements
      maxLatency - the max latency of the upstream elements
      Returns:
      true if the query succeeded.

    • setAsyncEnabled

      public void setAsyncEnabled(boolean enabled)
      Configures this BaseSink to perform all state changes asynchronously. When async is disabled, the sink will immediately go to PAUSED instead of waiting for a preroll buffer. This feature is useful if the sink does not synchronize against the clock or when it is dealing with sparse streams.
      Parameters:
      enabled - the new async value.

    • setBlocksize

      public void setBlocksize(int blocksize)
      Set the number of bytes that the sink will pull when it is operating in pull mode.
      Parameters:
      blocksize - the blocksize in bytes

    • setDropOutOfSegment

      public void setDropOutOfSegment(boolean dropOutOfSegment)
      Configure this BaseSink to drop buffers which are outside the current segment
      Parameters:
      dropOutOfSegment - drop buffers outside the segment
      Since:
      1.12

    • setLastSampleEnabled

      public void setLastSampleEnabled(boolean enabled)
      Configures this BaseSink to store the last received sample in the last-sample property.
      Parameters:
      enabled - the new enable-last-sample value.

    • setMaxBitrate

      public void setMaxBitrate(long maxBitrate)
      Set the maximum amount of bits per second that the sink will render.
      Parameters:
      maxBitrate - the max_bitrate in bits per second
      Since:
      1.2

    • setMaxLateness

      public void setMaxLateness(long maxLateness)
      Sets the new max lateness value to maxLateness. This value is used to decide if a buffer should be dropped or not based on the buffer timestamp and the current clock time. A value of -1 means an unlimited time.
      Parameters:
      maxLateness - the new max lateness value.

    • setProcessingDeadline

      public void setProcessingDeadline(ClockTime processingDeadline)

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

      This function is usually called by subclasses.

      Parameters:
      processingDeadline - the new processing deadline in nanoseconds.
      Since:
      1.16

    • setQosEnabled

      public void setQosEnabled(boolean enabled)
      Configures this BaseSink to send Quality-of-Service events upstream.
      Parameters:
      enabled - the new qos value.

    • setRenderDelay

      public void setRenderDelay(ClockTime delay)

      Set the render delay in this BaseSink to delay. The render delay is the time between actual rendering of a buffer and its synchronisation time. Some devices might delay media rendering which can be compensated for with this function.

      After calling this function, this sink will report additional latency and other sinks will adjust their latency to delay the rendering of their media.

      This function is usually called by subclasses.

      Parameters:
      delay - the new delay

    • setSync

      public void setSync(boolean sync)
      Configures this BaseSink to synchronize on the clock or not. When sync is false, incoming samples will be played as fast as possible. If sync is true, the timestamps of the incoming buffers will be used to schedule the exact render time of its contents.
      Parameters:
      sync - the new sync value.

    • setThrottleTime

      public void setThrottleTime(long throttle)
      Set the time that will be inserted between rendered buffers. This can be used to control the maximum buffers per second that the sink will render.
      Parameters:
      throttle - the throttle time in nanoseconds

    • setTsOffset

      public void setTsOffset(ClockTimeDiff offset)
      Adjust the synchronisation of this BaseSink with offset. A negative value will render buffers earlier than their timestamp. A positive value will delay rendering. This function can be used to fix playback of badly timestamped buffers.
      Parameters:
      offset - the new offset

    • wait_

      public FlowReturn wait_(ClockTime time, @Nullable ClockTimeDiff jitter)

      This function will wait for preroll to complete and will then block until time is reached. It is usually called by subclasses that use their own internal synchronisation but want to let some synchronization (like EOS) be handled by the base class.

      This function should only be called with the PREROLL_LOCK held (like when receiving an EOS event in the ::event vmethod or when handling buffers in ::render).

      The time argument should be the running_time of when the timeout should happen and will be adjusted with any latency and offset configured in the sink.

      Parameters:
      time - the running_time to be reached
      jitter - the jitter to be filled with time diff, or null
      Returns:
      GstFlowReturn

    • waitClock

      public ClockReturn waitClock(ClockTime time, @Nullable ClockTimeDiff jitter)

      This function will block until time is reached. It is usually called by subclasses that use their own internal synchronisation.

      If time is not valid, no synchronisation is done and ClockReturn.BADTIME is returned. Likewise, if synchronisation is disabled in the element or there is no clock, no synchronisation is done and ClockReturn.BADTIME is returned.

      This function should only be called with the PREROLL_LOCK held, like when receiving an EOS event in the GstBaseSinkClass::event vmethod or when receiving a buffer in the GstBaseSinkClass::render vmethod.

      The time argument should be the running_time of when this method should return and is not adjusted with any latency or offset configured in the sink.

      Parameters:
      time - the running_time to be reached
      jitter - the jitter to be filled with time diff, or null
      Returns:
      GstClockReturn

    • waitPreroll

      public FlowReturn waitPreroll()

      If the GstBaseSinkClass::render method performs its own synchronisation against the clock it must unblock when going from PLAYING to the PAUSED state and call this method before continuing to render the remaining data.

      If the GstBaseSinkClass::render method can block on something else than the clock, it must also be ready to unblock immediately on the GstBaseSinkClass::unlock method and cause the GstBaseSinkClass::render method to immediately call this function. In this case, the subclass must be prepared to continue rendering where it left off if this function returns FlowReturn.OK.

      This function will block until a state change to PLAYING happens (in which case this function returns FlowReturn.OK) or the processing must be stopped due to a state change to READY or a FLUSH event (in which case this function returns FlowReturn.FLUSHING).

      This function should only be called with the PREROLL_LOCK held, like in the render function.

      Returns:
      FlowReturn.OK if the preroll completed and processing can continue. Any other return value should be returned from the render vmethod.

    • activatePull

      protected boolean activatePull(boolean active)
      Subclasses should override this when they can provide an alternate method of spawning a thread to drive the pipeline in pull mode. Should start or stop the pulling thread, depending on the value of the "active" argument. Called after actually activating the sink pad in pull mode. The default implementation starts a task on the sink pad.

    • event

      protected boolean event(Event event)
      Override this to handle events arriving on the sink pad

    • fixate

      protected Caps fixate(Caps caps)
      Only useful in pull mode. Implement if you have ideas about what should be the default values for the caps you support.

    • getCaps

      protected Caps getCaps(@Nullable Caps filter)
      Called to get sink pad caps from the subclass.

    • getTimes

      protected void getTimes(Buffer buffer, ClockTime start, ClockTime end)
      Get the start and end times for syncing on this buffer.
      Parameters:
      start - the start GstClockTime
      end - the end GstClockTime

    • prepare

      protected FlowReturn prepare(Buffer buffer)
      Called to prepare the buffer for render and preroll. This function is called before synchronisation is performed.

    • prepareList

      protected FlowReturn prepareList(BufferList bufferList)
      Called to prepare the buffer list for renderList. This function is called before synchronisation is performed.

    • preroll

      protected FlowReturn preroll(Buffer buffer)
      Called to present the preroll buffer if desired.

    • proposeAllocation

      protected boolean proposeAllocation(Query query)
      configure the allocation query

    • query

      public boolean query(Query query)
      perform a GstQuery on the element.
      Overrides:
      query in class Element
      Parameters:
      query - the GstQuery.
      Returns:

      true if the query could be performed.

      MT safe.

    • render

      protected FlowReturn render(Buffer buffer)
      Called when a buffer should be presented or output, at the correct moment if the GstBaseSink has been set to sync to the clock.

    • renderList

      protected FlowReturn renderList(BufferList bufferList)
      Same as render but used with buffer lists instead of buffers.

    • setCaps

      protected boolean setCaps(Caps caps)
      Notify subclass of changed caps

    • start

      protected boolean start()
      Start processing. Ideal for opening resources in the subclass

    • stop

      protected boolean stop()
      Stop processing. Subclasses should use this to close resources.

    • unlock

      protected boolean unlock()
      Unlock any pending access to the resource. Subclasses should unblock any blocked function ASAP and call gst_base_sink_wait_preroll()

    • unlockStop

      protected boolean unlockStop()
      Clear the previous unlock request. Subclasses should clear any state they set during GstBaseSinkClass::unlock, and be ready to continue where they left off after gst_base_sink_wait_preroll(), gst_base_sink_wait() or gst_wait_sink_wait_clock() return or GstBaseSinkClass::render is called again.

    • waitEvent

      protected FlowReturn waitEvent(Event event)
      Override this to implement custom logic to wait for the event time (for events like EOS and GAP). Subclasses should always first chain up to the default implementation.