Package ch.bailu.gtk.gst

Klasse Bus

java.lang.Object
ch.bailu.gtk.type.Type
ch.bailu.gtk.type.Pointer
ch.bailu.gtk.gobject.Object
ch.bailu.gtk.type.PropertyHolder
ch.bailu.gtk.gst.Bus
Alle implementierten Schnittstellen:
PointerInterface
public class Bus extends PropertyHolder
The #GstBus is an object responsible for delivering #GstMessage packets in
a first-in first-out way from the streaming threads (see #GstTask) to the
application.

Since the application typically only wants to deal with delivery of these
messages from one thread, the GstBus will marshall the messages between
different threads. This is important since the actual streaming of media
is done in another thread than the application.

The GstBus provides support for #GSource based notifications. This makes it
possible to handle the delivery in the glib #GMainLoop.

The #GSource callback function gst_bus_async_signal_func() can be used to
convert all bus messages into signal emissions.

A message is posted on the bus with the gst_bus_post() method. With the
gst_bus_peek() and gst_bus_pop() methods one can look at or retrieve a
previously posted message.

The bus can be polled with the gst_bus_poll() method. This methods blocks
up to the specified timeout value until one of the specified messages types
is posted on the bus. The application can then gst_bus_pop() the messages
from the bus to handle them.
Alternatively the application can register an asynchronous bus function
using gst_bus_add_watch_full() or gst_bus_add_watch(). This function will
install a #GSource in the default glib main loop and will deliver messages
a short while after they have been posted. Note that the main loop should
be running for the asynchronous callbacks.

It is also possible to get messages from the bus without any thread
marshalling with the gst_bus_set_sync_handler() method. This makes it
possible to react to a message in the same thread that posted the
message on the bus. This should only be used if the application is able
to deal with messages from different threads.

Every #GstPipeline has one bus.

Note that a #GstPipeline will set its bus into flushing state when changing
from READY to NULL state.

https://gstreamer.freedesktop.org/documentation/gstreamer/gi-index.html

  • Felddetails

  • Konstruktordetails

    • Bus

      public Bus(PointerContainer pointer)

    • Bus

      public Bus()
      Creates a new #GstBus instance.

  • Methodendetails

    • getClassHandler

      public static ClassHandler getClassHandler()

    • addSignalWatch

      public void addSignalWatch()
      Adds a bus signal watch to the default main context with the default priority
      ( %G_PRIORITY_DEFAULT ). It is also possible to use a non-default
      main context set up using g_main_context_push_thread_default() (before
      one had to create a bus watch source and attach it to the desired main
      context 'manually').

      After calling this statement, the bus will emit the "message" signal for each
      message posted on the bus.

      This function may be called multiple times. To clean up, the caller is
      responsible for calling gst_bus_remove_signal_watch() as many times as this
      function is called.

    • addSignalWatchFull

      public void addSignalWatchFull(int priority)
      Adds a bus signal watch to the default main context with the given @priority
      (e.g. %G_PRIORITY_DEFAULT). It is also possible to use a non-default main
      context set up using g_main_context_push_thread_default()
      (before one had to create a bus watch source and attach it to the desired
      main context 'manually').

      After calling this statement, the bus will emit the "message" signal for each
      message posted on the bus when the #GMainLoop is running.

      This function may be called multiple times. To clean up, the caller is
      responsible for calling gst_bus_remove_signal_watch() as many times as this
      function is called.

      There can only be a single bus watch per bus, you must remove any signal
      watch before you can set another type of watch.
      Parameter:
      priority - The priority of the watch.

    • addWatch

      public int addWatch(Bus.OnBusFunc func, @Nullable Pointer user_data)
      Adds a bus watch to the default main context with the default priority
      ( %G_PRIORITY_DEFAULT ). It is also possible to use a non-default main
      context set up using g_main_context_push_thread_default() (before
      one had to create a bus watch source and attach it to the desired main
      context 'manually').

      This function is used to receive asynchronous messages in the main loop.
      There can only be a single bus watch per bus, you must remove it before you
      can set a new one.

      The bus watch will only work if a #GMainLoop is being run.

      The watch can be removed using gst_bus_remove_watch() or by returning %FALSE
      from @func. If the watch was added to the default main context it is also
      possible to remove the watch using g_source_remove().

      The bus watch will take its own reference to the @bus, so it is safe to unref
      @bus using gst_object_unref() after setting the bus watch.
      Parameter:
      func - A function to call when a message is received.
      user_data - user data passed to @func.
      Gibt zurück:
      The event source id or 0 if @bus already got an event source.

    • addWatchFull

      public int addWatchFull(int priority, Bus.OnBusFunc func, @Nullable Pointer user_data, Bus.OnDestroyNotify notify)
      Adds a bus watch to the default main context with the given @priority (e.g.
      %G_PRIORITY_DEFAULT). It is also possible to use a non-default main
      context set up using g_main_context_push_thread_default() (before
      one had to create a bus watch source and attach it to the desired main
      context 'manually').

      This function is used to receive asynchronous messages in the main loop.
      There can only be a single bus watch per bus, you must remove it before you
      can set a new one.

      The bus watch will only work if a #GMainLoop is being run.

      When @func is called, the message belongs to the caller; if you want to
      keep a copy of it, call gst_message_ref() before leaving @func.

      The watch can be removed using gst_bus_remove_watch() or by returning %FALSE
      from @func. If the watch was added to the default main context it is also
      possible to remove the watch using g_source_remove().

      The bus watch will take its own reference to the @bus, so it is safe to unref
      @bus using gst_object_unref() after setting the bus watch.
      Parameter:
      priority - The priority of the watch.
      func - A function to call when a message is received.
      user_data - user data passed to @func.
      notify - the function to call when the source is removed.
      Gibt zurück:
      The event source id or 0 if @bus already got an event source.

    • asyncSignalFunc

      public boolean asyncSignalFunc(@Nonnull Message message, @Nullable Pointer data)
      A helper #GstBusFunc that can be used to convert all asynchronous messages
      into signals.
      Parameter:
      message - the #GstMessage received
      data - user data
      Gibt zurück:
      %TRUE

    • createWatch

      public Source createWatch()
      Create watch for this bus. The #GSource will be dispatched whenever
      a message is on the bus. After the GSource is dispatched, the
      message is popped off the bus and unreffed.

      As with other watches, there can only be one watch on the bus, including
      any signal watch added with #gst_bus_add_signal_watch.
      Gibt zurück:
      a #GSource that can be added to a #GMainLoop.

    • disableSyncMessageEmission

      public void disableSyncMessageEmission()
      Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
      See gst_bus_enable_sync_message_emission() for more information.

      In the event that multiple pieces of code have called
      gst_bus_enable_sync_message_emission(), the sync-message emissions will only
      be stopped after all calls to gst_bus_enable_sync_message_emission() were
      "cancelled" by calling this function. In this way the semantics are exactly
      the same as gst_object_ref() that which calls enable should also call
      disable.

    • enableSyncMessageEmission

      public void enableSyncMessageEmission()
      Instructs GStreamer to emit the "sync-message" signal after running the bus's
      sync handler. This function is here so that code can ensure that they can
      synchronously receive messages without having to affect what the bin's sync
      handler is.

      This function may be called multiple times. To clean up, the caller is
      responsible for calling gst_bus_disable_sync_message_emission() as many times
      as this function is called.

      While this function looks similar to gst_bus_add_signal_watch(), it is not
      exactly the same -- this function enables *synchronous* emission of
      signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
      to pop messages off the bus *asynchronously*. The sync-message signal
      comes from the thread of whatever object posted the message; the "message"
      signal is marshalled to the main thread via the #GMainLoop.

    • getPollfd

      public void getPollfd(@Nonnull PollFD fd)
      Gets the file descriptor from the bus which can be used to get notified about
      messages being available with functions like g_poll(), and allows integration
      into other event loops based on file descriptors.
      Whenever a message is available, the POLLIN / %G_IO_IN event is set.

      Warning: NEVER read or write anything to the returned fd but only use it
      for getting notifications via g_poll() or similar and then use the normal
      GstBus API, e.g. gst_bus_pop().
      Parameter:
      fd - A GPollFD to fill

    • havePending

      public boolean havePending()
      Checks if there are pending messages on the bus that
      should be handled.
      Gibt zurück:
      %TRUE if there are messages on the bus to be handled, %FALSE otherwise.

    • peek

      public Message peek()
      Peeks the message on the top of the bus' queue. The message will remain
      on the bus' message queue.
      Gibt zurück:
      the #GstMessage that is on the bus, or %NULL if the bus is empty.

    • poll

      public Message poll(int events, long timeout)
      Polls the bus for messages. Will block while waiting for messages to come.
      You can specify a maximum time to poll with the @timeout parameter. If
      @timeout is negative, this function will block indefinitely.

      All messages not in @events will be popped off the bus and will be ignored.
      It is not possible to use message enums beyond #GST_MESSAGE_EXTENDED in the
      @events mask

      Because poll is implemented using the "message" signal enabled by
      gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
      signal to be emitted for every message that poll sees. Thus a "message"
      signal handler will see the same messages that this function sees -- neither
      will steal messages from the other.

      This function will run a #GMainLoop from the default main context when
      polling.

      You should never use this function, since it is pure evil. This is
      especially true for GUI applications based on Gtk+ or Qt, but also for any
      other non-trivial application that uses the GLib main loop. As this function
      runs a GLib main loop, any callback attached to the default GLib main
      context may be invoked. This could be timeouts, GUI events, I/O events etc.;
      even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
      may do things you do not expect, e.g. destroy the main application window or
      some other resource; change other application state; display a dialog and
      run another main loop until the user clicks it away. In short, using this
      function may add a lot of complexity to your code through unexpected
      re-entrancy and unexpected changes to your application's state.

      For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
      other short timeouts use gst_bus_timed_pop_filtered(); everything else is
      better handled by setting up an asynchronous bus watch and doing things
      from there.
      Parameter:
      events - a mask of #GstMessageType, representing the set of message types to poll for (note special handling of extended message types below)
      timeout - the poll timeout, as a #GstClockTime, or #GST_CLOCK_TIME_NONE to poll indefinitely.
      Gibt zurück:
      the message that was received, or %NULL if the poll timed out.

    • pop

      public Message pop()
      Gets a message from the bus.
      Gibt zurück:
      the #GstMessage that is on the bus, or %NULL if the bus is empty.

    • popFiltered

      public Message popFiltered(int types)
      Gets a message matching @type from the bus. Will discard all messages on
      the bus that do not match @type and that have been posted before the first
      message that does match @type. If there is no message matching @type on
      the bus, all messages will be discarded. It is not possible to use message
      enums beyond #GST_MESSAGE_EXTENDED in the @events mask.
      Parameter:
      types - message types to take into account
      Gibt zurück:
      the next #GstMessage matching @type that is on the bus, or %NULL if the bus is empty or there is no message matching @type.

    • post

      public boolean post(@Nonnull Message message)
      Posts a message on the given bus. Ownership of the message
      is taken by the bus.
      Parameter:
      message - the #GstMessage to post
      Gibt zurück:
      %TRUE if the message could be posted, %FALSE if the bus is flushing.

    • removeSignalWatch

      public void removeSignalWatch()
      Removes a signal watch previously added with gst_bus_add_signal_watch().

    • removeWatch

      public boolean removeWatch()
      Removes an installed bus watch from @bus.
      Gibt zurück:
      %TRUE on success or %FALSE if @bus has no event source.

    • setFlushing

      public void setFlushing(boolean flushing)
      If @flushing, flushes out and unrefs any messages queued in the bus. Releases
      references to the message origin objects. Will flush future messages until
      gst_bus_set_flushing() sets @flushing to %FALSE.
      Parameter:
      flushing - whether or not to flush the bus

    • setSyncHandler

      public void setSyncHandler(Bus.OnBusSyncHandler func, @Nullable Pointer user_data, Bus.OnDestroyNotify notify)
      Sets the synchronous handler on the bus. The function will be called
      every time a new message is posted on the bus. Note that the function
      will be called in the same thread context as the posting object. This
      function is usually only called by the creator of the bus. Applications
      should handle messages asynchronously using the gst_bus watch and poll
      functions.

      Before 1.16.3 it was not possible to replace an existing handler and
      clearing an existing handler with %NULL was not thread-safe.
      Parameter:
      func - The handler function to install
      user_data - User data that will be sent to the handler function.
      notify - called when @user_data becomes unused

    • syncSignalHandler

      public int syncSignalHandler(@Nonnull Message message, @Nullable Pointer data)
      A helper #GstBusSyncHandler that can be used to convert all synchronous
      messages into signals.
      Parameter:
      message - the #GstMessage received
      data - user data
      Gibt zurück:
      %GST_BUS_PASS

    • timedPop

      public Message timedPop(long timeout)
      Gets a message from the bus, waiting up to the specified timeout.

      If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
      #GST_CLOCK_TIME_NONE, this function will block forever until a message was
      posted on the bus.
      Parameter:
      timeout - a timeout
      Gibt zurück:
      the #GstMessage that is on the bus after the specified timeout or %NULL if the bus is empty after the timeout expired.

    • timedPopFiltered

      public Message timedPopFiltered(long timeout, int types)
      Gets a message from the bus whose type matches the message type mask @types,
      waiting up to the specified timeout (and discarding any messages that do not
      match the mask provided).

      If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
      @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
      matching message was posted on the bus.
      Parameter:
      timeout - a timeout in nanoseconds, or %GST_CLOCK_TIME_NONE to wait forever
      types - message types to take into account, %GST_MESSAGE_ANY for any type
      Gibt zurück:
      a #GstMessage matching the filter in @types, or %NULL if no matching message was found on the bus until the timeout expired.

    • onMessage

      public SignalHandler onMessage(Bus.OnMessage signal)
      Connect to signal "message".
      See Bus.OnMessage.onMessage(ch.bailu.gtk.gst.Message) for signal description.
      Field SIGNAL_ON_MESSAGE contains original signal name and can be used as resource reference.
      Parameter:
      signal - callback function (lambda).
      Gibt zurück:
      SignalHandler. Can be used to disconnect signal and to release callback function.

    • onSyncMessage

      public SignalHandler onSyncMessage(Bus.OnSyncMessage signal)
      Connect to signal "sync-message".
      See Bus.OnSyncMessage.onSyncMessage(ch.bailu.gtk.gst.Message) for signal description.
      Field SIGNAL_ON_SYNC_MESSAGE contains original signal name and can be used as resource reference.
      Parameter:
      signal - callback function (lambda).
      Gibt zurück:
      SignalHandler. Can be used to disconnect signal and to release callback function.

    • getTypeID

      public static long getTypeID()

    • getParentTypeID

      public static long getParentTypeID()

    • getTypeSize

      public static TypeSystem.TypeSize getTypeSize()

    • getParentTypeSize

      public static TypeSystem.TypeSize getParentTypeSize()

    • getInstanceSize

      public static int getInstanceSize()