GstPipeline

GstPipeline — Top-level bin with clocking and bus management functionality.

Synopsis


#include <gst/gst.h>


                    GstPipeline;
enum                GstPipelineFlags;
GstElement*         gst_pipeline_new                    (const gchar *name);
GstBus*             gst_pipeline_get_bus                (GstPipeline *pipeline);
gboolean            gst_pipeline_set_clock              (GstPipeline *pipeline,
                                                         GstClock *clock);
GstClock*           gst_pipeline_get_clock              (GstPipeline *pipeline);
void                gst_pipeline_use_clock              (GstPipeline *pipeline,
                                                         GstClock *clock);
void                gst_pipeline_auto_clock             (GstPipeline *pipeline);
void                gst_pipeline_set_new_stream_time    (GstPipeline *pipeline,
                                                         GstClockTime time);
GstClockTime        gst_pipeline_get_last_stream_time   (GstPipeline *pipeline);
void                gst_pipeline_set_auto_flush_bus     (GstPipeline *pipeline,
                                                         gboolean auto_flush);
gboolean            gst_pipeline_get_auto_flush_bus     (GstPipeline *pipeline);
void                gst_pipeline_set_delay              (GstPipeline *pipeline,
                                                         GstClockTime delay);
GstClockTime        gst_pipeline_get_delay              (GstPipeline *pipeline);


Object Hierarchy


  GObject
   +----GstObject
         +----GstElement
               +----GstBin
                     +----GstPipeline

Implemented Interfaces

GstPipeline implements GstChildProxy.

Properties


  "auto-flush-bus"           gboolean              : Read / Write
  "delay"                    guint64               : Read / Write

Description

A GstPipeline is a special GstBin used as the toplevel container for the filter graph. The GstPipeline will manage the selection and distribution of a global GstClock as well as provide a GstBus to the application. It will also implement a default behavour for managing seek events (see gst_element_seek()).

gst_pipeline_new() is used to create a pipeline. when you are done with the pipeline, use gst_object_unref() to free its resources including all added GstElement objects (if not otherwise referenced).

Elements are added and removed from the pipeline using the GstBin methods like gst_bin_add() and gst_bin_remove() (see GstBin).

Before changing the state of the GstPipeline (see GstElement) a GstBus can be retrieved with gst_pipeline_get_bus(). This bus can then be used to receive GstMessage from the elements in the pipeline.

By default, a GstPipeline will automatically flush the pending GstBus messages when going to the NULL state to ensure that no circular references exist when no messages are read from the GstBus. This behaviour can be changed with gst_pipeline_set_auto_flush_bus().

When the GstPipeline performs the PAUSED to PLAYING state change it will select a clock for the elements. The clock selection algorithm will by default select a clock provided by an element that is most upstream (closest to the source). For live pipelines (ones that return GST_STATE_CHANGE_NO_PREROLL from the gst_element_set_state() call) this will select the clock provided by the live source. For normal pipelines this will select a clock provided by the sinks (most likely the audio sink). If no element provides a clock, a default GstSystemClock is used.

The clock selection can be controlled with the gst_pipeline_use_clock() method, which will enforce a given clock on the pipeline. With gst_pipeline_auto_clock() the default clock selection algorithm can be restored.

A GstPipeline maintains a stream time for the elements. The stream time is defined as the difference between the current clock time and the base time. When the pipeline goes to READY or a flushing seek is performed on it, the stream time is reset to 0. When the pipeline is set from PLAYING to PAUSED, the current clock time is sampled and used to configure the base time for the elements when the pipeline is set to PLAYING again. This default behaviour can be changed with the gst_pipeline_set_new_stream_time() method.

When sending a flushing seek event to a GstPipeline (see gst_element_seek()), it will make sure that the pipeline is properly PAUSED and resumed as well as set the new stream time to 0 when the seek succeeded.

Last reviewed on 2006-03-12 (0.10.5)

Details

GstPipeline

typedef struct {
  GstClock      *fixed_clock;

  GstClockTime   stream_time;	
  GstClockTime   delay;
} GstPipeline;

The GstPipeline structure.

GstClock *fixed_clock; The fixed clock of the pipeline, used when GST_PIPELINE_FLAG_FIXED_CLOCK is set.
GstClockTime stream_time; The stream time of the pipeline. A better name for this property would be the running_time, the total time spent in the PLAYING state without being flushed.
GstClockTime delay; Extra delay added to base_time to compensate for computing delays when setting elements to PLAYING.

enum GstPipelineFlags

typedef enum {
  GST_PIPELINE_FLAG_FIXED_CLOCK        = (GST_BIN_FLAG_LAST << 0),
  /* padding */
  GST_PIPELINE_FLAG_LAST               = (GST_BIN_FLAG_LAST << 4)
} GstPipelineFlags;

Pipeline flags

GST_PIPELINE_FLAG_FIXED_CLOCK this pipeline works with a fixed clock
GST_PIPELINE_FLAG_LAST offset to define more flags

gst_pipeline_new ()

GstElement*         gst_pipeline_new                    (const gchar *name);

Create a new pipeline with the given name.

name : name of new pipeline
Returns : newly created GstPipeline MT safe.

gst_pipeline_get_bus ()

GstBus*             gst_pipeline_get_bus                (GstPipeline *pipeline);

Gets the GstBus of pipeline.

pipeline : a GstPipeline
Returns : a GstBus, unref after usage. MT safe.

gst_pipeline_set_clock ()

gboolean            gst_pipeline_set_clock              (GstPipeline *pipeline,
                                                         GstClock *clock);

Set the clock for pipeline. The clock will be distributed to all the elements managed by the pipeline.

pipeline : a GstPipeline
clock : the clock to set
Returns : TRUE if the clock could be set on the pipeline. FALSE if some element did not accept the clock. MT safe.

gst_pipeline_get_clock ()

GstClock*           gst_pipeline_get_clock              (GstPipeline *pipeline);

Gets the current clock used by pipeline.

pipeline : a GstPipeline
Returns : a GstClock, unref after usage.

gst_pipeline_use_clock ()

void                gst_pipeline_use_clock              (GstPipeline *pipeline,
                                                         GstClock *clock);

Force pipeline to use the given clock. The pipeline will always use the given clock even if new clock providers are added to this pipeline.

If clock is NULL all clocking will be disabled which will make the pipeline run as fast as possible.

MT safe.

pipeline : a GstPipeline
clock : the clock to use

gst_pipeline_auto_clock ()

void                gst_pipeline_auto_clock             (GstPipeline *pipeline);

Let pipeline select a clock automatically. This is the default behaviour.

Use this function if you previous forced a fixed clock with gst_pipeline_use_clock() and want to restore the default pipeline clock selection algorithm.

MT safe.

pipeline : a GstPipeline

gst_pipeline_set_new_stream_time ()

void                gst_pipeline_set_new_stream_time    (GstPipeline *pipeline,
                                                         GstClockTime time);

Set the new stream time of pipeline to time. The stream time is used to set the base time on the elements (see gst_element_set_base_time()) in the PAUSED->PLAYING state transition.

Setting time to GST_CLOCK_TIME_NONE will disable the pipeline's management of element base time. The application will then be responsible for performing base time distribution. This is sometimes useful if you want to synchronize capture from multiple pipelines, and you can also ensure that the pipelines have the same clock.

MT safe.

pipeline : a GstPipeline
time : the new stream time to set

gst_pipeline_get_last_stream_time ()

GstClockTime        gst_pipeline_get_last_stream_time   (GstPipeline *pipeline);

Gets the last stream time of pipeline. If the pipeline is PLAYING, the returned time is the stream time used to configure the element's base time in the PAUSED->PLAYING state. If the pipeline is PAUSED, the returned time is the stream time when the pipeline was paused.

This function returns GST_CLOCK_TIME_NONE if the pipeline was configured to not handle the management of the element's base time (see gst_pipeline_set_new_stream_time()).

pipeline : a GstPipeline
Returns : a GstClockTime. MT safe.

gst_pipeline_set_auto_flush_bus ()

void                gst_pipeline_set_auto_flush_bus     (GstPipeline *pipeline,
                                                         gboolean auto_flush);

Usually, when a pipeline goes from READY to NULL state, it automatically flushes all pending messages on the bus, which is done for refcounting purposes, to break circular references.

This means that applications that update state using (async) bus messages (e.g. do certain things when a pipeline goes from PAUSED to READY) might not get to see messages when the pipeline is shut down, because they might be flushed before they can be dispatched in the main thread. This behaviour can be disabled using this function.

It is important that all messages on the bus are handled when the automatic flushing is disabled else memory leaks will be introduced.

MT safe.

pipeline : a GstPipeline
auto_flush : whether or not to automatically flush the bus when the pipeline goes from READY to NULL state

Since 0.10.4


gst_pipeline_get_auto_flush_bus ()

gboolean            gst_pipeline_get_auto_flush_bus     (GstPipeline *pipeline);

Check if pipeline will automatically flush messages when going to the NULL state.

pipeline : a GstPipeline
Returns : whether the pipeline will automatically flush its bus when going from READY to NULL state or not. MT safe.

Since 0.10.4


gst_pipeline_set_delay ()

void                gst_pipeline_set_delay              (GstPipeline *pipeline,
                                                         GstClockTime delay);

Set the expected delay needed for all elements to perform the PAUSED to PLAYING state change. delay will be added to the base time of the elements so that they wait an additional delay amount of time before starting to process buffers and cannot be GST_CLOCK_TIME_NONE.

This option is used for tuning purposes and should normally not be used.

MT safe.

pipeline : a GstPipeline
delay : the delay

Since 0.10.5


gst_pipeline_get_delay ()

GstClockTime        gst_pipeline_get_delay              (GstPipeline *pipeline);

Get the configured delay (see gst_pipeline_set_delay()).

pipeline : a GstPipeline
Returns : The configured delay. MT safe.

Since 0.10.5

Property Details

The "auto-flush-bus" property

  "auto-flush-bus"           gboolean              : Read / Write

Whether or not to automatically flush all messages on the pipeline's bus when going from READY to NULL state. Please see gst_pipeline_set_auto_flush_bus() for more information on this option.

Default value: TRUE

Since 0.10.4


The "delay" property

  "delay"                    guint64               : Read / Write

The expected delay needed for elements to spin up to the PLAYING state expressed in nanoseconds. see gst_pipeline_set_delay() for more information on this option.

Default value: 0

Since 0.10.5

See Also

GstElement, GstBin, GstClock, GstBus