GStreamer Core Reference Manual
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GstEvent

Name

GstEvent -- Event definitions.

Synopsis


#include <gst/gst.h>


enum        GstEventType;
#define     GST_EVENT_TYPE                  (event)
#define     GST_EVENT_SRC                   (event)
#define     GST_EVENT_TIMESTAMP             (event)
enum        GstEventFlag;
enum        GstSeekType;
enum        GstSeekAccuracy;
#define     GST_EVENT_SEEK_TYPE             (event)
#define     GST_EVENT_SEEK_FORMAT           (event)
#define     GST_EVENT_SEEK_METHOD           (event)
#define     GST_EVENT_SEEK_FLAGS            (event)
#define     GST_EVENT_SEEK_OFFSET           (event)
#define     GST_EVENT_SEEK_ACCURACY         (event)
#define     GST_SEEK_FLAGS_MASK
#define     GST_SEEK_FLAGS_SHIFT
#define     GST_SEEK_FORMAT_MASK
#define     GST_SEEK_FORMAT_SHIFT
#define     GST_SEEK_METHOD_MASK
#define     GST_SEEK_METHOD_SHIFT
#define     GST_EVENT_DISCONT_NEW_MEDIA     (event)
#define     GST_EVENT_DISCONT_OFFSET        (event,i)
#define     GST_EVENT_DISCONT_OFFSET_LEN    (event)
#define     GST_EVENT_RATE_VALUE            (event)
#define     GST_EVENT_SEEK_ENDOFFSET        (event)
#define     GST_EVENT_SIZE_FORMAT           (event)
#define     GST_EVENT_SIZE_VALUE            (event)
struct      GstEvent;
GstEvent*   gst_event_new                   (GstEventType type);
#define     gst_event_copy                  (ev)
#define     gst_event_ref                   (ev)
#define     gst_event_ref_by_count          (ev,c)
#define     gst_event_unref                 (ev)
GstEvent*   gst_event_new_seek              (GstSeekType type,
                                             gint64 offset);
GstEvent*   gst_event_new_segment_seek      (GstSeekType type,
                                             gint64 start,
                                             gint64 stop);
GstEvent*   gst_event_new_size              (GstFormat format,
                                             gint64 value);
GstEvent*   gst_event_new_discontinuous     (gboolean new_media,
                                             GstFormat format1,
                                             ...);
gboolean    gst_event_discont_get_value     (GstEvent *event,
                                             GstFormat format,
                                             gint64 *value);
#define     gst_event_new_filler            ()
#define     gst_event_new_flush             ()
void        gst_event_print_stats           (void);
#define     GST_EVENT_MASK_FUNCTION         (type,functionname, ...)

Description

The event classes are used to construct and query events.

Events are usually created with gst_event_new() which takes the event type as an argument. properties specific to the event can be set afterwards with the provided macros. The event should be unreferenced with gst_event_unref().

gst_event_new_seek() is a usually used to create a seek event and it takes the needed parameters for a seek event.

gst_event_new_flush() creates a new flush event.

Details

enum GstEventType

typedef enum {
  GST_EVENT_UNKNOWN,
  GST_EVENT_EOS,
  GST_EVENT_FLUSH,
  GST_EVENT_EMPTY,
  GST_EVENT_DISCONTINUOUS,
  GST_EVENT_NEW_MEDIA,
  GST_EVENT_QOS,
  GST_EVENT_SEEK,
  GST_EVENT_SEEK_SEGMENT,
  GST_EVENT_SEGMENT_DONE,
  GST_EVENT_SIZE,
  GST_EVENT_RATE,
  GST_EVENT_FILLER,
  GST_EVENT_TS_OFFSET,
  GST_EVENT_INTERRUPT
} GstEventType;

The different major types of events.

GST_EVENT_UNKNOWN

unknown event.

GST_EVENT_EOS

an end-of-stream event.

GST_EVENT_FLUSH

a flush event.

GST_EVENT_EMPTY

an empty event.

GST_EVENT_DISCONTINUOUS

a discontinuous event to indicate the stream has a discontinuity.

GST_EVENT_NEW_MEDIA

a new media stream is started

GST_EVENT_QOS

a quality of service event

GST_EVENT_SEEK

a seek event.

GST_EVENT_SEEK_SEGMENT

a segment seek with start and stop position

GST_EVENT_SEGMENT_DONE

the event that will be emited when the segment seek has ended

GST_EVENT_SIZE

a size suggestion for a peer element

GST_EVENT_RATE

adjust the output rate of an element

GST_EVENT_FILLER

a dummy event that should be ignored by plugins

GST_EVENT_TS_OFFSET

an event to set the time offset on buffers

GST_EVENT_INTERRUPT

GST_EVENT_TYPE()

#define GST_EVENT_TYPE(event)		(GST_EVENT(event)->type)

Get the event type.

event :

The event to query.

GST_EVENT_SRC()

#define GST_EVENT_SRC(event)		(GST_EVENT(event)->src)

The source object that generated this event

event :

The event to query

GST_EVENT_TIMESTAMP()

#define GST_EVENT_TIMESTAMP(event)	(GST_EVENT(event)->timestamp)

Get the timestamp of the event.

event :

The event to query.

enum GstEventFlag

typedef enum {
  GST_EVENT_FLAG_NONE 		= 0,

  /* indicates negative rates are supported */
  GST_RATE_FLAG_NEGATIVE  	= (1 << 1) 
} GstEventFlag;

Event flags are used when querying for supported events

GST_EVENT_FLAG_NONE

no value

GST_RATE_FLAG_NEGATIVE

indicates negative rates are supported

enum GstSeekType

typedef enum {
  /* | with some format */
  /* | with one of these */
  GST_SEEK_METHOD_CUR		= (1 << (GST_SEEK_METHOD_SHIFT + 0)),
  GST_SEEK_METHOD_SET		= (1 << (GST_SEEK_METHOD_SHIFT + 1)),
  GST_SEEK_METHOD_END		= (1 << (GST_SEEK_METHOD_SHIFT + 2)),

  /* | with optional seek flags */
  /* seek flags */
  GST_SEEK_FLAG_FLUSH		= (1 << (GST_SEEK_FLAGS_SHIFT + 0)),
  GST_SEEK_FLAG_ACCURATE	= (1 << (GST_SEEK_FLAGS_SHIFT + 1)),
  GST_SEEK_FLAG_KEY_UNIT	= (1 << (GST_SEEK_FLAGS_SHIFT + 2)),
  GST_SEEK_FLAG_SEGMENT_LOOP	= (1 << (GST_SEEK_FLAGS_SHIFT + 3))
	
} GstSeekType;

The different types of seek events.

GST_SEEK_METHOD_CUR

Seek to an relative position

GST_SEEK_METHOD_SET

Seek to an absolute position

GST_SEEK_METHOD_END

Seek relative to the end of the stream

GST_SEEK_FLAG_FLUSH

Flush any pending data while seeking

GST_SEEK_FLAG_ACCURATE

Seek as accuratly as possible

GST_SEEK_FLAG_KEY_UNIT

Seek to a nearby key unit

GST_SEEK_FLAG_SEGMENT_LOOP

Loop between start and stop in a segmented seek

enum GstSeekAccuracy

typedef enum {
  GST_SEEK_CERTAIN,
  GST_SEEK_FUZZY
} GstSeekAccuracy;

The seekaccuracy gives more information of how the seek was performed, if the seek was accurate or fuzzy.

GST_SEEK_CERTAIN

The seek was exact

GST_SEEK_FUZZY

The seek was fuzzy, exact position can not be guaranteed

GST_EVENT_SEEK_TYPE()

#define GST_EVENT_SEEK_TYPE(event)		(GST_EVENT(event)->event_data.seek.type)

Get the seektype of the GST_EVENT_SEEK.

event :

The event to query.

GST_EVENT_SEEK_FORMAT()

#define GST_EVENT_SEEK_FORMAT(event)		(GST_EVENT_SEEK_TYPE(event) & GST_SEEK_FORMAT_MASK)

The format of the seek value

event :

The event operate on

GST_EVENT_SEEK_METHOD()

#define GST_EVENT_SEEK_METHOD(event)		(GST_EVENT_SEEK_TYPE(event) & GST_SEEK_METHOD_MASK)

The seek method to use as one of GstSeekType

event :

The event operate on

GST_EVENT_SEEK_FLAGS()

#define GST_EVENT_SEEK_FLAGS(event)		(GST_EVENT_SEEK_TYPE(event) & GST_SEEK_FLAGS_MASK)

The optional seek flags

event :

The event operate on

GST_EVENT_SEEK_OFFSET()

#define GST_EVENT_SEEK_OFFSET(event)		(GST_EVENT(event)->event_data.seek.offset)

Get the offset of the seek event.

event :

The event to query.

GST_EVENT_SEEK_ACCURACY()

#define GST_EVENT_SEEK_ACCURACY(event)		(GST_EVENT(event)->event_data.seek.accuracy)

Indicates how accurate the event was performed.

event :

The event to query

GST_SEEK_FLAGS_MASK

#define GST_SEEK_FLAGS_MASK	0xfff00000

Mask for the flags in the GstSeekType

GST_SEEK_FLAGS_SHIFT

#define GST_SEEK_FLAGS_SHIFT	20

Shift for the flags in the GstSeekType

GST_SEEK_FORMAT_MASK

#define GST_SEEK_FORMAT_MASK	0x0000ffff

Mask for the format in the GstSeekType

GST_SEEK_FORMAT_SHIFT

#define GST_SEEK_FORMAT_SHIFT	0

Shift for the format in the GstSeekType

GST_SEEK_METHOD_MASK

#define GST_SEEK_METHOD_MASK	0x000f0000

Mask for the method in the GstSeekType

GST_SEEK_METHOD_SHIFT

#define GST_SEEK_METHOD_SHIFT	16

Shift for the method in the GstSeekType

GST_EVENT_DISCONT_NEW_MEDIA()

#define GST_EVENT_DISCONT_NEW_MEDIA(event)	(GST_EVENT(event)->event_data.discont.new_media)

Flag that indicates the discont event was because of a new media type.

event :

The event to operate on

GST_EVENT_DISCONT_OFFSET()

#define GST_EVENT_DISCONT_OFFSET(event,i)	(GST_EVENT(event)->event_data.discont.offsets[i])

The offset of the discont event. A discont evetn can hold up to 8 different format/value pairs.

event :

The event to query

i :

The offset/value pair.

GST_EVENT_DISCONT_OFFSET_LEN()

#define GST_EVENT_DISCONT_OFFSET_LEN(event)	(GST_EVENT(event)->event_data.discont.noffsets)

Get the number of offset/value pairs this event has.

event :

The event to query.

GST_EVENT_RATE_VALUE()

#define GST_EVENT_RATE_VALUE(event)		(GST_EVENT(event)->event_data.rate.value)

Get access to the rate vale field

event :

The event to query

GST_EVENT_SEEK_ENDOFFSET()

#define GST_EVENT_SEEK_ENDOFFSET(event)		(GST_EVENT(event)->event_data.seek.endoffset)

The event stop position for a segment seek

event :

The event to query

GST_EVENT_SIZE_FORMAT()

#define GST_EVENT_SIZE_FORMAT(event)		(GST_EVENT(event)->event_data.size.format)

The format of the size event.

event :

The event to query

GST_EVENT_SIZE_VALUE()

#define GST_EVENT_SIZE_VALUE(event)		(GST_EVENT(event)->event_data.size.value)

The value of the size event

event :

The event to query

struct GstEvent

struct GstEvent {
  GstData data;

  GstEventType  type;
  guint64	timestamp;
  GstObject	*src;

  union {
    struct {
      GstSeekType 	type;
      gint64      	offset;
      gint64      	endoffset;
      GstSeekAccuracy 	accuracy;
    } seek;
    struct {
      GstFormatValue 	offsets[8];
      gint      	noffsets;
      gboolean		new_media;
    } discont;
    struct {
      GstFormat 	format;
      gint64      	value;
    } size;
    struct {
      gdouble      	value;
    } rate;
  } event_data;
};

The event structure

gst_event_new ()

GstEvent*   gst_event_new                   (GstEventType type);

Allocate a new event of the given type.

type :

The type of the new event

Returns :

A new event.

gst_event_copy()

#define         gst_event_copy(ev)         	GST_EVENT (gst_data_copy (GST_DATA (ev)))

Copy the event using the event specific copy function

ev :

The event to copy

Returns :

A new event that is a copy of the given input event

gst_event_ref()

#define         gst_event_ref(ev)             	gst_data_ref (GST_DATA (ev))

Increase the refcount of this event

ev :

The event to refcount

gst_event_ref_by_count()

#define         gst_event_ref_by_count(ev,c)  	gst_data_ref_by_count (GST_DATA (ev), c)

Increase the refcount of the event with the given value

ev :

The event to refcount

c :

The value to add to the refcount

gst_event_unref()

#define         gst_event_unref(ev)           	gst_data_unref (GST_DATA (ev))

Decrease the refcount of an event, freeing it if the refcount reaches 0

ev :

The event to unref

gst_event_new_seek ()

GstEvent*   gst_event_new_seek              (GstSeekType type,
                                             gint64 offset);

Allocate a new seek event with the given parameters.

type :

The type of the seek event

offset :

The offset of the seek

Returns :

A new seek event.

gst_event_new_segment_seek ()

GstEvent*   gst_event_new_segment_seek      (GstSeekType type,
                                             gint64 start,
                                             gint64 stop);

Allocate a new segment seek event with the given parameters.

type :

The type of the seek event

start :

The start offset of the seek

stop :

The stop offset of the seek

Returns :

A new segment seek event.

gst_event_new_size ()

GstEvent*   gst_event_new_size              (GstFormat format,
                                             gint64 value);

Create a new size event with the given values.

format :

The format of the size value

value :

The value of the size event

Returns :

The new size event.

gst_event_new_discontinuous ()

GstEvent*   gst_event_new_discontinuous     (gboolean new_media,
                                             GstFormat format1,
                                             ...);

Allocate a new discontinuous event with the geven format/value pairs.

new_media :

A flag indicating a new media type starts

format1 :

The format of the discont value

... :

more discont values and formats

Returns :

A new discontinuous event.

gst_event_discont_get_value ()

gboolean    gst_event_discont_get_value     (GstEvent *event,
                                             GstFormat format,
                                             gint64 *value);

Get the value for the given format in the dicont event.

event :

The event to query

format :

The format of the discont value

value :

A pointer to the value

Returns :

TRUE if the discont event caries the specified format/value pair.

gst_event_new_filler()

#define		gst_event_new_filler()		gst_event_new(GST_EVENT_FILLER)

Create a new dummy event that should be ignored

gst_event_new_flush()

#define		gst_event_new_flush()		gst_event_new(GST_EVENT_FLUSH)

Create a new flush event.

gst_event_print_stats ()

void        gst_event_print_stats           (void);

Logs statistics about live events (using g_log).

GST_EVENT_MASK_FUNCTION()

#define     GST_EVENT_MASK_FUNCTION(type,functionname, ...)

A convenience macro to create event mask functions

type :

The type of the first argument of the function

functionname :

the name of the function

... :

event masks, the last element is marked with 0

See Also

GstPad



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