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GStreamer 0.10 Core Reference Manual | ![]() |
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#include <gst/gst.h> GstEvent; enum GstEventTypeFlags; #define GST_EVENT_TYPE_BOTH #define GST_EVENT_MAKE_TYPE (num,flags) enum GstEventType; #define GST_EVENT_TRACE_NAME #define GST_EVENT_TYPE (event) #define GST_EVENT_TYPE_NAME (event) #define GST_EVENT_TIMESTAMP (event) #define GST_EVENT_SRC (event) #define GST_EVENT_IS_UPSTREAM (ev) #define GST_EVENT_IS_DOWNSTREAM (ev) #define GST_EVENT_IS_SERIALIZED (ev) GstEventTypeFlags gst_event_type_get_flags (GstEventType type); const gchar* gst_event_type_get_name (GstEventType type); GQuark gst_event_type_to_quark (GstEventType type); GstEvent* gst_event_ref (GstEvent *event); void gst_event_unref (GstEvent *event); #define gst_event_replace (old_event,new_event) void gst_event_copy (GstEvent *event); GstEvent* gst_event_new_custom (GstEventType type, GstStructure *structure); const GstStructure* gst_event_get_structure (GstEvent *event); gboolean gst_event_has_name (GstEvent *event, const gchar *name); guint32 gst_event_get_seqnum (GstEvent *event); void gst_event_set_seqnum (GstEvent *event, guint32 seqnum); GstEvent* gst_event_new_flush_start (void); GstEvent* gst_event_new_flush_stop (void); GstEvent* gst_event_new_eos (void); GstEvent* gst_event_new_new_segment (gboolean update, gdouble rate, GstFormat format, gint64 start, gint64 stop, gint64 position); GstEvent* gst_event_new_new_segment_full (gboolean update, gdouble rate, gdouble applied_rate, GstFormat format, gint64 start, gint64 stop, gint64 position); void gst_event_parse_new_segment (GstEvent *event, gboolean *update, gdouble *rate, GstFormat *format, gint64 *start, gint64 *stop, gint64 *position); void gst_event_parse_new_segment_full (GstEvent *event, gboolean *update, gdouble *rate, gdouble *applied_rate, GstFormat *format, gint64 *start, gint64 *stop, gint64 *position); GstEvent* gst_event_new_tag (GstTagList *taglist); void gst_event_parse_tag (GstEvent *event, GstTagList **taglist); GstEvent* gst_event_new_buffer_size (GstFormat format, gint64 minsize, gint64 maxsize, gboolean async); void gst_event_parse_buffer_size (GstEvent *event, GstFormat *format, gint64 *minsize, gint64 *maxsize, gboolean *async); GstEvent* gst_event_new_qos (gdouble proportion, GstClockTimeDiff diff, GstClockTime timestamp); void gst_event_parse_qos (GstEvent *event, gdouble *proportion, GstClockTimeDiff *diff, GstClockTime *timestamp); enum GstSeekType; enum GstSeekFlags; GstEvent* gst_event_new_seek (gdouble rate, GstFormat format, GstSeekFlags flags, GstSeekType start_type, gint64 start, GstSeekType stop_type, gint64 stop); void gst_event_parse_seek (GstEvent *event, gdouble *rate, GstFormat *format, GstSeekFlags *flags, GstSeekType *start_type, gint64 *start, GstSeekType *stop_type, gint64 *stop); GstEvent* gst_event_new_navigation (GstStructure *structure); GstEvent* gst_event_new_latency (GstClockTime latency); void gst_event_parse_latency (GstEvent *event, GstClockTime *latency); GstEvent* gst_event_new_step (GstFormat format, guint64 amount, gdouble rate, gboolean flush, gboolean intermediate); void gst_event_parse_step (GstEvent *event, GstFormat *format, guint64 *amount, gdouble *rate, gboolean *flush, gboolean *intermediate);
The event class provides factory methods to construct and functions query (parse) events.
Events are usually created with gst_event_new_*() which takes event-type
specific parameters as arguments.
To send an event application will usually use gst_element_send_event()
and
elements will use gst_pad_send_event()
or gst_pad_push_event()
.
The event should be unreffed with gst_event_unref()
if it has not been sent.
Events that have been received can be parsed with their respective
gst_event_parse_*() functions. It is valid to pass NULL
for unwanted details.
Events are passed between elements in parallel to the data stream. Some events are serialized with buffers, others are not. Some events only travel downstream, others only upstream. Some events can travel both upstream and downstream.
The events are used to signal special conditions in the datastream such as EOS (end of stream) or the start of a new stream-segment. Events are also used to flush the pipeline of any pending data.
Most of the event API is used inside plugins. Applications usually only
construct and use seek events.
To do that gst_event_new_seek()
is used to create a seek event. It takes
the needed parameters to specity seeking time and mode.
Example 11. performing a seek on a pipeline
GstEvent *event; gboolean result; ... // construct a seek event to play the media from second 2 to 5, flush // the pipeline to decrease latency. event = gst_event_new_seek (1.0, GST_FORMAT_TIME, GST_SEEK_FLAG_FLUSH, GST_SEEK_TYPE_SET, 2 * GST_SECOND, GST_SEEK_TYPE_SET, 5 * GST_SECOND); ... result = gst_element_send_event (pipeline, event); if (!result) g_warning ("seek failed"); ...
Last reviewed on 2006-09-6 (0.10.10)
typedef struct { GstMiniObject mini_object; GstEventType type; guint64 timestamp; GstObject *src; GstStructure *structure; } GstEvent;
A GstEvent.
GstMiniObject mini_object ; |
the parent structure |
GstEventType type ; |
the GstEventType of the event |
guint64 timestamp ; |
the timestamp of the event |
GstObject *src ; |
the src of the event |
GstStructure *structure ; |
the GstStructure containing the event info. |
typedef enum { GST_EVENT_TYPE_UPSTREAM = 1 << 0, GST_EVENT_TYPE_DOWNSTREAM = 1 << 1, GST_EVENT_TYPE_SERIALIZED = 1 << 2 } GstEventTypeFlags;
GstEventTypeFlags indicate the aspects of the different GstEventType
values. You can get the type flags of a GstEventType with the
gst_event_type_get_flags()
function.
#define GST_EVENT_TYPE_BOTH
The same thing as GST_EVENT_TYPE_UPSTREAM | GST_EVENT_TYPE_DOWNSTREAM.
#define GST_EVENT_MAKE_TYPE(num,flags)
when making custom event types, use this macro with the num and the given flags
num : |
the event number to create |
flags : |
the event flags |
typedef enum { GST_EVENT_UNKNOWN = GST_EVENT_MAKE_TYPE (0, 0), /* bidirectional events */ GST_EVENT_FLUSH_START = GST_EVENT_MAKE_TYPE (1, FLAG(BOTH)), GST_EVENT_FLUSH_STOP = GST_EVENT_MAKE_TYPE (2, FLAG(BOTH) | FLAG(SERIALIZED)), /* downstream serialized events */ GST_EVENT_EOS = GST_EVENT_MAKE_TYPE (5, FLAG(DOWNSTREAM) | FLAG(SERIALIZED)), GST_EVENT_NEWSEGMENT = GST_EVENT_MAKE_TYPE (6, FLAG(DOWNSTREAM) | FLAG(SERIALIZED)), GST_EVENT_TAG = GST_EVENT_MAKE_TYPE (7, FLAG(DOWNSTREAM) | FLAG(SERIALIZED)), GST_EVENT_BUFFERSIZE = GST_EVENT_MAKE_TYPE (8, FLAG(DOWNSTREAM) | FLAG(SERIALIZED)), /* upstream events */ GST_EVENT_QOS = GST_EVENT_MAKE_TYPE (15, FLAG(UPSTREAM)), GST_EVENT_SEEK = GST_EVENT_MAKE_TYPE (16, FLAG(UPSTREAM)), GST_EVENT_NAVIGATION = GST_EVENT_MAKE_TYPE (17, FLAG(UPSTREAM)), GST_EVENT_LATENCY = GST_EVENT_MAKE_TYPE (18, FLAG(UPSTREAM)), GST_EVENT_STEP = GST_EVENT_MAKE_TYPE (19, FLAG(UPSTREAM)), /* custom events start here */ GST_EVENT_CUSTOM_UPSTREAM = GST_EVENT_MAKE_TYPE (32, FLAG(UPSTREAM)), GST_EVENT_CUSTOM_DOWNSTREAM = GST_EVENT_MAKE_TYPE (32, FLAG(DOWNSTREAM) | FLAG(SERIALIZED)), GST_EVENT_CUSTOM_DOWNSTREAM_OOB = GST_EVENT_MAKE_TYPE (32, FLAG(DOWNSTREAM)), GST_EVENT_CUSTOM_BOTH = GST_EVENT_MAKE_TYPE (32, FLAG(BOTH) | FLAG(SERIALIZED)), GST_EVENT_CUSTOM_BOTH_OOB = GST_EVENT_MAKE_TYPE (32, FLAG(BOTH)) } GstEventType;
GstEventType lists the standard event types that can be sent in a pipeline.
The custom event types can be used for private messages between elements that can't be expressed using normal GStreamer buffer passing semantics. Custom events carry an arbitrary GstStructure. Specific custom events are distinguished by the name of the structure.
#define GST_EVENT_TRACE_NAME "GstEvent"
The name used for memory allocation tracing
#define GST_EVENT_TYPE(event) (GST_EVENT_CAST(event)->type)
Get the GstEventType of the event.
event : |
the event to query |
#define GST_EVENT_TYPE_NAME(event) (gst_event_type_get_name(GST_EVENT_TYPE(event)))
Get a constant string representation of the GstEventType of the event.
event : |
the event to query |
#define GST_EVENT_TIMESTAMP(event) (GST_EVENT_CAST(event)->timestamp)
Get the GstClockTime timestamp of the event. This is the time when the event was created.
event : |
the event to query |
#define GST_EVENT_SRC(event) (GST_EVENT_CAST(event)->src)
The source GstObject that generated this event.
event : |
the event to query |
#define GST_EVENT_IS_UPSTREAM(ev) !!(GST_EVENT_TYPE (ev) & GST_EVENT_TYPE_UPSTREAM)
Check if an event can travel upstream.
ev : |
the event to query |
#define GST_EVENT_IS_DOWNSTREAM(ev) !!(GST_EVENT_TYPE (ev) & GST_EVENT_TYPE_DOWNSTREAM)
Check if an event can travel downstream.
ev : |
the event to query |
#define GST_EVENT_IS_SERIALIZED(ev) !!(GST_EVENT_TYPE (ev) & GST_EVENT_TYPE_SERIALIZED)
Check if an event is serialized with the data stream.
ev : |
the event to query |
GstEventTypeFlags gst_event_type_get_flags (GstEventType type);
Gets the GstEventTypeFlags associated with type
.
type : |
a GstEventType |
Returns : | a GstEventTypeFlags. |
const gchar* gst_event_type_get_name (GstEventType type);
Get a printable name for the given event type. Do not modify or free.
type : |
the event type |
Returns : | a reference to the static name of the event. |
GQuark gst_event_type_to_quark (GstEventType type);
Get the unique quark for the given event type.
type : |
the event type |
Returns : | the quark associated with the event type |
GstEvent* gst_event_ref (GstEvent *event);
Increase the refcount of this event.
event : |
The event to refcount |
Returns : | event (for convenience when doing assignments)
|
void gst_event_unref (GstEvent *event);
Decrease the refcount of an event, freeing it if the refcount reaches 0.
event : |
The event to refcount |
#define gst_event_replace(old_event,new_event)
Modifies a pointer to a GstEvent to point to a different GstEvent. The modification is done atomically (so this is useful for ensuring thread safety in some cases), and the reference counts are updated appropriately (the old event is unreffed, the new one is reffed).
Either new_event
or the GstEvent pointed to by old_event
may be NULL.
old_event : |
pointer to a pointer to a GstEvent to be replaced. |
new_event : |
pointer to a GstEvent that will replace the event pointed to
by old_event .
|
Since 0.10.3
void gst_event_copy (GstEvent *event);
Copy the event using the event specific copy function.
event : |
The event to copy |
GstEvent* gst_event_new_custom (GstEventType type, GstStructure *structure);
Create a new custom-typed event. This can be used for anything not handled by other event-specific functions to pass an event to another element.
Make sure to allocate an event type with the GST_EVENT_MAKE_TYPE macro, assigning a free number and filling in the correct direction and serialization flags.
New custom events can also be created by subclassing the event type if needed.
type : |
The type of the new event |
structure : |
The structure for the event. The event will take ownership of the structure. |
Returns : | The new custom event. |
const GstStructure* gst_event_get_structure (GstEvent *event);
Access the structure of the event.
event : |
The GstEvent. |
Returns : | The structure of the event. The structure is still owned by the event, which means that you should not free it and that the pointer becomes invalid when you free the event. MT safe. |
gboolean gst_event_has_name (GstEvent *event, const gchar *name);
Checks if event
has the given name
. This function is usually used to
check the name of a custom event.
event : |
The GstEvent. |
name : |
name to check |
Returns : | TRUE if name matches the name of the event structure.
|
Since 0.10.20
guint32 gst_event_get_seqnum (GstEvent *event);
Retrieve the sequence number of a event.
Events have ever-incrementing sequence numbers, which may also be set
explicitly via gst_event_set_seqnum()
. Sequence numbers are typically used to
indicate that a event corresponds to some other set of events or messages,
for example an EOS event corresponding to a SEEK event. It is considered good
practice to make this correspondence when possible, though it is not
required.
Note that events and messages share the same sequence number incrementor; two events or messages will never not have the same sequence number unless that correspondence was made explicitly.
event : |
A GstEvent. |
Returns : | The event's sequence number. MT safe. |
Since 0.10.22
void gst_event_set_seqnum (GstEvent *event, guint32 seqnum);
Set the sequence number of a event.
This function might be called by the creator of a event to indicate that the
event relates to other events or messages. See gst_event_get_seqnum()
for
more information.
MT safe.
event : |
A GstEvent. |
seqnum : |
A sequence number. |
Since 0.10.22
GstEvent* gst_event_new_flush_start (void);
Allocate a new flush start event. The flush start event can be sent upstream and downstream and travels out-of-bounds with the dataflow.
It marks pads as being flushing and will make them return
GST_FLOW_WRONG_STATE when used for data flow with gst_pad_push()
,
gst_pad_chain()
, gst_pad_alloc_buffer()
, gst_pad_get_range()
and
gst_pad_pull_range()
. Any event (except a GST_EVENT_FLUSH_STOP) received
on a flushing pad will return FALSE
immediately.
Elements should unlock any blocking functions and exit their streaming functions as fast as possible when this event is received.
This event is typically generated after a seek to flush out all queued data in the pipeline so that the new media is played as soon as possible.
Returns : | A new flush start event. |
GstEvent* gst_event_new_flush_stop (void);
Allocate a new flush stop event. The flush stop event can be sent upstream and downstream and travels out-of-bounds with the dataflow. It is typically sent after sending a FLUSH_START event to make the pads accept data again.
Elements can process this event synchronized with the dataflow since the preceeding FLUSH_START event stopped the dataflow.
This event is typically generated to complete a seek and to resume dataflow.
Returns : | A new flush stop event. |
GstEvent* gst_event_new_eos (void);
Create a new EOS event. The eos event can only travel downstream synchronized with the buffer flow. Elements that receive the EOS event on a pad can return GST_FLOW_UNEXPECTED as a GstFlowReturn when data after the EOS event arrives.
The EOS event will travel down to the sink elements in the pipeline which will then post the GST_MESSAGE_EOS on the bus after they have finished playing any buffered data.
When all sinks have posted an EOS message, an EOS message is forwarded to the application.
Returns : | The new EOS event. |
GstEvent* gst_event_new_new_segment (gboolean update, gdouble rate, GstFormat format, gint64 start, gint64 stop, gint64 position);
Allocate a new newsegment event with the given format/values tripplets
This method calls gst_event_new_new_segment_full()
passing a default
value of 1.0 for applied_rate
update : |
is this segment an update to a previous one |
rate : |
a new rate for playback |
format : |
The format of the segment values |
start : |
the start value of the segment |
stop : |
the stop value of the segment |
position : |
stream position |
Returns : | A new newsegment event. |
GstEvent* gst_event_new_new_segment_full (gboolean update, gdouble rate, gdouble applied_rate, GstFormat format, gint64 start, gint64 stop, gint64 position);
Allocate a new newsegment event with the given format/values triplets.
The newsegment event marks the range of buffers to be processed. All
data not within the segment range is not to be processed. This can be
used intelligently by plugins to apply more efficient methods of skipping
unneeded data. The valid range is expressed with the start
and stop
values.
The position value of the segment is used in conjunction with the start
value to convert the buffer timestamps into the stream time. This is
usually done in sinks to report the current stream_time.
position
represents the stream_time of a buffer carrying a timestamp of
start
. position
cannot be -1.
start
cannot be -1, stop
can be -1. If there
is a valid stop
given, it must be greater or equal the start
, including
when the indicated playback rate
is < 0.
The applied_rate
value provides information about any rate adjustment that
has already been made to the timestamps and content on the buffers of the
stream. (rate
* applied_rate
) should always equal the rate that has been
requested for playback. For example, if an element has an input segment
with intended playback rate
of 2.0 and applied_rate of 1.0, it can adjust
incoming timestamps and buffer content by half and output a newsegment event
with rate
of 1.0 and applied_rate
of 2.0
After a newsegment event, the buffer stream time is calculated with:
position + (TIMESTAMP(buf) - start) * ABS (rate * applied_rate)
update : |
Whether this segment is an update to a previous one |
rate : |
A new rate for playback |
applied_rate : |
The rate factor which has already been applied |
format : |
The format of the segment values |
start : |
The start value of the segment |
stop : |
The stop value of the segment |
position : |
stream position |
Returns : | A new newsegment event. |
Since 0.10.6
void gst_event_parse_new_segment (GstEvent *event, gboolean *update, gdouble *rate, GstFormat *format, gint64 *start, gint64 *stop, gint64 *position);
Get the update flag, rate, format, start, stop and position in the
newsegment event. In general, gst_event_parse_new_segment_full()
should
be used instead of this, to also retrieve the applied_rate value of the
segment. See gst_event_new_new_segment_full()
for a full description
of the newsegment event.
event : |
The event to query |
update : |
A pointer to the update flag of the segment |
rate : |
A pointer to the rate of the segment |
format : |
A pointer to the format of the newsegment values |
start : |
A pointer to store the start value in |
stop : |
A pointer to store the stop value in |
position : |
A pointer to store the stream time in |
void gst_event_parse_new_segment_full (GstEvent *event, gboolean *update, gdouble *rate, gdouble *applied_rate, GstFormat *format, gint64 *start, gint64 *stop, gint64 *position);
Get the update, rate, applied_rate, format, start, stop and
position in the newsegment event. See gst_event_new_new_segment_full()
for a full description of the newsegment event.
event : |
The event to query |
update : |
A pointer to the update flag of the segment |
rate : |
A pointer to the rate of the segment |
applied_rate : |
A pointer to the applied_rate of the segment |
format : |
A pointer to the format of the newsegment values |
start : |
A pointer to store the start value in |
stop : |
A pointer to store the stop value in |
position : |
A pointer to store the stream time in |
Since 0.10.6
GstEvent* gst_event_new_tag (GstTagList *taglist);
Generates a metadata tag event from the given taglist
.
taglist : |
metadata list. The event will take ownership of taglist .
|
Returns : | a new GstEvent |
void gst_event_parse_tag (GstEvent *event, GstTagList **taglist);
Parses a tag event
and stores the results in the given taglist
location.
event : |
a tag event |
taglist : |
pointer to metadata list |
GstEvent* gst_event_new_buffer_size (GstFormat format, gint64 minsize, gint64 maxsize, gboolean async);
Create a new buffersize event. The event is sent downstream and notifies elements that they should provide a buffer of the specified dimensions.
When the async
flag is set, a thread boundary is prefered.
format : |
buffer format |
minsize : |
minimum buffer size |
maxsize : |
maximum buffer size |
async : |
thread behavior |
Returns : | a new GstEvent |
void gst_event_parse_buffer_size (GstEvent *event, GstFormat *format, gint64 *minsize, gint64 *maxsize, gboolean *async);
Get the format, minsize, maxsize and async-flag in the buffersize event.
event : |
The event to query |
format : |
A pointer to store the format in |
minsize : |
A pointer to store the minsize in |
maxsize : |
A pointer to store the maxsize in |
async : |
A pointer to store the async-flag in |
GstEvent* gst_event_new_qos (gdouble proportion, GstClockTimeDiff diff, GstClockTime timestamp);
Allocate a new qos event with the given values. The QOS event is generated in an element that wants an upstream element to either reduce or increase its rate because of high/low CPU load or other resource usage such as network performance. Typically sinks generate these events for each buffer they receive.
proportion
indicates the real-time performance of the streaming in the
element that generated the QoS event (usually the sink). The value is
generally computed based on more long term statistics about the streams
timestamps compared to the clock.
A value < 1.0 indicates that the upstream element is producing data faster
than real-time. A value > 1.0 indicates that the upstream element is not
producing data fast enough. 1.0 is the ideal proportion
value. The
proportion value can safely be used to lower or increase the quality of
the element.
diff
is the difference against the clock in running time of the last
buffer that caused the element to generate the QOS event. A negative value
means that the buffer with timestamp
arrived in time. A positive value
indicates how late the buffer with timestamp
was.
timestamp
is the timestamp of the last buffer that cause the element
to generate the QOS event. It is expressed in running time and thus an ever
increasing value.
The upstream element can use the diff
and timestamp
values to decide
whether to process more buffers. For possitive diff
, all buffers with
timestamp <= timestamp
+ diff
will certainly arrive late in the sink
as well. A (negative) diff
value so that timestamp
+ diff
would yield a
result smaller than 0 is not allowed.
The application can use general event probes to intercept the QoS event and implement custom application specific QoS handling.
proportion : |
the proportion of the qos message |
diff : |
The time difference of the last Clock sync |
timestamp : |
The timestamp of the buffer |
Returns : | A new QOS event. |
void gst_event_parse_qos (GstEvent *event, gdouble *proportion, GstClockTimeDiff *diff, GstClockTime *timestamp);
Get the proportion, diff and timestamp in the qos event. See
gst_event_new_qos()
for more information about the different QoS values.
event : |
The event to query |
proportion : |
A pointer to store the proportion in |
diff : |
A pointer to store the diff in |
timestamp : |
A pointer to store the timestamp in |
typedef enum { /* one of these */ GST_SEEK_TYPE_NONE = 0, GST_SEEK_TYPE_CUR = 1, GST_SEEK_TYPE_SET = 2, GST_SEEK_TYPE_END = 3 } GstSeekType;
The different types of seek events. When constructing a seek event with
gst_event_new_seek()
, a format, a seek method and optional flags are to
be provided. The seek event is then inserted into the graph with
gst_pad_send_event()
or gst_element_send_event()
.
typedef enum { GST_SEEK_FLAG_NONE = 0, GST_SEEK_FLAG_FLUSH = (1 << 0), GST_SEEK_FLAG_ACCURATE = (1 << 1), GST_SEEK_FLAG_KEY_UNIT = (1 << 2), GST_SEEK_FLAG_SEGMENT = (1 << 3), GST_SEEK_FLAG_SKIP = (1 << 4) } GstSeekFlags;
Flags to be used with gst_element_seek()
or gst_event_new_seek()
. All flags
can be used together.
A non flushing seek might take some time to perform as the currently playing data in the pipeline will not be cleared.
An accurate seek might be slower for formats that don't have any indexes or timestamp markers in the stream. Specifying this flag might require a complete scan of the file in those cases.
When performing a segment seek: after the playback of the segment completes, no EOS will be emmited by the element that performed the seek, but a GST_MESSAGE_SEGMENT_DONE message will be posted on the bus by the element. When this message is posted, it is possible to send a new seek event to continue playback. With this seek method it is possible to perform seemless looping or simple linear editing.
When doing fast forward (rate > 1.0) or fast reverse (rate < -1.0) trickmode
playback, the GST_SEEK_FLAG_SKIP
flag can be used to instruct decoders
and demuxers to adjust the playback rate by skipping frames. This can improve
performance and decrease CPU usage because not all frames need to be decoded.
GstEvent* gst_event_new_seek (gdouble rate, GstFormat format, GstSeekFlags flags, GstSeekType start_type, gint64 start, GstSeekType stop_type, gint64 stop);
Allocate a new seek event with the given parameters.
The seek event configures playback of the pipeline between start
to stop
at the speed given in rate
, also called a playback segment.
The start
and stop
values are expressed in format
.
A rate
of 1.0 means normal playback rate, 2.0 means double speed.
Negatives values means backwards playback. A value of 0.0 for the
rate is not allowed and should be accomplished instead by PAUSING the
pipeline.
A pipeline has a default playback segment configured with a start position of 0, a stop position of -1 and a rate of 1.0. The currently configured playback segment can be queried with GST_QUERY_SEGMENT.
start_type
and stop_type
specify how to adjust the currently configured
start and stop fields in playback segment. Adjustments can be made relative
or absolute to the last configured values. A type of GST_SEEK_TYPE_NONE
means that the position should not be updated.
When the rate is positive and start
has been updated, playback will start
from the newly configured start position.
For negative rates, playback will start from the newly configured stop position (if any). If the stop position if updated, it must be different from -1 for negative rates.
It is not possible to seek relative to the current playback position, to do this, PAUSE the pipeline, query the current playback position with GST_QUERY_POSITION and update the playback segment current position with a GST_SEEK_TYPE_SET to the desired position.
rate : |
The new playback rate |
format : |
The format of the seek values |
flags : |
The optional seek flags |
start_type : |
The type and flags for the new start position |
start : |
The value of the new start position |
stop_type : |
The type and flags for the new stop position |
stop : |
The value of the new stop position |
Returns : | A new seek event. |
void gst_event_parse_seek (GstEvent *event, gdouble *rate, GstFormat *format, GstSeekFlags *flags, GstSeekType *start_type, gint64 *start, GstSeekType *stop_type, gint64 *stop);
Parses a seek event
and stores the results in the given result locations.
event : |
a seek event |
rate : |
result location for the rate |
format : |
result location for the stream format |
flags : |
result location for the GstSeekFlags |
start_type : |
result location for the GstSeekType of the start position |
start : |
result location for the start postion expressed in format
|
stop_type : |
result location for the GstSeekType of the stop position |
stop : |
result location for the stop postion expressed in format
|
GstEvent* gst_event_new_navigation (GstStructure *structure);
Create a new navigation event from the given description.
structure : |
description of the event. The event will take ownership of the structure. |
Returns : | a new GstEvent |
GstEvent* gst_event_new_latency (GstClockTime latency);
Create a new latency event. The event is sent upstream from the sinks and
notifies elements that they should add an additional latency
to the
running time before synchronising against the clock.
The latency is mostly used in live sinks and is always expressed in the time format.
latency : |
the new latency value |
Returns : | a new GstEvent |
Since 0.10.12
void gst_event_parse_latency (GstEvent *event, GstClockTime *latency);
Get the latency in the latency event.
event : |
The event to query |
latency : |
A pointer to store the latency in. |
Since 0.10.12
GstEvent* gst_event_new_step (GstFormat format, guint64 amount, gdouble rate, gboolean flush, gboolean intermediate);
Create a new step event. The purpose of the step event is to instruct a sink
to skip amount
(expressed in format
) of media. It can be used to implement
stepping through the video frame by frame or for doing fast trick modes.
A rate of <= 0.0 is not allowed, pause the pipeline or reverse the playback direction of the pipeline to get the same effect.
The flush
flag will clear any pending data in the pipeline before starting
the step operation.
The intermediate
flag instructs the pipeline that this step operation is
part of a larger step operation.
format : |
the format of amount
|
amount : |
the amount of data to step |
rate : |
the step rate |
flush : |
flushing steps |
intermediate : |
intermediate steps |
Returns : | a new GstEvent |
Since 0.10.24
void gst_event_parse_step (GstEvent *event, GstFormat *format, guint64 *amount, gdouble *rate, gboolean *flush, gboolean *intermediate);
Parse the step event.
event : |
The event to query |
format : |
A pointer to store the format in. |
amount : |
A pointer to store the amount in. |
rate : |
A pointer to store the rate in. |
flush : |
A pointer to store the flush boolean in. |
intermediate : |
A pointer to store the intermediate boolean in. |
Since 0.10.24