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Functions
Types and Values
struct | GstEvent |
enum | GstEventTypeFlags |
#define | GST_EVENT_TYPE_BOTH |
enum | GstEventType |
enum | GstStreamFlags |
enum | GstQOSType |
enum | GstSeekType |
enum | GstSeekFlags |
Description
The event class provides factory methods to construct events for sending and functions to query (parse) received 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 specify seeking time and mode.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 |
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"); ... |
Functions
GST_EVENT_MAKE_TYPE()
#define GST_EVENT_MAKE_TYPE(num,flags)
when making custom event types, use this macro with the num and the given flags
GST_EVENT_TYPE()
#define GST_EVENT_TYPE(event) (GST_EVENT_CAST(event)->type)
Get the GstEventType of the event.
GST_EVENT_TYPE_NAME()
#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.
GST_EVENT_TIMESTAMP()
#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.
GST_EVENT_SEQNUM()
#define GST_EVENT_SEQNUM(event) (GST_EVENT_CAST(event)->seqnum)
The sequence number of event
.
GST_EVENT_IS_UPSTREAM()
#define GST_EVENT_IS_UPSTREAM(ev) !!(GST_EVENT_TYPE (ev) & GST_EVENT_TYPE_UPSTREAM)
Check if an event can travel upstream.
GST_EVENT_IS_DOWNSTREAM()
#define GST_EVENT_IS_DOWNSTREAM(ev) !!(GST_EVENT_TYPE (ev) & GST_EVENT_TYPE_DOWNSTREAM)
Check if an event can travel downstream.
GST_EVENT_IS_SERIALIZED()
#define GST_EVENT_IS_SERIALIZED(ev) !!(GST_EVENT_TYPE (ev) & GST_EVENT_TYPE_SERIALIZED)
Check if an event is serialized with the data stream.
GST_EVENT_IS_STICKY()
#define GST_EVENT_IS_STICKY(ev) !!(GST_EVENT_TYPE (ev) & GST_EVENT_TYPE_STICKY)
Check if an event is sticky on the pads.
gst_event_type_get_flags ()
GstEventTypeFlags
gst_event_type_get_flags (GstEventType type
);
Gets the GstEventTypeFlags associated with type
.
gst_event_type_get_name ()
const gchar *
gst_event_type_get_name (GstEventType type
);
Get a printable name for the given event type. Do not modify or free.
gst_event_type_to_quark ()
GQuark
gst_event_type_to_quark (GstEventType type
);
Get the unique quark for the given event type.
gst_event_unref ()
void
gst_event_unref (GstEvent *event
);
Decrease the refcount of an event, freeing it if the refcount reaches 0.
gst_event_replace ()
gboolean gst_event_replace (GstEvent **old_event
,GstEvent *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
.
gst_event_copy ()
GstEvent *
gst_event_copy (const GstEvent *event
);
Copy the event using the event specific copy function.
gst_event_steal ()
GstEvent *
gst_event_steal (GstEvent **old_event
);
Atomically replace the GstEvent pointed to by old_event
with NULL
and
return the original event.
Parameters
old_event |
pointer to a pointer to a GstEvent to be stolen. |
[inout][transfer full][nullable] |
gst_event_take ()
gboolean gst_event_take (GstEvent **old_event
,GstEvent *new_event
);
Modifies a pointer to a GstEvent to point to a different GstEvent. This
function is similar to gst_event_replace()
except that it takes ownership of
new_event
.
Either new_event
or the GstEvent pointed to by old_event
may be NULL
.
gst_event_is_writable()
#define gst_event_is_writable(ev) gst_mini_object_is_writable (GST_MINI_OBJECT_CAST (ev))
Tests if you can safely write data into a event's structure or validly modify the seqnum and timestamp field.
gst_event_make_writable()
#define gst_event_make_writable(ev) GST_EVENT_CAST (gst_mini_object_make_writable (GST_MINI_OBJECT_CAST (ev)))
Makes a writable event from the given event. If the source event is
already writable, this will simply return the same event. A copy will
otherwise be made using gst_event_copy()
.
gst_event_writable_structure ()
GstStructure *
gst_event_writable_structure (GstEvent *event
);
Get a writable version of the structure.
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.
This function checks if event
is writable and will never return
NULL
.
MT safe.
[transfer none]
gst_event_new_custom ()
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.
gst_event_get_structure ()
const GstStructure *
gst_event_get_structure (GstEvent *event
);
Access the structure of the event.
gst_event_has_name ()
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.
gst_event_get_seqnum ()
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 have the same sequence number unless that correspondence was made explicitly.
gst_event_set_seqnum ()
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.
gst_event_get_running_time_offset ()
gint64
gst_event_get_running_time_offset (GstEvent *event
);
Retrieve the accumulated running time offset of the event.
Events passing through GstPads that have a running time
offset set via gst_pad_set_offset()
will get their offset
adjusted according to the pad's offset.
If the event contains any information that related to the running time, this information will need to be updated before usage with this offset.
Since: 1.4
gst_event_set_running_time_offset ()
void gst_event_set_running_time_offset (GstEvent *event
,gint64 offset
);
Set the running time offset of a event. See
gst_event_get_running_time_offset()
for more information.
MT safe.
Since: 1.4
gst_event_new_flush_start ()
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_FLUSHING when used for data flow with gst_pad_push()
,
gst_pad_chain()
, 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.
gst_event_new_flush_stop ()
GstEvent *
gst_event_new_flush_stop (gboolean reset_time
);
Allocate a new flush stop event. The flush stop event can be sent upstream and downstream and travels serialized 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 preceding FLUSH_START event stopped the dataflow.
This event is typically generated to complete a seek and to resume dataflow.
gst_event_parse_flush_stop ()
void gst_event_parse_flush_stop (GstEvent *event
,gboolean *reset_time
);
Parse the FLUSH_STOP event and retrieve the reset_time
member.
gst_event_new_eos ()
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_EOS 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.
The EOS event itself will not cause any state transitions of the pipeline.
gst_event_new_gap ()
GstEvent * gst_event_new_gap (GstClockTime timestamp
,GstClockTime duration
);
Create a new GAP event. A gap event can be thought of as conceptually equivalent to a buffer to signal that there is no data for a certain amount of time. This is useful to signal a gap to downstream elements which may wait for data, such as muxers or mixers or overlays, especially for sparse streams such as subtitle streams.
gst_event_parse_gap ()
void gst_event_parse_gap (GstEvent *event
,GstClockTime *timestamp
,GstClockTime *duration
);
Extract timestamp and duration from a new GAP event.
Parameters
event |
a GstEvent of type GST_EVENT_GAP |
|
timestamp |
location where to store the
start time (pts) of the gap, or |
[out][allow-none] |
duration |
location where to store the duration of
the gap, or |
[out][allow-none] |
gst_event_new_stream_start ()
GstEvent *
gst_event_new_stream_start (const gchar *stream_id
);
Create a new STREAM_START event. The stream start event can only travel downstream synchronized with the buffer flow. It is expected to be the first event that is sent for a new stream.
Source elements, demuxers and other elements that create new streams are supposed to send this event as the first event of a new stream. It should not be sent after a flushing seek or in similar situations and is used to mark the beginning of a new logical stream. Elements combining multiple streams must ensure that this event is only forwarded downstream once and not for every single input stream.
The stream_id
should be a unique string that consists of the upstream
stream-id, / as separator and a unique stream-id for this specific
stream. A new stream-id should only be created for a stream if the upstream
stream is split into (potentially) multiple new streams, e.g. in a demuxer,
but not for every single element in the pipeline.
gst_pad_create_stream_id()
or gst_pad_create_stream_id_printf()
can be
used to create a stream-id. There are no particular semantics for the
stream-id, though it should be deterministic (to support stream matching)
and it might be used to order streams (besides any information conveyed by
stream flags).
gst_event_parse_stream_start ()
void gst_event_parse_stream_start (GstEvent *event
,const gchar **stream_id
);
Parse a stream-id event
and store the result in the given stream_id
location. The string stored in stream_id
must not be modified and will
remain valid only until event
gets freed. Make a copy if you want to
modify it or store it for later use.
gst_event_set_stream_flags ()
void gst_event_set_stream_flags (GstEvent *event
,GstStreamFlags flags
);
Since: 1.2
gst_event_parse_stream_flags ()
void gst_event_parse_stream_flags (GstEvent *event
,GstStreamFlags *flags
);
Parameters
event |
a stream-start event |
|
flags |
address of variable where to store the stream flags. |
[out] |
Since: 1.2
gst_event_set_group_id ()
void gst_event_set_group_id (GstEvent *event
,guint group_id
);
All streams that have the same group id are supposed to be played together, i.e. all streams inside a container file should have the same group id but different stream ids. The group id should change each time the stream is started, resulting in different group ids each time a file is played for example.
Use gst_util_group_id_next()
to get a new group id.
Since: 1.2
gst_event_parse_group_id ()
gboolean gst_event_parse_group_id (GstEvent *event
,guint *group_id
);
Parameters
event |
a stream-start event |
|
group_id |
address of variable where to store the group id. |
[out] |
Since: 1.2
gst_event_set_stream ()
void gst_event_set_stream (GstEvent *event
,GstStream *stream
);
Set the stream
on the stream-start event
Since: 1.10
gst_event_parse_stream ()
void gst_event_parse_stream (GstEvent *event
,GstStream **stream
);
Parse a stream-start event
and extract the GstStream from it.
Parameters
event |
a stream-start event |
|
stream |
adress of variable to store the stream. |
[out][transfer full] |
Since: 1.10
gst_event_new_segment ()
GstEvent *
gst_event_new_segment (const GstSegment *segment
);
Create a new SEGMENT event for segment
. The segment event can only travel
downstream synchronized with the buffer flow and contains timing information
and playback properties for the buffers that will follow.
The segment 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 time 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.
time
represents the stream_time of a buffer carrying a timestamp of
start
. time
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 segment event
with rate
of 1.0 and applied_rate
of 2.0
After a segment event, the buffer stream time is calculated with:
time + (TIMESTAMP(buf) - start) * ABS (rate * applied_rate)
gst_event_parse_segment ()
void gst_event_parse_segment (GstEvent *event
,const GstSegment **segment
);
Parses a segment event
and stores the result in the given segment
location.
segment
remains valid only until the event
is freed. Don't modify the segment
and make a copy if you want to modify it or store it for later use.
gst_event_copy_segment ()
void gst_event_copy_segment (GstEvent *event
,GstSegment *segment
);
Parses a segment event
and copies the GstSegment into the location
given by segment
.
gst_event_new_tag ()
GstEvent *
gst_event_new_tag (GstTagList *taglist
);
Generates a metadata tag event from the given taglist
.
The scope of the taglist specifies if the taglist applies to the complete medium or only to this specific stream. As the tag event is a sticky event, elements should merge tags received from upstream with a given scope with their own tags with the same scope and create a new tag event from it.
gst_event_parse_tag ()
void gst_event_parse_tag (GstEvent *event
,GstTagList **taglist
);
Parses a tag event
and stores the results in the given taglist
location.
No reference to the taglist will be returned, it remains valid only until
the event
is freed. Don't modify or free the taglist, make a copy if you
want to modify it or store it for later use.
gst_event_new_buffer_size ()
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 preferred.
gst_event_parse_buffer_size ()
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.
gst_event_new_qos ()
GstEvent * gst_event_new_qos (GstQOSType type
,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 or throttling. Typically sinks generate these events for each buffer they receive.
type
indicates the reason for the QoS event. GST_QOS_TYPE_OVERFLOW is
used when a buffer arrived in time or when the sink cannot keep up with
the upstream datarate. GST_QOS_TYPE_UNDERFLOW is when the sink is not
receiving buffers fast enough and thus has to drop late buffers.
GST_QOS_TYPE_THROTTLE is used when the datarate is artificially limited
by the application, for example to reduce power consumption.
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. When throttling is
enabled, diff
will be set to the requested throttling interval.
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 positive 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.
gst_event_parse_qos ()
void gst_event_parse_qos (GstEvent *event
,GstQOSType *type
,gdouble *proportion
,GstClockTimeDiff *diff
,GstClockTime *timestamp
);
Get the type, proportion, diff and timestamp in the qos event. See
gst_event_new_qos()
for more information about the different QoS values.
timestamp
will be adjusted for any pad offsets of pads it was passing through.
gst_event_new_seek ()
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 is updated, it must be different from -1 (GST_CLOCK_TIME_NONE) 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.
gst_event_parse_seek ()
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.
Parameters
event |
a seek event |
|
rate |
result location for the rate. |
[out] |
format |
result location for the stream format. |
[out] |
flags |
result location for the GstSeekFlags. |
[out] |
start_type |
result location for the GstSeekType of the start position. |
[out] |
start |
result location for the start position expressed in |
[out] |
stop_type |
result location for the GstSeekType of the stop position. |
[out] |
stop |
result location for the stop position expressed in |
[out] |
gst_event_new_navigation ()
GstEvent *
gst_event_new_navigation (GstStructure *structure
);
Create a new navigation event from the given description.
gst_event_new_latency ()
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.
gst_event_parse_latency ()
void gst_event_parse_latency (GstEvent *event
,GstClockTime *latency
);
Get the latency in the latency event.
gst_event_new_step ()
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, for the effect of rate = 0.0 or first reverse the direction of playback using a seek event to get the same effect as rate < 0.0.
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.
gst_event_parse_step ()
void gst_event_parse_step (GstEvent *event
,GstFormat *format
,guint64 *amount
,gdouble *rate
,gboolean *flush
,gboolean *intermediate
);
Parse the step event.
Parameters
event |
The event to query |
|
format |
a pointer to store the format in. |
[out][allow-none] |
amount |
a pointer to store the amount in. |
[out][allow-none] |
rate |
a pointer to store the rate in. |
[out][allow-none] |
flush |
a pointer to store the flush boolean in. |
[out][allow-none] |
intermediate |
a pointer to store the intermediate boolean in. |
[out][allow-none] |
gst_event_new_sink_message ()
GstEvent * gst_event_new_sink_message (const gchar *name
,GstMessage *msg
);
Create a new sink-message event. The purpose of the sink-message event is to instruct a sink to post the message contained in the event synchronized with the stream.
name
is used to store multiple sticky events on one pad.
gst_event_parse_sink_message ()
void gst_event_parse_sink_message (GstEvent *event
,GstMessage **msg
);
Parse the sink-message event. Unref msg
after usage.
gst_event_new_reconfigure ()
GstEvent *
gst_event_new_reconfigure (void
);
Create a new reconfigure event. The purpose of the reconfigure event is to travel upstream and make elements renegotiate their caps or reconfigure their buffer pools. This is useful when changing properties on elements or changing the topology of the pipeline.
gst_event_new_caps ()
GstEvent *
gst_event_new_caps (GstCaps *caps
);
Create a new CAPS event for caps
. The caps event can only travel downstream
synchronized with the buffer flow and contains the format of the buffers
that will follow after the event.
gst_event_parse_caps ()
void gst_event_parse_caps (GstEvent *event
,GstCaps **caps
);
Get the caps from event
. The caps remains valid as long as event
remains
valid.
gst_event_new_toc ()
GstEvent * gst_event_new_toc (GstToc *toc
,gboolean updated
);
Generate a TOC event from the given toc
. The purpose of the TOC event is to
inform elements that some kind of the TOC was found.
gst_event_parse_toc ()
void gst_event_parse_toc (GstEvent *event
,GstToc **toc
,gboolean *updated
);
Parse a TOC event
and store the results in the given toc
and updated
locations.
Parameters
event |
a TOC event. |
|
toc |
pointer to GstToc structure. |
[out][transfer full] |
updated |
pointer to store TOC updated flag. |
[out] |
gst_event_new_toc_select ()
GstEvent *
gst_event_new_toc_select (const gchar *uid
);
Generate a TOC select event with the given uid
. The purpose of the
TOC select event is to start playback based on the TOC's entry with the
given uid
.
gst_event_parse_toc_select ()
void gst_event_parse_toc_select (GstEvent *event
,gchar **uid
);
Parse a TOC select event
and store the results in the given uid
location.
gst_event_new_segment_done ()
GstEvent * gst_event_new_segment_done (GstFormat format
,gint64 position
);
Create a new segment-done event. This event is sent by elements that finish playback of a segment as a result of a segment seek.
gst_event_parse_segment_done ()
void gst_event_parse_segment_done (GstEvent *event
,GstFormat *format
,gint64 *position
);
Extracts the position and format from the segment done message.
gst_event_new_protection ()
GstEvent * gst_event_new_protection (const gchar *system_id
,GstBuffer *data
,const gchar *origin
);
Creates a new event containing information specific to a particular
protection system (uniquely identified by system_id
), by which that
protection system can acquire key(s) to decrypt a protected stream.
In order for a decryption element to decrypt media protected using a specific system, it first needs all the protection system specific information necessary to acquire the decryption key(s) for that stream. The functions defined here enable this information to be passed in events from elements that extract it (e.g., ISOBMFF demuxers, MPEG DASH demuxers) to protection decrypter elements that use it.
Events containing protection system specific information are created using gst_event_new_protection, and they can be parsed by downstream elements using gst_event_parse_protection.
In Common Encryption, protection system specific information may be located within ISOBMFF files, both in movie (moov) boxes and movie fragment (moof) boxes; it may also be contained in ContentProtection elements within MPEG DASH MPDs. The events created by gst_event_new_protection contain data identifying from which of these locations the encapsulated protection system specific information originated. This origin information is required as some protection systems use different encodings depending upon where the information originates.
The events returned by gst_event_new_protection()
are implemented
in such a way as to ensure that the most recently-pushed protection info
event of a particular origin
and system_id
will
be stuck to the output pad of the sending element.
Parameters
system_id |
a string holding a UUID that uniquely identifies a protection system. |
[transfer none] |
data |
a GstBuffer holding protection system specific information. The reference count of the buffer will be incremented by one. |
[transfer none] |
origin |
a string indicating where the protection information carried in the event was extracted from. The allowed values of this string will depend upon the protection scheme. |
Since: 1.6
gst_event_parse_protection ()
void gst_event_parse_protection (GstEvent *event
,const gchar **system_id
,GstBuffer **data
,const gchar **origin
);
Parses an event containing protection system specific information and stores
the results in system_id
, data
and origin
. The data stored in system_id
,
origin
and data
are valid until event
is released.
Parameters
event |
a GST_EVENT_PROTECTION event. |
|
system_id |
pointer to store the UUID string uniquely identifying a content protection system. |
[out][allow-none][transfer none] |
data |
pointer to store a GstBuffer holding protection system specific information. |
[out][allow-none][transfer none] |
origin |
pointer to store a value that
indicates where the protection information carried by |
[out][allow-none][transfer none] |
Since: 1.6
gst_event_new_select_streams ()
GstEvent *
gst_event_new_select_streams (GList *streams
);
Allocate a new select-streams event.
The select-streams event requests the specified streams
to be activated.
The list of streams
corresponds to the "Stream ID" of each stream to be
activated. Those ID can be obtained via the GstStream objects present
in GST_EVENT_STREAM_START, GST_EVENT_STREAM_COLLECTION or
GST_MESSAGE_STREAM_COLLECTION.
Note: The list of streams
can not be empty.
Returns
a new select-streams event or NULL
in case of
an error (like an empty streams list).
[transfer full]
Since: 1.10
gst_event_parse_select_streams ()
void gst_event_parse_select_streams (GstEvent *event
,GList **streams
);
Parse the SELECT_STREAMS event and retrieve the contained streams.
Since: 1.10
gst_event_new_stream_collection ()
GstEvent *
gst_event_new_stream_collection (GstStreamCollection *collection
);
Create a new STREAM_COLLECTION event. The stream collection event can only travel downstream synchronized with the buffer flow.
Source elements, demuxers and other elements that manage collections of streams and post GstStreamCollection messages on the bus also send this event downstream on each pad involved in the collection, so that activation of a new collection can be tracked through the downstream data flow.
Since: 1.10
gst_event_parse_stream_collection ()
void gst_event_parse_stream_collection (GstEvent *event
,GstStreamCollection **collection
);
Retrieve new GstStreamCollection from STREAM_COLLECTION event event
.
Since: 1.10
gst_event_new_stream_group_done ()
GstEvent *
gst_event_new_stream_group_done (guint group_id
);
Create a new Stream Group Done event. The stream-group-done event can only travel downstream synchronized with the buffer flow. Elements that receive the event on a pad should handle it mostly like EOS, and emit any data or pending buffers that would depend on more data arriving and unblock, since there won't be any more data.
This event is followed by EOS at some point in the future, and is generally used when switching pads - to unblock downstream so that new pads can be exposed before sending EOS on the existing pads.
Since: 1.10
gst_event_parse_stream_group_done ()
void gst_event_parse_stream_group_done (GstEvent *event
,guint *group_id
);
Parse a stream-group-done event
and store the result in the given
group_id
location.
Parameters
event |
a stream-group-done event. |
|
group_id |
address of variable to store the group id into. |
[out] |
Since: 1.10
Types and Values
struct GstEvent
struct GstEvent { GstMiniObject mini_object; GstEventType type; guint64 timestamp; guint32 seqnum; };
A GstEvent.
Members
GstMiniObject |
the parent structure |
|
GstEventType |
the GstEventType of the event |
|
guint64 |
the timestamp of the event |
|
guint32 |
the sequence number of the event |
enum 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.
GST_EVENT_TYPE_BOTH
#define GST_EVENT_TYPE_BOTH
The same thing as GST_EVENT_TYPE_UPSTREAM | GST_EVENT_TYPE_DOWNSTREAM.
enum 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.
Members
unknown event. |
||
Start a flush operation. This event clears all data from the pipeline and unblock all streaming threads. |
||
Stop a flush operation. This event resets the running-time of the pipeline. |
||
Event to mark the start of a new stream. Sent before any other serialized event and only sent at the start of a new stream, not after flushing seeks. |
||
GstCaps event. Notify the pad of a new media type. |
||
A new media segment follows in the dataflow. The segment events contains information for clipping buffers and converting buffer timestamps to running-time and stream-time. |
||
A new GstStreamCollection is available (Since 1.10) |
||
A new set of metadata tags has been found in the stream. |
||
Notification of buffering requirements. Currently not used yet. |
||
An event that sinks turn into a message. Used to send messages that should be emitted in sync with rendering. |
||
Indicates that there is no more data for the stream group ID in the message. Sent before EOS in some instances and should be handled mostly the same. (Since 1.10) |
||
End-Of-Stream. No more data is to be expected to follow without either a STREAM_START event, or a FLUSH_STOP and a SEGMENT event. |
||
An event which indicates that a new table of contents (TOC) was found or updated. |
||
An event which indicates that new or updated encryption information has been found in the stream. |
||
Marks the end of a segment playback. |
||
Marks a gap in the datastream. |
||
A quality message. Used to indicate to upstream elements that the downstream elements should adjust their processing rate. |
||
A request for a new playback position and rate. |
||
Navigation events are usually used for communicating user requests, such as mouse or keyboard movements, to upstream elements. |
||
Notification of new latency adjustment. Sinks will use the latency information to adjust their synchronisation. |
||
A request for stepping through the media. Sinks will usually execute the step operation. |
||
A request for upstream renegotiating caps and reconfiguring. |
||
A request for a new playback position based on TOC entry's UID. |
||
A request to select one or more streams (Since 1.10) |
||
Upstream custom event |
||
Downstream custom event that travels in the data flow. |
||
Custom out-of-band downstream event. |
||
Custom sticky downstream event. |
||
Custom upstream or downstream event. In-band when travelling downstream. |
||
Custom upstream or downstream out-of-band event. |
enum GstStreamFlags
Members
This stream has no special attributes |
||
This stream is a sparse stream (e.g. a subtitle stream), data may flow only in irregular intervals with large gaps in between. |
||
This stream should be selected by default. This flag may be used by demuxers to signal that a stream should be selected by default in a playback scenario. |
||
This stream should not be selected by default. This flag may be used by demuxers to signal that a stream should not be selected by default in a playback scenario, but only if explicitly selected by the user (e.g. an audio track for the hard of hearing or a director's commentary track). |
Since: 1.2
enum GstQOSType
The different types of QoS events that can be given to the
gst_event_new_qos()
method.
Members
The QoS event type that is produced when upstream elements are producing data too quickly and the element can't keep up processing the data. Upstream should reduce their production rate. This type is also used when buffers arrive early or in time. |
||
The QoS event type that is produced when upstream elements are producing data too slowly and need to speed up their production rate. |
||
The QoS event type that is produced when the application enabled throttling to limit the data rate. |
enum GstSeekType
The different types of seek events. When constructing a seek event with
gst_event_new_seek()
or when doing gst_segment_do_seek()
.
enum 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 emitted 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 seamless
looping or simple linear editing.
When doing fast forward (rate > 1.0) or fast reverse (rate < -1.0) trickmode
playback, the GST_SEEK_FLAG_TRICKMODE
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.
Beyond that, the GST_SEEK_FLAG_TRICKMODE_KEY_UNITS
flag can be used to
request that decoders skip all frames except key units, and
GST_SEEK_FLAG_TRICKMODE_NO_AUDIO
flags can be used to request that audio
decoders do no decoding at all, and simple output silence.
The GST_SEEK_FLAG_SNAP_BEFORE
flag can be used to snap to the previous
relevant location, and the GST_SEEK_FLAG_SNAP_AFTER
flag can be used to
select the next relevant location. If GST_SEEK_FLAG_KEY_UNIT
is specified,
the relevant location is a keyframe. If both flags are specified, the nearest
of these locations will be selected. If none are specified, the implementation is
free to select whichever it wants.
The before and after here are in running time, so when playing backwards, the next location refers to the one that will played in next, and not the one that is located after in the actual source stream.
Also see part-seeking.txt in the GStreamer design documentation for more details on the meaning of these flags and the behaviour expected of elements that handle them.
Members
no flag |
||
flush pipeline |
||
accurate position is requested, this might be considerably slower for some formats. |
||
seek to the nearest keyframe. This might be faster but less accurate. |
||
perform a segment seek. |
||
when doing fast forward or fast reverse playback, allow elements to skip frames instead of generating all frames. (Since 1.6) |
||
Deprecated backward compatibility flag, replaced
by |
||
go to a location before the requested position,
if |
||
go to a location after the requested position,
if |
||
go to a position near the requested position,
if |
||
when doing fast forward or fast reverse playback, request that elements only decode keyframes and skip all other content, for formats that have keyframes. (Since 1.6) |
||
when doing fast forward or fast reverse playback, request that audio decoder elements skip decoding and output only gap events or silence. (Since 1.6) |