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/* GStreamer aggregator base class
* Copyright (C) 2014 Mathieu Duponchelle <>
* Copyright (C) 2014 Thibault Saunier <>
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* Library General Public License for more details.
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
#ifndef __GST_AGGREGATOR_H__
#define __GST_AGGREGATOR_H__
#include <gst/gst.h>
#include <gst/base/base-prelude.h>
* GstAggregator Structs *
typedef struct _GstAggregator GstAggregator;
typedef struct _GstAggregatorPrivate GstAggregatorPrivate;
typedef struct _GstAggregatorClass GstAggregatorClass;
* GstAggregatorPad API *
#define GST_TYPE_AGGREGATOR_PAD (gst_aggregator_pad_get_type())
#define GST_AGGREGATOR_PAD_CAST(obj) ((GstAggregatorPad *)(obj))
* GstAggregatorPad Structs *
typedef struct _GstAggregatorPad GstAggregatorPad;
typedef struct _GstAggregatorPadClass GstAggregatorPadClass;
typedef struct _GstAggregatorPadPrivate GstAggregatorPadPrivate;
* GstAggregatorPad:
* @segment: last segment received.
* The implementation the GstPad to use with #GstAggregator
struct _GstAggregatorPad
GstPad parent;
/* Protected by the OBJECT_LOCK */
GstSegment segment;
/* < Private > */
GstAggregatorPadPrivate * priv;
gpointer _gst_reserved[GST_PADDING];
* GstAggregatorPadClass:
* @flush: Optional
* Called when the pad has received a flush stop, this is the place
* to flush any information specific to the pad, it allows for individual
* pads to be flushed while others might not be.
* @skip_buffer: Optional
* Called before input buffers are queued in the pad, return %TRUE
* if the buffer should be skipped.
struct _GstAggregatorPadClass
GstPadClass parent_class;
GstFlowReturn (*flush) (GstAggregatorPad * aggpad, GstAggregator * aggregator);
gboolean (*skip_buffer) (GstAggregatorPad * aggpad, GstAggregator * aggregator, GstBuffer * buffer);
/*< private >*/
gpointer _gst_reserved[GST_PADDING_LARGE];
GType gst_aggregator_pad_get_type (void);
* GstAggregatorPad methods *
GstBuffer * gst_aggregator_pad_pop_buffer (GstAggregatorPad * pad);
GstBuffer * gst_aggregator_pad_peek_buffer (GstAggregatorPad * pad);
gboolean gst_aggregator_pad_drop_buffer (GstAggregatorPad * pad);
gboolean gst_aggregator_pad_has_buffer (GstAggregatorPad * pad);
gboolean gst_aggregator_pad_is_eos (GstAggregatorPad * pad);
* GstAggregator API *
#define GST_TYPE_AGGREGATOR (gst_aggregator_get_type())
#define GST_AGGREGATOR_CAST(obj) ((GstAggregator *)(obj))
* GstAggregator:
* @srcpad: the aggregator's source pad
* @segment: the output segment
* Aggregator base class object structure.
struct _GstAggregator
GstElement parent;
GstPad * srcpad;
/*< private >*/
GstAggregatorPrivate * priv;
gpointer _gst_reserved[GST_PADDING_LARGE];
* GstAggregatorClass:
* @flush: Optional.
* Called after a successful flushing seek, once all the flush
* stops have been received. Flush pad-specific data in
* #GstAggregatorPad->flush.
* @clip: Optional.
* Called when a buffer is received on a sink pad, the task of
* clipping it and translating it to the current segment falls
* on the subclass. The function should use the segment of data
* and the negotiated media type on the pad to perform
* clipping of input buffer. This function takes ownership of
* buf and should output a buffer or return NULL in
* if the buffer should be dropped.
* @finish_buffer: Optional.
* Called when a subclass calls gst_aggregator_finish_buffer()
* from their aggregate function to push out a buffer.
* Subclasses can override this to modify or decorate buffers
* before they get pushed out. This function takes ownership
* of the buffer passed. Subclasses that override this method
* should always chain up to the parent class virtual method.
* @sink_event: Optional.
* Called when an event is received on a sink pad, the subclass
* should always chain up.
* @sink_query: Optional.
* Called when a query is received on a sink pad, the subclass
* should always chain up.
* @src_event: Optional.
* Called when an event is received on the src pad, the subclass
* should always chain up.
* @src_query: Optional.
* Called when a query is received on the src pad, the subclass
* should always chain up.
* @src_activate: Optional.
* Called when the src pad is activated, it will start/stop its
* pad task right after that call.
* @aggregate: Mandatory.
* Called when buffers are queued on all sinkpads. Classes
* should iterate the GstElement->sinkpads and peek or steal
* buffers from the #GstAggregatorPads. If the subclass returns
* GST_FLOW_EOS, sending of the eos event will be taken care
* of. Once / if a buffer has been constructed from the
* aggregated buffers, the subclass should call _finish_buffer.
* @stop: Optional.
* Called when the element goes from PAUSED to READY.
* The subclass should free all resources and reset its state.
* @start: Optional.
* Called when the element goes from READY to PAUSED.
* The subclass should get ready to process
* aggregated buffers.
* @get_next_time: Optional.
* Called when the element needs to know the running time of the next
* rendered buffer for live pipelines. This causes deadline
* based aggregation to occur. Defaults to returning
* GST_CLOCK_TIME_NONE causing the element to wait for buffers
* on all sink pads before aggregating.
* @update_src_caps: Lets subclasses update the #GstCaps representing
* the src pad caps before usage. The result should end up
* in @ret. Return %GST_AGGREGATOR_FLOW_NEED_DATA to indicate that the
* element needs more information (caps, a buffer, etc) to
* choose the correct caps. Should return ANY caps if the
* stream has not caps at all.
* @fixate_src_caps: Optional.
* Fixate and return the src pad caps provided. The function takes
* ownership of @caps and returns a fixated version of
* @caps. @caps is not guaranteed to be writable.
* @negotiated_src_caps: Optional.
* Notifies subclasses what caps format has been negotiated
* @decide_allocation: Optional.
* Allows the subclass to influence the allocation choices.
* Setup the allocation parameters for allocating output
* buffers. The passed in query contains the result of the
* downstream allocation query.
* The aggregator base class will handle in a thread-safe way all manners of
* concurrent flushes, seeks, pad additions and removals, leaving to the
* subclass the responsibility of clipping buffers, and aggregating buffers in
* the way the implementor sees fit.
* It will also take care of event ordering (stream-start, segment, eos).
* Basically, a simple implementation will override @aggregate, and call
* _finish_buffer from inside that function.
struct _GstAggregatorClass {
GstElementClass parent_class;
GstFlowReturn (*flush) (GstAggregator * aggregator);
GstBuffer * (*clip) (GstAggregator * aggregator,
GstAggregatorPad * aggregator_pad,
GstBuffer * buf);
GstFlowReturn (*finish_buffer) (GstAggregator * aggregator,
GstBuffer * buffer);
/* sinkpads virtual methods */
gboolean (*sink_event) (GstAggregator * aggregator,
GstAggregatorPad * aggregator_pad,
GstEvent * event);
gboolean (*sink_query) (GstAggregator * aggregator,
GstAggregatorPad * aggregator_pad,
GstQuery * query);
/* srcpad virtual methods */
gboolean (*src_event) (GstAggregator * aggregator,
GstEvent * event);
gboolean (*src_query) (GstAggregator * aggregator,
GstQuery * query);
gboolean (*src_activate) (GstAggregator * aggregator,
GstPadMode mode,
gboolean active);
GstFlowReturn (*aggregate) (GstAggregator * aggregator,
gboolean timeout);
gboolean (*stop) (GstAggregator * aggregator);
gboolean (*start) (GstAggregator * aggregator);
GstClockTime (*get_next_time) (GstAggregator * aggregator);
GstAggregatorPad * (*create_new_pad) (GstAggregator * self,
GstPadTemplate * templ,
const gchar * req_name,
const GstCaps * caps);
* GstAggregatorClass::update_src_caps:
* @ret: (out) (allow-none):
GstFlowReturn (*update_src_caps) (GstAggregator * self,
GstCaps * caps,
GstCaps ** ret);
GstCaps * (*fixate_src_caps) (GstAggregator * self,
GstCaps * caps);
gboolean (*negotiated_src_caps) (GstAggregator * self,
GstCaps * caps);
gboolean (*decide_allocation) (GstAggregator * self,
GstQuery * query);
gboolean (*propose_allocation) (GstAggregator * self,
GstAggregatorPad * pad,
GstQuery * decide_query,
GstQuery * query);
/*< private >*/
gpointer _gst_reserved[GST_PADDING_LARGE];
* GstAggregator convenience macros *
* @agg: a #GstAggregator
* Convenience macro to access the source pad of #GstAggregator
* Since: 1.6
#define GST_AGGREGATOR_SRC_PAD(agg) (((GstAggregator *)(agg))->srcpad)
* GstAggregator methods *
GstFlowReturn gst_aggregator_finish_buffer (GstAggregator * aggregator,
GstBuffer * buffer);
void gst_aggregator_set_src_caps (GstAggregator * self,
GstCaps * caps);
void gst_aggregator_set_latency (GstAggregator * self,
GstClockTime min_latency,
GstClockTime max_latency);
GType gst_aggregator_get_type(void);
GstClockTime gst_aggregator_get_latency (GstAggregator * self);
GstBufferPool * gst_aggregator_get_buffer_pool (GstAggregator * self);
void gst_aggregator_get_allocator (GstAggregator * self,
GstAllocator ** allocator,
GstAllocationParams * params);
#endif /* __GST_AGGREGATOR_H__ */