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/* GStreamer
* Copyright (C) 1999,2000 Erik Walthinsen <>
* 2005 Wim Taymans <>
* 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.
#include <gst/gst.h>
#define GST_TYPE_BASE_TRANSFORM (gst_base_transform_get_type())
#define GST_BASE_TRANSFORM_CAST(obj) ((GstBaseTransform *)(obj))
* The name of the templates for the sink pad.
* The name of the templates for the source pad.
* @obj: base transform instance
* Gives the pointer to the source #GstPad object of the element.
* @obj: base transform instance
* Gives the pointer to the sink #GstPad object of the element.
* A #GstFlowReturn that can be returned from transform and transform_ip to
* indicate that no output buffer was generated.
typedef struct _GstBaseTransform GstBaseTransform;
typedef struct _GstBaseTransformClass GstBaseTransformClass;
typedef struct _GstBaseTransformPrivate GstBaseTransformPrivate;
* GstBaseTransform:
* The opaque #GstBaseTransform data structure.
struct _GstBaseTransform {
GstElement element;
/*< protected >*/
/* source and sink pads */
GstPad *sinkpad;
GstPad *srcpad;
/* MT-protected (with STREAM_LOCK) */
gboolean have_segment;
GstSegment segment;
/* Default submit_input_buffer places the buffer here,
* for consumption by the generate_output method: */
GstBuffer *queued_buf;
/*< private >*/
GstBaseTransformPrivate *priv;
gpointer _gst_reserved[GST_PADDING_LARGE-1];
* GstBaseTransformClass:
* @parent_class: Element parent class
* @passthrough_on_same_caps: If set to %TRUE, passthrough mode will be
* automatically enabled if the caps are the same.
* Set to %FALSE by default.
* @transform_ip_on_passthrough: If set to %TRUE, @transform_ip will be called in
* passthrough mode. The passed buffer might not be
* writable. When %FALSE, neither @transform nor
* @transform_ip will be called in passthrough mode.
* Set to %TRUE by default.
* @transform_caps: Optional. Given the pad in this direction and the given
* caps, what caps are allowed on the other pad in this
* element ?
* @fixate_caps: Optional. Given the pad in this direction and the given
* caps, fixate the caps on the other pad. The function takes
* ownership of @othercaps and returns a fixated version of
* @othercaps. @othercaps is not guaranteed to be writable.
* @accept_caps: Optional.
* Subclasses can override this method to check if @caps can be
* handled by the element. The default implementation might not be
* the most optimal way to check this in all cases.
* @set_caps: allows the subclass to be notified of the actual caps set.
* @query: Optional.
* Handle a requested query. Subclasses that implement this
* should must chain up to the parent if they didn't handle the
* query
* @decide_allocation: Setup the allocation parameters for allocating output
* buffers. The passed in query contains the result of the
* downstream allocation query. This function is only called
* when not operating in passthrough mode. The default
* implementation will remove all memory dependent metadata.
* If there is a @filter_meta method implementation, it will
* be called for all metadata API in the downstream query,
* otherwise the metadata API is removed.
* @filter_meta: Return %TRUE if the metadata API should be proposed in the
* upstream allocation query. The default implementation is %NULL
* and will cause all metadata to be removed.
* @propose_allocation: Propose buffer allocation parameters for upstream elements.
* This function must be implemented if the element reads or
* writes the buffer content. The query that was passed to
* the decide_allocation is passed in this method (or %NULL
* when the element is in passthrough mode). The default
* implementation will pass the query downstream when in
* passthrough mode and will copy all the filtered metadata
* API in non-passthrough mode.
* @transform_size: Optional. Given the size of a buffer in the given direction
* with the given caps, calculate the size in bytes of a buffer
* on the other pad with the given other caps.
* The default implementation uses get_unit_size and keeps
* the number of units the same.
* @get_unit_size: Required if the transform is not in-place.
* get the size in bytes of one unit for the given caps.
* @start: Optional.
* Called when the element starts processing.
* Allows opening external resources.
* @stop: Optional.
* Called when the element stops processing.
* Allows closing external resources.
* @sink_event: Optional.
* Event handler on the sink pad. The default implementation
* handles the event and forwards it downstream.
* @src_event: Optional.
* Event handler on the source pad. The default implementation
* handles the event and forwards it upstream.
* @prepare_output_buffer: Optional.
* Subclasses can override this to do their own
* allocation of output buffers. Elements that only do
* analysis can return a subbuffer or even just
* return a reference to the input buffer (if in
* passthrough mode). The default implementation will
* use the negotiated allocator or bufferpool and
* transform_size to allocate an output buffer or it
* will return the input buffer in passthrough mode.
* @copy_metadata: Optional.
* Copy the metadata from the input buffer to the output buffer.
* The default implementation will copy the flags, timestamps and
* offsets of the buffer.
* @transform_meta: Optional. Transform the metadata on the input buffer to the
* output buffer. By default this method copies all meta without
* tags. subclasses can implement this method and return %TRUE if
* the metadata is to be copied.
* @before_transform: Optional.
* This method is called right before the base class will
* start processing. Dynamic properties or other delayed
* configuration could be performed in this method.
* @transform: Required if the element does not operate in-place.
* Transforms one incoming buffer to one outgoing buffer.
* The function is allowed to change size/timestamp/duration
* of the outgoing buffer.
* @transform_ip: Required if the element operates in-place.
* Transform the incoming buffer in-place.
* @submit_input_buffer: Function which accepts a new input buffer and pre-processes it.
* The default implementation performs caps (re)negotiation, then
* QoS if needed, and places the input buffer into the @queued_buf
* member variable. If the buffer is dropped due to QoS, it returns
* GST_BASE_TRANSFORM_FLOW_DROPPED. If this input buffer is not
* contiguous with any previous input buffer, then @is_discont
* is set to #TRUE. (Since 1.6)
* @generate_output: Called after each new input buffer is submitted repeatedly
* until it either generates an error or fails to generate an output
* buffer. The default implementation takes the contents of the
* @queued_buf variable, generates an output buffer if needed
* by calling the class @prepare_output_buffer, and then
* calls either @transform or @transform_ip. Elements that don't
* do 1-to-1 transformations on input to output buffers can either
* return GST_BASE_TRANSFORM_FLOW_DROPPED or simply not generate
* an output buffer until they are ready to do so. (Since 1.6)
* Subclasses can override any of the available virtual methods or not, as
* needed. At minimum either @transform or @transform_ip need to be overridden.
* If the element can overwrite the input data with the results (data is of the
* same type and quantity) it should provide @transform_ip.
struct _GstBaseTransformClass {
GstElementClass parent_class;
/*< public >*/
gboolean passthrough_on_same_caps;
gboolean transform_ip_on_passthrough;
/* virtual methods for subclasses */
GstCaps* (*transform_caps) (GstBaseTransform *trans,
GstPadDirection direction,
GstCaps *caps, GstCaps *filter);
GstCaps* (*fixate_caps) (GstBaseTransform *trans,
GstPadDirection direction, GstCaps *caps,
GstCaps *othercaps);
gboolean (*accept_caps) (GstBaseTransform *trans, GstPadDirection direction,
GstCaps *caps);
gboolean (*set_caps) (GstBaseTransform *trans, GstCaps *incaps,
GstCaps *outcaps);
gboolean (*query) (GstBaseTransform *trans, GstPadDirection direction,
GstQuery *query);
/* decide allocation query for output buffers */
gboolean (*decide_allocation) (GstBaseTransform *trans, GstQuery *query);
gboolean (*filter_meta) (GstBaseTransform *trans, GstQuery *query,
GType api, const GstStructure *params);
/* propose allocation query parameters for input buffers */
gboolean (*propose_allocation) (GstBaseTransform *trans, GstQuery *decide_query,
GstQuery *query);
/* transform size */
gboolean (*transform_size) (GstBaseTransform *trans,
GstPadDirection direction,
GstCaps *caps, gsize size,
GstCaps *othercaps, gsize *othersize);
gboolean (*get_unit_size) (GstBaseTransform *trans, GstCaps *caps,
gsize *size);
/* states */
gboolean (*start) (GstBaseTransform *trans);
gboolean (*stop) (GstBaseTransform *trans);
/* sink and src pad event handlers */
gboolean (*sink_event) (GstBaseTransform *trans, GstEvent *event);
gboolean (*src_event) (GstBaseTransform *trans, GstEvent *event);
GstFlowReturn (*prepare_output_buffer) (GstBaseTransform * trans,
GstBuffer *input, GstBuffer **outbuf);
/* metadata */
gboolean (*copy_metadata) (GstBaseTransform *trans, GstBuffer *input,
GstBuffer *outbuf);
gboolean (*transform_meta) (GstBaseTransform *trans, GstBuffer *outbuf,
GstMeta *meta, GstBuffer *inbuf);
void (*before_transform) (GstBaseTransform *trans, GstBuffer *buffer);
/* transform */
GstFlowReturn (*transform) (GstBaseTransform *trans, GstBuffer *inbuf,
GstBuffer *outbuf);
GstFlowReturn (*transform_ip) (GstBaseTransform *trans, GstBuffer *buf);
GstFlowReturn (*submit_input_buffer) (GstBaseTransform *trans, gboolean is_discont, GstBuffer *input);
GstFlowReturn (*generate_output) (GstBaseTransform *trans, GstBuffer **outbuf);
/*< private >*/
gpointer _gst_reserved[GST_PADDING_LARGE - 2];
GType gst_base_transform_get_type (void);
void gst_base_transform_set_passthrough (GstBaseTransform *trans,
gboolean passthrough);
gboolean gst_base_transform_is_passthrough (GstBaseTransform *trans);
void gst_base_transform_set_in_place (GstBaseTransform *trans,
gboolean in_place);
gboolean gst_base_transform_is_in_place (GstBaseTransform *trans);
void gst_base_transform_update_qos (GstBaseTransform *trans,
gdouble proportion,
GstClockTimeDiff diff,
GstClockTime timestamp);
void gst_base_transform_set_qos_enabled (GstBaseTransform *trans,
gboolean enabled);
gboolean gst_base_transform_is_qos_enabled (GstBaseTransform *trans);
void gst_base_transform_set_gap_aware (GstBaseTransform *trans,
gboolean gap_aware);
void gst_base_transform_set_prefer_passthrough (GstBaseTransform *trans,
gboolean prefer_passthrough);
GstBufferPool * gst_base_transform_get_buffer_pool (GstBaseTransform *trans);
void gst_base_transform_get_allocator (GstBaseTransform *trans,
GstAllocator **allocator,
GstAllocationParams *params);
void gst_base_transform_reconfigure_sink (GstBaseTransform *trans);
void gst_base_transform_reconfigure_src (GstBaseTransform *trans);
gboolean gst_base_transform_update_src_caps (GstBaseTransform *trans,
GstCaps *updated_caps);
#endif /* __GST_BASE_TRANSFORM_H__ */