GStreamer (GST) Element and Bin API Reference

The GST API is used to create Custom DSL Pipeline Components. Once created, Custom Components are added to a Pipeline the same as other built-in DSL Components.

IMPORTANT! All DSL Pipeline Components, custom or built-in, are derived from the GStreamer (GST) Bin container class. Bins are used to contain GST Elements. Bins allow you to combine a group of linked Elements into one logical Element.

There are restrictions imposed on the type of Elements that can be created and added to a Bin:

Single input pad and output pad only.
Therefore, no tees, muxers, aggregators, or demuxers (this list may not be complete).

The first Element in each Bin is typically a queue. Adding a queue creates a new thread on the queue's source pad (output) which decouples the processing between input and output, effectively creating a new thread for the custom Pipeline Component.

Construction and Destruction

GST Elements are created by calling dsl_gst_element_new and deleted by calling dsl_gst_element_delete, dsl_gst_element_delete_many, or dsl_gst_element_delete_all.

GST Bins are created by calling dsl_gst_bin_new or dsl_gst_bin_new_element_add_many. As with all Pipeline Components, GST Bins are deleted by calling dsl_component_delete, dsl_component_delete_many, or dsl_component_delete_all.

Adding and Removing

The relationship between GST Bins and GST Elements is one to many. Once added to a Bin, an Element must be removed before it can be used with another. Elements can be added to bins when constructed by calling dsl_gst_bin_new_element_add_many, or after construction by calling dsl_gst_bin_element_add and dsl_gst_bin_element_add_many. GST Elements can be removed from a GST Bin by calling dsl_gst_bin_element_remove or dsl_gst_bin_element_remove_many.

The relationship between Pipelines/Branches and GST Bins is one to many. Once added to a Pipeline or Branch, a Bin must be removed before it can be used with another. GST Bins are added to a Pipeline by calling dsl_pipeline_component_add or dsl_pipeline_component_add_many and removed with dsl_pipeline_component_remove, dsl_pipeline_component_remove_many, or dsl_pipeline_component_remove_all.

A similar set of Services are used when adding/removing a to/from a branch: dsl_branch_component_add, dsl_branch_component_add_many, dsl_branch_component_remove, dsl_branch_component_remove_many, and dsl_branch_component_remove_all.

Below is a simple example that creats two GST Elements and adds them to a new GST Bin.

# IMPORTANT! We create a queue element to be our first element of our bin.
# The queue will create a new thread on the source pad (output) to decouple
# the processing on sink and source pad, effectively creating a new thread for
# our custom component.
retval = dsl_gst_element_new('my-queue', 'queue')

# Create a new element from a proprietary plugin
retval = dsl_gst_element_new('my-element', 'my-plugin-name')
          
# Create a new bin and add the elements to it. The elements will be linked
# in the order they're added.
ret_val = dsl_gst_bin_new_element_add_many('my-custom-bin',
   elements = ['my-queue', 'my-element', None])

# The Custom Component can now be added to our Pipeline along with
# the other Pipeline components. Add in the order to be linked.
retval = dsl_pipeline_new_component_add_many('pipeline',
   ['my-source', 'my-primary-gie', 'my-iou-tracker', 'my-custom-bin',
   'my-on-screen-display', 'my-egl-sink', None])
          
# IMPORTANT! set the link method for the Pipeline to link by
# add order (and not by fixed position - default)
retval = dsl_pipeline_link_method_set('pipeline',
   DSL_PIPELINE_LINK_METHOD_BY_ADD_ORDER)

Adding/Removing Pad-Probe-handlers

Multiple sink (input) and/or source (output) Pad-Probe Handlers can be added to any Primary or Secondary GIE or TIS by calling dsl_gst_element_pph_add and removed with dsl_gst_element_pph_remove.

Relevant Examples

For relevant examples see:

pipeline_with_custom_gst_bin_and_elements.py
pipeline_with_custom_gst_bin_and_elements.cpp

GST API

Constructors

dsl_gst_element_new
dsl_gst_bin_new
dsl_gst_bin_new_element_add_many

Destructors

dsl_gst_element_delete
dsl_gst_element_delete_many
dsl_gst_element_delete_all

Methods

dsl_gst_element_property_boolean_get
dsl_gst_element_property_boolean_set
dsl_gst_element_property_float_get
dsl_gst_element_property_float_set
dsl_gst_element_property_uint_get
dsl_gst_element_property_uint_set
dsl_gst_element_property_int_get
dsl_gst_element_property_int_set
dsl_gst_element_property_uint64_get
dsl_gst_element_property_uint64_set
dsl_gst_element_property_int64_get
dsl_gst_element_property_int64_set
dsl_gst_element_property_string_get
dsl_gst_element_property_string_set
dsl_gst_element_pph_add
dsl_gst_element_pph_remove
dsl_gst_bin_element_add
dsl_gst_bin_element_add_many
dsl_gst_bin_element_remove
dsl_gst_bin_element_remove_many

Return Values

The following return codes are used by the GStreamer Element API

#define DSL_RESULT_GST_ELEMENT_RESULT                               0x00D00000
#define DSL_RESULT_GST_ELEMENT_NAME_NOT_UNIQUE                      0x00D00001
#define DSL_RESULT_GST_ELEMENT_NAME_NOT_FOUND                       0x00D00002
#define DSL_RESULT_GST_ELEMENT_THREW_EXCEPTION                      0x00D00003
#define DSL_RESULT_GST_ELEMENT_IN_USE                               0x00D00004
#define DSL_RESULT_GST_ELEMENT_SET_FAILED                           0x00D00005
#define DSL_RESULT_GST_ELEMENT_HANDLER_ADD_FAILED                   0x00D00006
#define DSL_RESULT_GST_ELEMENT_HANDLER_REMOVE_FAILED                0x00D00007
#define DSL_RESULT_GST_ELEMENT_PAD_TYPE_INVALID                     0x00D00008

The following return codes are used by the GStreamer Element API

#define DSL_RESULT_GST_BIN_RESULT                                   0x00E00000
#define DSL_RESULT_GST_BIN_NAME_NOT_UNIQUE                          0x00E00001
#define DSL_RESULT_GST_BIN_NAME_NOT_FOUND                           0x00E00002
#define DSL_RESULT_GST_BIN_NAME_BAD_FORMAT                          0x00E00003
#define DSL_RESULT_GST_BIN_THREW_EXCEPTION                          0x00E00004
#define DSL_RESULT_GST_BIN_IS_IN_USE                                0x00E00005
#define DSL_RESULT_GST_BIN_SET_FAILED                               0x00E00006
#define DSL_RESULT_GST_BIN_ELEMENT_ADD_FAILED                       0x00E00007
#define DSL_RESULT_GST_BIN_ELEMENT_REMOVE_FAILED                    0x00E00008
#define DSL_RESULT_GST_BIN_ELEMENT_NOT_IN_USE                       0x00E00009

Constructors

dsl_gst_element_new

DslReturnType dsl_gst_element_new(const wchar_t* name, const wchar_t* factory_name);

This constructor creates a uniquely named GStreamer Element from a plugin factory name. Construction will fail if the name is currently in use.

Parameters

name - [in] unique name for the GStreamer Element to create.
factory_name - [in] factory (plugin) name for the Element to create.

Returns DSL_RESULT_SUCCESS on successful creation. One of the Return Values defined above on failure

Python Example

retval = dsl_gst_element_new('my-element', 'my-plugin)

dsl_gst_bin_new

DslReturnType dsl_gst_bin_new(const wchar_t* name);

This constructor creates a uniquely named GStreamer Bin. Construction will fail if the name is currently in use.

Parameters

name - [in] unique name for the GStreamer Been to create.

Returns DSL_RESULT_SUCCESS on successful creation. One of the Return Values defined above on failure

Python Example

retval = dsl_gst_bin_new('my-bin')

dsl_gst_bin_new_element_add_many

DslReturnType dsl_gst_bin_new_element_add_many(const wchar_t* name,
   const wchar_t** components);

This constructor creates a uniquely named GStreamer Bin and adds a list of Elements to it. Construction will fail if the name is currently in use.

Parameters

name - [in] unique name for the GStreamer Been to create.
components - [in] NULL terminated array of Element names to add.

Returns DSL_RESULT_SUCCESS on successful creation. One of the Return Values defined above on failure

Python Example

retval = dsl_gst_bin_new_element_add_many('my-bin',
   [my-element-1, my-element-2, my-element-3, None])

Destructors

dsl_gst_element_delete

DslReturnType dsl_gst_element_delete(const wchar_t* name);

This destructor deletes a uniquely named GStreamer Element. This service will fail if the element is currently in-use with a GST Bin.

Parameters

name - [in] unique name for the GStreamer Element to delete.

Returns DSL_RESULT_SUCCESS on successful deletion. One of the Return Values defined above on failure

Python Example

retval = dsl_gst_element_delete('my-element')

dsl_gst_element_delete_many

DslReturnType dsl_gst_element_delete_many(const wchar_t** names);

This destructor deletes a NULL terminated list of GStreamer Elements. This service will return with an error if any of the Elements are currently in-use or not found.

Parameters

names - [in] NULL terminated list of GStreamer Elements to delete.

Returns DSL_RESULT_SUCCESS on successful deletion. One of the Return Values defined above on failure

Python Example

retval = dsl_gst_element_delete_many('my-element-1',
   'my-element-2', 'my-element-3', None)

dsl_gst_element_delete_all

DslReturnType dsl_gst_element_delete_all();

This destructor deletes a NULL terminated list of GStreamer Elements. This service will return with an error if any of the Elements are currently in-use.

Returns DSL_RESULT_SUCCESS on successful deletion. One of the Return Values defined above on failure

Python Example

retval = dsl_gst_element_delete_all()

Methods

dsl_gst_element_property_boolean_get

DslReturnType dsl_gst_element_property_boolean_get(const wchar_t* name,
   const wchar_t* property, boolean* value);

This service gets a named boolean property from a named Element.

Parameters

name - [in] unique name for the Element to query.
property - [in] unique name of the property to query.
value - [out] current value for the named property.

Returns DSL_RESULT_SUCCESS on successful query. One of the Return Values defined above on failure.

Python Example

retval, value = dsl_gst_element_property_boolean_get('my-element',
   'some-boolean-property')

dsl_gst_element_property_boolean_set

DslReturnType dsl_gst_element_property_boolean_set(const wchar_t* name,
   const wchar_t* property, boolean value);

This service sets a named boolean property for a named Element.

Parameters

name - [in] unique name for the Element to update.
property - [in] unique name of the property to update.
value - [in] new value for the named property.

Returns DSL_RESULT_SUCCESS on successful update. One of the Return Values defined above on failure.

Python Example

retval = dsl_gst_element_property_boolean_set('my-element',
   'some-boolean-property', True)

dsl_gst_element_property_float_get

DslReturnType dsl_gst_element_property_float_get(const wchar_t* name,
   const wchar_t* property, float* value);

This service gets a named float property from a named Element.

Parameters

name - [in] unique name for the Element to query.
property - [in] unique name of the property to query.
value - [out] current value for the named property.

Returns DSL_RESULT_SUCCESS on successful query. One of the Return Values defined above on failure.

Python Example

retval, value = dsl_gst_element_property_float_get('my-element',
   'some-float-property')

dsl_gst_element_property_float_set

DslReturnType dsl_gst_element_property_float_set(const wchar_t* name,
   const wchar_t* property, float value);

This service sets a named float property for a named Element.

Parameters

name - [in] unique name for the Element to update.
property - [in] unique name of the property to update.
value - [in] new value for the named property.

Returns DSL_RESULT_SUCCESS on successful update. One of the Return Values defined above on failure.

Python Example

retval = dsl_gst_element_property_float_set('my-element',
   'some-float-property', 0.99)

dsl_gst_element_property_uint_get

DslReturnType dsl_gst_element_property_uint_get(const wchar_t* name,
   const wchar_t* property, uint* value);

This service gets a named unsigned integer property from a named Element.

Parameters

name - [in] unique name for the Element to query.
property - [in] unique name of the property to query.
value - [out] current value for the named property.

Returns DSL_RESULT_SUCCESS on successful query. One of the Return Values defined above on failure.

Python Example

retval, value = dsl_gst_element_property_uint_get('my-element',
   'some-uint-property')

dsl_gst_element_property_uint_set

DslReturnType dsl_gst_element_property_uint_set(const wchar_t* name,
   const wchar_t* property, uint value);

This service sets a named unsigned integer property for a named Element.

Parameters

name - [in] unique name for the Element to update.
property - [in] unique name of the property to update.
value - [in] new value for the named property.

Returns DSL_RESULT_SUCCESS on successful update. One of the Return Values defined above on failure.

Python Example

retval = dsl_gst_element_property_uint_set('my-element',
   'some-uint-property', 1234)

dsl_gst_element_property_int_get

DslReturnType dsl_gst_element_property_int_get(const wchar_t* name,
   const wchar_t* property, int* value);

This service gets a named signed integer property from a named Element.

Parameters

name - [in] unique name for the Element to query.
property - [in] unique name of the property to query.
value - [out] current value for the named property.

Returns DSL_RESULT_SUCCESS on successful query. One of the Return Values defined above on failure.

Python Example

retval, value = dsl_gst_element_property_int_get('my-element',
   'some-int-property')

dsl_gst_element_property_int_set

DslReturnType dsl_gst_element_property_int_set(const wchar_t* name,
   const wchar_t* property, int value);

This service sets a named signed integer property for a named Element.

Parameters

name - [in] unique name for the Element to update.
property - [in] unique name of the property to update.
value - [in] new value for the named property.

Returns DSL_RESULT_SUCCESS on successful update. One of the Return Values defined above on failure.

Python Example

retval = dsl_gst_element_property_int_set('my-element',
   'some-int-property', 1234)

dsl_gst_element_property_uint64_get

DslReturnType dsl_gst_element_property_uint64_get(const wchar_t* name,
   const wchar_t* property, uint64_t* value);

This service gets a named 64 bit unsigned integer property from a named Element.

Parameters

name - [in] unique name for the Element to query.
property - [in] unique name of the property to query.
value - [out] current value for the named property.

Returns DSL_RESULT_SUCCESS on successful query. One of the Return Values defined above on failure.

Python Example

retval, value = dsl_gst_element_property_uint64_get('my-element',
   'some-uint64-property')

dsl_gst_element_property_uint64_set

DslReturnType dsl_gst_element_property_uint64_set(const wchar_t* name,
   const wchar_t* property, uint64_t value);

This service sets a named 64 bit unsigned integer property for a named Element.

Parameters

name - [in] unique name for the Element to update.
property - [in] unique name of the property to update.
value - [in] new value for the named property.

Returns DSL_RESULT_SUCCESS on successful update. One of the Return Values defined above on failure.

Python Example

retval = dsl_gst_element_property_uint64_set('my-element',
   'some-uint64-property', 0x0123456789abcdef)

dsl_gst_element_property_int64_get

DslReturnType dsl_gst_element_property_int64_get(const wchar_t* name,
   const wchar_t* property, int64_t* value);

This service gets a named 64 bit signed integer property from a named Element.

Parameters

name - [in] unique name for the Element to query.
property - [in] unique name of the property to query.
value - [out] current value for the named property.

Returns DSL_RESULT_SUCCESS on successful query. One of the Return Values defined above on failure.

Python Example

retval, value = dsl_gst_element_property_int64_get('my-element',
   'some-int64-property')

dsl_gst_element_property_int64_set

DslReturnType dsl_gst_element_property_int64_set(const wchar_t* name,
   const wchar_t* property, int64_t value);

This service sets a named 64 bit signed integer property for a named Element.

Parameters

name - [in] unique name for the Element to update.
property - [in] unique name of the property to update.
value - [in] new value for the named property.

Returns DSL_RESULT_SUCCESS on successful update. One of the Return Values defined above on failure.

Python Example

retval = dsl_gst_element_property_int64_set('my-element',
   'some-int64-property', 0x0123456789abcdef)

dsl_gst_element_property_string_get

DslReturnType dsl_gst_element_property_string_get(const wchar_t* name,
   const wchar_t* property, const wchar_t** value);

This service gets a named string property from a named Element.

Parameters

name - [in] unique name for the Element to query.
property - [in] unique name of the property to query.
value - [out] current value for the named property.

Returns DSL_RESULT_SUCCESS on successful query. One of the Return Values defined above on failure.

Python Example

retval, value = dsl_gst_element_property_string_get('my-element',
   'some-string-property')

dsl_gst_element_property_string_set

DslReturnType dsl_gst_element_property_string_set(const wchar_t* name,
   const wchar_t* property, const wchar_t* value);

This service sets a named string property for a named Element.

Parameters

name - [in] unique name for the Element to update.
property - [in] unique name of the property to update.
value - [in] new value for the named property.

Returns DSL_RESULT_SUCCESS on successful update. One of the Return Values defined above on failure.

Python Example

retval = dsl_gst_element_property_string_set('my-element',
   'some-string-property', 'some-string-value')

dsl_gst_element_pph_add

DslReturnType dsl_gst_element_pph_add(const wchar_t* name,
   const wchar_t* handler, uint pad);

This service adds a Pad Probe Handler to either the Sink or Source pad of the named Element.

Parameters

name - [in] unique name of the Element to update.
handler - [in] unique name of Pad Probe Handler to add.
pad - [in] which of the two pads to add the handler to: DSL_PAD_SIK or DSL_PAD SRC

Returns

DSL_RESULT_SUCCESS on successful add. One of the Return Values defined above on failure.

Python Example

retval = dsl_gst_element_pph_add('my-element', 'my-pph-handler', DSL_PAD_SINK)

dsl_gst_element_pph_remove

DslReturnType dsl_gst_element_pph_remove(const wchar_t* name,
   const wchar_t* handler, uint pad);

This service removes a Pad Probe Handler from either the Sink or Source pad of the named GST Element. This service will fail if the named handler is not owned by the Inference Component

Parameters

name - [in] unique name of the Element to update.
handler - [in] unique name of Pad Probe Handler to remove
pad - [in] to which of the two pads to remove the handler from: DSL_PAD_SIK or DSL_PAD SRC

Returns

DSL_RESULT_SUCCESS on successful remove. One of the Return Values defined above on failure.

Python Example

retval = dsl_gst_element_pph_remove('my-element', 'my-pph-handler', DSL_PAD_SINK)

dsl_gst_bin_element_add

DslReturnType dsl_gst_bin_element_add(const wchar_t* name, const wchar_t* element);

This service adds a single named Element to a named Bin. The add service will fail if the Element is currently in-use by any Bin. The Element's in-use state will be set to true on successful add.

Parameters

name - [in] unique name for the Bin to update.
element - [in] unique name of the Element to add.

Returns

DSL_RESULT_SUCCESS on successful addition. One of the Return Values defined above on failure

Python Example

retval = dsl_gst_bin_element_add('my-bin', 'my-element')

dsl_gst_bin_element_add_many

DslReturnType dsl_gst_bin_element_add_many(const wchar_t* name, const wchar_t** elements);

Adds a list of named Elements to a named Bin. The add service will fail if any of the Elements are currently in-use by any Bin. All of the Element's in-use state will be set to true on successful add.

name - [in] unique name for the Bin to update.
elements - [in] a NULL terminated array of uniquely named Elements to add.

Returns

DSL_RESULT_SUCCESS on successful addition. One of the Return Values defined above on failure.

Python Example

retval = dsl_gst_bin_element_add_many('my-bin',
   ['my-element-1', 'my-element-2', None])

dsl_gst_bin_element_remove

DslReturnType dsl_gst_bin_element_remove(const wchar_t* name, const wchar_t* element);

This service removes a single named Element from a named Bin.

Parameters

name - [in] unique name for the Bin to update.
element - [in] unique name of the Element to remove.

Returns

DSL_RESULT_SUCCESS on successful removal. One of the Return Values defined above on failure

Python Example

retval = dsl_gst_bin_element_remove('my-bin', 'my-element')

dsl_gst_bin_element_remove_many

DslReturnType dsl_gst_bin_element_remove_many(const wchar_t* name, const wchar_t** elements);

Removes a list of named Elements from a named Bin.

name - [in] unique name for the Bin to update.
elements - [in] a NULL terminated array of uniquely named Elements to remove.

Returns

DSL_RESULT_SUCCESS on successful removal. One of the Return Values defined above on failure.

Python Example

retval = dsl_gst_bin_element_remove_many('my-bin',
   ['my-element-1', 'my-element-2', None])

API Reference

List of all Services
Pipeline
Player
Source
Tap
Dewarper
Preprocessor
Primary and Secondary Inference
Tracker
Segmentation Visualizer
Tiler
Demuxer and Splitter Tees
Remuxer
On-Screen Display
Sink
Custom Component
Pad Probe Handler
ODE Trigger
ODE Accumulator
ODE Acton
ODE Area
ODE Heat-Mapper
Display Types
branch
Component
Mailer
WebSocket Server
Message Broker
Info API

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