Gst.BufferPool¶

Subclasses:: None

Methods¶

Inherited:: Gst.Object (27), GObject.Object (37)
Structs:: GObject.ObjectClass (5)

class	`config_add_option` (config, option)
class	`config_get_allocator` (config)
class	`config_get_option` (config, index)
class	`config_get_params` (config)
class	`config_has_option` (config, option)
class	`config_n_options` (config)
class	`config_set_allocator` (config, allocator, params)
class	`config_set_params` (config, caps, size, min_buffers, max_buffers)
class	`config_validate_params` (config, caps, size, min_buffers, max_buffers)
class	`new` ()
	`acquire_buffer` (params)
	`get_config` ()
	`get_options` ()
	`has_option` (option)
	`is_active` ()
	`release_buffer` (buffer)
	`set_active` (active)
	`set_config` (config)
	`set_flushing` (flushing)

Virtual Methods¶

Inherited:: Gst.Object (1), GObject.Object (7)

	`do_acquire_buffer` (params)
	`do_alloc_buffer` (params)
	`do_flush_start` ()
	`do_flush_stop` ()
	`do_free_buffer` (buffer)
	`do_get_options` ()
	`do_release_buffer` (buffer)
	`do_reset_buffer` (buffer)
	`do_set_config` (config)
	`do_start` ()
	`do_stop` ()

Properties¶

Inherited:: Gst.Object (2)

Signals¶

Inherited:: Gst.Object (1), GObject.Object (1)

Fields¶

Inherited:: Gst.Object (1), GObject.Object (1)

Name	Type	Access	Description
flushing	`int`	r	whether the pool is currently gathering back outstanding buffers
object	`Gst.Object`	r	the parent structure

Class Details¶

class Gst.BufferPool(**kwargs)¶

Bases:: Gst.Object
Abstract:: No
Structure:: Gst.BufferPoolClass

A Gst.BufferPool is an object that can be used to pre-allocate and recycle buffers of the same size and with the same properties.

A Gst.BufferPool is created with Gst.BufferPool.new().

Once a pool is created, it needs to be configured. A call to Gst.BufferPool.get_config() returns the current configuration structure from the pool. With Gst.BufferPool.config_set_params() and Gst.BufferPool.config_set_allocator() the bufferpool parameters and allocator can be configured. Other properties can be configured in the pool depending on the pool implementation.

A bufferpool can have extra options that can be enabled with Gst.BufferPool.config_add_option(). The available options can be retrieved with Gst.BufferPool.get_options(). Some options allow for additional configuration properties to be set.

After the configuration structure has been configured, Gst.BufferPool.set_config() updates the configuration in the pool. This can fail when the configuration structure is not accepted.

After the pool has been configured, it can be activated with Gst.BufferPool.set_active(). This will preallocate the configured resources in the pool.

When the pool is active, Gst.BufferPool.acquire_buffer() can be used to retrieve a buffer from the pool.

Buffers allocated from a bufferpool will automatically be returned to the pool with Gst.BufferPool.release_buffer() when their refcount drops to 0.

The bufferpool can be deactivated again with Gst.BufferPool.set_active(). All further Gst.BufferPool.acquire_buffer() calls will return an error. When all buffers are returned to the pool they will be freed.

classmethod config_add_option(config, option)[source]¶

Parameters:

config (Gst.Structure) – a Gst.BufferPool configuration
option (str) – an option to add

Enables the option in config. This will instruct the bufferpool to enable the specified option on the buffers that it allocates.

The options supported by pool can be retrieved with Gst.BufferPool.get_options().

classmethod config_get_allocator(config)[source]¶

Parameters:

config (Gst.Structure) – a Gst.BufferPool configuration

Returns:

True, if the values are set.

allocator:: a Gst.Allocator, or None
params:: Gst.AllocationParams, or None

Return type:

(bool, allocator: Gst.Allocator or None, params: Gst.AllocationParams)

Gets the allocator and params from config.

classmethod config_get_option(config, index)[source]¶

Parameters:

config (Gst.Structure) – a Gst.BufferPool configuration
index (int) – position in the option array to read

Returns:

the option at index.

Return type:

str or None

Parses an available config and gets the option at index of the options API array.

classmethod config_get_params(config)[source]¶

Parameters:

config (Gst.Structure) – a Gst.BufferPool configuration

Returns:

True if all parameters could be fetched.

caps:: the caps of buffers
size:: the size of each buffer, not including prefix and padding
min_buffers:: the minimum amount of buffers to allocate.
max_buffers:: the maximum amount of buffers to allocate or 0 for unlimited.

Return type:

(bool, caps: Gst.Caps or None, size: int, min_buffers: int, max_buffers: int)

Gets the configuration values from config.

classmethod config_has_option(config, option)[source]¶

Parameters:

config (Gst.Structure) – a Gst.BufferPool configuration
option (str) – an option

Returns:

True if the options array contains option.

Return type:

bool

Checks if config contains option.

classmethod config_n_options(config)[source]¶

Parameters:: config (Gst.Structure) – a Gst.BufferPool configuration
Returns:: the options array size as a int.
Return type:: int

Retrieves the number of values currently stored in the options array of the config structure.

classmethod config_set_allocator(config, allocator, params)[source]¶

Parameters:

config (Gst.Structure) – a Gst.BufferPool configuration
allocator (Gst.Allocator or None) – a Gst.Allocator
params (Gst.AllocationParams or None) – Gst.AllocationParams

Sets the allocator and params on config.

One of allocator and params can be None, but not both. When allocator is None, the default allocator of the pool will use the values in param to perform its allocation. When param is None, the pool will use the provided allocator with its default Gst.AllocationParams.

A call to Gst.BufferPool.set_config() can update the allocator and params with the values that it is able to do. Some pools are, for example, not able to operate with different allocators or cannot allocate with the values specified in params. Use Gst.BufferPool.get_config() to get the currently used values.

classmethod config_set_params(config, caps, size, min_buffers, max_buffers)[source]¶

Parameters:

config (Gst.Structure) – a Gst.BufferPool configuration
caps (Gst.Caps or None) – caps for the buffers
size (int) – the size of each buffer, not including prefix and padding
min_buffers (int) – the minimum amount of buffers to allocate.
max_buffers (int) – the maximum amount of buffers to allocate or 0 for unlimited.

Configures config with the given parameters.

classmethod config_validate_params(config, caps, size, min_buffers, max_buffers)[source]¶

Parameters:

config (Gst.Structure) – a Gst.BufferPool configuration
caps (Gst.Caps or None) – the excepted caps of buffers
size (int) – the expected size of each buffer, not including prefix and padding
min_buffers (int) – the expected minimum amount of buffers to allocate.
max_buffers (int) – the expect maximum amount of buffers to allocate or 0 for unlimited.

Returns:

True, if the parameters are valid in this context.

Return type:

bool

Validates that changes made to config are still valid in the context of the expected parameters. This function is a helper that can be used to validate changes made by a pool to a config when Gst.BufferPool.set_config() returns False. This expects that caps haven’t changed and that min_buffers aren’t lower then what we initially expected. This does not check if options or allocator parameters are still valid, won’t check if size have changed, since changing the size is valid to adapt padding.

New in version 1.4.

classmethod new()[source]¶

Returns:: a new Gst.BufferPool instance
Return type:: Gst.BufferPool

Creates a new Gst.BufferPool instance.

acquire_buffer(params)[source]¶

Parameters:

params (Gst.BufferPoolAcquireParams or None) – parameters.

Returns:

a Gst.FlowReturn such as Gst.FlowReturn.FLUSHING when the pool is inactive.

buffer:: a location for a Gst.Buffer

Return type:

(Gst.FlowReturn, buffer: Gst.Buffer or None)

Acquires a buffer from self. buffer should point to a memory location that can hold a pointer to the new buffer. When the pool is empty, this function will by default block until a buffer is released into the pool again or when the pool is set to flushing or deactivated.

params can contain optional parameters to influence the allocation.

get_config()[source]¶

Returns:: a copy of the current configuration of self.
Return type:: Gst.Structure

Gets a copy of the current configuration of the pool. This configuration can be modified and used for the Gst.BufferPool.set_config() call.

get_options()[source]¶

Returns:: a None terminated array of strings.
Return type:: [str]

Gets a None terminated array of string with supported bufferpool options for self. An option would typically be enabled with Gst.BufferPool.config_add_option().

has_option(option)[source]¶

Parameters:: option (str) – an option
Returns:: True if the buffer pool contains option.
Return type:: bool

Checks if the bufferpool supports option.

is_active()[source]¶

Returns:: True when the pool is active.
Return type:: bool

Checks if self is active. A pool can be activated with the Gst.BufferPool.set_active() call.

release_buffer(buffer)[source]¶

Parameters:: buffer (Gst.Buffer) – a Gst.Buffer

Releases buffer to self. buffer should have previously been allocated from self with Gst.BufferPool.acquire_buffer().

This function is usually called automatically when the last ref on buffer disappears.

set_active(active)[source]¶

Parameters:: active (bool) – the new active state
Returns:: False when the pool was not configured or when preallocation of the buffers failed.
Return type:: bool

Controls the active state of self. When the pool is inactive, new calls to Gst.BufferPool.acquire_buffer() will return with Gst.FlowReturn.FLUSHING.

Activating the bufferpool will preallocate all resources in the pool based on the configuration of the pool.

Deactivating will free the resources again when there are no outstanding buffers. When there are outstanding buffers, they will be freed as soon as they are all returned to the pool.

set_config(config)[source]¶

Parameters:: config (Gst.Structure) – a Gst.Structure
Returns:: True when the configuration could be set.
Return type:: bool

Sets the configuration of the pool. If the pool is already configured, and the configuration hasn’t changed, this function will return True. If the pool is active, this method will return False and active configuration will remain. Buffers allocated from this pool must be returned or else this function will do nothing and return False.

config is a Gst.Structure that contains the configuration parameters for the pool. A default and mandatory set of parameters can be configured with Gst.BufferPool.config_set_params(), Gst.BufferPool.config_set_allocator() and Gst.BufferPool.config_add_option().

If the parameters in config can not be set exactly, this function returns False and will try to update as much state as possible. The new state can then be retrieved and refined with Gst.BufferPool.get_config().

This function takes ownership of config.

set_flushing(flushing)[source]¶

Parameters:: flushing (bool) – whether to start or stop flushing

Enables or disables the flushing state of a self without freeing or allocating buffers.

New in version 1.4.

do_acquire_buffer(params) virtual¶

Parameters:

params (Gst.BufferPoolAcquireParams or None) – parameters.

Returns:

a Gst.FlowReturn such as Gst.FlowReturn.FLUSHING when the pool is inactive.

buffer:: a location for a Gst.Buffer

Return type:

(Gst.FlowReturn, buffer: Gst.Buffer or None)

Acquires a buffer from pool. buffer should point to a memory location that can hold a pointer to the new buffer. When the pool is empty, this function will by default block until a buffer is released into the pool again or when the pool is set to flushing or deactivated.

params can contain optional parameters to influence the allocation.

do_alloc_buffer(params) virtual¶

Parameters:

params (Gst.BufferPoolAcquireParams or None) – parameters.

Returns:

a Gst.FlowReturn to indicate whether the allocation was successful.

buffer:: a location for a Gst.Buffer

Return type:

(Gst.FlowReturn, buffer: Gst.Buffer or None)

Allocate a buffer. the default implementation allocates buffers from the configured memory allocator and with the configured parameters. All metadata that is present on the allocated buffer will be marked as Gst.MetaFlags.POOLED and Gst.MetaFlags.LOCKED and will not be removed from the buffer in #GstBufferPoolClass::reset_buffer. The buffer should have the Gst.BufferFlags.TAG_MEMORY cleared.

do_flush_start() virtual¶: Enter the flushing state.

New in version 1.4.

do_flush_stop() virtual¶: Leave the flushing state.

New in version 1.4.

do_free_buffer(buffer) virtual¶

Parameters:: buffer (Gst.Buffer) – the Gst.Buffer to free

Free a buffer. The default implementation unrefs the buffer.

do_get_options() virtual¶

Returns:: a None terminated array of strings.
Return type:: [str]

Gets a None terminated array of string with supported bufferpool options for pool. An option would typically be enabled with Gst.BufferPool.config_add_option().

do_release_buffer(buffer) virtual¶

Parameters:: buffer (Gst.Buffer) – a Gst.Buffer

Releases buffer to pool. buffer should have previously been allocated from pool with Gst.BufferPool.acquire_buffer().

This function is usually called automatically when the last ref on buffer disappears.

do_reset_buffer(buffer) virtual¶

Parameters:: buffer (Gst.Buffer) – the Gst.Buffer to reset

Reset the buffer to its state when it was freshly allocated. The default implementation will clear the flags, timestamps and will remove the metadata without the Gst.MetaFlags.POOLED flag (even the metadata with Gst.MetaFlags.LOCKED). If the Gst.BufferFlags.TAG_MEMORY was set, this function can also try to restore the memory and clear the Gst.BufferFlags.TAG_MEMORY again.

do_set_config(config) virtual¶

Parameters:: config (Gst.Structure) – a Gst.Structure
Returns:: True when the configuration could be set.
Return type:: bool

Sets the configuration of the pool. If the pool is already configured, and the configuration hasn’t changed, this function will return True. If the pool is active, this method will return False and active configuration will remain. Buffers allocated from this pool must be returned or else this function will do nothing and return False.

config is a Gst.Structure that contains the configuration parameters for the pool. A default and mandatory set of parameters can be configured with Gst.BufferPool.config_set_params(), Gst.BufferPool.config_set_allocator() and Gst.BufferPool.config_add_option().

If the parameters in config can not be set exactly, this function returns False and will try to update as much state as possible. The new state can then be retrieved and refined with Gst.BufferPool.get_config().

This function takes ownership of config.

do_start() virtual¶

Returns:: whether the pool could be started.
Return type:: bool

Start the bufferpool. The default implementation will preallocate min-buffers buffers and put them in the queue.

do_stop() virtual¶

Returns:: whether the pool could be stopped.
Return type:: bool

Stop the bufferpool. the default implementation will free the preallocated buffers. This function is called when all the buffers are returned to the pool.