Gst.BufferPool

g GObject.InitiallyUnowned GObject.InitiallyUnowned Gst.Object Gst.Object GObject.InitiallyUnowned->Gst.Object GObject.Object GObject.Object GObject.Object->GObject.InitiallyUnowned Gst.BufferPool Gst.BufferPool Gst.Object->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 (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)

Fields

Inherited:Gst.Object (1), GObject.Object (1)
Name Type Access Description
flushing int r  
object Gst.Object r  
priv Gst.BufferPoolPrivate r  

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 a 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.

Use Gst.Object.unref() to release the reference to a bufferpool. If the refcount of the pool reaches 0, the pool will be freed.

classmethod config_add_option(config, option)[source]
Parameters:

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

The supported options 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, params: Gst.AllocationParams)

Get the allocator and params from config.

classmethod config_get_option(config, index)[source]
Parameters:
Returns:

a str of the option at index.

Return type:

str

Parse an available config and get 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, size: int, min_buffers: int, max_buffers: int)

Get the configuration values from config.

classmethod config_has_option(config, option)[source]
Parameters:
Returns:

True if the options array contains option.

Return type:

bool

Check 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

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

classmethod config_set_allocator(config, allocator, params)[source]
Parameters:

Set 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) – 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.

Configure 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) – 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

Validate 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)

Acquire a buffer from self. buffer should point to a memory location that can hold a pointer to the new buffer.

params can be None or contain optional parameters to influence the allocation.

get_config()[source]
Returns:a copy of the current configuration of self. use Gst.Structure.free() after usage or Gst.BufferPool.set_config().
Return type:Gst.Structure

Get a copy of the current configuration of the pool. This configuration can either be modified and used for the Gst.BufferPool.set_config() call or it must be freed after usage.

get_options()[source]
Returns:a None terminated array of strings.
Return type:[str]

Get 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

Check if the bufferpool supports option.

is_active()[source]
Returns:True when the pool is active.
Return type:bool

Check 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

Release 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

Control 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

Set the configuration of the pool. If the pool is already configured, and the configuration haven’t change, this function will return True. If the pool is active, this method will return False and active configuration will remain. Buffers allocated form 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

Enable or disable 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)

Acquire a buffer from pool. buffer should point to a memory location that can hold a pointer to the new buffer.

params can be None or contain optional parameters to influence the allocation.

do_alloc_buffer(buffer, params) virtual
Parameters:
Return type:

Gst.FlowReturn

do_flush_start() virtual
do_flush_stop() virtual
do_free_buffer(buffer) virtual
Parameters:buffer (Gst.Buffer) –
do_get_options() virtual
Returns:a None terminated array of strings.
Return type:[str]

Get 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

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

Set the configuration of the pool. If the pool is already configured, and the configuration haven’t change, this function will return True. If the pool is active, this method will return False and active configuration will remain. Buffers allocated form 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
Return type:bool
do_stop() virtual
Return type:bool