Membrane.Pipeline behaviour (Membrane Core v0.7.0) View Source

Module containing functions for constructing and supervising pipelines.

Pipelines are units that make it possible to instantiate, link and manage elements and bins in convenient way (actually they should always be used inside a pipeline). Linking pipeline children together enables them to pass data to one another, and process it in different ways.

To create a pipeline, use the __using__/1 macro and implement callbacks of Membrane.Pipeline behaviour. For details on instantiating and linking children, see Membrane.ParentSpec.

Link to this section Summary

Types

callback_return_t()

Defines return values from Pipeline callback functions.

pipeline_options_t()

Defines options that can be passed to start/3 / start_link/3 and received in handle_init/1 callback.

state_t()

Functions

__using__(options)

Brings all the stuff necessary to implement a pipeline.

pipeline?(module)

Checks whether module is a pipeline.

play(pid)

Changes playback state to :playing.

prepare(pid)

Changes playback state to :prepared.

start(module, pipeline_options \\ nil, process_options \\ [])

Does the same as start_link/3 but starts process outside of supervision tree.

start_link(module, pipeline_options \\ nil, process_options \\ [])

Starts the Pipeline based on given module and links it to the current process.

stop(pid)

Changes playback state to :stopped.

stop_and_terminate(pipeline, opts \\ [])

Changes pipeline's playback state to :stopped and terminates its process. It accpets two options

Callbacks

handle_crash_group_down(group_name, context, state)

Callback invoked when crash of the crash group happens.

handle_element_end_of_stream({}, context, state)

Callback invoked when a child element finishes processing stream via given pad.

handle_element_start_of_stream({}, context, state)

Callback invoked when a child element starts processing stream via given pad.

handle_init(options)

Callback invoked on initialization of pipeline process. It should parse options and initialize pipeline's internal state. Internally it is invoked inside GenServer.init/1 callback.

handle_notification(notification, element, context, state)

Callback invoked when a notification comes in from an element.

handle_other(message, context, state)

Callback invoked when pipeline receives a message that is not recognized as an internal membrane message.

handle_playing_to_prepared(context, state)

Callback invoked when pipeline transition from :playing to :prepared state has finished, that is all of its children are prepared to be stopped.

handle_prepared_to_playing(context, state)

Callback invoked when pipeline is in :playing state, i.e. all its children are in this state.

handle_prepared_to_stopped(context, state)

Callback invoked when pipeline is in :playing state, i.e. all its children are in this state.

handle_shutdown(reason, state)

Callback invoked when pipeline is shutting down. Internally called in GenServer.terminate/2 callback.

handle_spec_started(children, context, state)

Callback invoked when Membrane.ParentSpec is linked and in the same playback state as pipeline.

handle_stopped_to_prepared(context, state)

Callback invoked when pipeline transition from :stopped to :prepared state has finished, that is all of its children are prepared to enter :playing state.

handle_stopped_to_terminating(context, state)

Callback invoked when pipeline is in :terminating state, i.e. all its children are in this state.

handle_tick(timer_id, context, state)

Callback invoked upon each timer tick. A timer can be started with Membrane.Pipeline.Action.start_timer_t action.

membrane_pipeline?()

Enables to check whether module is membrane pipeline

Link to this section Types

callback_return_t()

Specs

callback_return_t() ::
  {:ok | {:ok, [Membrane.Pipeline.Action.t()]} | {:error, any()}, state_t()}
  | {:error, any()}

Defines return values from Pipeline callback functions.

Return values

{:ok, state} - Save process state, with no actions to change the pipeline.
{{:ok, [action]}, state} - Return a list of actions that will be performed within the pipline. This can be used to start new children, or to send messages to specific children, for example. Actions are a tuple of {type, arguments}, so may be written in the form a keyword list. See Membrane.Pipeline.Action for more info.
{{:error, reason}, state} - Terminates the pipeline with the given reason.
{:error, reason} - raises a Membrane.CallbackError with the error tuple.

pipeline_options_t()

Specs

pipeline_options_t() :: any()

Defines options that can be passed to start/3 / start_link/3 and received in handle_init/1 callback.

state_t()

Specs

state_t() :: map() | struct()

Link to this section Functions

using(options)

(macro)

Brings all the stuff necessary to implement a pipeline.

Options:

:bring_spec? - if true (default) imports and aliases Membrane.ParentSpec
:bring_pad? - if true (default) requires and aliases Membrane.Pad

pipeline?(module)

Specs

pipeline?(module()) :: boolean()

Checks whether module is a pipeline.

play(pid)

Specs

play(pid()) :: :ok

Changes playback state to :playing.

An alias for Membrane.Core.PlaybackHandler.change_playback_state/2 with proper state.

prepare(pid)

Specs

prepare(pid()) :: :ok

Changes playback state to :prepared.

An alias for Membrane.Core.PlaybackHandler.change_playback_state/2 with proper state.

start(module, pipeline_options \\ nil, process_options \\ [])

Specs

start(
  module(),
  pipeline_options :: pipeline_options_t(),
  process_options :: GenServer.options()
) :: GenServer.on_start()

Does the same as start_link/3 but starts process outside of supervision tree.

start_link(module, pipeline_options \\ nil, process_options \\ [])

Specs

start_link(
  module(),
  pipeline_options :: pipeline_options_t(),
  process_options :: GenServer.options()
) :: GenServer.on_start()

Starts the Pipeline based on given module and links it to the current process.

Pipeline options are passed to module's handle_init/1 callback.

Process options are internally passed to GenServer.start_link/3.

Returns the same values as GenServer.start_link/3.

stop(pid)

Specs

stop(pid()) :: :ok

Changes playback state to :stopped.

An alias for Membrane.Core.PlaybackHandler.change_playback_state/2 with proper state.

stop_and_terminate(pipeline, opts \\ [])

Specs

stop_and_terminate(pipeline :: pid(), Keyword.t()) :: :ok | {:error, :timeout}

Changes pipeline's playback state to :stopped and terminates its process. It accpets two options:

blocking? - tells whether to stop the pipeline synchronously
timeout - if blocking? is set to true it tells how much time (ms) to wait for pipeline to get terminated. Defaults to 5000.

Link to this section Callbacks

handle_crash_group_down(group_name, context, state)

(optional)

Specs

handle_crash_group_down(
  group_name :: Membrane.CrashGroup.name_t(),
  context :: Membrane.Pipeline.CallbackContext.CrashGroupDown.t(),
  state :: state_t()
) :: callback_return_t()

Callback invoked when crash of the crash group happens.

handle_element_end_of_stream({}, context, state)

(optional)

Specs

handle_element_end_of_stream(
  {Membrane.Child.name_t(), Membrane.Pad.ref_t()},
  context :: Membrane.Pipeline.CallbackContext.StreamManagement.t(),
  state :: state_t()
) :: callback_return_t()

Callback invoked when a child element finishes processing stream via given pad.

handle_element_start_of_stream({}, context, state)

(optional)

Specs

handle_element_start_of_stream(
  {Membrane.Child.name_t(), Membrane.Pad.ref_t()},
  context :: Membrane.Pipeline.CallbackContext.StreamManagement.t(),
  state :: state_t()
) :: callback_return_t()

Callback invoked when a child element starts processing stream via given pad.

handle_init(options)

(optional)

Specs

handle_init(options :: pipeline_options_t()) :: callback_return_t()

Callback invoked on initialization of pipeline process. It should parse options and initialize pipeline's internal state. Internally it is invoked inside GenServer.init/1 callback.

handle_notification(notification, element, context, state)

(optional)

Specs

handle_notification(
  notification :: Membrane.Notification.t(),
  element :: Membrane.Child.name_t(),
  context :: Membrane.Pipeline.CallbackContext.Notification.t(),
  state :: state_t()
) :: callback_return_t()

Callback invoked when a notification comes in from an element.

handle_other(message, context, state)

(optional)

Specs

handle_other(
  message :: any(),
  context :: Membrane.Pipeline.CallbackContext.Other.t(),
  state :: state_t()
) :: callback_return_t()

Callback invoked when pipeline receives a message that is not recognized as an internal membrane message.

Useful for receiving data sent from NIFs or other stuff.

handle_playing_to_prepared(context, state)

(optional)

Specs

handle_playing_to_prepared(
  context :: Membrane.Pipeline.CallbackContext.PlaybackChange.t(),
  state :: state_t()
) :: callback_return_t()

Callback invoked when pipeline transition from :playing to :prepared state has finished, that is all of its children are prepared to be stopped.

handle_prepared_to_playing(context, state)

(optional)

Specs

handle_prepared_to_playing(
  context :: Membrane.Pipeline.CallbackContext.PlaybackChange.t(),
  state :: state_t()
) :: callback_return_t()

Callback invoked when pipeline is in :playing state, i.e. all its children are in this state.

handle_prepared_to_stopped(context, state)

(optional)

Specs

handle_prepared_to_stopped(
  context :: Membrane.Pipeline.CallbackContext.PlaybackChange.t(),
  state :: state_t()
) :: callback_return_t()

Callback invoked when pipeline is in :playing state, i.e. all its children are in this state.

handle_shutdown(reason, state)

(optional)

Specs

handle_shutdown(reason, state :: state_t()) :: :ok
when reason: :normal | :shutdown | {:shutdown, any()} | term()

Callback invoked when pipeline is shutting down. Internally called in GenServer.terminate/2 callback.

Useful for any cleanup required.

handle_spec_started(children, context, state)

(optional)

Specs

handle_spec_started(
  children :: [Membrane.Child.name_t()],
  context :: Membrane.Pipeline.CallbackContext.SpecStarted.t(),
  state :: state_t()
) :: callback_return_t()

Callback invoked when Membrane.ParentSpec is linked and in the same playback state as pipeline.

This callback can be started from handle_init/1 callback or as Membrane.Pipeline.Action.spec_t/0 action.

handle_stopped_to_prepared(context, state)

(optional)

Specs

handle_stopped_to_prepared(
  context :: Membrane.Pipeline.CallbackContext.PlaybackChange.t(),
  state :: state_t()
) :: callback_return_t()

Callback invoked when pipeline transition from :stopped to :prepared state has finished, that is all of its children are prepared to enter :playing state.

handle_stopped_to_terminating(context, state)

(optional)

Specs

handle_stopped_to_terminating(
  context :: Membrane.Pipeline.CallbackContext.PlaybackChange.t(),
  state :: state_t()
) :: callback_return_t()

Callback invoked when pipeline is in :terminating state, i.e. all its children are in this state.

handle_tick(timer_id, context, state)

(optional)

Specs

handle_tick(
  timer_id :: any(),
  context :: Membrane.Pipeline.CallbackContext.Tick.t(),
  state :: state_t()
) :: callback_return_t()

Callback invoked upon each timer tick. A timer can be started with Membrane.Pipeline.Action.start_timer_t action.

membrane_pipeline?()

Specs

membrane_pipeline?() :: true

Enables to check whether module is membrane pipeline