Membrane Core

v0.3.0

Membrane Core v0.3.0 Membrane.Element.Pad View Source

Pads are units defined by each element, allowing it to be linked with another elements. This module consists of pads typespecs and utils.

Each pad is described by its name, direction, availability, mode and possible caps. For pads to be linkable, these properties have to be compatible. For more information on each of them, check appropriate type in this module.

Each link can only consist of exactly two pads.

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Types

availability_mode_t()

Type describing availability mode of a created pad

availability_t()

Values used when defining pad availability

common_spec_options_t()

Pad options used in spec_t/0

description_t()

Type describing a pad. Contains data parsed from spec_t/0

direction_t()

Defines possible pad directions

input_spec_t()

Describes how an input pad should be declared inside an element

mode_t()

Describes how an element sends and receives data. Modes are strictly related to pad directions

name_t()

Defines the name of pad or group of dynamic pads

output_spec_t()

Describes how an output pad should be declared inside an element

ref_t()

Defines the term by which the pad instance is identified

spec_t()

Describes how a pad should be declared in element

Functions

availability_mode(atom)

Returns pad availability mode for given availability

availability_mode_by_ref(ref)

Returns pad availability mode based on pad reference

is_availability(term)
is_availability_dynamic(availability)
is_availability_static(availability)
is_pad_name(term)
is_pad_ref(term)
name_by_ref(ref)

Returns the name for the given pad reference

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availability_mode_t() View Source 
availability_mode_t() :: :static | :dynamic

Type describing availability mode of a created pad:

  • :static - there always exist exactly one instance of such pad.
  • :dynamic - multiple instances of such pad may be created and removed (which entails executing handle_pad_added and handle_pad_removed callbacks, respectively).
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availability_t() View Source 
availability_t() :: :on_request | :always

Values used when defining pad availability:

  • :always - a static pad, which can remain unlinked in stopped state only.
  • :on_request - a dynamic pad, instance of which is created every time it is linked to another pad. Thus linking the pad with k other pads, creates k instances of the pad, and links each with another pad.
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common_spec_options_t() View Source 
common_spec_options_t() ::
  {:availability, availability_t()}
  | {:mode, mode_t()}
  | {:caps, Membrane.Caps.Matcher.caps_specs_t()}
  | {:options, Keyword.t()}

Pad options used in spec_t/0

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description_t() View Source 
description_t() :: %{
  :availability => availability_t(),
  :mode => mode_t(),
  :caps => Membrane.Caps.Matcher.caps_specs_t(),
  optional(:demand_unit) => Membrane.Buffer.Metric.unit_t(),
  :direction => direction_t(),
  :options => nil | Keyword.t()
}

Type describing a pad. Contains data parsed from spec_t/0

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direction_t() View Source 
direction_t() :: :output | :input

Defines possible pad directions:

  • :output - data can only be sent through such pad,
  • :input - data can only be received through such pad.

One cannot link two pads with the same direction.

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input_spec_t() View Source 
input_spec_t() ::
  {name_t(),
   [common_spec_options_t() | {:demand_unit, Membrane.Buffer.Metric.unit_t()}]}

Describes how an input pad should be declared inside an element.

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mode_t() View Source 
mode_t() :: :push | :pull

Describes how an element sends and receives data. Modes are strictly related to pad directions:

  • :push output pad - element can send data through such pad whenever it wants.
  • :push input pad - element has to deal with data whenever it comes through such pad, and do it fast enough not to let data accumulate on such pad, what may lead to overflow of element process erlang queue, which is highly unwanted.
  • :pull output pad - element can send data through such pad only if it have already received demand on the pad. Sending small, limited amount of undemanded data is supported and handled by Membrane.Core.InputBuffer.
  • :pull input pad - element receives through such pad only data that it has previously demanded, so that no undemanded data can arrive.

Linking pads with different modes is possible, but only in case of output pad working in push mode, and input in pull mode. Moreover, toilet mode of Membrane.Core.InputBuffer has to be enabled then.

For more information on transfering data and demands, see docs for element callbacks in Membrane.Element.Base.*.

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name_t() View Source 
name_t() :: atom()

Defines the name of pad or group of dynamic pads

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output_spec_t() View Source 
output_spec_t() :: {name_t(), [common_spec_options_t()]}

Describes how an output pad should be declared inside an element.

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ref_t() View Source 
ref_t() :: atom() | {:dynamic, atom(), non_neg_integer()}

Defines the term by which the pad instance is identified.

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spec_t() View Source 
spec_t() :: output_spec_t() | input_spec_t()

Describes how a pad should be declared in element.

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availability_mode(atom) View Source 
availability_mode(availability_t()) :: availability_mode_t()

Returns pad availability mode for given availability.

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availability_mode_by_ref(ref) View Source 
availability_mode_by_ref(ref_t()) :: availability_mode_t()

Returns pad availability mode based on pad reference.

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is_availability(term) View Source (macro)

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is_availability_dynamic(availability) View Source (macro)

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is_availability_static(availability) View Source (macro)

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is_pad_name(term) View Source (macro)

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is_pad_ref(term) View Source (macro)

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name_by_ref(ref) View Source

Returns the name for the given pad reference