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membrane_rtp_plugin

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Membrane Multimedia Framework plugin for RTP

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membrane_rtp_plugin lib membrane rtp utils.ex
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lib/membrane/rtp/utils.ex 

defmodule Membrane.RTP.Utils do

  @moduledoc false



  alias Membrane.RTP.Packet



  @spec strip_padding(binary, padding_present? :: boolean) ::

          {:ok, {binary, padding_size :: non_neg_integer()}} | :error

  def strip_padding(binary, padding_present?)

  def strip_padding(binary, false), do: {:ok, {binary, 0}}



  def strip_padding(binary, true) do

    with size when size > 0 <- byte_size(binary),

         padding_size = :binary.last(binary),

         payload_size = byte_size(binary) - padding_size,

         <<stripped_payload::binary-size(payload_size), _::binary-size(padding_size)>> <- binary do

      {:ok, {stripped_payload, padding_size}}

    else

      _error -> :error

    end

  end



  @spec generate_padding(Packet.padding_size()) :: binary()

  def generate_padding(0), do: <<>>



  def generate_padding(padding_size) when padding_size in 1..255 do

    zeros_no = padding_size - 1

    <<0::size(zeros_no)-unit(8), padding_size>>

  end



  @spec from_which_rollover(number() | nil, number(), number()) :: :current | :previous | :next

  def from_which_rollover(previous_value, new_value, rollover_length)



  def from_which_rollover(nil, _new, _rollover_length), do: :current



  def from_which_rollover(previous_value, new_value, rollover_length) do

    # a) current rollover

    distance_if_current = abs(previous_value - new_value)

    # b) new_value is from the previous rollover

    distance_if_previous = abs(previous_value - (new_value - rollover_length))

    # c) new_value is in the next rollover

    distance_if_next = abs(previous_value - (new_value + rollover_length))



    [

      {:current, distance_if_current},

      {:previous, distance_if_previous},

      {:next, distance_if_next}

    ]

    |> Enum.min_by(fn {_atom, distance} -> distance end)

    |> then(fn {result, _value} -> result end)

  end

end