defmodule Membrane.H264.FFmpeg.Common do
  @moduledoc false
  use Ratio
  @h264_time_base 90_000

  @doc """
  Decoder and encoder requires timestamps in h264 time base, that is 1/90_000 [s]
  timestamps produced by this function are passed to the decoder so
  they must be integers.
  """
  @spec to_h264_time_base(number | Ratio.t()) :: integer
  def to_h264_time_base(timestamp) do
    (timestamp * @h264_time_base / Membrane.Time.second()) |> Ratio.trunc()
  end

  @doc """
  All timestamps in membrane should be represented in the internal units, that is 1 [ns]
  this function can return rational number.
  """
  @spec to_membrane_time_base(number | Ratio.t()) :: number | Ratio.t()
  def to_membrane_time_base(timestamp) do
    (timestamp * Membrane.Time.second() / @h264_time_base) |> Ratio.trunc()
  end
end