# `Expresso.Element.Audio`
[🔗](https://github.com/rellen/expresso/blob/main/lib/expresso/element/audio.ex#L1)

An element that plays a sound file in a slide

The `audio` entity takes the path of an MP3, an M4A, an Ogg or a WAV file
as its first argument, relative to the working directory of the command or
to the `root` option of the deck. The `title` option names the sound for a
screen reader, and the handout view and paper show it with a note symbol.

The `audio` element holds only `data-audio`, the number of the element in
the deck, and the renderer writes each file one time, as a data URI, into
the element `expresso-audios`. `Expresso.Media` gives the reasons.

The sound plays in the present view only, with the rules of a video: while
its slide shows and the element shows at the current step. A black screen,
the menu and the overview pause it, and it starts again from the start when
its slide shows again. A browser plays sound only after the first key or
click in the document, so a sound of the first slide starts at the first
key. Without `controls`, the present view shows nothing in the place of
the element. `docs/reference/audio-element.md` gives the rules.

# `t`

```elixir
@type t() :: %Expresso.Element.Audio{
  __spark_metadata__: term(),
  at: term(),
  class: term(),
  controls: term(),
  easing: term(),
  effect: term(),
  el: term(),
  index: term(),
  loop: term(),
  morph: term(),
  on: term(),
  signature: term(),
  speed: term(),
  src: term(),
  steps: term(),
  title: term()
}
```

The struct of an audio element

# `get_assigns`

```elixir
@spec get_assigns(t()) :: map()
```

Make the assigns of the render function from the struct

# `json`

```elixir
@spec json(Expresso.Deck.t()) :: String.t() | nil
```

Write the sounds of a deck as JSON, or return `nil` for a deck with none

# `number`

```elixir
@spec number(Expresso.Deck.t()) :: Expresso.Deck.t()
```

Give each sound of a deck its number

`Expresso.Renderer` calls this function before the render, and the render
function writes the number into `data-audio`.

# `render`

```elixir
@spec render(map()) :: Phoenix.HTML.safe()
```

Make the HTML of a sound

The `audio` element has no source, and the presenter gives it one. An
element with no controls gets `tabindex="-1"`, so the key Tab does not go
into it. The caption shows the title with a note symbol in the handout
view and on paper, and the style sheet hides it in the present view.

# `source`

```elixir
@spec source(term()) :: {:ok, String.t()} | {:error, String.t()}
```

Make sure that the source of a sound is the path of an MP3, an M4A, an Ogg
or a WAV file

This function is the custom type of the first argument. It does not read
the file, so a missing file gives an error at render time.

    iex> Expresso.Element.Audio.source("sounds/bell.mp3")
    {:ok, "sounds/bell.mp3"}

    iex> {:error, _message} = Expresso.Element.Audio.source("sounds/bell.flac")

# `sources`

```elixir
@spec sources(Expresso.Deck.t()) :: [String.t()]
```

Return the data URI of each file of the sounds of a deck, in the order of
their numbers

---

*Consult [api-reference.md](api-reference.md) for complete listing*