# Audio Track Selection plugin

This plugin adds a selection menu for multiple audio tracks in HLS or DASH streams.

## Prerequisites

* The [HLS plugin](/docs/wowza-flowplayer/plugins/hls) or [DASH plugin](/docs/wowza-flowplayer/plugins/mpeg-dash).
* An HLS or DASH media source with multiple separate audio tracks in the manifest.


## Installation

Load the `audio selection` plugin next to the core player and the [HLS plugin](/docs/wowza-flowplayer/plugins/hls) or the [DASH plugin](/docs/wowza-flowplayer/plugins/mpeg-dash).


```html
<script src="//cdn.flowplayer.com/releases/native/3/stable/flowplayer.min.js"></script>
<script src="//cdn.flowplayer.com/releases/native/3/stable/plugins/hls.min.js"></script>
<!-- or
<script src="//cdn.flowplayer.com/releases/native/3/stable/plugins/dash.min.js"></script>
-->
<script src="//cdn.flowplayer.com/releases/native/3/stable/plugins/asel.min.js"></script>
```

## Configuration (optional)

You can configure the plugin with top level configuration option `asel`.

The configuration option can either be `false` which disables audio selection or
a configuration object with properties:

* `default_lang` - a string containing the desired default language. It has to match an existing language attribute in the HLS manifest.
* `sort` - a sorting function to control the order of the items in the menu. Signature `(a: object, b: object) => number`.


Info
In order for `default_lang` to have an effect, make sure your m3u8 manifest alllows autoselecting a track. For example, the tag for the audio should look like:
`#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="audio_0",CHANNELS="1",NAME="English",LANGUAGE="en",DEFAULT=NO,AUTOSELECT=YES,URI="somemanifest.m3u8"`

`AUTOSELECT=NO` will prevent the parameter from working.

### Sorting

You can control in which order the items will be rendered into the menu by passing a sorting function as the `asel.sort` configuration option. For example, to sort by a pre-defined order in an array you might use the following function:


```js
function sort_by_lang(order) {
  return function(a, b) {
    return order.indexOf(a.lang) - order.indexOf(b.lang)
  }
}
```

Configured with:


```js
{
  // Other player configuration
  asel: {
    sort: sort_by_lang(["en", "es"])
  }

}
```

## API

embed
## Sample code


```js
var api = flowplayer('#container', {
  src: "https://wowzaec2demo.streamlock.net/vod-multitrack/_definst_/smil:ElephantsDream/ElephantsDream.smil/playlist.m3u8"
  asel: {
    default_lang: 'es'
  }
})

api.on(api.asel.events.SWITCH, function() {
  console.log('Track switched, current track', api.asel.get().name)
})
```

## Demo

[Codepen](https://codepen.io/team/flowplayer/pen/MPMojx)