# How to configure a different stream to Chromecast on Web

Some streaming setups require you to cast a different stream to a Chromecast Receiver device than the one playing on a Chromecast Receiver device. For example, if you're playing HLS + FairPlay DRM on your iOS application, you need to cast a different source with DASH + Widevine DRM to your Chromecast application, because Chromecast applications aren't able to support FairPlay.

You can achieve this use case with the ChromecastConnection API.

## ChromecastConnection API

The ChromecastConnection API allows you to implement callbacks related to Chromecast playback. To achieve the described use case you can use the `onStart` (i.e. the start of a Chromecast session) to set a new stream, and `onStop` (i.e. the end of a Chromecast session) to (re)set your previous stream.

You may also be interested in `onJoin` (i.e. joining an existing Chromecast session with a new device) or `onLeave` (i.e. leaving an existing Chromecast session on a device).

The snippet below has two [sources](https://optiview.dolby.com/docs/theoplayer/v11/api-reference/web/interfaces/SourceDescription):

1. `senderSource` is intended for playback on your sender device (i.e. your browser)
2. `chromecastSource` is intended for playback on your Chromecast application

The [`ChromecastConnectionCallback`](https://optiview.dolby.com/docs/theoplayer/v11/api-reference/web/interfaces/ChromecastConnectionCallback) interface is used to:

1. Set the `chromecastSource` when Chromecast playback starts through the `onStart` callback.
2. Revert to the `senderSource` when Chromecast playback stops through the `onStop` callback.

```js
var senderSource = {
  sources: {
    src: 'https://cdn.theoplayer.com/video/elephants-dream/playlist.m3u8',
    type: 'application/x-mpegurl',
  },
};
var chromecastSource = {
  sources: {
    src: 'https://cdn.theoplayer.com/video/big_buck_bunny/big_buck_bunny_metadata.m3u8',
    type: 'application/x-mpegurl',
  },
};
player.source = senderSource;
player.cast.chromecast.connectionCallback = {
  onStart: function (source) {
    return chromecastSource;
  },
  onStop: function (source) {
    return senderSource;
  },
  onJoin: function (source) {
    return source;
  },
  onLeave: function (source) {
    return source;
  },
};
```

The `onJoin` and `onLeave` implementations in the above snippet adhere to the default behavior.