# How to configure a different stream to Chromecast on iOS

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).

To achieve this use case on the iOS SDK, you have to leverage the [`ChromecastConnectionDelegate`](https://optiview.dolby.com/docs/theoplayer/v11/api-reference/ios/Protocols/Chromecast_Objc#/c:@M@THEOplayerSDK@objc\(pl\)THEOplayerChromecast\(im\)setConnectionDelegate:) of your [`THEOplayer`](https://optiview.dolby.com/docs/theoplayer/v11/api-reference/ios/Classes/THEOplayer) object.

The snippet below is an example of how your `ChromecastConnectionDelegate` could look like. This particular snippet has two [sources](https://optiview.dolby.com/docs/theoplayer/v11/api-reference/ios/Classes/SourceDescription):

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

The `ChromecastConnectionDelegate` 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.

```swift
import UIKit
import THEOplayerSDK

class ChromecastController: ChromecastConnectionDelegate {

    weak var theoplayer : THEOplayer?

    private var senderSource: SourceDescription {
        let typedSource = TypedSource(
            src: "https://cdn.theoplayer.com/video/big_buck_bunny/big_buck_bunny_metadata.m3u8",
            type: "application/x-mpegurl"
        )
        return SourceDescription(source: typedSource)
    }

    private var chromecastSource: SourceDescription {
        let typedSource = TypedSource(
            src: "https://amssamples.streaming.mediaservices.windows.net/622b189f-ec39-43f2-93a2-201ac4e31ce1/BigBuckBunny.ism/manifest(format=mpd-time-csf)",
            type: "application/dash+xml",
            drm: WidevineDRMConfiguration(licenseAcquisitionURL: "https://amssamples.keydelivery.mediaservices.windows.net/Widevine/?KID=1ab45440-532c-4399-94dc-5c5ad9584bac")
        )
        return SourceDescription(source: typedSource)
    }

    init(theo : THEOplayer) {
        self.theoplayer = theo
        self.theoplayer?.cast?.chromecast?.setConnectionDelegate(self)
    }

    func onStart(sourceDescription: SourceDescription?) -> SourceDescription? {
        return chromecastSource
    }

    func onStop(sourceDescription: SourceDescription?) -> SourceDescription? {
        return senderSource
    }

    func onJoin(sourceDescription: SourceDescription?) -> SourceDescription? {
        return sourceDescription
    }

    func onLeave(sourceDescription: SourceDescription?) -> SourceDescription? {
        return sourceDescription
    }

}
```

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

Once you've implemented your `ChromecastConnectionDelegate`, you have to initialize an instance of this near the code of your where you're setting your `player.source` (e.g. <https://github.com/THEOplayer/samples-ios-sdk/blob/master/Google-Cast/Google_Cast/PlayerViewController.swift>). The snippet below demonstrates this concept:

```swift
...
class PlayerViewController: UIViewController {

    ...
    var chromecastController : ChromecastController!
    var senderSource: SourceDescription {
        let typedSource = TypedSource(
            src: "https://cdn.theoplayer.com/video/big_buck_bunny/big_buck_bunny_metadata.m3u8",
            type: "application/x-mpegurl"
        )
        return SourceDescription(source: typedSource)
    }
    ...

    override func viewDidLoad() {

        ...
        player.source = senderSource
        chromecastController = ChromecastController(theo: theoplayer)
        ...

    }

    ...

}
...
```