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add iOS how-to guide

Author: valindrae

articles/communication-services/how-tos/calling-sdk/includes/closed-captions/ios.quickstart.md

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+---
+title: include file
+description: iOS how-to guide for enabling Closed captions during a call .
+author: Kunaal
+ms.service: azure-communication-services
+ms.subservice: calling
+ms.topic: include
+ms.topic: include file
+ms.date: 03/20/20223
+ms.author: kpunjabi
+---
+
+## Prerequisites
+- Azure account with an active subscription, for details see [Create an account for free.](https://azure.microsoft.com/free/)
+- Azure Communication Services resource. See [Create an Azure Communication Services resource](../../../quickstarts/create-communication-resource.md?tabs=windows&pivots=platform-azp). Save the connection string for this resource. 
+- An app with voice and video calling, refer to our [Voice](../../quickstarts/voice-video-calling/getting-started-with-calling.md) and [Video](../../quickstarts/voice-video-calling/get-started-with-video-calling.md) calling quickstarts.
+- [Access tokesn](../../quickstarts/manage-teams-identity.md) for Microsoft 365 users. 
+- [Access tokesn](../../quickstarts/identity/access-tokens.md) for External identity users.
+- For Translated captions you will need to have a [Teams premium](https://www.microsoft.com/en-us/microsoft-teams/premium#tabx93f55452286a4264a2778ef8902fb81a) license. 
+
+>[!NOTE]
+>Please note that you will need to have a voice calling app using ACS calling SDKs to access the closed captions feature that is described in the QuickStart below.
+
+## Models
+| Name | Description |
+|------|-------------|
+| TeamsCaptionsCallFeature | API for TeamsCall captions |
+| StartCaptionOptions | Closed caption options like spoken language |
+| TeamsCaptionsCallFeatureDelegate | Delegate for events |
+| TeamsCaptionsInfo | Data object received for each didReceiveCaptions event |
+
+## Get closed captions feature 
+
+### External Identity users
+
+If you're building an application that allows ACS users to join a Teams meeting 
+
+``` swift
+if let call = self.call { @State var captionsCallFeature = call.feature(Features.teamsCaptions) }
+```
+
+### Microsoft 365 users 
+
+``` swift
+if let teamsCall = self.teamsCall { @State var captionsCallFeature = call.feature(Features.teamsCaptions) }
+```
+
+## Subscribe to listeners
+
+### Add a listener to receive captions active/inactive status and data received
+
+```swift
+extension CallObserver: TeamsCaptionsCallFeatureDelegate {
+    // Add a listener to receive captions active/inactive status
+    public func teamsCaptionsCallFeature(_ teamsCaptionsFeature: TeamsCaptionsCallFeature, didChangeCaptionsActiveState args: PropertyChangedEventArgs) {
+        if(captionsCallFeature.isCaptionsFeatureActive) {
+            
+        }
+    }
+    
+    // Add listener for captions data received
+    public func teamsCaptionsCallFeature(_ teamsCaptionsFeature: TeamsCaptionsCallFeature, didReceiveCaptions: TeamsCaptionsInfo) {
+        
+    }
+}
+
+teamsCaptionsFeature.delegate = self.callObserver
+```
+
+## Start captions
+
+Once you've got all your listeners setup you can now start captions.
+
+``` swift
+func startCaptions() {
+    guard let captionsCallFeature = captionsCallFeature else {
+        return
+    }
+    let startCaptionsOptions = StartCaptionsOptions()
+    startCaptionsOptions.spokenLanguage = "en-us"
+    captionsCallFeature.startCaptions(startCaptionsOptions: startCaptionsOptions, completionHandler: { (error) in
+        if error != nil {
+            
+        }
+    })
+}
+```
+
+## Stop captions
+
+``` swift
+func stopCaptions() {
+    captionsCallFeature.stopCaptions(completionHandler: { (error) in
+        if error != nil {
+            
+        }
+    })
+}
+```
+
+## Remove caption received listener
+
+``` swift
+captionsCallFeature?.delegate = nil
+```
+
+## Spoken language support 
+
+### Get list of supported spoken languages
+Get a list of supported spoken languages that your users can select from when enabling closed captions. 
+
+``` swift
+// bcp 47 formatted language code
+let spokenLanguage : String = "en-us"
+for language in captionsCallFeature?.supportedSpokenLanguages ?? [] {
+    // choose required language
+    spokenLanguage = language
+}
+```
+
+### Set spoken language 
+When the user selects the spoken language, your app can set the spoken language that it expects captions to be generated from. 
+
+``` swift 
+func setSpokenLanguage() {
+    guard let captionsCallFeature = self.captionsCallFeature else {
+        return
+    }
+
+    captionsCallFeature.set(spokenLanguage: spokenLanguage, completionHandler: { (error) in
+        if let error = error {
+        }
+    })
+}
+```
+
+## Caption language support 
+
+### Get supported caption language 
+
+If your organization has an active Teams premium license, then your ACS users can enable translated captions as long as the organizer of the meeting has a Teams premium license. As for users with Microsoft 365 identities this check will be done against their own user account if they meeting organizer doesn't have a Teams premium license.
+
+``` swift
+// ISO 639-1 formatted language code
+let captionLanguage : String = "en"
+for language in captionsCallFeature?.supportedCaptionLanguages ?? [] {
+    // choose required language
+    captionLanguage = language
+}
+```
+### Set caption language 
+
+``` swift
+func setCaptionLanguage() {
+    guard let captionsCallFeature = self.captionsCallFeature else {
+        return
+    }
+
+    captionsCallFeature.set(captionLanguage: captionLanguage, completionHandler: { (error) in
+        if let error = error {
+        }
+    })
+}
+```