Add and customize captions (iOS)

Captions provide your viewers synchronized text of the audio and non-speech elements of your video content. In addition, complimenting your video content with captions can have the following benefits:

• Improved video SEO
• Increased content retention
• Increased engagement with autoplay content
• Environment-independent content viewing
• Legal compliance

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The same processes are used to add or customize both captions and subtitles in your iOS app. For simplicity, we refer only to captions in our documentation.

Supported caption types

Captions can either be embedded in the video (embedded captions) or loaded from a separate file (side-loaded or sidecar captions). The iOS SDK supports both types of captions.

You can add embedded captions, sidecar captions, or both.

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We strongly advise that you remotely self-host video content with embedded captions. If video content with embedded captions is uploaded to your JWP account, the embedded captions may be removed during the encoding process.

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When the list of available caption tracks is retrieved from the player, the captions appear in the following order:

• None track, denoting that no captions are available.
• Embedded captions
• Side-loaded captions

This is also the order in which the captions are listed in the player menu.

The following table lists common caption formats that the iOS SDK supports.

Add captions to your app

JWP supports embedded and side-loaded captions. The following sections explain how to add each type of caption to your video.

Embedded captions

The recipe below demonstrates how to embed captions in your iOS app.

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Do not add videos or streams with embedded captions to your JWP library. The embedded captions tracks of the content may be removed during JWP's video transcoding process.

Side-loaded captions

The recipe below demonstrates how to side-load captions in your iOS app.

iOS settings mapping

The following tables map the specific iOS Settings > Accessibility > Subtitles & Captioning settings to the iOS SDK property.

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Remember that viewers must enable Video Override in each of these areas for your customizations to render when they use your app.

Text

Background

Advanced

Listening for caption events

The following table describes the JWAVDelegate methods that correspond to captions events.

override func jwplayer(_ player: JWPlayer, updatedCaptionList options: [JWMediaSelectionOption]) {
    super.jwplayer(player, updatedCaptionList: options)
}

override func jwplayer(_ player: JWPlayer, captionTrackChanged index: Int) {
    super.jwplayer(player, captionTrackChanged: index)
}

override func jwplayer(_ player: JWPlayer, captionPresented caption: [String], at time: JWTimeData) {
    super.jwplayer(player, updatedCues: cues)
}

- (void)jwplayer:(id<JWPlayer> _Nonnull)player updatedCaptionList:(NSArray<JWMediaSelectionOption *> * _Nonnull)options {
}
- (void)jwplayer:(id<JWPlayer> _Nonnull)player captionTrackChanged:(NSInteger)index 
{
}
- (void)jwplayer:(id<JWPlayer> _Nonnull)player captionPresented:(NSArray<NSString *> * _Nonnull)caption at:(JWTimeData * _Nonnull)time 
{
}

Setting a caption track programmatically

Setting a caption track programmatically has many benefits, including

• Knowing and setting the language your user prefers
• Mirroring a user’s language selection outside of the UI in JWPlayerViewController
• Use in conjunction with your UI implementation when the user selects a language if you are only using JWPlayerView

To set the captions track programmatically, use the index of the captions according to the captions list or with the locale that was set for the captions.

try { 
    player.setCaptionTrack(index: 2)
} catch {
    // handle error
}

try { 
    player.setCaptionTrack(locale: “en”)
} catch {
    // handle error
}

NSError *setWithIndexError;
 [player setCaptionTrackWithIndex:1 error: &setWithIndexError];
    
 if (setWithIndexError) {
     // handle error if not null
 }
    
 NSError *setWithLocaleError;
 [player setCaptionTrackWithLocale:@"en" error: &setWithLocaleError];
    
 if (setWithLocaleError) {
    // handle error if not null
 }

Caption Rendering

Our SDK renders all side-loaded captions. For embedded captions, such as in an HLS stream, AVPlayer renders the captions. Specifying values within JWCaptionStyle will only affect side-loaded captions.

Disabling Rendering

For some uses of our player, it may be desired that the player not render the captions. Instead, perhaps you wish to render the captions into a different view, elsewhere on the screen.

In JWPlayer, there is a property called suppressesCaptionRendering. If true, the player will not render captions on the screen if a caption track is selected, however, you will still receive caption events, including func jwplayer(_ player: JWPlayer, captionPresented caption: [String], at time: JWTimeData). By default, this flag is false.

class CustomPlayerViewController: JWPlayerViewController {
  override func viewDidLoad() {
    super.viewDidLoad()
    
    // Suppress caption rendering
    player.suppressesCaptionRendering = true

    // Initialize configuration and the player below.
  }
}

Setting Caption Insets

We can set the amount of space from the edges of the player to the captions container using the JWPlayerView.captionInsets API. This property is a UIEdgeInsets, which lets us specify the top, bottom, left, and right distance from the player edges you require.

// The new insets that will be used
let newInsets = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)

// Set them to the JWPlayerView instance
playerView.captionInsets = newInsets

// The new insets that will be used
UIEdgeInsets newInsets = UIEdgeInsetsMake(0, 0, 0, 0);

// Set them to your JWPlayerView instance
self.playerView.captionInsets = newInsets;

Accessibility

On iOS devices, users can permit the SDK to select captions based on their device settings. When the caption tracks have been loaded for a video, the SDK chooses the initial caption track based on the following considerations in order:

1. User's Chosen Track: If a user chooses a caption locale while watching videos in a playlist, the SDK will choose a caption in the same locale for subsequent videos in the playlist during the playback session.
2. User's Language if User has Disability: If a user has enabled the Close Caption & Subtitles for the Deaf and Hard of Hearing (CC+SDH) on the device, the SDK will query the user's native language on the device and choose a caption with the same locale.
3. Default Caption Track: The SDK chooses the default captions track as specified in the player configuration.
4. No Captions: The SDK will turn off captions if the previous steps cannot determine a starting caption track