Subtitles and/or captions are terms sometimes used indistinctly to refer to the text version of the speech and non-speech audio information needed to understand the content, that is displayed as a layer on top of the video screen. W3C describes:
Subtitles are implemented the same way as captions. Subtitles/interlingual subtitles are usually only the spoken audio (for people who can hear the audio but do not know the spoken language). They can be a translation of the caption content, including non-speech audio information.
Captions are needed for accessibility, whereas subtitles in other languages are not directly an accessibility accommodation. (Source: Captions/Subtitles)
Some of the most popular formats for subtitles used on the industry right now are listed below with references to their correspondent specification:
CEA-608: Line 21 Data Services (ANSI/CTA-608-E S-2019) (latest revision of the standard, free of charge)
- CEA-708: Digital Television (DTV) Closed Captioning (ANSI/CTA-708-E R-2018) (latest revision of the standard, free of charge)
For a more detailed explanation and comparison between subtitles format, please refer to: TTML and derivated captions formats
Subtitles styling and positioning depends on the type of UI used. Either Bitmovin Web UI (available for Desktop browsers, iOS and Android) or the NativeUI (Android, iOS, tvOS, Roku).
For further details on styling subtitles on Web SDK please visit: https://bitmovin.com/demos/caption-styling
Also this Github repository contains a full example of customising the subtitles view: bitmovin-player-web-samples/subtitles at main · bitmovin/bitmovin-player-web-samples
On the other hand, a Custom Native UI can be also used, please refer to Bitmovin’s Android samples repository to see a sample of using Custom UI Subtitle View.
When using SystemUI styling capabilities are restricted to the ones offered by AVFoundation. Please check the SystemUI sample in our Github repository.
The main difference between tvOS with iOS is that it does not support Bitmovin UI only System UI or a Custom NativeUI . So, styling and positioning capabilities are restricted to AVFoundation entirely.