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Subtitles in a DCP
Cinema subtitles are either burned into the picture, rendered by the server over it, or delivered to a personal device — and the three fail in completely different ways.
The three kinds
| Kind | How it works | How it fails |
|---|---|---|
| Burned in | Part of the picture, baked into the JPEG 2000 | Cannot fail separately — but cannot be turned off either |
| Open (rendered) | Server draws them over the picture from a subtitle asset | Missing font assets, or a player that will not render that flavour |
| Closed | Sent to a seat-back display or personal glasses | Hardware not charged, not issued, or not paired |
Interop and SMPTE handle rendered subtitles very differently — Interop uses PNG sub-pictures, SMPTE uses Timed Text with real fonts. An old server given a SMPTE subtitle package is the classic source of a title that plays with no subtitles at all.
Why this is an operations problem, not a technical one
A subtitled screening that plays without subtitles is worse than a cancelled one. The audience is in the room, the film is running, and it is nobody's job to notice for the first ten minutes.
The defences are unglamorous. Confirm at booking which version you are getting — a subtitled version is often a separate package with its own CPL UUID and its own key, not a setting. Test the first minute on the actual screen before the first performance, not on a different one. And if you sell subtitled screenings as an access service, say plainly on the website and in the app which kind they are, because a hard-of-hearing customer needs to know whether the words are on the screen or on a device they have to collect.
Frequently asked questions
Why do subtitles not appear even though the package ingested?
Most often the subtitle assets or fonts did not come with it, or the server cannot render that subtitle flavour. Ingest verifies integrity, not that every asset is present and renderable.
Is a subtitled version a different DCP?
Usually yes — a separate composition with its own UUID, and if it is encrypted, its own KDM.
What is the difference between subtitles and closed captions?
Subtitles carry dialogue translation on the screen. Closed captions include speaker and sound information and are delivered to a personal device. Closed captions require a SMPTE package.
Keep reading
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