science

Timed text

Timed text is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Timed text rather than just read about it. In short: Timed text is the presentation of text media in synchrony with other media, such as audio and video. Applications Typical applications of timed text are the real-time subtitling of foreign-language movies on the Web, captioning for people lacking audio devices or having hearing impairments, karaoke, scrolling news items or teleprompter applications.

Key takeaways

Timed text belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Timed text to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Timed text from memory before moving on to harder problems.

Reference excerpt

Timed text is the presentation of text media in synchrony with other media, such as audio and video.

Applications Typical applications of timed text are the real-time subtitling of foreign-language movies on the Web, captioning for people lacking audio devices or having hearing impairments, karaoke, scrolling news items or teleprompter applications. Timed text for MPEG-4 movies and cellphone media is specified in MPEG-4 Part 17 Timed Text, and its MIME type is specified by RFC 3839.

Markup language specifications The W3C keeps two standards intended to regulate timed text on the Internet: the Timed Text Markup Language (TTML) and WebVTT. SMPTE created additional metadata structures for use in TTML and developed a profile of TTML called SMPTE-TT. The DECE incorporated the SMPTE Timed Text in their UltraViolet Common File Format specification.

Competing formats Interoperability for timed text came up during the development of the SMIL 2.0 specification. Today, incompatible formats for captioning, subtitling and other forms of timed text are used on the Web. This means that when creating a SMIL presentation, the text portion often needs to be targeted to a particular playback environment. Moreover, the accessibility community relies heavily on captioning to make audiovisual content accessible. The lack of an interoperable format adds a significant additional cost to the costs of captioning Web content, which are already high.

Example The following is an extract from the English closed captioning file, in SubRip format, for the 1916 Krazy Kat Bugolist film.

1 00:00:22,000 --> 00:00:27,000 I'll teach thee Bugology, Ignatzes

2 00:00:40,000 --> 00:00:43,000 Something tells me

3 00:00:58,000 --> 00:01:59,000 Look, Ignatz, a sleeping bee

The equivalent in W3C WebVTT is the following:

WEBVTT

00:22.000 --> 00:27.000 I'll teach thee Bugology, Ignatzes

00:40.000 --> 00:43.000 Something tells me

00:58.000 --> 01:59.000 Look, Ignatz, a sleeping bee

The equivalent in W3C TTML is the following:

See also Text over IP Subtitle (captioning)

References

External links

The W3C timed text homepage W3C's Video in the Web Activity Statement Also see DAISY Digital Talking Book standard

Worked examples

Example 1 — a first encounter with Timed text

Start with the simplest possible case. Write down what Timed text claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Timed text before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Timed text ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Timed text

In research: Timed text appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Timed text in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Timed text is common in secondary-school and first-year university syllabi. It links to neighbouring topics Subtitle file formats, Subtitling, Text codecs, so understanding it makes those chapters shorter.
In everyday life: Look for Timed text outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Timed text in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Timed text means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Timed text out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Timed text in simple terms?

Timed text is the presentation of text media in synchrony with other media, such as audio and video. Applications Typical applications of timed text are the real-time subtitling of foreign-language movies on the Web, captioning for people lacking audio devices or having hearing impairments, karaoke…

Why does Timed text matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Timed text?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Timed text.