Codes & Guidance Notes

Guidance on Standards for Subtitling

1  GENERAL REQUIREMENTS FOR SUBTITLE DISPLAY


1.1  Basic Text Display Subtitle legibility studies result in the following requirements:

i) Teletext characters should be displayed in double height and mixed (upper and lower) case.

ii) Words within a subtitle should be separated by a single space.

iii)Text should normally be presented in a black box. (See 2.3 Speaker Identification and 2.6 Sound Effects for other background colours).

iv) To aid readability, text can be justified left, centre or right depending on speaker position. (See 1.4 Formatting and 1.5 Line Breaks for examples of justified text).

v) The standard punctuation of printed English should be used. Punctuation gives valuable clues to syntactic structure and must be carefully displayed in order to be effective. One means of enhancing the effectiveness of punctuation is by the use of a single space before exclamation marks and question marks, after commas, colons, semi-colons and mid-subtitle full-stops, on both sides of dashes (but not mid-word hyphens), before opening brackets and inverted commas and after closing brackets and inverted commas.
1.2  Colour
The teletext specification currently used in the UK is limited to the availability of seven different text colours, including white; and eight different background (boxing) colours, including black and white. For normal subtitling purposes, black background should be used. Some early teletext decoders do not display coloured background and instead default to black. Therefore, if coloured background is used, a text colour should be chosen which will remain legible on a black background.

The majority of text/background colour combinations are not satisfactory for subtitling, being insufficiently legible. The most legible text colours on a black background are white, yellow, cyan and green. Use of magenta, red and blue should be avoided.

Of the combinations with coloured background, the most legible are blue on white, white on blue, red on white, white on red, cyan on blue and blue on cyan. Of these, white on red, white on blue and cyan on blue are preferable, because certain older decoders will reduce these combinations to highly legible white on black, or cyan on black.

The principal ways of using colour in television subtitling are discussed in Sections 2.3 Speaker Identification and 2.6 Sound Effects.

1.3  Control Characters
The use of double-height boxed coloured text generally requires six control characters in the teletext line, or eight control characters if coloured background is used. Thus, the maximum space available for subtitle text is only 32 or 34 characters per line.

1.4  Formatting
A maximum subtitle length of two lines is recommended. Three lines may be used if the subtitler is confident that no important picture information will be obscured. (See Section 1.6).

Ideally, each subtitle should also comprise a single complete sentence. Depending on the speed of speech, there are exceptions to this general recommendation, as follows:

a) Real-time subtitling (see Section 4).

b) Short sentences may be combined into a single subtitle if the available reading time is limited (see Section 2.5). Additional reading time is gained in this way because the viewer's gaze needs to be directed to the subtitle area only once, rather than two or three times if two or three short sentences are displayed on consecutive subtitles.

c) Very long sentences which are too long to fit into a single two-line subtitle. There are two procedures for dealing with such cases:

Example (i)

It may be possible to break a long sentence into two or more separate sentences and to display them as consecutive subtitles eg ‘We have standing orders, and we have procedures which have been handed down to us over the centuries.’ becomes:

  We have standing orders
and procedures.

They have been handed down to us
over the centuries.


This is especially appropriate for ‘compound’ sentences, ie sentences consisting of more than one main clause, joined by coordinating conjunctions ‘and’, ‘but’, ‘or’;

This procedure is also possible with some ‘complex’ sentences, ie sentences consisting of a main clause and one or more subordinate clauses joined by subordinating conjunctions such as ‘since’, ‘when’, ‘because’, etc or by relative pronouns such as ‘who’, ‘that’: ‘All we wanted was a quiet chat just you and me together, but you seemed to have other ideas.’ becomes:

  All we wanted was a quiet chat
just you and me together.

But you seemed to have
other ideas.


It is sometimes also possible to break single main clauses effectively into more than one subtitle; eg ‘I saw a tall, thin, bearded man with the stolen shopping basket disappearing into the crowd.’ becomes:

  I saw a tall, thin, bearded man
with the stolen shopping basket.

He disappeared into the crowd



Example (ii) If such sentence breaking procedures are inappropriate, it might be necessary to allow a single long sentence to extend over more than one subtitle. In this case, sentences should be segmented at natural linguistic breaks such that each subtitle forms an integrated linguistic unit. Thus, segmentation at clause boundaries is to be preferred. For example:

  When I jumped on the bus...

..I saw the man who had taken
the basket from the old lady.


Segmentation at major phrase boundaries can also be accepted as follows:

  On two minor occasions
immediately following the war,...

..small numbers of people
were seen crossing the border.


There is considerable evidence from the psycho-linguistic literature that normal reading is organised into word groups corresponding to syntactic clauses and phrases, and that linguistically coherent segmentation of text can significantly improve readability.

Random segmentation such as

  On two minor occasions
immediately following the war,...

..numbers of people, etc.


must certainly be avoided.

In the examples given above, sequences of dots (three at the end of a to-be-continued subtitle, and two at the beginning of a continuation) are used to mark the fact that a segmentation is taking place. Many viewers have found this technique helpful.

1.5  Line Breaks
Similar linguistic considerations should guide the subtitler in deciding how to format a single multi-line subtitle. Subtitle lines should end at natural linguistic breaks, ideally at clause or phrase boundaries. However, since the dictates of space within a subtitle are more severe than between subtitles, line breaks may also take place after a verb. For example:

  We are aiming to get
a better television service.


Line endings that break up a closely integrated phrase should be avoided where possible. For example:

  We are aiming to get a
better television service.


Similarly:

  He said it would increase
the number of shareholders.


  He said it would increase the
number of shareholders.


Line breaks within a word are especially disruptive to the reading process and should be avoided. Ideal formatting should therefore compromise between linguistic and geometric considerations but with priority given to linguistic considerations.

Line breaks must be carefully considered when using left, right and centre justification for speaker position. Justified subtitles should balance linguistic considerations with eye movement:

Example (i)

Left, right and centre justification can be useful to identify speaker position, especially in cases where there are more than three speakers on screen. In such cases, line breaks should be inserted at linguistically coherent points, taking eye-movement into careful consideration. For example:

 

We all hope
you are feeling much better.



This is left justified. The eye has least distance to travel from hope to you.

 

We all hope you are
feeling much better.



This is centre justified. The eye now has least distance to travel from are to feeling.

 

We all hope you are feeling
much better.



This is right justified. The eye has least distance to travel from feeling to much.

Example (ii)

Problems occur with justification when a short sentence or phrase is followed by a longer one. In this case, there is a risk that the bottom line of the subtitle is read first.

 

Oh.
He didn’t tell me you would be here.



 

Oh.
He didn’t tell me you would be here.



This could result in only half of the subtitle being read. Allowances would therefore have to be made by breaking the line at a linguistically non-coherent point:

 

Oh.
He didn’t tell me you would be here.



 

Oh. He didn’t tell me
you would be here.



 

Oh. He didn’t tell me you would be
here.



When the subtitler is forced to make a choice between formatting a subtitle into one long line or breaking it into two short lines, the decision should be made on the basis of the background picture. In general, ‘long and thin’ subtitles are less disruptive of picture content than are ‘short and fat’ subtitles, but this is not always the case.

Furthermore, in dialogue sequences it is often helpful to use horizontal displacement in order to distinguish between different speakers (see Section 2.3). ‘Short and fat’ subtitles permit greater latitude for this technique.

1.6  Positioning Subtitles on the Screen
The normally accepted position for subtitles is towards the bottom of the screen, but in obeying this convention it is most important to avoid obscuring 'on-screen' captions, any part of a speaker's mouth or any other important activity. Certain special programme types carry a lot of information in the lower part of the screen (eg snooker, where most of the activity tends to centre around the black ball) and in such cases top-screen positioning will be a more acceptable standard.

Subtitles should be displayed horizontally in the direction of the appropriate speaker, or source of sound effect (See 2.3 and 2.6).

When consecutive subtitles have boxes of similar size and shape and the second directly over-writes the first, it is useful to position them slightly differently on the screen. This makes it easier for the viewer to perceive that the subtitle has changed.

1.7  Timing and Synchronisation
It is crucial that subtitles are displayed for a sufficient length of time for viewers to read them. The subtitle presentation rate for pre-recorded programmes should not normally exceed 140 words per minute. In exceptional circumstances, for example in the case of add-ons, the higher rate of 180 words per minute is permitted.

Presentation rates will depend upon the programme content. For example, real-time subtitling documentaries where the speaker is not on screen, or chat shows which have a higher text complexity than drama.

A fundamental function of television subtitling is to reduce frustration caused to hearing-impaired viewers by being faced with silent moving mouths. Therefore, all obvious speech should have some form of subtitle accompaniment.

Eye movement research shows that hearing-impaired viewers make use of visual cues from the faces of television speakers in order to direct their gaze to the subtitle area. If no subtitle is present, the resulting ‘false alarm’ causes considerable frustration. Further research into eye movement has shown the following pattern developed by hard of hearing viewers:

i)   Change of subtitle detected
ii)   Read subtitle
iii)   Scan picture until another subtitle change is detected


Therefore, subtitle appearance should coincide with speech onset. Subtitle disappearance should coincide roughly with the end of the corresponding speech segment, since subtitles remaining too long on the screen are likely to be re-read by the viewer, ie another kind of ‘false alarm’.

The same rules of synchronisation should apply with off-camera speakers and even with off-screen narrators, since viewers with a certain amount of residual hearing make use of auditory cues to direct their attention to the subtitle area.

1.8  Leading and Lagging
The target point for synchronisation should be at naturally occurring pauses in speech-sentence boundaries, or changes of scene. However, there are bound to be cases where this is either impractical or inapplicable. Recent research indicates the following:

i)   Monologue Material For hard-of-hearing people viewing programmes which consist mainly of monologue, research has shown that perfect synchronisation is not an absolute necessity and delays of up to six seconds do not affect information retention. The same is true of leading subtitles (providing that the first subtitle of a long speech is in synchrony). It should still be recognised, however, that some viewers use subtitles to support heard speech and will require synchronisation. Therefore, the technique should not be over used.

ii)   ii) Dramatic Scenes

iii)   For drama and programmes with continuous changes of shot, subtitles which lag behind dialogue or commentary by more than two seconds should be avoided.



1.9  Shot Changes
Besides the general recommendation for subtitle/speech synchronisation, there are certain other aspects of the television picture which influence subtitle timing. Subtitles that are allowed to over-run shot changes can cause considerable perceptual confusion and should be avoided. Eye-movement research shows that camera-cuts in the middle of a subtitle presentation cause the viewer to return to the beginning of a partially read subtitle and to start re-reading. In practice, it is recognised that the frequency and speed of shot changes in many programmes present serious problems for the subtitler. A subtitle should, therefore, be ‘anchored’ over a shot change by at least one second to allow the reader time to adjust to the new picture. Shot changes normally reflect the beginning or end of speech. The subtitler should, therefore, attempt to insert a subtitle on a shot change when this is in synchrony with the speaker.

General rules for dealing with camera-cuts are as follows:

i)   Avoid inserting a subtitle less than one second before a camera-cut and removing a subtitle less than one second after a camera-cut.

ii)   Attempt to insert a subtitle in exact synchrony with a camera-cut.

iii)   A decision to segment a single sentence into more than one subtitle, to be placed around a camera-cut, should depend on whether the sentence can be segmented naturally and on whether the resulting subtitles can be allowed sufficient display time.


Camera fades and pans do not produce the same perceptual effect as camera-cuts, and accordingly need not influence the subtitler in the same way.

Major scene changes can cause the same problems as shot changes within a scene. A particular difficulty arises when a speaker's last line in a scene, especially a vital punch line, is followed instantaneously by a scene change. In this case, the subtitle should be removed before the scene change to avoid visual confusion.

Some film techniques introduce the soundtrack for the next scene before the scene change has occurred. If possible, the subtitler should wait for the scene change before displaying the subtitle. If this is not possible, the subtitle should be clearly labelled to explain the technique.

  JOHN: And what have we here?




Foreword    Subtitling 2