There are no nationally or internationally accepted standards for captions but a number of documents containing caption quality guidelines are available online.
- The Deafness Forum of Australia developed a Caption Quality Code of Practice, aimed at TV programs.
- The Described and Captioned Media Program (DCMP), an educational initiative in the US which supplies schools with captioned and audio described videos, has an online ‘Captioning Key’ with video samples.
- The UK communications regulator Ofcom has a section on captioning standards in its Code on Television Access Services.
Commercial caption suppliers will have their own guidelines which are usually not publicly available. The following is a summary of elements which are generally considered to be essential if captioning is to be considered of acceptable quality.
General principles
- All dialogue and important audio elements in a video need to be captioned.
- Captions should always be synchronised with the audio.
- Captions should be correctly spelled and punctuated.
Reading speed
- Captions should not be so fast that they are difficult to read. Most companies which produce captions for TV, cinema and DVDs adhere to minimum word speeds (typically 180-200 words per minute or about three words per second). If the dialogue is faster than this, then language should be condensed, with unimportant words and repetitions eliminated.
Positioning and colouring
- Captions should be displayed at the bottom of the screen (although they should be raised to prevent them from obscuring any other text on the screen).
- Captions for television are often coloured and positioned to help the viewer identify who is speaking, but media players will usually not allow this, and it is acceptable for captions to be all white and centred. In this situation, if there are two speakers in the one caption, they should be differentiated by placing dashes before their respective lines, e.g.:
– How are you?
– I’m fine.
- Offscreen speakers should be identified. If their names are known to the viewer, they should be named,
e.g. JOHN: Hello.
- If their names are not known, they should be identified as MAN, WOMAN, CHILD, etc. It is important to avoid giving the Deaf or hearing impaired viewer more information than the hearing viewer receives.
- Sound effects should be indicated in a consistent manner throughout a video, e.g.
GUNSHOT or (Gunshot)
Font size
- Captions should be in a font which is large enough to be easily readable, taking into account the size of the screen. While there are no generally accepted standards for this, captions on Australian television are a maximum of 37 characters per line.
Line breaks
- Line breaks within a two-line caption should be made where there is a natural linguistic break within the sentence (e.g. after a comma). This also applies to longer sentences which go over two captions.
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