Ofcom publishes first results on quality of TV subtitles

30 Apr 2014 03:23 PM

Ofcom today published its first report on the quality of live TV subtitles provided by broadcasters in the UK 

Subtitles are used by over a million people with hearing impairments to watch TV. Addressing concerns from viewers, Ofcom last year required broadcasters to start reporting on the quality of live subtitles to identify areas for improvement.

Today’s report samples the accuracy, speed and latency – the delay between speech and the corresponding subtitle appearing – of live TV subtitles. It is the first of four reports on live subtitling Ofcom is producing over a two-year period.

Viewers have told Ofcom that poor latency is one of the most frustrating aspects of live subtitling, often resulting in a disjointed viewing experience.

Samples of BBC, ITV, Channel 4, Channel 5 and Sky programmes showed that the median latency was 5.6 seconds, which exceeds the recommended guideline of a maximum 3 seconds delay.

Ofcom will ask broadcasters to consider how latency can be reduced and whether, for example, they can take advantage of any small delays in the transmission of live programmes to improve latency.

The speed of subtitling (words per minute displayed on screen) can also impact the viewing experience.

The subtitles sampled met the current guidelines for a maximum speed of 160-180 words per minute. Ofcom will review these guidelines in light of the data gathered over the four reports to see if they are appropriate for viewers.

Accuracy, another key measure, was rated as generally good by researchers that audited the data on behalf of Ofcom. They consider that 98% of subtitled words being accurate on live programmes is an acceptable standard. However, accuracy did fall below 98% on some occasions.

These measurements will be used with future samples to build a better understanding of the quality of live subtitling provided by the major broadcasters.

By requiring broadcasters to measure quality of subtitles regularly, Ofcom expects them to identify and act upon opportunities to improve live subtitling to benefit viewers.

Further improvements to subtitles

Today’s report also examines new approaches that broadcasters could take to tackle poor subtitling.

Ofcom is encouraged that broadcasters are making greater efforts to increase the amount of block subtitles used in live programmes. Block subtitles, where several words appear at once as a single block, are easier and quicker for viewers to read than scrolling subtitles.

However, Ofcom remains concerned that a significant number of pre-recorded programmes are provided to broadcasters too close to transmission to allow subtitles to be prepared in advance. This results in lower quality subtitles for viewers.

For this reason, Ofcom is asking broadcasters for a further report on how they produce subtitles for pre-recorded programmes during the second half of 2014, and will publish the findings next year.

Subtitled programmes double in a decade
Ofcom has also today published a report on the development of TV ‘access services’. These are the subtitling, signing and audio description of programmes, which benefit viewers with hearing and sight impairments.

The number of channels required to provide TV access services increased from 22 in 2004 to 73 in 2005, after Ofcom published strengthened requirements for broadcasters. Today, these services are provided by 76 channels, which account for over 90% of total TV viewing.

Since 2005, the new rules mean the access services targets that each broadcaster is required to meet rise each year from the launch of the service. For subtitling, this rises from 10% of programmes in the first year to at least 80% in the tenth year a channel is on air; for signing from 1% to 5%; and for audio description from 2% to 10%.

As a result, the availability of access services has increased substantially as a proportion of total broadcast hours for those channels required to provide them.

Between 2005 and 2013, subtitled hours doubled from 40.5% to 81.9% of hours of programming broadcast, audio description increased four-fold (from 5.9 % to 23.3%), and signing rose from 1.8% to 5.6% for channels required to provide access services.



  1. Under the Communications Act, Ofcom is required to have regard to the needs of persons with disabilities when carrying out its principal duty towards citizens and consumers under section 3. Ofcom also has a specific duty under section 303 of the Act to provide guidance to broadcasters on how they should promote the understanding and enjoyment of their services by people with sensory impairments, including people with hearing impairments.
  2. Last year, Ofcom published a statement on the quality of subtitles. This required broadcasters to measure the accuracy, latency and speed of subtitles at six monthly intervals for a period of two years, with the results to be included in a series of reports published by Ofcom.
  3. The measurements were carried out by broadcasters or their contractors, and were checked for accuracy and consistency by the University of Roehampton for Ofcom. The exercise measured a total of 60 ten-minute clips from 60 programmes, which were analysed. These were from three genres (news, entertainment and chat shows) and broadcast on five channels (BBC, ITV, Channel 4, Channel 5 and Sky). In total, the analysis comprises ten hours of live TV material including approximately 103,000 words and almost 15,000 subtitles.
  4. The Code on Television Access Services sets targets for the amount of TV subtitling, signing and audio description that broadcasters are required to provide. It also contains guidance about how access services should be presented.
  5. Audio description is a commentary woven around the soundtrack, exploiting pauses to explain on-screen action, describe characters, locations, costumes, body language and facial expressions to enhance meaning and enjoyment for blind or visually-impaired viewers.
  6. Sign language comprises the use of manual gestures, facial expression and body language to convey meaning. British Sign Language (BSL) is the most popular sign language in the UK.
  7. Viewers indicated in responses to our May 2013 consultation that they found latency one of the most frustrating aspects of live subtitling. Historical guidelines for latency recommended that subtitles should aim to have a latency of three seconds or lower.
  8. Today Ofcom also published its annual report on access services for 2013.