Measuring the quality of live subtitling

25 November 2015

In order to address continuing complaints about the quality of live subtitling, Ofcom consulted in May 2013 on proposals to incentivise broadcasters and access service providers to identify and act upon areas for improvement.

Following this consultation, Ofcom published a statement in October 2013 explaining that we would ask broadcasters to measure and report on the following dimensions of quality, on the basis of samples of live subtitling selected by Ofcom:

  1. the average speed of the subtitling;
  2. the average latency of the subtitling (the delay between speech and live subtitling), and the range of latencies; and 
  3. the number and type of errors (i.e. minor spelling errors, major omissions or factually misleading subtitles).

For this purpose, Ofcom will identify samples of live subtitling in three genres of programming - news, entertainment and chat shows - and ask broadcasters to carry out measurements. We shall ask broadcasters to collect data using a model which has been used for some years by academics, broadcasters and subtitle providers to categorise errors.

We intend that the measurement exercise should be carried out at six month intervals, starting later this year, for a period of two years.

Full Reports 


Measuring live subtitling quality: results from the first sampling exercise
Published 30Apr14

Measuring live subtitling quality: Results from the second sampling exercise
Published 05Nov14

Measuring live subtitling quality: Results from the third sampling exercise
Published 18May15

Measuring live subtitling quality: results from the fourth sampling exercise
Published 27Nov15