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Ofcom yesterday published its second report on the quality of live subtitles in UK TV programmes. The report shows that broadcasters are beginning to make improvements in some areas of subtitling. However, it finds that some issues - such as the delays between speech and the corresponding subtitle appearing on screen, known as latency - remain a problem.

Ofcom welcomes the fact that broadcasters are now making greater use of block subtitles in live programmes. These allow several words to appear at once as a single block and are easier and quicker for viewers to read than scrolling subtitles.

Last year, Ofcom required broadcasters to start measuring the quality of live TV subtitles. This work is intended to identify areas where broadcasters can improve subtitles to benefit viewers.

Yesterday’s report is the second of four Ofcom is publishing over two years. Each report samples data from broadcasters on the quality of live TV subtitles - measuring their accuracy, speed and latency. The first report was published in April 2014.

Latency

The latest report finds that delays in subtitles reaching the screen continue to be a problem for viewers. For example, when programmes with live subtitles have frequent changes of scene - such as on Channel 4’s Gogglebox - viewers can find it difficult to know which scene the subtitles relate to.

Poor latency is one of the most frustrating aspects of live subtitling for TV viewers, who say that these delays result in a disjointed viewing experience.

Samples from BBC, ITV, Channel 4, Channel 5 and Sky programmes showed that the average (median) latency was 5.8 seconds (Figure 1), which exceeds the recommended guideline of a maximum 3 seconds delay. This is a 0.2 second increase in average latency since our first report.