Since joining the BBC in 2000 - as a hearing-impaired graduate myself - I've taken a personal interest in the research and development of a top quality subtitling service for our online content, through subtitling trials on both bbc.co.uk (Dec 2005 and Jan-Mar 2007) and the iMP Content Trial (Oct 2005-Mar 2006).

The principal objective behind this work is to make sure that the sensory impaired community is always included, and has the opportunity of an accessible and enjoyable video experience on bbc.co.uk.

I'd like to thank the users who have participated in those trials for their invaluable feedback which has helped us to shape the access services for iPlayer.

Subtitles are now widely available for many downloadable programmes on iPlayer: look out for "include optional subtitles" within the programme information page, and please see the iPlayer accessibility help site for more information on how to get the best subtitling experience.

Currently we have been able to provide subtitles for downloadable, non-live "pre-recorded" programmes, through the development of a facility to repurpose pre-recorded broadcast subtitles (EBU-STL) files into the subtitling formats for different online media players. This development has been complicated because each media player currently has its own proprietary format for timed-text, such as Windows Media Player SAMI format, Real Player RealText format, and QuickTime Text format. Through our subtitling trials, we have gained experience in ensuring that we can deliver the same quality of subtitling output as for TV on each different media player, and the iPlayer download subtitles are the latest result of this work.

Unfortunately, some of you have experienced problems with the incorrect labelling of some programmes as having subtitles when they have not. We have identified this as bug in our current labelling system, which only happens when a programme is a repeat which does not have subtitles. We are in the process of fixing this and expect to have this fix go live in the next iPlayer release. We'll let you know when this happens.

Our next step is to ensure that subtitles can be delivered for the BBC Embedded Media Player (EMP), the new player which is being rolled out across bbc.co.uk to replace our old diversity of media players with a consistent, quality player.

The process of delivering subtitles for the Adobe Flash-based EMP has been made much simpler by the EMP team's choice to use the Timed Text open standard subtitling format from the W3C. This significant development will allow us to deliver one subtitle format for Flash video which can be made accessible on many different browsers and operating systems (including Apple Mac).

That's to come. In the meantime, we hope that you enjoy the subtitling service for iPlayer downloads.

Ceefax subtitling being prepared using a Palantype keyboard

Andrew Strachan is a Content Producer for BBC Future Media & Technology.