The BBC is conducting its first trial of two-screen playalong technology, using audio watermarking around Saturday night gameshow The National Lottery: Secret Fortune.

The technology allows viewers to launch a mobile or tablet app that uses the device’s speaker to recognise an audio file that is embedded in the TV broadcast, but which is inaudible to the human ear.

The file syncs the playalong game to the TV show so viewers at home are able to answer the same multiple-choice questions as the contestants, who are bidding to win £100,000 hidden in envelopes.

The closed trial is still in development but the ambition is to roll out the app and related watermarking technology for future series. If successful, the format could also be applied to other pre-recorded or live gameshows.

The trial builds on the success of Secret Fortune’s playalong red button game, which has attracted almost 2 million plays since it launched along with the series in February.

The mobile playalong app is expected to offer a much richer two-screen experience than is possible via the red button and is likely to include integration with social media.

The project supporting the Wild Rover Productions show is being led by the BBC’s general manager of programmes and on-demand Daniel Danker and head of IPTV and TV online content Victoria Jaye.

A BBC spokesman said it was trialling complementary experiences on secondary devices - such as phones and tablets - around some of its key TV programme formats.

He said: “While we’re very much at the early stages of testing, what’s exciting is bringing new technology closer to our broadcast output to increase audiences’ enjoyment of BBC programmes.”

Google chairman Eric Schmidt hinted at the BBC’s ambition to push into the synced two-screen viewing experience during his MacTaggart speech at this year’s Edinburgh TV Festival.

“I’m fascinated by the BBC’s notion of ‘orchestrated media’, where the show you’re watching triggers extra material on your tablet or mobile synchronised with the programme,” said Schmidt.

Rival broadcasters Channel 4, ITV and UKTV are also tapping into playalong gaming.