BRITAIN'S number three supermarket chain Asda is mulling the launch of a digital TV shopping channel. The tentative project is currently under discussion with a number of interested parties and could incorporate food, fashion, gardening and entertainment themes. However, Asda is waiting warily until the new year to gauge public reaction to the new medium. If the vibes are positive, its channel could be on-air before the end of 1999. Meantime, the chain plans a series of six-minute satellite TV infomercials in the run-up to Christmas, via incumbent agency Publicis.