A proposed four-layer, 128GB recordable Blu-ray Disc has become part of the official BD specification.

First announced in April this year, the new disc structure, dubbed the BD XL, will require new hardware.

That shouldn't trouble your average HD movie fan: BD XL is intended for professional broadcasters looking for a new programme archive medium.

Alongside the 128GB BD-R, the XL spec also includes a high-capacity re-writeable BD-RE, but its capacity is 100GB. ®