Hybrid discs are a failure; discs won't play and cause confusion

In an attempt to produce one disc that does it all, experimental
Multi Format hybrid discs were pressed by Warner. The discs have a CD
layer of the usual thickness, 1.2 millimetres, and a DVD layer halfway
down at 0.6 mm. The two layers are separated by a semi-reflective film,
which lets infra-red laser light through to the CD layer but reflects the
red laser light used to read DVDs.

The problem is that existing DVD players,
which are designed to play both DVDs and CDs, get confused when faced with
the hybrid disc. Half the DVD-Audio players used in the tests incorrectly
played the Multi Format discs as simple CDs, and a quarter of them either
refused to play at all or gave random results. And nearly two-thirds of
the DVD-Video players incorrectly played the hybrids as CDs; and a fifth
of the players refused or worked randomly.

The collaborating companies are now trying a different
kind of hybrid, which bonds two different discs back-to-back. This gives a
double-sided disc with a CD layer on one side and a DVD layer on the
other.

However, this creates a different problem. The CD and
DVD standards set a thickness tolerance of -0.1 mm and +0.3 mm, meaning
the double-sided disc may be too thick to fit in some players. Making the
layers thinner might appear to be a solution, but this can spoil playback
as the transparent part of the disc plays a role in focusing the laser
that reads the data.