>The full size
>120mm "Blu-Ray" disc will hold 27GB, making it a good candidate to
>substitute for the 20 to 40GB hard drives now being incorporated into
>high-end recorders (Nagra V, Deva V, HHB Portadrive, and so on).
Recording to a 120mm optical disc is something I would personally not
recommend for portable recorders due to the fact that laser tracking and
focus servos are quite easily pushed beyond their limits. Even in a static
recording environment, the vertical deflection and eccentricity of these
discs due to manfacture tolerances relies on tracking and focus servos
working hard.
In a mobile recording environment, like recording in a vehicle on a bumpy
road, the servos would most of the time be working out of limits, so audio
shock buffer would be in constant use - in other words you might as well
record direct to solid state - very expensive for 20GB!
Minidisc works reliably due to the fact that it has a small diameter, thus
less vertical deflection causing focus servos to lock easier. If there is an
extreme shock situation, buffer is used to store compressed audio until safe
to record again. Since audio is compressed, buffer need not be that large.
Now a 60mm blue ray disc may be a solution - not sure how reliable the
tracking and focus servos are for a disc where the track width is narrower
and pit/land size is smaller - remains to be seen!
In terms of large storage density, try holographic 120mm discs which are in
development now. I believe we are looking at half a terabyte on a single
disc!!!
Paul, HHB
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