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Posted by Bill Vermillion on 01/22/07 17:25
In article <ii8rp29a07pigd5m63s6vl6tp7d34f82hn@4ax.com>,
JoeBloe <joebloe@nosuchplace.org> wrote:
>On Thu, 4 Jan 2007 13:14:17 -0000, "M.I.5"
><no.one@no.where.NO_SPAM.co.uk> Gave us:
>>But that would have been an entirely new format. Same size disk maybe, but
>>a new format all the same.
>
> You don't get it. All optical disc technologies evolve.
> DVDs right now have different res previews and extras than the film
>segment, and it peels off the disc at a different bit rate.
> What I mentioned would be no harder than that, and using CLV, very
>little would need to be changed. DVDs are read at varying RPM rates
>as the disc progresses. An LD could be read the same way, providing
>the varying rate and best use of the optical data area real estate.
For the widest majority of LD's produced they were read the same
way. CLV - Constant Linear Velocity - means the disk speed varies
according to the place on the disk. CAV - constant angular
velocity - is the one that rotates at the same speed throughout.
Technically after the first few CLV disks were released, they found
that there was a herringbone problem, so while they were still
called CLV, there were CAA - Constant Angular Velocity. That meant
that there were bands of CAV - that changed rotational speed every
little bit - so that adjacent frames did not interfere with each
other as they did in pure CLV format.
> The physics are such that the data rate for the outer portion of the
>disc is capable of a higher data rate than the hub portion, for any
>given RPM.
Correct. And there is also a better way than changing the
rotational speed - and that is changing the data read/write
algorithms so you write more per revolution as you get further from
the center. That is how hard-drives work.
> That 12 inch platter would hold 4 times the data at least of a 5.25
>inch disc. Entire TV series seasons could end up on one disc.
And when the CD first came out it was Philips who came up with
the 12cm size. Sony had been so used to 12" LDs, and LPs, that
while they knew they could put audio on one, they did not think
anyone would want or buy something with 12+ hours playing time per
side. It took Philips to tell Sony that all they needed to do was
make the disk smaller. Typical "can't see the forest because
of the trees" scenario.
> Thing is, nobody will go back to 12" as there are just too many
>mechanical anomalies between the hardware and the discs themselves.
>You thought the yields on BluTurd production runs were bad... 12" is
>horrendous, and would quadruple with the tighter laser wavelength and
>track pitch.
The largest problem from my POV was NOT the size but the
manufacturing process where the sides were plated and then glued
together. Once you have different materials bonded together you
have problems with such things as delamination, oxidation, etc.,
between the different materials. This is where the laser rot came
from. I have 3 or 4 eight-inch LDs - that required a spacer to
play them on a standard player as they were only one side.
These were free demos that you could get from Warner Bros. [as I
recall] and were made more like large CDs. Just one side with
a printed label on one side and data on the other.
There are think and I suspect in a 12" format they would be far too
easy to break, bend, spindle, staple, or fold [as the printing on
bills years ago used to say].
> Maybe we should go back to piano roll methods. That's what a
>holocube is essentially.
Ah - multi-layer piano rolls. Interesting concept! Manufacturing
might be a pain though :-)
Bill
--
Bill Vermillion - bv @ wjv . com
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