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Posted by M.I.5 on 01/05/07 08:04
"JoeBloe" <joebloe@thebarattheendoftheuniverse.org> wrote in message
news:ii8rp29a07pigd5m63s6vl6tp7d34f82hn@4ax.com...
> 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.
>
Virtually all pre-mastered DVD are read at a variable it rate. They read at
a low rate for relatively static images increasing the rate where there is
much action. This helps extend the playing time.
> 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.
>
LDs could be mastered in CAV or CLV modes, the latter playing at varying
RPMs. The only downside was that the ability to have steady freeze frame
was lost (though later players had a frame store to overcome the
limitiation).
> 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.
>
Always true of any disk format.
> 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.
>
The only thing you overlooked is that the bandwidth of a DVD is far lower
than the bandwidth of a Laser Disc. This is a function of the MPEG2
compression used in the DVD format. Once uncompressed, the effective
bandwidth is nearly 5 times greater.
> 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 RPMs that some disks now run at (more in the data area than video) would
result in physical destruction of a disk much larger than 5 inches. Also,
any eccentricity does create intolerable forces on the mechanics.
The market has now got used to the compact size of a 5 inch disk and would
fiercely resist any attempt to go for something larger.
> Maybe we should go back to piano roll methods. That's what a
> holocube is essentially.
One of the oldest digital formats. I wonder if Alphonse Gavioli knew what
he was starting?
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