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Posted by M.I.5 on 01/05/07 08:40
"JoeBloe" <joebloe@thebarattheendoftheuniverse.org> wrote in message
news:3j9rp2ld9lmns8t9upqfqq4la9hjri3utv@4ax.com...
> On Thu, 4 Jan 2007 13:34:23 -0000, "M.I.5"
> <no.one@no.where.NO_SPAM.co.uk> Gave us:
>
>>This is largely because the resolution of a DVD is
>>fixed at 720x578 pixels (determined solely by the requirement to be
>>compatible with the legacy TV systems),
>
>
> Not true. If it were capable of delivering more, they would not
> have needed the new laser band or tighter tracked, higher capacity ,
> higher data rate discs and readers.
>
> It MIGHT be capable of delivering a little higher data rate, but the
> space would run out before the end of the flic, and you would have to
> have a flip disc to hold it all.
>
> So the fixed pixel rate was chosen for many more reasons than simple
> legacy compliance, or ONLY legacy compliance. Many factors were
> considered.
All sorts of reslutions could have been considered. The 576 (578 was a
typo) vertical pixels is precisely the number of active lines on a PAL-I
system legacy TV signal (The yanks were forced to accept 480 for the NTSC-M
system). If any other figure had been chosen it would have been
incompatible with existing TV displays. 720 was chosen for the horizontal
as a convenient round number that gave a good horizontal resolution.
Although close to 4:3 for PAL this was coincidental because it is nowhere
near 4:3 for NTSC. Widescreen necessitated the horizontal pixels to be
stretched.
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