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Posted by M.I.5 on 01/17/07 08:05
"Joshua Zyber" <joshzyber@comcast.net> wrote in message
news:WPidnRlR7ZXr9jDYnZ2dnUVZ_uuqnZ2d@comcast.com...
> "M.I.5" <no.one@no.where.NO_SPAM.co.uk> wrote in message
> news:45ace6f3$1_1@glkas0286.greenlnk.net...
>>>> ... or, of course, Joshua Zyber, doesn't know what he's talking about.
>>>> More likely since, I doubt that he has taken the trouble (or has the
>>>> ability) to actually see for himself.
>>>
>>> The trouble to do what? To watch DVD content on a higher resolution
>>> screen? I've been watching content on an HD projection screen likely
>>> larger than your entire body for years.
>>
>> But did you compare it with a comparable technology regular resolution
>> 720 x 576 projection system? If not, you are not in a position to
>> contribute.
>
> As a matter of fact, I have. And you're way off base in your assumptions.
>
> Upconversion of DVD content to a higher resolution does offer some
> benefits, in that it allows you to magnify the image to a larger size
> screen without exposing the DVD's meager pixel structure. But the extra
> pixels you're filling out on the display are entirely interpolated. They
> don't actually exist in the source, and are not true picture detail.
> They're just filler that smooths out the empty gaps between active picture
> content. To say that a 720x576 DVD requires a 1440x1152 screen to properly
> resolve it is a shocking misunderstanding of how digital resolution and
> scaling work. That you insist on this yet also believe that progressive
> scan offers no benefit over interlace is borderline insane.
>
Your choice of wording is suggesting to me that it is you who doesn't really
quite appreciate what is going on here. I think you (and many others here)
have assumed that when you play a 720 x 576 DVD source into a 720 x 576 LCD
or Plasma display device, that the pixels are mapped on a 1:1 basis. This
just doesn't happen. The DVD is converted to the analogue domain and sent
to the display as a CVBS, S-Video, RGB or YCBCR analogue signal (the last
two giving by far the best display). The display then maps the analogue
signal back to a digital granularity in the X and Y axis (though retains the
analogue in the Z axis). There is nothing in the analogue signal that
allows the display to map the original pixels 1:1. It might be close,
except that displays usually lose the outer parts of the picture (overscan).
The use of displays with larger numbers of pixels that are available in the
consumer market still are not an integral multiple of the original source,
but the finer granularity allows a better interpolation of what is contained
in the analogue video.
Some newer DVD players now feature HDMI (digital) interfaces, but as these
are used with HD ready displays, a 1:1 correspondence still does not occur.
> Where did you even come up with this ridiculous 1:2 ratio between DVD
> resolution and display pixels? Do you not realize that DVD pixels aren't
> square? A 720x576 DVD image directly 1:2 mapped to a 1440x1152 would give
> you a picture in the wrong shape!
>
And the pixels on most displays aren't square either. And that phrase
'directly mapped' tells me that haven't got it. See above.
> And puzzle this over, smarty pants: If a meager DVD really requires a
> 1440x1152 display to resolve it, wouldn't that also mean that a true High
> Definition image would require 3840x2160 pixels? So does that mean that
> all of the HDTVs out there aren't really capable of displaying HD content
> at all? And by the same logic, an HD signal on a current "HDTV" screen
> would show no improvement over a DVD, which is already barely taking
> advantage of the screen?
>
The current crop of HD displays are caoable of displaying an HD image. They
are just not capable of displaying it as well as they could, especially
given that the pixel resolution of displays in the consumer market does not
exactly match any of the recognised HD formats.
> Ludicrous. Simply ludicrous.
I suggest you research the issue, and once you see the flaws in your
arguments, it may all start to make sense.
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