[mythtv-users] OT: HDTV TV's

[Ivan Kowalenko]

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On May 11, 2006, at 12.46, Steven Adeff wrote:

> On 5/11/06, Michael T. Dean <mtdean at thirdcontact.com> wrote:
>> Basically, I'm saying there's more information available in the input
>> signal than can be represented by an output device using a 1:1 pixel
>> mapping.
>
> Um, what?! There is no way possible to have more information than the
> 1:1 pixel mapping. It's not there, sure, you could *guess* at what's
> there, but that doesn't mean the information is actually there, its
> just rounding math.
>
>
>> To get an idea of what I mean, play back a 720x480 anamorphic
>> widescreen, commercial DVD on a 4:3 CRT that's set to use 640x480  
>> (i.e.
>> with Xrandr/Ctrl-Alt-"Numpad +"/Ctrl-Alt-"Numpad -") and have the  
>> player
>> cut off the left and right (i.e. to get a 1:1 pixel mapping--a 4:3  
>> DVD
>> (whether a 4:3 show or letterboxed widescreen) uses non-square  
>> pixels,
>> but your display doesn't, so you'd get scaling).  Then, change the  
>> CRT
>> to 1280x960 and do the same.  The image is significantly better  
>> looking
>> at 1280x960 even though the pixels are "resolved" (by your  
>> definition)
>> at 640x480.
>
> Thats because if your displaying an anamorphic DVD on an non
> anamorphic compensated display unit your scaling. But if you take your
> monitor and squeeze the image and tell your computer not to
> de-anamorphize the image like *should* be done, then there is no
> scaling issue. Don't confuse digital scaling with true 1:1.
>
>
> On 5/11/06, Daniel Kristjansson <danielk at cuymedia.net> wrote:
>> On Thu, 2006-05-11 at 11:58 -0400, Michael T. Dean wrote:
>>> On 05/10/2006 03:01 PM, Mike Frisch wrote:
>>> Exactly.  And, technically, a 1920x1080 (1080p) display cannot fully
>>> resolve a 1920x1080 input signal (whether 1080i or 1080p).
>> Not true. A 1920x1080 display can fully resolve a 1080i/p image.

That's always confused me. There are 1920x1080 pixels, right? And  
there are 1920x1082 pixels coming at you, right? Why CAN'T a display  
show that properly? I understand those two pixels are cropped. I  
mean, a 1024x768 display can fully resolve a 1024x768 signal, why  
can't a HDTV resolve its signal? It's all digital.

>>
>> But if it is not a CRT, a 1920x1080 display can not fully resolve
>> a 720p image unless you severely letterbox that image. In order
>> to fully resolve both 720p and 1080i in an edge to edge display
>> you need 3840x2160 pixels.

Can you explain that? As an HD n00b (I don't even have an HDTV to  
play with...) that seems a little confusing, the way it's phrased.  
I've seen LCDs display resolutions lower than their maximum before  
(1024x768 LCDs displaying signals as low as 640x480). And since 720p  
and 1080i/p have 16:9 aspect ratios, shouldn't they scale properly?  
Or are we talking about scaling up the resolution in such a way that  
we don't have "half pixels" (or where pixel A from the 720p signal,  
when scaled up fills 1.5 pixels, or something like that)?

>> A 1920x1080 CRT will work with both resolutions because they in fact
>> do have a high resolution shadow mask (i.e > 3840x2160), and the
>> advertised resolution is actually limited by the scanning rate, which
>> is considerably less than the physical number of pixels.
>
> repeated for emphasis...
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