[mythtv-users] OT: HDTV TV's

[Ivan Kowalenko]

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On May 11, 2006, at 13.58, Steven Adeff wrote:

> On 5/11/06, Ivan Kowalenko <ivan.kowalenko at gmail.com> wrote:
>>> 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.
>
> By standard it should, and all fixed pixel displays have no excuse.

That's what I was assuming.

> The problem comes in non-fixed pixel displays (CRT, rear projection,
> etc). Where issues like hourglass effect, and other edge issues come
> in to play. Manufacturers decided to use overscan of the edges to make
> those issues "dissapear". The proper method would be to use overscan
> AND increase the output resolution so that the picture being displayed
> still sits in the frame of view. But this would increase the costs of
> the sets, which is not something they are willing to do yet. Once the
> prices come down I bet the higher end models will start doing this.
> Some manufactuers have a 1:1 mapping mode where they don't force
> overscan but you end up with possible the possible edge problems since
> its still only drawing the same number of pixels.
>
>
>>>> 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)?
>
> this is where scaling comes in to play. 720p=1280x720,
> 1080i/p=1920x1080. So when you have a fixed pixel display, each pixel
> is there, and you have to do something with it, so in order for a
> 1080p display to show a 720p signal it has to scale the image in such
> a manner that it will use all the 1920x1080 pixels. The problem is
> that this is not an evenly divisible scale, being that 1920/1280 does
> not equal an even number. In order for a screen to be able to show
> both 1080p and 720p resolution with out pixel mapping tradeoffs you
> need their least common denominator. this still ends up using more
> than the required number of pixels for "1:1" mapping, but its the
> least evil.

Ahh, I understand that now. Everything makes more sense now. Thanks you.
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