hoping to clarify standard video resolutions

Mon Nov 9 17:29:43 UTC 2009

On Sun, Nov 01, 2009 at 08:33:18AM -0500, Robert P. J. Day wrote:
> 
>   i'm currently considering getting a new laptop with better screen
> res that the one i have now (1280x800), and i'm going slightly bonkers
> trying to keep up with everyone's slightly shifting definitions of
> video standards, so let me be a bit verbose.
> 
>   let's start here --
> http://compreviews.about.com/od/video/a/NoteVidSpec.htm -- where we
> allegedly see a list of official screen resolutions:
> 
>     * WVGA: 800x480
>     * SVGA: 800x600
>     * WSVGA: 1024x600
>     * XGA: 1024x768
>     * WXGA: 1280x800 or 1366x768
Or 1280x768.

>     * SXGA: 1280x1024
I always hated that one.  It made weird pixels (1280x960 was proper 4:3
with square pixels).

>     * SXGA+: 1400x1050
>     * WXGA+: 1440x900
>     * WSXGA+: 1680x1050
That's what I have on my laptop.

>     * UXGA: 1600x1200
>     * WUXGA: 1920x1200 or 1920x1080
> 
> first, note the two possibilities for WXGA -- lately, i've seen
> 1366x768 labelled as "HD WXGA", which would make sense, i can live
> with that.

Except it is the one resolution that sucks MOST for viewing HD.  Just like
all cheap HDTVs that use the same totally idiotic resolution.  The TV
signal for HD is 1280x720 or 1920x1080.  Not 1366x768 or any other crap
like that.  If your native resolution is 1280x720 (or x768  or 800) you
can fit the picture full size with no scaling.  If it is 1366x768 then
you either get black borders all around, or a really nasty scaling job.
A 1920x1080 signal simply has to be scaled down 3x3 to 2x2 pixels which
is a rather clean scaling job, just like 2x2 scales up to 3x3 when a
1280x720 signal is viewed on a full 1920x1080 HD display.  Nice small
integer scale factors are what you want.

1366x768 is a scaling of 15x15 to 16x16 pixels.  Eww.

>   what is a bit puzzling is where that resolution came from.  i've
> seen the explanation that that's the largest native resolution that is
> still 16:9 and could fit into 1Meg of pixels -- in short, a totally
> arbitrary set of values that is simply pushed to the limit.  it sounds
> good, except that 1366*768 = 1049088, which is *larger* than 1Meg,
> which is 1048576.  so that explanation doesn't really make sense,
> unless that slight overage doesn't hurt anything.

My best guess for the resolution is that many controller chips were
designed for 1024x768 and hence supporting that on projectors fit
many computer users.  Making it support 1366x768 allowed both 1024x768
(with side black borders) and the ability to claim 16:9 aspect ratio
(even though 1280x720 would have been a better choice).

>   and here's where i'm going with this.  how does all this match up
> with *video* standards?   because, these days, it makes sense when
> selecting a laptop to try to get one that's compatible with HDTV
> standards, no?
> 
>   as i read it, HDTV is defined as having a 16:9 aspect ratio, the two
> standard resolutions being 1280x720 (720p), and 1920x1080 (1080i,
> given that 1080p is still way too high-end for consumer stuff, yes?)
> however, you can certainly purchase 1366x768 HD TVs that advertise
> being 720p.  i assume that means the incoming signal is upscaled to
> fit in 1366x768.

Correct.  Or black borders (preferable for sure in that case but almost
certainly not what you get on a TV).

>   and to tie this back to laptops, if i'm willing to spend more to
> get better resolution, where are laptop resolutions going these days?
> making any effort to converge on HD TV standards?  i was at future
> shop a while back and asked the salesweasel about models with full
> WUXGA (1920x1200) res, and he told me that they rarely see those
> anymore, as all laptop manufacturers are moving over to 1920x1080,
> allegedly to match HD 1080i.

Lots of 24" displays are 1920x1200.  Only the cheap ones are doing
1920x1080 now.  The more expensive quality screens are still 1920x1200.

>   it's even more annoying now that i'm seeing various laptops with
> screen resolutions of 1440x900 (yes, that's 1.6:1, HD aspect ratio)
> being marketed as being "900p".  to the best of my knowledge, there is
> no such video standard as 900p.  (i suspect that, in short order, i'll
> run across 1680x1050 being marketed as "1050p", another non-existent
> 1.6:1 standard.)

Some are 16:10 (like 1280x800), some are 16:9 (1280x720 for example),
some are 15:9 (like 1280x768).

>   bottom line - i'm interested in what video capabilities and display
> resolution i should look for in a new laptop that would be most
> compatible with current and upcoming video standards.  pointers to
> relevant web pages would be just fine, thanks.
> 
> rday
> 
> p.s.  i'm still interested in where 1366x768 came from.  is it really
> based on that 1M pixel count, so that a single frame would fit in 1M
> of video memory, even though it doesn't quite match?

-- 
Len Sorensen
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