I am just curious. How is it that a DVD player, XBox, Set top box, etc can hook up to any HDTV and "just work" in HD mode with no editing of files and different modelines, etc?

This isn't really meant to be a complaint or anything, I just don't understand how those can all "just work", but the computer can not be hooked up to "just work" with all TV's. Can anyone explain how/why this is to a curious mind?

Thanks,
~Matt

That is indeed a curious question, and one that in all of my searching I've never come across a satisfying answer to, but maybe someone here will surprise me.

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Xsecrets

I doubt this will be very satisfactory, but basically, I would say that your DVD player or Xbox only have to be hardwired to output one "modeline"--the one that is correct for 480p output. Remember they can't do HD yet.

Your settop box (or Xbox 360 in a month or so) has to be set to 720p or 1080i, so again, it's hardwired to do the prescribed "correct" frequencies.

The computer doesn't "know" what it's going to be hooked to, so you have to pick the appropriate modeline.

EDIT: the specifications the set-top boxes have to meet are called SMPTE 274M (1080i) and SMPTE 296M (720p)... so somewhere there's a definition for both of those that states what frequencies have to be output to meet those specs. Source: http://www.accupel.com/HDG2000_FAQ_f.html

well what gets me is fine there's a set standard for 1080i and 720p so why can't there be a be all end all modeline for X that outputs exactly 1080i or 720p and works on every set? the stand alone hd boxes work on every set, so why can't one mode line? Never could wrap my head around this one.

_________________
Have a question search the forum and have a look at the KnoppMythWiki.

Xsecrets

I agree that's puzzling... further down in the doc I referenced there is this section:

http://www.accupel.com/HDG2000_FAQ_f.html#5.1

which specifies the rates for 720p as 74.17582 MHz sampling rate and 44.955 kHz horiz scan rate, and 1080i as 74.1758 MHz sampling and 33.716 kHz horiz scan. That agrees with the following modelines from:
http://www.linuxis.us/linux/media/howto ... ation.html



But then on that same page of modelines there's "PC-tweaked" ones that have slightly different dot clocks. So I dunno.

Oh ya, dot clock... if I'm not mistaken, that has something to do with the video card itself. So each different brand/manufacturer of video card could be completely different, making it nearly impossible to have a 'standard' modeline for the PC.... bummer.

The "ATSC-720-59.94p" and "ATSC-1080-59.94i" modelines will not work with a video card, because the computer video card drivers require that the timings be divisible by 8, (1650 is not, for example).
If you check the timings for the "PC-tweaked" modelines, then all timings are multiples of 8.
BTW, nVidia is going to support non-8 numbers in a future driver. It will adjust to a multiple of 8 automatically.

Excellent info--makes sense. Thanks for explaining that.