[Open-graphics] Re: HDMI Cards Debut (Re: Good news..)

[Peter TB Brett]

On Thursday 15 March 2007 02:30:06 sinkam wrote:
> On Thu, 22 Feb 2007 13:41:39 +0500, Peter TB Brett <peter at peter-b.co.uk>
>
> wrote:
> > Once again, your idea is impractical.
>
> From: Carlo Salinari <csali at tiscali.it>
> Subject: [Open-graphics] Slashdot | HDMI-Enabled Graphics Cards Debut
> http://hardware.slashdot.org/article.pl?sid=07/03/13/126250
>
> There are 10s comments in the discussion, people want to buy long HDMI
> cable
>

<snip>

> And they are ready to spend $150 for that. Peter, say them 'your demand is
> impractical' :-)

Then clearly someone should design a standard for VGA over a bundle of, say, 
four optical fibres.  And design it so that Joe Bloggs can install it without 
breaking it.  And make it affordable.

There are good electrical reasons why there are problems with 100 ft cables 
for transmitting HD video.  At the sorts of frequencies required to be able 
to transfer data at the rate required, the impedance of a long cable is very 
significant, resulting in considerable attenuation of the signal (probably 
resulting in a fractional S/N ratio by the time you get to about 100 ft).  
This is in addition to the problems generated by cross-talk between the 
several conductors you'll need.

If you want to have an electrical connection at that length, it's sure to be a 
trade-off between using high-quality coax connections (which will result in a 
really fat cable) or using more conductors (which will result in a really fat 
cable).

Don't suggest compressing the data before transmission -- I've already 
explained why that's a daft idea.

The idea -- long video cable -- is not a bad one per se.  It's the physics of 
the problem that make it difficult to implement in reality.  If I'm totally 
wrong and it is practical, come back with some calculations and results that 
make sense, and an explanation of why it doesn't exist already.

Peter

-- 

v3sw6YChw7$ln3pr6$ck3ma8u7+Lw3+2m0l7Ci6e4+8t4Gb8en6g6Pa2Xs5Mr4p4
  hackerkey.com                                  peter-b.co.uk
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