* kony:
Nonsense, same vague thing could be said about analog cable
and would be equally untrue.
Nope. With analog transmission image quality is directly proportional to
the various influences over the transmission line. With digital, it's not.
The signal level can in fact
degrade and this is WHY there are always (ALWAYS) cable
length limitations for digital signal cables. You must use
a repeater of some sort to overcome the problem at some
length (which may well be longer than the spec calls for, as
it should be, but nevertheless IS necessary at *some*
length).
Right. So what? Of course you can't use as much extension cords as you
want with DVI. But that doesn't change a thing on the fact that digital
transmission unlike analog transmission has no image quality degradation
due to longer cables or the fact that there is a KVM switch in the line.
In fact, with ANY digital cable, the signal itself does
ALWAYS degrade. That's just what wire does.
Right, the _signal_quality_ degrades. But that doesn't mean the
_image_quality_ degrades, too.
The question
is whether this always-present degradation of signal is too
much for the receiver to differentiate the data.
Is there a checksum on the data?
Yes.
That may preserve it (if
enough bandwidth remained for resends), but it does nothing
to prevent the bits flipping in the first place.
"Bit flipping" as you call it doesn't happen over cables. What happens,
though is that there are various types of influences (crosstalk, wave
effects, reflections, irradiation etc) that are effective in cables (and
any other type of signal transmission). One of the advantages of digital
transmission over analog transmission however is that digital
transmission is way more robust to these influences than analog
transmissions. With analog, the data integrity is directly proportional
to the amount of disturbance. With digital transmission the data
integrity remains constant up to a certain extend where no valid data
can be recovered from the received signal. Since unlike with analog
transmission the data integrity remains constant over a certain area of
noise level the image quality also remains constant, no matter if the
cable is say 1m or 5m or if there is a KVM in the line or not.
Your very basic thinking of degradation because of "flipping bits"
doesn't really fit to DVI because the TMDS signalling used in PanelLink
communications (the technology that is used in DVI) is more than the
plain transmission of a few bits. PanelLink uses quite complex data
words with ecc schemes which makes it even more robust.
Benjamin
