Re: [gentoo-user] Re: Problem with xf86-video-ati & nvidia-drivers

[Grant]

...
>> >>> I still think it's a driver problem.  Again: it's *physically*
>> >>> impossible to
>> >>> have these problems with the HDMI signal.  At most you get "digital
>> >>> noise",
>> >>> which means some pixels get stuck or are missing.  But not what you
>> >>> get; that's just something that can't be explained.
>> >>
>> >> I was thinking about this.  The digital HDMI signal must be converted
>> >> into an analog signal at some point if it's being represented as light
>> >> on a TV screen.  Electrical interference generated by the computer and
>> >> traveling up the HDMI wire should have its chance to affect things
>> >> (i.e. create weird shadows) at that point, right?
>> >
>> > Not with DFPs.  Those work digital even internally.  I assume of course
>> > that his HDMI TV *is* a DFP.
>>
>> But at some point the 1s and 0s must be converted to some sort of an
>> analog signal if only right behind the diode.  A diode must be
>> presented with a signal in some sort of analog form in order to
>> illuminate, right?
>
> no.
>
> If your tv is a standard flat panel, the sub pixels only go from on to off and
> back. Nothing else. There is no analog signal, no transformation nothing. And
> off means 'let light through' and on 'black'

Every digital signal is encoded into an analog signal.  I think it
would take some serious EMI to sufficiently change the characteristics
of an analog signal so as to create an error in the overlying digital
signal if that signal is traveling along a wire.  I can imagine it
happens but I would think it's rare.  Even if that signal were
altered, I would think it just about impossible that anything but an
error could be produced.

Whether an LED is on or off is determined by whether or not it is
forward biased.  Biasing is established by analog voltages and/or
currents, and those can be altered by EMI.  Again, I would think it's
very rare that EMI could affect an LED's forward biasing and change
its state from on to off or off to on.

However, what color an LED emits is determined by the energy gap of
the semiconductor which is very much an analog process.  How could it
be anything else?  How do you tell a photon to emit a certain color by
feeding it 1's and 0's?  There has to be at least one D/A conversion
somewhere between the digital signal and the emittance of the LED, and
that is the most likely point for EMI to affect the final output.

> If you have an led display it is pretty much the same. All the levels you see
> are achieved with fast switching. There are no analog levels.
>
> Stroller is probably correct with overscan/underscan.
>
> But that has nothing to do with digital/analog conversion.
>
>
>> Digital is just a figment of our imagination after
>> all.
>
> emm, no, seriously not.

It is though.  It only exists in the conceptual world, not the
physical world.  If you want to do anything with your digital signal
besides change it, store it, or transfer it, there must be a D/A
conversion.

- Grant