>> ... >>>> >> 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. > > You're thinking of PCM. (And that's what I was thinking of, earlier, > too). I assume Stroller and Volker are talking about PWM, where a > perceived analog value is achieved by rapidly turning a signal from > full-on to full-off. > > (Yes, there's no such thing as pure-digital in the physical world. The > confusion here appears to be in PWM vs PCM.) > -- > :wq
Everything I said above applies to both PCM and PWM. They are only conceptual layers built on top of a physical/analog base. PWM switching from full-on to full-off and back is an analog process representing digital data in order to represent an analog signal. - Grant
