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>> ... |
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>>>> >> I was thinking about this. The digital HDMI signal must be converted |
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>>>> >> into an analog signal at some point if it's being represented as light |
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>>>> >> on a TV screen. Electrical interference generated by the computer and |
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>>>> >> traveling up the HDMI wire should have its chance to affect things |
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>>>> >> (i.e. create weird shadows) at that point, right? |
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>>>> > |
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>>>> > Not with DFPs. Those work digital even internally. I assume of course |
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>>>> > that his HDMI TV *is* a DFP. |
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>>>> |
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>>>> But at some point the 1s and 0s must be converted to some sort of an |
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>>>> analog signal if only right behind the diode. A diode must be |
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>>>> presented with a signal in some sort of analog form in order to |
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>>>> illuminate, right? |
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>>> |
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>>> no. |
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>>> |
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>>> If your tv is a standard flat panel, the sub pixels only go from on to off and |
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>>> back. Nothing else. There is no analog signal, no transformation nothing. And |
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>>> off means 'let light through' and on 'black' |
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>> |
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>> Every digital signal is encoded into an analog signal. I think it |
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>> would take some serious EMI to sufficiently change the characteristics |
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>> of an analog signal so as to create an error in the overlying digital |
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>> signal if that signal is traveling along a wire. I can imagine it |
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>> happens but I would think it's rare. Even if that signal were |
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>> altered, I would think it just about impossible that anything but an |
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>> error could be produced. |
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>> |
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>> Whether an LED is on or off is determined by whether or not it is |
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>> forward biased. Biasing is established by analog voltages and/or |
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>> currents, and those can be altered by EMI. Again, I would think it's |
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>> very rare that EMI could affect an LED's forward biasing and change |
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>> its state from on to off or off to on. |
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>> |
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>> However, what color an LED emits is determined by the energy gap of |
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>> the semiconductor which is very much an analog process. How could it |
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>> be anything else? How do you tell a photon to emit a certain color by |
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>> feeding it 1's and 0's? There has to be at least one D/A conversion |
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>> somewhere between the digital signal and the emittance of the LED, and |
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>> that is the most likely point for EMI to affect the final output. |
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>> |
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>>> If you have an led display it is pretty much the same. All the levels you see |
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>>> are achieved with fast switching. There are no analog levels. |
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>>> |
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>>> Stroller is probably correct with overscan/underscan. |
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>>> |
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>>> But that has nothing to do with digital/analog conversion. |
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>>> |
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>>> |
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>>>> Digital is just a figment of our imagination after |
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>>>> all. |
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>>> |
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>>> emm, no, seriously not. |
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>> |
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>> It is though. It only exists in the conceptual world, not the |
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>> physical world. If you want to do anything with your digital signal |
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>> besides change it, store it, or transfer it, there must be a D/A |
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>> conversion. |
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> |
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> You're thinking of PCM. (And that's what I was thinking of, earlier, |
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> too). I assume Stroller and Volker are talking about PWM, where a |
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> perceived analog value is achieved by rapidly turning a signal from |
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> full-on to full-off. |
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> |
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> (Yes, there's no such thing as pure-digital in the physical world. The |
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> confusion here appears to be in PWM vs PCM.) |
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> -- |
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> :wq |
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|
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Everything I said above applies to both PCM and PWM. They are only |
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conceptual layers built on top of a physical/analog base. PWM |
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switching from full-on to full-off and back is an analog process |
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representing digital data in order to represent an analog signal. |
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|
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- Grant |