[PD] Spectrum graphing amplitude problem

[Mathieu Bouchard]

On Sat, 27 Oct 2007, Martin Peach wrote:
> Mathieu Bouchard wrote:
>> You have seen a lot of analog equipment and you know that it does time-wise 
>> sampling. analog vs digital is not what we are debating.
> Analog equipment works continuously in time. Digital is almost always 
> clocked. If your eyes are clocked I'd like to see through them.

My point is that analog is also often clocked, so saying that eyes are 
analog doesn't actually say much on how they work.

> If we are debating something here it involves a difference between 
> continuous and discrete time systems, which constitutes part of the 
> distinction between analog and digital in common parlance.

Yes, and it's only part of the distinction. You have to distinguish 
between continuous-time analog and discrete-time analog.

> Photons impinging on my eyes drive the illusion of vision.

It's not an illusion. You are really seeing. Perhaps the knowledge of 
photons seems to you like you lost your childhood conception of vision, 
but it's still vision.

> rather the rod or cone is continually integrating the photon flux and 
> outputting a stream of pulses in proportion to the incident intensity;

Any camera is integrating the intensity of incoming photons. In case of 
video cameras it's a quite continuous process, as far as quantum phenomena 
can be continuous to you. it's at the output that it's discretised. 
Depending on the exact integration weighting in effect, it will look 
either more "sampled/choppy" or more "motion-blur".

> the output is an analog of the input. In the brain the streams of pulses 
> could be interpreted as digital but the streams from all the receptors 
> are not synchronized by a central clock so the overall effect is of a 
> continuous-time system.

do you know about asynchronous digital circuits?

that said, PWM is not digital, because it's not interpreted as 
digits, even though the signal may look like a digital signal on the 
surface. a digital interpretation of a PWM is in effect an ADC.

> The aliasing is induced by illumination by a periodic light source which 
> the mind interprets using a "most likely" scenario in which a spoke that 
> reappears closest to one that was previously visible is probably the 
> same spoke.

Yes, we agree on that, it was my mistake.

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| Mathieu Bouchard - tél:+1.514.383.3801, Montréal QC Canada