On 21/08/2015, Ethan Duni <ethan.d...@gmail.com> wrote: > The details of how the graphs were generated don't really matter.
Then why do you keep insisting that they're generated by plotting sinc^2(x) ? > The point > is that the only effect shown is the spectrum of the continuous-time > polynomial interpolator. Which contains alias images of the original spectrum, which was my point. > The additional spectral effects of delaying and > resampling that continuous-time signal (to get fractional delay, for > example) are not shown. No one claimed there was fractional delay involved. > There is no "resampling" to be seen in the graphs. I recreated the exact same graph via resampling a signal, proving that is one method of generating that graph. >>I claim that they are aliases of the original spectrum. > > What we see in the graph is simply the spectra of the continuous-time > interpolators. Then how do you explain that taking noise sampled at 500 Hz, and resampling it to 44.1 kHz gives an identical FFT graph? How do you explain that an 50 Hz sine wave, resampled to 44.1 kHz, contains alias frequencies at 450 Hz, 550 Hz, 950 Hz, 1050 Hz, 1450 Hz, 1550 Hz, etc. ? What are those, if not "aliases" ? > Whether those are ultimately expressed as aliases depends on what you then > do with that continuous time signal. They're already "aliases"... You may filter them out, or do whatever you want with them - that doesn't change the fact that they're aliases of the original spectrum... > If you resample to the original rate > (in order to implement a fractional delay, say), then those weighted images > will be folded back to the same place they came from. That's exactly why they're called aliases. > In that case, there > is no aliasing, you just end up with a modified frequency response of your > fractional interpolator. Which is not the case on Olli's graph. > It is only if the interpolated continuous-time signal is resampled at a > different rate, or just used directly, that those signal images end up > expressed as aliases. Which was presented on Olli's graph, and that's what we're talking about. > The rest of your accusations are your usual misreadings and straw men. I > won't be legitimating them by responding, and I hope you will accept that > and give up on these childish tactics. It would be better for everyone if > you could make a point of engaging in good faith and trying to stick to the > subject rather than attacking the intellects of others. I spent (wasted?) a considerate amount of time creating various demonstrations and FFT graphs showing my point. And you accuse me of "childish tactics". You are lame. -P _______________________________________________ music-dsp mailing list music-dsp@music.columbia.edu https://lists.columbia.edu/mailman/listinfo/music-dsp
