On 10/20/07, <b class="gmail_sendername">Spencer Salazar</b> <<a href="mailto:ssalazar@cs.princeton.edu">ssalazar@cs.princeton.edu</a>> wrote:<div><span class="gmail_quote"></span><div> </div><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Ideally when you upsample your low sample rate signal back to<br>44100Hz, you convolve it with the sinc function, which is an ideal<br>low pass filter with a cutoff at Nyquist. See:<br><a href="http://en.wikipedia.org/wiki/Whittaker%E2%80%">
http://en.wikipedia.org/wiki/Whittaker%E2%80%</a><br>93Shannon_interpolation_formula<br>for more info.</blockquote><div><br>Yes, I wrote about that just a few days back when we had another discussion about Nyquist use/abuse.
<br><br></div><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">I wonder if this could be implemented in ChucK without resorting to<br>1::samp... maybe with lots of Delay ugens..
</blockquote><div><br>I tried and couldn't get it to work at a realistic CPU usage buit that was a long time ago. I also went about it rather literally, using a actual sine.<br><br>What if we'd allow negative targets for
Envelope.target()? that would make linear interpolation a breeze. I still don't see what would be wrong with negative Envelope targets and if I remember corectly that would work with the removal of one check from the code.
<br> </div><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">. as far as C code goes,<br>there is a PRC classic here for doing sinc interpolation:
<br><a href="http://www.cs.princeton.edu/courses/archive/spr07/cos325/src/OLD/">http://www.cs.princeton.edu/courses/archive/spr07/cos325/src/OLD/</a><br>TimeStuf/srconvrt.c</blockquote><div><br>There is also a implementation in SndBuf, maybe LiSa could use one too.
</div><br>We could also think about a dedicated Ugen for this, I'm still very interested in having something like SndBuf but asigning (I'd like to keep it editable) a array of floats to it instead of a .wav file.
<br><br>Yours,<br>Kas.<br></div>