hi all ... i just saw this fascinating video where stefan stenzel from german synth designer waldorf explains how to use BLITs for sample rate conversion but cant figure out how to do this in PD.

specifically im trying to simulate a mid 80s sample based synth with variable sample rate oscillators. maybe thats the way to go? does anybody have a patch that demonstrates BLITs?

there seems to be hardly any info on this around the only thing i can find is this:

https://dsp.stackexchange.com/questions/15779/band-limited-impulse-train-synthesis

@lilakmonoke Maybe useful..... blit.zip although you will have to look for the external for [impulse~] if you are not using windows..... (extended?.... deken?).
Resampling can be done with [block~] but only in power of 2 multiples of the standard block size (64), and I would not expect to be able to change it without glitches.
Not much help.... sorry.
David.

hi david ... thanks! impulse~ seems to be what im interested in. whats in that abstraction? weiss-archive.de is the author?

i know how to do an impulse train, its described in the miller puckette book and based on half a sine wave that can be shaped via ring modulation with another sine wave. but the one in the video seems to be based on another transfer function + a low pass filter for bandwidth limiting. also he describes that it can be integrated into a saw, pulse and triangle wave. but how?

all this should be easy to do in pure data but without a description of the process i dont know where to start.

here is a description of the waveform generation. now we need a patch for this ...

"the main idea behind BLIT is that these analog synth waveforms that we are trying to generate digitally can be thought of as the integral (over tt) of impulse trains.

a sawtooth can be thought of as the integral of the sum of a little bit of DC and an impulse train. a square wave is the integral of impulses of alternating signs. the triangle wave is the integral of the square wave.

so, to create bandlimited waveforms of the above, the impulse trains are bandlimited which means that each impulse δ(t−tn)δ(t−tn) is replaced by a sinc(t−tn)sinc⁡(t−tn) function, which is that impulse bandlimited through a Nyquist brick-wall LPF. that sequence of bandlimited impulses is a BLIT.

then, since integration is a filter with s-plane transfer function of H(s)=1sH(s)=1s and is LTI (Linear, Time-Invariant), integrating the BLITs will introduce no new frequency components. if your BLITs are bandlimited, so are the other waveforms that are derived from filtering the BLITs."