Can you explain your notation a little bit? Is x[t] the sample index into your signal? And t is time in samples?
I might formulate it as a Delta of indicies where a Delta of 1 is a normal playback speed and you have some exponential rate. Would something like this work? delta *= rate t += delta y[n] = x[n - t + N] My notation probably means something different from yours, but the idea is the time varying index t accelerates or decelerates at a given rate. I've kind of written a hybrid of pseudocode and DSP notation, sorry. You would probably actually want some interpolation and for an application like this one I would probably stick with linear interpolation (even though most people on this list will probably disagree with me on that). Keep in mind, though, that skipping samples might mean aliasing which will mean low-pass filtering your signal (unless you know that there's no frequency content in offensive ranges), and since you're essentially doing a variable skip rate your low pass filter might either need to be aggressive or variable. Something about this algorithm scares me in it's seemingly unbounded need for memory. Seems like a lot of heuristic constraints... Stefan On Feb 6, 2018 06:45, "Maximiliano Estudies" <maxiestud...@gmail.com> wrote: I am having trouble with this concept for quite some time now, I hope that I can explain it well enough so you can understand what I mean. I have signal stored in a buffer of known length. The buffer must be read at a variable speed, and the variations in speed have to be exponential, so that the resulting glissandi are (aurally) linear. In order to do that I came up with the following formula: x[t] = t * sample_rate * end_speed^(x[t] / T) where T is the total length of the buffer in samples. This doesn’t seem to work and I can’t understand why. And my second question is, how can I get the resulting length in milliseconds? (how long will it take to play the whole buffer) I hope I managed to be clear enough! Maxi -- Maximiliano Estudies +49 176 36784771 <+49%20176%2036784771> maxiestudies.com _______________________________________________ dupswapdrop: music-dsp mailing list music-dsp@music.columbia.edu https://lists.columbia.edu/mailman/listinfo/music-dsp
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