Selecting delay memory for pitch shifters

Algorithm development and general DSP issues

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livingston
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Selecting delay memory for pitch shifters

Post by livingston »

We're given a few choices of delay memory for pitch shifters - 4096, 2048, 1024 or 512 samples with equal ramp amplitude.

First, why does the delay memory need to be one of these specific values?

Second, what are the factors in deciding which value to use? Is longer delay memory necessarily tied to maximum pitch shift available? Shorter delay memories equal less latency, right?

I also saw some mention in a thread about the quality of the pitch shift in low notes being related to delay memory - can you elaborate on that a bit?
frank
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Post by frank »

In theory, the delay could have been any length but the hardware was much easier if I fixed the selections (note they are multiples of 2 from each other) so you need to use one of the four fixed lengths.

Which delay length to use is a trade-off, a shorter length is less latency but since the wavelength of really low notes is longer than the delay, low frequencies will not sound as good.
Frank Thomson
Experimental Noize
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