---------------------------- Original Message ----------------------------

Subject: Re: [music-dsp] Antialias question

From: "Sound of L.A. Music and Audio" <solastu...@gmx.de>

Date: Fri, June 1, 2018 4:48 am

To: music-dsp@music.columbia.edu



> What you can / must do is an internal upsampling, since I expect to

> operate with normal 192kHz/24Bit input (?)



> j

the anonymous "j" is right.� that's better (simpler) than what i suggested.� as 
long as you know that you'll never be pitching up more than an octave, then 
whatever your intended output pointer stepsize is, whether it's more than one 
(but less than two) or
less than one, always cut it in half and generate two output samples per sample 
period and put those two output samples in another stream that doesn't need to 
be all that long.� that other stream is at twice your original sample rate and 
you will be tossing every odd-sample (keeping just the
even samples), but don't do that until *after* you low-pass filter that 
upsampled stream to half of that stream's Nyquist frequency (which is a nice 
fixed filter, could be an IIR, maybe 4th-order Butterworth).� after LPFing, 
throw away every odd sample and output the even samples at your
original sample rate.

r b-j� � � � � � � � � � � � �r...@audioimagination.com

"Imagination is more important than knowledge."

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