[LAD] DSP: Band limiting wavetable oscillator

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To: Linux Audio Developers <linux-audio-dev@...>
Date: Saturday, July 13, 2013 - 4:04 pm

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Hi all,

I'm working on a wavetable oscillator class, and I'm wondering about how to
best go about bandlimiting. I see two ways to achieve bandlimiting, i'll
detail as A and B.

A) Create different wavetables for each octave. Base octave includes all
harmonics. Octave 1 has the top half of the harmonics removed by FFT. Oct 2
has the harmonic content halved again.

B) Oversample the single waveform x8. Play the oversampled audio back, and
lowpass with a steep rolloff just below the nyquist of the output
samplerate. Removal of the otherwise aliasing harmonics is done at the
higher samplerate, so its not aliased yet at that stage.

I'm asking in terms of quality and CPU usage: this is for a synth which has
3 oscillators per voice, and 16 / 32 voices..

Cheers, -Harry

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Hi all,I'm working on a wavetable oscillator c=
lass, and I'm wondering about how to best go about bandlimiting. I see =
two ways to achieve bandlimiting, i'll detail as A and B.A) Cre=
ate different wavetables for each octave. Base octave includes all harmonic=
s. Octave 1 has the top half of the harmonics removed by FFT. Oct 2 has the=
harmonic content halved again.
B) Oversample the single waveform x8. Play the oversampled audio back, =
and lowpass with a steep rolloff just below the nyquist of the output sampl=
erate. Removal of the otherwise aliasing harmonics is done at the higher sa=
mplerate, so its not aliased yet at that stage.
I'm asking in terms of quality and CPU usage: this is for a synth w=
hich has 3 oscillators per voice, and 16 / 32 voices..Cheers, -Harr=
y

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Messages in current thread:
[LAD] DSP: Band limiting wavetable oscillator, Harry van Haaren, (Sat Jul 13, 4:04 pm)
Re: [LAD] DSP: Band limiting wavetable oscillator, Fons Adriaensen, (Sat Jul 13, 4:32 pm)
Re: [LAD] DSP: Band limiting wavetable oscillator, Harry van Haaren, (Sat Jul 13, 4:56 pm)