Diva , lookuptables for osc ?

[gentleclockdivider]

According to markus Krause 0f 2Tone , diva uses lookup tables for the osc generation
Is this correct ?
quote

DIVA as well as most other analog-emulations use a common wavetable technique called 'lookup table'. It is used to prevent aliasing and to keep the CPU low while still providing a analog-like sound. In DIVA the 'single-cycle waveatable' stores not a linear, but a soft-saturated sawtooth. It is a sawtoth with 'a little more bass'. The F0 harmonic is slightly boosted, which results in a sawtooth with a 'belly'.

unquote

Topic ,

viewtopic.php?f=1&t=575908&start=165

[Ploki]

beat me to it

[zvenx]

I too saw it and am very curious about it.

[whyterabbyt]

From viewtopic.php?p=7567927#p7567927

Urs :

Diva therefore uses BLEPs.

From https://pbat.ch/sndkit/blep/

BLEPs aim to create better versions of what we would call wavetable oscillators, or table-lookup oscillators

[mystran]

From https://pbat.ch/sndkit/blep/

BLEPs aim to create better versions of what we would call wavetable oscillators, or table-lookup oscillators

I'd like to point out that the link describes a slightly simplified PolyBLEP approximation that won't be able to reach the quality of the "proper" BLEP algorithm... but yeah, the basic idea is still the same.

edit: Also the triangle approach described on that page is essentially the approach taken by the older BLIT method for sawtooth, where as it's also possible to apply the BLEP-principle with special "BLAMPs" (as they are sometimes called) and synthesize a triangle (and even higher-order piecewise polynomial waveforms) directly with much more accurate behaviour that doesn't need to rely on any adhoc DC blocking.

[whyterabbyt]

Yeah, that was basically just a confirmatory link of BLEPs being wavetable based, chosen because I thought it was a relatively plain-language explanation.

[mystran]

Yeah, that was basically just a confirmatory link of BLEPs being wavetable based, chosen because I thought it was a relatively plain-language explanation.

Well.. BLEPs being "wavetable based" is very misleading, because while BLEPs might use lookup tables (and they usually do if you want high quality), those don't actually contain any waveforms, but rather just the "aliasing" that needs to be subtracted from an individual discontinuity. It's more like a preprocessed filter kernel that is (relatively) cheap to apply only where the aliasing comes from (ie. where you have discontinuities), while generating the rest of the waveform algorithmically.

Both wavetables and BLEPs have their own, distinct advantages depending on what you want to do, with BLEPs being particularly well suited for modelling traditional analog oscillators with things like PWM and hard-sync with relatively simple base waveforms.

[Urs]

Diva uses BLEPs and BLAMs in the first place. There are few exceptions, e.g. the sine wave IIRC because waveshaping a BLAM-generated triangle into a sine doesn't work that well.

[Ploki]

what's a blam

[Urs]

what's a blam

Bandlimited Ramp. A way to reduce aliasing for waveforms which change direction. Triangle for instance moves in one direction then into the other. The turning point is a discontinuity which would cause aliasing unless treated.

Basically, a BLAM is an integrated BLEP.

[whyterabbyt]

Yeah, that was basically just a confirmatory link of BLEPs being wavetable based, chosen because I thought it was a relatively plain-language explanation.

Well.. BLEPs being "wavetable based" is very misleading

my bad, i substituted 'wavetable' for 'lookup table'

[EvilDragon]

Wavetables ARE basically lookup tables with (optional) interpolation.

[Urs]

Wavetables ARE basically lookup tables with (optional) interpolation.

Yes, but wavetable synthesis is much more than that, and the terms are often used ambiguously.

BLEPs and BLAMs are often implemented with lookup tables, but not all are, and I'd never call any of them a "wavetable".

[AnX]

Not sure what Alchemy used, it was a RAW file with a single cycle for each Octave.... similar thing?