Re: [music-dsp] minBLEP: advantages/disadvantages of ripple-after-step

[Nigel Redmon]

I played with minBLEPs about 15 years ago, and came to the same conclusion that 
I’ve seen many others come to over the years: there’s no significant advantage 
to minimum phase in typical synth use. Mainly, you need to have some delay to 
line up a minBLEP, and there’s no tangible downside to having a little more 
delay to align a symmetrical BLEP, and the latter is more convenient.

I would worry about the difference with non-linear processing exactly as much 
as you worry about filter phase characteristics when using filters ahead of 
non-linear processes—which is to say, typically not at all. ;-)


> On Dec 3, 2017, at 4:23 AM, Stefan Westerfeld  wrote:
> 
>   Hi!
> 
> I'm working on a minBLEP based oscillator. This means that my output signal
> will contain all ripple needed for bandlimiting the output after each step.
> 
> Other methods of generating bandlimited signals, for instance interpolation in
> an oversampled table will produce half of the ripple before and half of the
> ripple after each step. In frequency domain, both are equally valid results,
> that is, the frequencies contained in a minBLEP and those for other methods 
> are
> exactly the same, given similar filter desgin contstraints.
> 
> However, I have a vague idea that this is not all there is to know about the
> quality. For instance, what happens if I apply a non linear effect such as
> distortion after producing my signal. It could be that one of the two ways of
> introducing ripple in the oscillator would produce better results when 
> combined
> with such an effect.
> 
> I already know that the minBLEP provides a faster reaction for input from
> outside, for instance resetting the phase will be quicker if all ripple is
> introduced afterwards, but for my application that doesn't matter much. But if
> the time signal of one of the two methods would produce better results when
> using effects, this would matter to me. So are there advantages/disadvantages
> for each method?
> 
>   Cu... Stefan
> -- 
> Stefan Westerfeld, http://space.twc.de/~stefan
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Re: [music-dsp] minBLEP: advantages/disadvantages of ripple-after-step

[gm]

In informal listening tests I found that there is a miniscule audible 
difference
between a linear phase and minimum phase transition in a sawtooth wave 
when using headphones.


The minimum phase transistion sounded "sharper" or "harder" IIRC.

The difference was barely noticable and possibly even just imagined.
But when you create a wavetable that morphes between random phases and 
minimum phase
alignment of the harmonics there is an audible difference during the 
minimum phase transistion.


I didnt make listening tests with nonlinearities but I assume in 
practice the
difference doesn't matter much, since you usually have some lowpass on 
the sawtooth
and the linear phase and minimum phase versions are more or less the 
same in this case.



Am 03.12.2017 um 13:23 schrieb Stefan Westerfeld:

Hi!

I'm working on a minBLEP based oscillator. This means that my output signal
will contain all ripple needed for bandlimiting the output after each step.

Other methods of generating bandlimited signals, for instance interpolation in
an oversampled table will produce half of the ripple before and half of the
ripple after each step. In frequency domain, both are equally valid results,
that is, the frequencies contained in a minBLEP and those for other methods are
exactly the same, given similar filter desgin contstraints.

However, I have a vague idea that this is not all there is to know about the
quality. For instance, what happens if I apply a non linear effect such as
distortion after producing my signal. It could be that one of the two ways of
introducing ripple in the oscillator would produce better results when combined
with such an effect.

I already know that the minBLEP provides a faster reaction for input from
outside, for instance resetting the phase will be quicker if all ripple is
introduced afterwards, but for my application that doesn't matter much. But if
the time signal of one of the two methods would produce better results when
using effects, this would matter to me. So are there advantages/disadvantages
for each method?

Cu... Stefan


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[music-dsp] minBLEP: advantages/disadvantages of ripple-after-step

[Stefan Westerfeld]

   Hi!

I'm working on a minBLEP based oscillator. This means that my output signal
will contain all ripple needed for bandlimiting the output after each step.

Other methods of generating bandlimited signals, for instance interpolation in
an oversampled table will produce half of the ripple before and half of the
ripple after each step. In frequency domain, both are equally valid results,
that is, the frequencies contained in a minBLEP and those for other methods are
exactly the same, given similar filter desgin contstraints.

However, I have a vague idea that this is not all there is to know about the
quality. For instance, what happens if I apply a non linear effect such as
distortion after producing my signal. It could be that one of the two ways of
introducing ripple in the oscillator would produce better results when combined
with such an effect.

I already know that the minBLEP provides a faster reaction for input from
outside, for instance resetting the phase will be quicker if all ripple is
introduced afterwards, but for my application that doesn't matter much. But if
the time signal of one of the two methods would produce better results when
using effects, this would matter to me. So are there advantages/disadvantages
for each method?

   Cu... Stefan
-- 
Stefan Westerfeld, http://space.twc.de/~stefan
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