Re: [Jack-Devel] Variable delay line problem

Le 13 avr. 2012 à 18:59, Chris Caudle a écrit :

> On Fri, April 13, 2012 8:20 am, Stéphane VAXELAIRE wrote:
>> I understood that a flanger is just an extremely short delay line (max
>> 15ms) with a variable delay length.
>> The variable length can follow an LFO wave, I tried with a simple cosine
>> here.
> 
> 
> The LFO should be very low frequency.   You are effectively phase
> modulating the input signal with the LFO, which is going to produce
> sidebands (in the frequency domain) around the input signal at the offset
> of the LFO frequency.
> 
>>    // Compute an index between 0 and max based on a LFO, in this case
>> simple cos(2*PI*n)
> 
> Wouldn't that make the cosine wave at the same frequency as the sampling
> rate?  e.g. 48kHz?

Err, I don't really know...
Sample rate is 44,1 kHz.

> 
>> distorted version of the original sound
> 
> Phase modulation at 48kHz would not sound nice.  Maybe that is the
> problem, although I may made a simple mental error due to not having
> enough coffee circulating through my brain yet.
> 
> Check just the LFO signal you are using to modulate the delay.  I think
> you want something around 1Hz or 0.5Hz as a starting point.

I read that too, but I thought I could consider that a 1Hz LFO would give cos(2*PI*n*lfo_freq) with lfo_freq=1 thus cos(2*PI*n)...
Is that wrong ?

> -- 
> Chris Caudle
> 
> 
> 
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