block filters (was Re: [PD] [erratum] question about [lop~] and [hip~])

[Lex Ein]

julien.breval at tremplin-utc.net wrote:

>Actually, I am making a kind of brick-shaped band pass filter, 
>
For true brick shape, use series higher order filters.
The full iemabs lib has 2nd through 10th order butterworth and other 
filters available.
Make your cutoff frequencies track as well.

[r audio]
|
|      [r cf]
|      [/ 1.2 ]
|       |
[hp10_butt~]
|
|      [r cf]
|      [* 1.2]
|       |
[lp10_butt~]

>as an alternative
>to [vcf~] which has a triangular shape. If this kind of filter already exists in
>a library, I will use it but I haven't found anything yet. 
>The first solution is to use first a series of [lop~] and to pass it into a
>series of [hip~]. I still have some DSP problems with all this when I change the
>frequencies (I got surprisingly high levels sometimes). Maybe another solution
>is to use a kind of narrow filter bank using some [vcf~], but it's not very easy
>to control as I would need lots of filters, like in FFTs.
>The FFT is not a good solution here either, because time precision is very
>important.
>
>  
>
>>>>I may want to change the cutoff very fast, with big jumps
>>>>        
>>>>
>>>hmm, this is worrying then.
>>>Are there not any low-pass or high-pass filters in the latest iemlib that
>>>take signal inputs for the cutoff freqs?  I'm sorry, I haven't got Pd
>>>      
>>>
>>here
>>    
>>
>>>at work, so I can't check.  But I must say I HAVE noticed clicks even
>>>      
>>>
>>using
>>    
>>
>>>the control (ie. non signal) version of [line].  
>>>      
>>>
>>that's what I feared actually
>>    
>>
>>>I think my block size was
>>>64, but whatever this value is the output from [line] will always be a
>>>significant jump compared to using [line~] - unless you make the [line]
>>>change REALLY slowly of course!
>>>      
>>>
>>I will try to use [line] with a very small time grain
>>
>>
>>thanks for your help
>>
>>-j
>>
>>    
>>
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>
>  
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