[PD] I wanna sing like Paris - zerocrossing for vanilla

Martin Schied crinimal at gmx.net
Wed Aug 18 01:40:14 CEST 2010


I made a cheap vanilla zero crossing patch some time ago. it doesn't 
work properly if the signal has zero samples between crossings though.

Martin

Roman Haefeli wrote:
> On Tue, 2010-08-17 at 13:59 +0200, Matteo Sisti Sette wrote:
>   
>> On 08/17/2010 01:39 PM, Roman Haefeli wrote:
>>     
>>> On Tue, 2010-08-17 at 12:59 +0200, martin brinkmann wrote:
>>>
>>>       
>>>> i will try this when i have found a way to extract
>>>> single-cycle waves from audio input in pd...
>>>>         
>>> Not yet tried it myself, but what about writing live input to a table
>>> (for instance with [tabwrite~]) in order to have access to the audio
>>> data with message based objects? With those it should be fairly easy to
>>> the detect the exact position of a zero crossing. For finding a single
>>> cycle, it would be sufficient to find a positive crossing - for
>>> instance-  and from there find the next one, so you have the exact end
>>> points of one single cycle.
>>>
>>>       
>> How would you look for zero crossings? With message based objects such 
>> as [until], a counter, [tabread] and comparing to zero?
>> Is that feasible?
>>
>> (sorry for hijacking the discussion, I am curious about that)
>>     
>
> yeah, actually that's what I thought about. I guess, one would not
> compare to zero, but compare to the previous sample and check whether
> the sign has changed. One could even perform linear (or even polynomial
> interpolation) to find the subsample accurate location of the crossing. 
>
> Roman
>
>
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