[Csnd] pvs question
| Date | 2011-07-08 18:54 |
| From | peiman khosravi |
| Subject | [Csnd] pvs question |
I am wondering why is it that the number of usable bins is FFT_size+1
and not just FFT_size? Is this the case with all FFT algorithms or
just csound's PVS?
Thanks in advance
Peiman
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| Date | 2011-07-08 19:00 |
| From | joachim heintz |
| Subject | Re: [Csnd] pvs question |
i think you mean HALF OF fft size plus one, right?
for instance, for fft-size = 1024 -> 513.
regards -
joachim
Am 08.07.2011 19:54, schrieb peiman khosravi:
> I am wondering why is it that the number of usable bins is FFT_size+1
> and not just FFT_size? Is this the case with all FFT algorithms or
> just csound's PVS?
>
> Thanks in advance
>
> Peiman
>
>
> Send bugs reports to the Sourceforge bug tracker
> https://sourceforge.net/tracker/?group_id=81968&atid=564599
> Discussions of bugs and features can be posted here
> To unsubscribe, send email sympa@lists.bath.ac.uk with body "unsubscribe csound"
>
>
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|
| Date | 2011-07-08 19:16 |
| From | Victor Lazzarini |
| Subject | Re: [Csnd] pvs question |
yes, that is correct. It's 1/2 the size because we don't need the
negative frequency bins, and +1 because we need the bin at the Nyquist
frequency.
Victor
On 8 Jul 2011, at 19:00, joachim heintz wrote:
> i think you mean HALF OF fft size plus one, right?
> for instance, for fft-size = 1024 -> 513.
> regards -
> joachim
>
>
> Am 08.07.2011 19:54, schrieb peiman khosravi:
>> I am wondering why is it that the number of usable bins is FFT_size+1
>> and not just FFT_size? Is this the case with all FFT algorithms or
>> just csound's PVS?
>>
>> Thanks in advance
>>
>> Peiman
>>
>>
>> Send bugs reports to the Sourceforge bug tracker
>> https://sourceforge.net/tracker/?
>> group_id=81968&atid=564599
>> Discussions of bugs and features can be posted here
>> To unsubscribe, send email sympa@lists.bath.ac.uk with body
>> "unsubscribe csound"
>>
>>
>
>
> Send bugs reports to the Sourceforge bug tracker
> https://sourceforge.net/tracker/?group_id=81968&atid=564599
> Discussions of bugs and features can be posted here
> To unsubscribe, send email sympa@lists.bath.ac.uk with body
> "unsubscribe csound"
>
Dr Victor Lazzarini
Senior Lecturer
Dept. of Music
NUI Maynooth Ireland
tel.: +353 1 708 3545
Victor dot Lazzarini AT nuim dot ie
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|
| Date | 2011-07-16 11:50 |
| From | peiman khosravi |
| Subject | Re: [Csnd] pvs question |
| Mhh I had missed the replies! yes sorry that is what I meant. Half of fft size + 1. P On 8 July 2011 19:00, joachim heintz <jh@joachimheintz.de> wrote: i think you mean HALF OF fft size plus one, right? |
| Date | 2011-07-16 11:52 |
| From | peiman khosravi |
| Subject | Re: [Csnd] pvs question |
| Thanks Victor, So this applies to all conventional FFT algorithms (e.g. pd, msp and so on)? From reading the msp tutorials I get the feeling that they just say fft/2 without +1. Best, Peiman On 8 July 2011 19:16, Victor Lazzarini <Victor.Lazzarini@nuim.ie> wrote: yes, that is correct. It's 1/2 the size because we don't need the negative frequency bins, and +1 because we need the bin at the Nyquist frequency. |
| Date | 2011-07-16 17:40 |
| From | Victor Lazzarini |
| Subject | Re: [Csnd] pvs question |
| Sometimes they pack in the zero + nyquist in the first two positions of the array (as they are real-valued), making it fftsize/2 pairs of numbers. I reckon that is what PD does too. Victor On 16 Jul 2011, at 11:52, peiman khosravi wrote: Thanks Victor, Dr Victor Lazzarini Senior Lecturer Dept. of Music NUI Maynooth Ireland tel.: +353 1 708 3545 Victor dot Lazzarini AT nuim dot ie |
| Date | 2011-07-16 17:56 |
| From | peiman khosravi |
| Subject | Re: [Csnd] pvs question |
| Thanks. Peiman On 16 July 2011 17:40, Victor Lazzarini <Victor.Lazzarini@nuim.ie> wrote:
|
| Date | 2011-07-16 17:59 |
| From | Victor Lazzarini |
| Subject | Re: [Csnd] pvs question |
| By the way, this is covered in the spectral processing section of the Audio Programming Book, if you'd like to consult it. Victor On 16 Jul 2011, at 17:56, peiman khosravi wrote: Thanks. Dr Victor Lazzarini Senior Lecturer Dept. of Music NUI Maynooth Ireland tel.: +353 1 708 3545 Victor dot Lazzarini AT nuim dot ie |
| Date | 2011-07-16 18:07 |
| From | Olivier Bélanger |
| Subject | Re: [Csnd] pvs question |
| But what happens to the first bin during a cartesian to polar conversion if you have the nyquist value as imaginary instead of a 0? Olivier 2011/7/16 Victor Lazzarini <Victor.Lazzarini@nuim.ie>
|
| Date | 2011-07-16 18:17 |
| From | Victor Lazzarini |
| Subject | Re: [Csnd] pvs question |
Well, the system would know to avoid bin 0 and not convert it ( I expect that the MSP coders were clever enough to do this, but god knows). On 16 Jul 2011, at 18:07, Olivier Bélanger wrote: But what happens to the first bin during a cartesian to polar conversion if you have the nyquist value as imaginary instead of a 0? Dr Victor Lazzarini Senior Lecturer Dept. of Music NUI Maynooth Ireland tel.: +353 1 708 3545 Victor dot Lazzarini AT nuim dot ie |
| Date | 2011-07-16 18:36 |
| From | Olivier Bélanger |
| Subject | Re: [Csnd] pvs question |
| Ok, that's what I concluded! it's really annoying not having access to source code of MaxMSP... Thanks! Olivier p.s.: PD has both implementations, rfft~ (fftsize/2+1) and bfft~ (fftsize/2),they call it normalized fft! 2011/7/16 Victor Lazzarini <Victor.Lazzarini@nuim.ie>
|
| Date | 2011-07-16 18:39 |
| From | peiman khosravi |
| Subject | Re: [Csnd] pvs question |
| Thanks Victor, I have been so busy that I haven't had time to read all the desired sections of the book yet. I shall pick it up as soon as I have a bit of time. Best, Peiman
On 16 July 2011 17:59, Victor Lazzarini <Victor.Lazzarini@nuim.ie> wrote:
|