Yup, I was asking because I found that on the M4 it is difficult to do proper 
overlap and add while keeping reasonably small block sizes for FFTs of useful 
length, so I was just curious whether you had to implement threads or just went 
for block sizes synchronous with the FFT step.
If I remember correctly I was using 2048 samples per block and 512 samples 
step, with good results.
Best,Giulio

 
      From: Eric Brombaugh <ebrombau...@cox.net>
 To: music-dsp@music.columbia.edu 
 Sent: Friday, 16 September 2016, 19:50
 Subject: Re: [music-dsp] Help with "Sound Retainer"/Sostenuto Effect
   
Probably shouldn't reveal too much of the detail, but it likely comes as 
no surprise that the tradeoff between time and frequency resolution is 
critical in systems that have limited CPU horsepower. The FFTs in this 
case do run in the audio processing thread which is synchronous to the 
buffer processing rate.

I'd love to have a go at doing this kind of stuff on something like a 
SHARC where 16kpt FFTs are apparently easy to do at audio rates...

Eric

On 09/16/2016 11:15 AM, Giulio Moro wrote:
> Nice that it runs on the M4F, what FFT size, overlap and audio
> processing block size are you using? Are you running the FFT in a
> separate thread?
>
> Giulio
>
>
>    ------------------------------------------------------------------------
>    *From:* Eric Brombaugh <ebrombau...@cox.net>
>    *To:* music-dsp@music.columbia.edu
>    *Sent:* Friday, 16 September 2016, 19:12
>    *Subject:* Re: [music-dsp] Help with "Sound Retainer"/Sostenuto Effect
>
>    I coded up the spectral freeze core of the Audio Damage "Spectre"
>    module
>    in a similar way:
>
>    http://www.audiodamage.com/hardware/product.php?pid=ADM15
>
>    It's a basic phase vocoder with forward and inverse FFTs but we added
>    some fun little tweaks to shift, stretch and randomize the spectrum. It
>    runs nicely on an STM32F405 ARM Cortex M4F processor.

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