frequency analysis with alsa and fftw

frequency analysis with alsa and fftw

[Markus Vogl]

hello,
 
i´m absolute newbie in programming alsa, but for my school project
i have to do so.
my project is to analyse the mic input frequency from my asus eepc
1008ha with ubuntu 9.10  and show it in a terminal window. i would
use my acoustic 6 string guitar to play in front of my netbook.
 
i´ve testet the howto from linuxjornal.com ..
http://www.linuxjournal.com/article/6735
 
...but i´ve no plan to use the mic input and  then analyse it with fftw.
 
regards
markus
 
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Re: frequency analysis with alsa and fftw

[Jan-Benedict Glaw]

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On Sun, 2009-12-27 13:26:31 +0100, Markus Vogl <markus.vogl@gmx.net> wrote:
> my project is to analyse the mic input frequency from my asus eepc
> 1008ha with ubuntu 9.10  and show it in a terminal window. i would
> use my acoustic 6 string guitar to play in front of my netbook.
>  
> i´ve testet the howto from linuxjornal.com ..
> http://www.linuxjournal.com/article/6735
>  
> ...but i´ve no plan to use the mic input and  then analyse it with fftw.

Why do you need to do ALSA programming in the first place? Isn't it
enough to use any given ALSA-capable audio recorder (eg. arecord) to
record some sound, convert it to raw PCM data (eg. cut off the WAV
header) and then shift all the data into the FFT lib?

MfG, JBG

-- 
      Jan-Benedict Glaw      jbglaw@lug-owl.de              +49-172-7608481
 Signature of:                            If it doesn't work, force it.
 the second  :                   If it breaks, it needed replacing anyway.

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Re: frequency analysis with alsa and fftw

[Markus Vogl]

hi,

i have to do this in realtime (like a guitartuner) and with my "project" i
have to see the frequency shift in realtime in a terminal window.

regards
markus 

-----Ursprüngliche Nachricht-----
Von: Jan-Benedict Glaw [mailto:jbglaw@lug-owl.de] 
Gesendet: Sonntag, 27. Dezember 2009 13:54
An: Markus Vogl
Cc: alsa-devel@alsa-project.org
Betreff: Re: [alsa-devel] frequency analysis with alsa and fftw

On Sun, 2009-12-27 13:26:31 +0100, Markus Vogl <markus.vogl@gmx.net> wrote:
> my project is to analyse the mic input frequency from my asus eepc 
> 1008ha with ubuntu 9.10  and show it in a terminal window. i would use 
> my acoustic 6 string guitar to play in front of my netbook.
>  
> i´ve testet the howto from linuxjornal.com ..
> http://www.linuxjournal.com/article/6735
>  
> ...but i´ve no plan to use the mic input and  then analyse it with fftw.

Why do you need to do ALSA programming in the first place? Isn't it enough
to use any given ALSA-capable audio recorder (eg. arecord) to record some
sound, convert it to raw PCM data (eg. cut off the WAV
header) and then shift all the data into the FFT lib?

MfG, JBG

-- 
      Jan-Benedict Glaw      jbglaw@lug-owl.de              +49-172-7608481
 Signature of:                            If it doesn't work, force it.
 the second  :                   If it breaks, it needed replacing anyway.

Re: frequency analysis with alsa and fftw

[Jan-Benedict Glaw]

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On Sun, 2009-12-27 14:50:20 +0100, Markus Vogl <markus.vogl@gmx.net> wrote:
> Von: Jan-Benedict Glaw [mailto:jbglaw@lug-owl.de]:
> > On Sun, 2009-12-27 13:26:31 +0100, Markus Vogl <markus.vogl@gmx.net> wrote:
> > > my project is to analyse the mic input frequency from my asus
> > > eepc 1008ha with ubuntu 9.10  and show it in a terminal window.
> > > i would use my acoustic 6 string guitar to play in front of my
> > > netbook.
> > >  
> > > i´ve testet the howto from linuxjornal.com ..
> > > http://www.linuxjournal.com/article/6735
> > >  
> > > ...but i´ve no plan to use the mic input and  then analyse it
> > > with fftw.
> > 
> > Why do you need to do ALSA programming in the first place? Isn't
> > it enough to use any given ALSA-capable audio recorder (eg.
> > arecord) to record some sound, convert it to raw PCM data (eg. cut
> > off the WAV header) and then shift all the data into the FFT lib?
>
> i have to do this in realtime (like a guitartuner) and with my
> "project" i have to see the frequency shift in realtime in a
> terminal window.

Sure. Just let eg. arecord write to stdout or to a FIFO and read the
data from there. You can directly request raw output, all you need to
do is to shouvle the data through the FTT lib...

MfG, JBG
PS: I did some clean-up of your TOFU email.

-- 
      Jan-Benedict Glaw      jbglaw@lug-owl.de              +49-172-7608481
Signature of:                     Eine Freie Meinung in einem Freien Kopf
the second  :                   für einen Freien Staat voll Freier Bürger.

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Re: frequency analysis with alsa and fftw

[Markus Vogl]

 

> -----Ursprüngliche Nachricht-----
> Von: Jan-Benedict Glaw [mailto:jbglaw@lug-owl.de] 
> Gesendet: Sonntag, 27. Dezember 2009 15:05
> An: Markus Vogl
> Cc: alsa-devel@alsa-project.org
> Betreff: Re: [alsa-devel] frequency analysis with alsa and fftw
> 
> On Sun, 2009-12-27 14:50:20 +0100, Markus Vogl 
> <markus.vogl@gmx.net> wrote:
> > Von: Jan-Benedict Glaw [mailto:jbglaw@lug-owl.de]:
> > > On Sun, 2009-12-27 13:26:31 +0100, Markus Vogl 
> <markus.vogl@gmx.net> wrote:
> > > > my project is to analyse the mic input frequency from 
> my asus eepc 
> > > > 1008ha with ubuntu 9.10  and show it in a terminal window.
> > > > i would use my acoustic 6 string guitar to play in front of my 
> > > > netbook.
> > > >  
> > > > i´ve testet the howto from linuxjornal.com ..
> > > > http://www.linuxjournal.com/article/6735
> > > >  
> > > > ...but i´ve no plan to use the mic input and  then 
> analyse it with 
> > > > fftw.
> > > 
> > > Why do you need to do ALSA programming in the first 
> place? Isn't it 
> > > enough to use any given ALSA-capable audio recorder (eg.
> > > arecord) to record some sound, convert it to raw PCM data 
> (eg. cut 
> > > off the WAV header) and then shift all the data into the FFT lib?
> >
> > i have to do this in realtime (like a guitartuner) and with my 
> > "project" i have to see the frequency shift in realtime in 
> a terminal 
> > window.
> 
> Sure. Just let eg. arecord write to stdout or to a FIFO and 
> read the data from there. You can directly request raw 
> output, all you need to do is to shouvle the data through the 
> FTT lib...

Who can me explain how i can transfer the frame/buffer to the
fftw3.lib? This is from the howto example at linuxjournal
and in the "while loop" is the frame that i can use for DFT 
...or i´m wrong? 

while (loops > 0) {
    loops--;
    rc = snd_pcm_readi(handle, buffer, frames);
    if (rc == -EPIPE) {
      /* EPIPE means overrun */
      fprintf(stderr, "overrun occurred\n");
      snd_pcm_prepare(handle);
    } else if (rc < 0) {
      fprintf(stderr,
              "error from read: %s\n",
              snd_strerror(rc));
    } else if (rc != (int)frames) {
      fprintf(stderr, "short read, read %d frames\n", rc);
    }
    rc = write(1, buffer, size);
    if (rc != size)
      fprintf(stderr,
              "short write: wrote %d bytes\n", rc);
  }

regards
markus