[LAU] [ANN] spectrojack 0.4

[Robin Gareus]

Bonjour Cedric,

On 10/21/2011 10:03 AM, Cedric Roux wrote:
> ----- Original Message -----
>> From: "Fons Adriaensen" <fons at linuxaudio.org>
>> I don't think that the DSP code is doing what the parameters
>> would suggest - the visual results don't match.
>>
>> Could it be that 'l' sets the window size ? It shouldn't,
>> the window size should be the fft size. Then, if you have
>> both 'l' and 's', then both together determine the overlap,
>> so this can't be a separate parameter.
>>
>> Also, with just a 1 kHz sine as the input, I'd expect all
>> spectra to be identical, but they are not...
> 
> that's a bit unfortunate...
> I'll have a look at all this, thanks to report.
> 
> for s, l and overlap:
> s is the fft size (let's say 1024 for an example)
> l is the sample count, if set at 512 we compute an fft
> each 512 samples. Since fft size is 1024, we append with 512 zeros.
> Overlap is how much we advance the input to compute the
> next fft. In our example: set to 0, at time 0 we compute with input[0..511]
> and next iteration we compute with x[512..1023].
> Set to 0.5, next iteration is computed with x[256..767].
> Set to 1, next iteration would compute with x[1..512] (normally it should
> not advance at all, so setting to 1 is in fact setting to 1-epsilon with
> epsilon such that we advance by 1 sample)
> 
> The window is computed on the l samples.
> 
> I guess all this is not done the standard way... (and I hope
> the code does what I say above...)
> 
> For your 1k sine, I'll have a look. If you have some time,
> it would be great to have a screenshot just
> to be sure I see the same thing than you?

You can compare it to http://www.baudline.com/ which can also provide
some inspiration on default settings. jaaa and japa may come in handy to
verify the math.

> And thanks for the testing. The code does not crash on at least
> three and half computers! that's great.

Many thanks for taking up that task. A FLOSS version of baudline has
been on my wishlist for a while.

Cheers!
robin