[vorbis] bark_noise

[David Balazic]

Michael Smith wrote :

>    At 11:23 AM 11/8/00 +0000, you wrote:
>    >I would like to understand what is going on, I freely admit. Having no 
>    >signal processing knowledge means that looking at the code gives me 
>    >headaches 8-) I would, however, be more than happy to read any weighty 
>    >tomes if you could point me to any relevant ones. 
>    > 
>    >Given that the arrival time of beta 3 has been discussed in the past, I shall 
>    >refrain from asking. However, I would appreciate knowing how to fix this 
>    >particular problem so that I can move ahead and play with the alpha a bit 
>    >more ;-) 
> 
>    I think the particular problem you were encountering has been fixed in CVS
>    as of yesterday. Please try again.
> 
>    Short description: the code was converting some value to dB at one point.
>    You can't do this (you get -INF) if the value is 0, so the code was using a
>    large negative number instead. Too large.
> 
>    In the particular case it was being used in, anything negative got clipped
>    to 0 about 2 lines later, so it didn't matter. The code now uses -400
>    instead.
> 
>    There may be other problems, but I think they've all been cleared up - let
>    us know (preferably with a backtrace of where things are dying) if anything
>    else breaks.
> 
>    Michael

What are those problems with -INF and large negative numbers ?
AFAIK -INF is a valid value and the following code works
( almost ) as expected :

/* BEGIN PROGRAM */

#include <math.h>
#include <stdio.h>

int main()
{
double a;

 a = log((double)0.0);

printf ("isinf : %d\n",isinf(a));
printf ("3.0/a  : %e\n",3.0/a);
printf ("a  : %e\n-----\n",a);

a=a+a;
printf ("isinf : %d\n",isinf(a));
printf ("3.0/a  : %e\n",3.0/a);
printf ("a  : %e\n=====\n=====\n",a);

a = HUGE_VAL;

printf ("isinf : %d\n",isinf(a));
printf ("3.0/a  : %e\n",3.0/a);
printf ("a  : %e\n-----\n",a);

a=a+a;
printf ("isinf : %d\n",isinf(a));
printf ("3.0/a  : %e\n",3.0/a);
printf ("a  : %e\n-----\n",a);
}
/* END PROGRAM */

The output on HP-UX 10.20 :
------------------------------------
isinf : 0
3.0/a  : -1.668805e-308
a  : -1.797693e+308
-----
isinf : -1
3.0/a  : -0.000000e+00
a  : -inf
=====
=====
isinf : 0
3.0/a  : 1.668805e-308
a  : 1.797693e+308
-----
isinf : 1
3.0/a  : 0.000000e+00
a  : inf
-----
------------------------------------

And on HP-UX 11.00 :

isinf : 1
3.0/a  : -0.000000e+00
a  : -inf
-----
isinf : 1
3.0/a  : -0.000000e+00
a  : -inf
=====
=====
isinf : 1
3.0/a  : 0.000000e+00
a  : inf
-----
isinf : 1
3.0/a  : 0.000000e+00
a  : inf
-----


-- 
David Balazic
--------------
"Be excellent to each other." - Bill & Ted
- - - - - - - - - - - - - - - - - - - - - -

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