[Speex-dev] A technical question about the speex preprocessor.

John Ridges
Wed, 22 Jul 2009 15:33:37 -0000

Thanks for the confirmation  Jean-Marc. I kind of suspected from the
comments that it was the confluent hypergoemetric function, which I was
trying to evaluate using Kummer's equation, namely:

M(a;b;x) is the sum from n=0 to infinity of (a)n*x^n / (b)n*n!
where (a)n = a(a+1)(a+2) ... (a+n-1)

But when I use Kummer's equation, I don't get the values in the
"hypergeom_gain" table. Did you use a different solution to the
confluent hypergoemetric function when you created the table?

John Ridges


Jean-Marc Valin wrote:
> Hi John,
>
> M(;;) is the confluent hypergeometric function.
>
> 	Jean-Marc
>
> John Ridges a ?crit :
>
>> Hi,
>>
>> I've been trying to re-create the table in the function
"hypergeom_gain"
>> in preprocess.c, and I just simply can't get the same values. I get
the
>> same value for the first element, so I know I'm computing
gamma(1.25)^2
>> correctly, but I can't get the same numbers for M(-.25;1;-x), which
I
>> assume is Kummer's function. Is it possible that the comment is out
of
>> date and the values of Kummer's function used to make the table
were
>> different? Any help would be greatly appreciated.
>>
>> John Ridges
>>
>>
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>>
>>
>
>
>