[FFmpeg-devel] [PATCH] Box-Muller gaussian generator

[Vitor Sessak]

Stefano Sabatini wrote:
> Hi,
> 
> I'm going to use this for a noise filter, I believe this could be
> useful in other part of libav* though.

> +double av_bmg_get(AVBMG *bmg)
> +{
> +    double x1, x2, w, y;
> +    AVLFG *lfg = &bmg->lfg;
> +
> +    do {
> +        x1 = 2.0 * ranf(lfg) - 1.0;
> +        x2 = 2.0 * ranf(lfg) - 1.0;
> +        w = x1*x1 + x2*x2;
> +    } while (w >= 1.0);
> +
> +    w = sqrt((-2.0 * log(w)) / w);
> +    y = x2 * w;
> +
> +    return bmg->mean + y * bmg->std_dev;
> +}

This generates two numbers to use only one. Isn't it faster to store the 
second number for the next call or have a function to fill a buffer of 
random numbers?

-Vitor