[FFmpeg-devel] [PATCH 7/9] lavfi/nlmeans: switch from double to float

[Moritz Barsnick]

On Sun, May 06, 2018 at 13:40:58 +0200, Clément Bœsch wrote:
> Overall speed appears to be 1.1x faster with no noticeable quality impact.

Probably platform dependant?

>  struct weighted_avg {
> -    double total_weight;
> -    double sum;
> +    float total_weight;
> +    float sum;
>  };

I believe these calculaions in nlmeans_plane() will promote to double
before being cast back to float:

           // Also weight the centered pixel
            wa->total_weight += 1.0;
            wa->sum += 1.0 * src[y*src_linesize + x];

(At least the second one. The first one - just an assignment of a
constant - is covered by the preprocessor, IIUC.) They need to use
"1.0f".

(There are others, but only in init(), which don't matter for
performance.)

Cheers,
Moritz