[FFmpeg-devel] [PATCH] avfilter: add normalize filter

[Moritz Barsnick]

On Mon, Nov 20, 2017 at 19:01:12 +1100, Richard Ling wrote:
> Patch attached.

You code nicely sticks to floats throughout, but at points like these:

> +        min[c].smoothed = (min[c].smoothed  *        s->independence)
> +                        + (rgb_min_smoothed * (1.0 - s->independence));
> +        max[c].smoothed = (max[c].smoothed  *        s->independence)
> +                        + (rgb_max_smoothed * (1.0 - s->independence));

and this:

> +        min[c].out = (s->blackpt[c] *        s->strength)
> +                   + (min[c].in     * (1.0 - s->strength));
> +        max[c].out = (s->whitept[c] *        s->strength)
> +                   + (max[c].in     * (1.0 - s->strength));

and this:

> +                int out_val = (in_val - min[c].smoothed) * scale + min[c].out + 0.5;

your calculation gets promoted to double. You need to write e.g. "1.0f".

(This only matters on shitty old ARMs and similar processors, which are
really slow on doubles [soft emulation]. But just for sanity, please
let the compiler stick to float or double.)

> +    { "smoothing",  "amount of temporal smoothing of the input range, to reduce flicker", OFFSET(smoothing), AV_OPT_TYPE_INT, {.i64=0}, 0, INT_MAX, FLAGS },
[...]
> +    s->history_len = (int)s->smoothing + 1;

Certainly a corner case, but this can overflow. And why do you cast an
int to an int? (Perhaps it was an unsigned int before?)

Cheers,
Moritz