[FFmpeg-devel] [PATCH 1/2] avfilter/vf_gblur: fix divide by zero

[Paul B Mahol]

I do not like this "fix"

On 1/4/20, quinkblack at foxmail.com <quinkblack at foxmail.com> wrote:
> From: Zhao Zhili <zhilizhao at tencent.com>
>
> ./ffmpeg -i ~/Pictures/test.jpg -vf 'gblur=sigma=0' -f null -
> ...
> src/libavfilter/vf_gblur.c:260:59: runtime error: division by zero
> src/libavfilter/vf_gblur.c:261:26: runtime error: division by zero
> ---
>  libavfilter/vf_gblur.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/libavfilter/vf_gblur.c b/libavfilter/vf_gblur.c
> index 2e587f6a0a..e057937fb7 100644
> --- a/libavfilter/vf_gblur.c
> +++ b/libavfilter/vf_gblur.c
> @@ -37,11 +37,17 @@
>  #define OFFSET(x) offsetof(GBlurContext, x)
>  #define FLAGS
> AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_RUNTIME_PARAM
>
> +/* Consider the three-sigma rule, for minimum radius of 1 sigma should not
> + * be smaller than 1/3. Relax it to 0.25 if the user want to try.
> + */
> +#define SIGMA_MIN   0.25
> +#define SIGMA_MAX   1024.0
> +
>  static const AVOption gblur_options[] = {
> -    { "sigma",  "set sigma",            OFFSET(sigma),  AV_OPT_TYPE_FLOAT,
> {.dbl=0.5}, 0.0, 1024, FLAGS },
> +    { "sigma",  "set sigma",            OFFSET(sigma),  AV_OPT_TYPE_FLOAT,
> {.dbl=0.5},  SIGMA_MIN, SIGMA_MAX, FLAGS },
>      { "steps",  "set number of steps",  OFFSET(steps),  AV_OPT_TYPE_INT,
> {.i64=1},     1,    6, FLAGS },
>      { "planes", "set planes to filter", OFFSET(planes), AV_OPT_TYPE_INT,
> {.i64=0xF},   0,  0xF, FLAGS },
> -    { "sigmaV", "set vertical sigma",   OFFSET(sigmaV), AV_OPT_TYPE_FLOAT,
> {.dbl=-1},   -1, 1024, FLAGS },
> +    { "sigmaV", "set vertical sigma",   OFFSET(sigmaV), AV_OPT_TYPE_FLOAT,
> {.dbl=-1},   -1, SIGMA_MAX, FLAGS },
>      { NULL }
>  };
>
> @@ -244,7 +250,7 @@ static int config_input(AVFilterLink *inlink)
>      if (!s->buffer)
>          return AVERROR(ENOMEM);
>
> -    if (s->sigmaV < 0) {
> +    if (s->sigmaV < SIGMA_MIN) {
>          s->sigmaV = s->sigma;
>      }
>      ff_gblur_init(s);
> --
> 2.22.0
>
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