> On Jan 4, 2020, at 7:04 PM, Paul B Mahol <one...@gmail.com> wrote:
>
> I do not like this “fix"
What do you suggest? It’s numerical unstable for small sigma.
>
> On 1/4/20, quinkbl...@foxmail.com <quinkbl...@foxmail.com> wrote:
>> From: Zhao Zhili <zhiliz...@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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