> On Jan 4, 2020, at 9:09 PM, Paul B Mahol <one...@gmail.com> wrote:
>
> On 1/4/20, zhilizhao <quinkbl...@foxmail.com> wrote:
>>
>>
>>> 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.
>
> For small sigma return frames unchanged as it currently does.
Then which valud should be selected as the threshold:
1. A value from which it becomes unstable (it’s not fun to figure it out).
2. A reasonable (and random) selected value like 0.25
>
>>
>>>
>>> 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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>>
>>
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