[FFmpeg-devel] [PATCH] avfilter: add radial and circular blur video filter

[Paul B Mahol]

On 7/19/20, Steinar H. Gunderson <steinar+ffmpeg at gunderson.no> wrote:
> On Sun, Jul 19, 2020 at 08:20:40PM +0200, Paul B Mahol wrote:
>>> If you can explain what you mean the difference between radial and zoom
>>> blur
>>> is, it would probably be possible to adapt the idea.
>> That algorithm is very slow for big lengths, it takes ages to process
>> single small image.
>
> Yes, this is the non-recursive version, which is O(n) in the number of
> samples. This is why I recommended the recursive version, which is O(log n)
> in the number of samples and thus avoids the problem with big lengths.
> It is fairly straightforward to convert one to the other.

Really? How so?

>
>>> It also has a somewhat more efficient implementation of bilinear
>>> filtering
>>> than in your patch (three multiplies instead of eight, and also fewer
>>> add/sub), although it's likely that a fixed-point implementation would
>>> save
>>> yet more time if you're interested in trying that.
>> Such micro-optimizations could be added any time later.
>
> Sure.
>
> /* Steinar */
> --
> Homepage: https://www.sesse.net/
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