[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 07:32:18PM +0200, Paul B Mahol wrote:
>> I see nothing wrong with that image.
>
> Let me provide some zooms. First, center artifacts (the “flower” should not
> be there):
>
>   http://storage.sesse.net/ffmpeg-radialblur3-zoom1.png
>
> Then, staircase/uneven horizontal line near the edge (the line should not
> wobble up and down):
>
>   http://storage.sesse.net/ffmpeg-radialblur3-zoom2.png

Huh, since when we look at such small differences?

>
>> You still provided 0 valuable information for your perfect solution
>> algorithm.
>
> I haven't claimed any perfect solutions, but I have suggested two different
> algorithms with details that I both believe would be more performant and
> sport higher output quality (actually three, but the last one was not with
> a lot of details). Could you suggest which information you would regard as
> valuable?
>
> Here's the source code for GIMP's zoom blur implementation, which works
> without any similar artifacts, and has no trigonometry per-pixel:
>
>
> https://gitlab.gnome.org/GNOME/gegl/-/blob/master/operations/common-gpl3+/motion-blur-zoom.c#L160
>
> 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.

>
> 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.