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

[Steinar H. Gunderson]

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

> 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.

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.

/* Steinar */
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