[FFmpeg-devel] [PATCH] lavfi: add xbr filter

[Timothy Gu]

On Sunday, November 2, 2014, Stefano Sabatini <stefasab at gmail.com> wrote:

> On date Sunday 2014-11-02 13:28:05 +0100, Michael Niedermayer encoded:
> > On Sun, Nov 02, 2014 at 09:09:51AM +0530, arwa arif wrote:
> [...]
> > > The reference code I used was "
> https://github.com/carlosascari/2xBR-Filter".
> >
> > I see, and i understand now where the abs bug in your code came from
> > i dont think this was a good choice as reference
> > Its readme even says:
> >     Research: Hyllian mentions a few optional implementations besides
> level 2 interpolation, but i can't find any documentation on the filter
> other than the byuu forum, where he only mentions them:
> >         Font Enhancement
> >         Using LVL2 Interpolation in regions plagued by shades of colors
> >         Using linear equation of the Straight Line to interpolate in odd
> scale factors
> >
> > so it seems to me the reference used was not a complete implementation
> > of xBR
> >
> > does anyone have the actual sources of the original xbr filter ?
> > i did find some links but they all just redirect to some spy/add/crap
> > ware download-manager
> >
> > also i found an example on how one of the reference pics should
> > look with 2x xbr on:
> >
> http://forums.getpaint.net/index.php?/topic/23601-2d-image-scaling-algorithms/page-2
>
> This is the link mentioned by ubitux:
> http://filthypants.blogspot.it/2012/03/xbr-vs-hqx-interpolation-filter.html
>
> in ticket:
> https://trac.ffmpeg.org/ticket/3404
>
> This blog mentions Hyllian xBR algorithm:
> http://board.byuu.org/viewtopic.php?f=10&t=2248
>
> but the link above is dead.
>
> Googling for Hyllian and xBR I found this Hyallian's repository:
> https://github.com/libretro/common-shaders
>
> The forum mentioned by Michael:
>
> http://forums.getpaint.net/index.php?/topic/23601-2d-image-scaling-algorithms/
>
> is about a Paint.NET Plugin:
> http://code.google.com/p/2dimagefilter/
>
> A short description of xBR is here:
> https://code.google.com/p/2dimagefilter/wiki/ImageScaling#xBR
>
> Since Hyllian code seems to be mentioned for the first time in
> relation to byuu (a SNES emulation project), I looked for:
> http://byuu.org/
>
> I downloaded the higan (name of the SNES emulator) code, and grepped
> for xBR but with no luck.
>
> So at the end I was not able to find a C reference for xBR. Probably
> we should contact Hyllian himself to get advice about a (possibly
> C-language) reference implementation.
>

Found a C++ implementation:
http://sourceforge.net/p/paintown/code/HEAD/tree/trunk/src/util/graphics/sdl/xbr.cpp


It says "xBR 3.3b" and I'm not sure what variant that is in the filthy
pants blog.

It's close to C and standalone enough, and it is licensed under the LGPL
(v3 though).

Found via
http://wayofthepixel.net/index.php?PHPSESSID=lm3asavrs3g8u63g8k28d62u82&topic=13508.10

Timothy