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

[Stefano Sabatini]

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.

Comments/insight are welcome.
-- 
FFmpeg = Faithful Furious MultiPurpose Enhanced Geek