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

[Michael Niedermayer]

On Sun, Nov 02, 2014 at 09:09:51AM +0530, arwa arif wrote:
> On Sun, Nov 2, 2014 at 3:36 AM, Michael Niedermayer <michaelni at gmx.at>
> wrote:
> 
> > On Sat, Nov 01, 2014 at 11:35:11PM +0530, arwa arif wrote:
> > > Scale2x and xBR are very different. But they have implemented xBR also in
> > > their source code. Anyways, I found a good link --> "
> > > http://imgur.com/a/XAwx5" for reference pictures. But, the answers are
> > > coming out to be different. Not sure, why this is happening. Maybe, it is
> > > because of different versions.
> >
> > the version which you implemented, where is the reference code for
> > that ?
> > can it be build on linux or windows ?
> > if so we could build it and test against that
> >
> >
> > >
> > > On Sat, Nov 1, 2014 at 10:02 PM, Michael Niedermayer <michaelni at gmx.at>
> > > wrote:
> > >
> > > > On Sat, Nov 01, 2014 at 07:30:32PM +0530, arwa arif wrote:
> > > > > On Sat, Nov 1, 2014 at 4:40 PM, Stefano Sabatini <stefasab at gmail.com
> > >
> > > > wrote:
> > > > >
> > > > > > On date Saturday 2014-11-01 04:27:24 +0530, arwa arif encoded:
> > > > > > [...]
> > > > > > > On Fri, Oct 31, 2014 at 6:31 PM, Stefano Sabatini <
> > > > stefasab at gmail.com>
> > > > > > > From 9b6b1d546247cf61b2f696835fb8a5e782d353ea Mon Sep 17 00:00:00
> > > > 2001
> > > > > > > From: Arwa Arif <arwaarif1994 at gmail.com>
> > > > > > > Date: Thu, 30 Oct 2014 22:06:20 +0530
> > > > > > > Subject: [PATCH] [PATCH]lvafi: add xbr filter
> > > > > >
> > > > > > typo: lvafi
> > > > > >
> > > > > > >
> > > > > > > ---
> > > > > > >  doc/filters.texi         |    5 +
> > > > > > >  libavfilter/Makefile     |    1 +
> > > > > > >  libavfilter/allfilters.c |    1 +
> > > > > > >  libavfilter/vf_xbr.c     |  331
> > > > > > ++++++++++++++++++++++++++++++++++++++++++++++
> > > > > > >  4 files changed, 338 insertions(+)
> > > > > > >  create mode 100644 libavfilter/vf_xbr.c
> > > > > > [...]
> > > > > >
> > > > > > Code looks good to me, apart a few cosmetics nits which I can fix
> > > > > > myself before pushing.
> > > > > >
> > > > > > About Michael's question, is it possible to compare it with the
> > > > > > reference filter?
> > > > > >
> > > > >
> > > > > I compared the output with the code from scale2x "
> > > > > http://scale2x.sourceforge.net/". I have attached the ouput with
> > this
> > > > mail.
> > > > > foobar.png denotes the original image.
> > > > > foobar_ref,png denotes the output from scale2x.
> > > > > foobar_out.png denotes the output from the code written.
> > > >
> > > > the ref and out images look somewhat different
> > > > also, what is the relation between scale2x and xbr ?
> > > >
> > > > http://scale2x.sourceforge.net/index.html
> > > > states that
> > > > "Other interesting effects are HQx and xBR. These effects are a bit
> > slower
> > > > than Scale2x, but surely in the grasp of modern processors. "
> > > >
> > > > This does not sound like scale2x and xbr are the same thing
> > > >
> > > > [...]
> > > >
> > > >
> > > > --
> > > > Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> > > >
> > > > Freedom in capitalist society always remains about the same as it was
> > in
> > > > ancient Greek republics: Freedom for slave owners. -- Vladimir Lenin
> > > >
> > > > _______________________________________________
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> > > >
> > > >
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> > >
> >
> > --
> > Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> >
> >
> 
> > Opposition brings concord. Out of discord comes the fairest harmony.
> > -- Heraclitus
> >
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> >
> >
> 
> 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

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you think the mosad wants you dead since a long time then you are either
wrong or dead since a long time.
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