[FFmpeg-devel] [PATCH][RFC] perspective filter port

Michael Niedermayer michaelni at gmx.at
Mon May 2 14:36:03 CEST 2011

On Sat, Apr 30, 2011 at 07:04:33PM +0200, Stefano Sabatini wrote:
> Hi all,
> in attachment a mechanical port of the libmpcodecs perspective filter.
> Todo:
> * add support to RGB path
> * add support to more formats (many of them should be already
>   supported out of the box)
> * make the filter parametric
> * make the filter support outw/h != inw/h
> * write an affine transform wrapper (perspective transforms are a
>   superclass of the affine transforms)
> * add support to a fill color for filling the background
> * rework the interface, maybe we could make the filter accepts a
>   matrix textual representation (e.g. adopting the MATLAB/Octave
>   notation), the parsing routines may be useful in other parts of the
>   code
> Note that this filter uses float arithmetic, so I believe it is still
> a good idea to keep a separate non-float implementation of a rotozoom
> filter (I have no idea at this point if the same could be done with
> this filter).
> But in order to do this I need to understand the math behind the code.
> Michael, can you describe the meaning of
>     int32_t coeff[1<<SUB_PIXEL_BITS][4];
>     int32_t (*pv)[2];
>     int pvStride;
> ?

coeff are resample coeffs
pv are pointers into the source
their useage should make the rest clear

> and eventually provide a link to some reference material?

my brain ;)

> pvStride in particular is defined like the input width, so maybe at
> least that parameter may be removed.

> The accidental motivation for this patch is adding support to affine
> transforms, in order to support transforms annotated in MOV metadata
> through the automatic insertion of a filter in the filterchain.

nice idea

> Note: I changed the license from GPL to LGPL, Micheal are you fine
> with that?

I thought we could leave it GPL and when some company wants it under
a more permissive license they could pay for the relicensing
whats your oppinion about that?

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

it is not once nor twice but times without number that the same ideas make
their appearance in the world. -- Aristotle
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