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

[mike.gorchak.qnx at gmail.com]

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  Original Message  
From: Michael Niedermayer
Sent: Tuesday, October 28, 2014 17:51
To: FFmpeg development discussions and patches
Reply To: FFmpeg development discussions and patches
Subject: Re: [FFmpeg-devel] [PATCH] lavfi: add xbr filter

On Tue, Oct 28, 2014 at 07:16:45PM +0100, Clément Bœsch wrote:
> On Tue, Oct 28, 2014 at 06:30:34PM +0100, Stefano Sabatini wrote:
> [...]
> > How much effort would it take to implement the remaining scaling modes?
> > 
> 
> According to
> https://ffmpeg.org/pipermail/ffmpeg-devel/2014-October/164574.html
> 
> "I think 4x can be done fast enough, but 3x will take time."
> 
> [...]
> > > +typedef struct {
> > > + uint32_t rgbtoyuv[1<<24];
> > 
> > We should avoid this 64MiB. Also the table should be possibly static,
> > so you don't have to fill it per each xBR instance.
> > 
> 
> So, I requested to do it exactly the same as HQx because this part is
> common according to the specifications. This should be kept the same
> vf_hqx, and then factorized.
> 

> Now about removing this allocation, I did benchmark this LUT vs
> computation (see attached patch for comp. version). And the problem is
> that it's slightly slower, probably due to the /1000.

why do you divide at all ?
cant you do the computations with full precission ?
also instead of doing 2 rgb2yuv and then taking their difference you
can do the difference in rgb space and convert the rgb difference to
a yuv difference
its just aM - bM = (a-b)M

[...]

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