[FFmpeg-devel] [PATCH V2] lavfi/vf_nlmeans: Improve the performance for nlmeans

[Clément Bœsch]

On Fri, Feb 01, 2019 at 04:57:37PM +0800, mypopy at gmail.com wrote:
[...]
> > > -#define WEIGHT_LUT_NBITS 9
> > > -#define WEIGHT_LUT_SIZE  (1<<WEIGHT_LUT_NBITS)
> > > +#define WEIGHT_LUT_SIZE  (800000) // need to >  300 * 300 * log(255)
> >
> > So the LUT is now 3.2MB?
> >
> > Why 300? 300*300*log(255) is closer to 500 000 than 800 000
> I just seleted a value > 300*300*log(255) (500 000 more precise) for
> this case at liberty in fact , the other option is use a dynamic
> allocation memory for weight_lut table size base on the
> max_meaningful_diff :), but maybe seems pretty obvious, I think 3M is
> not a big burden for nlmeans

It's probably fine yes, I'm just confused at the comment: why does it
*needs* to be > 300 * 300 * log(255)?

-- 
Clément B.
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