On Tue, Mar 15, 2016 at 11:37:30PM +0000, Derek Buitenhuis wrote: > On 3/15/2016 10:26 PM, Ganesh Ajjanagadde wrote: > > If one wants good Gaussian samples, then yes, I need a 64 bit rng. > > Please also note that I can use av_lfg_get, it does not result in > > slowdown, since speed benefits here come from the ziggurat algo. > > Concretely, it is 82 cycles vs 81 cycles; too little to clearly > > distinguish. I was just not too happy with av_lfg_get << 32 | > > av_lfg_get as it resulted in some bad values in the Anderson Darling > > tests. > > "If one wants good Gaussian samples" doesn't explain at all how it is > relevant to a set of multimedia libraries like FFmpeg. Why do we want > those? That is the relevant information which should be mentioned > in the commit message. > > > I don't know if good quality Gaussian samples are needed, I welcome > > comments from AAC coding people. > > The impression I have from them (atomnuker in previous email) is that > it is not that important, but I'm not an 'AAC' person. > > > In particular, I have already mentioned in the patch notes that this > > yields ~ 1-2% in aac encoding speed. If you do a profile run, > > av_bmg_get does show up with nearly 2-3% time spent in it overall. > > There is no mention of AAC in the patch notes for this patch, actually. > > I'll defer to Rostislav (atomnuker) and other on whether adding yet another > public API that Is Not Multimedia Related is worth 1-2% yield.
IMO 1-2% speedup is significant i dont think a new API is needed, there already is a Gaussian RNG API (av_bmg_get()) that can be deprecated after a new API is added or replaced or whatever [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Let us carefully observe those good qualities wherein our enemies excel us and endeavor to excel them, by avoiding what is faulty, and imitating what is excellent in them. -- Plutarch
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