On Sun, Mar 13, 2016 at 06:14:18PM +0100, Reimar Döffinger wrote: > On Sun, Mar 13, 2016 at 01:12:57PM -0400, Ganesh Ajjanagadde wrote: > > On Sun, Mar 13, 2016 at 12:49 PM, Reimar Döffinger > > <reimar.doeffin...@gmx.de> wrote: > > > On Sun, Mar 13, 2016 at 12:24:25PM -0400, Ganesh Ajjanagadde wrote: > > >> On Sat, Mar 12, 2016 at 1:24 PM, Reimar Döffinger > > >> <reimar.doeffin...@gmx.de> wrote: > > >> > for (i = 0; i < 1<<13; i++) > > >> > - cbrt_tab[i] = CBRT(cbrt_tab_dbl[i]); > > >> > + AAC_RENAME(ff_cbrt_tab)[i] = CBRT(cbrt_tab_dbl[i]); > > >> > } > > >> > } > > >> > > >> Note that cbrt_tab_dbl is really intended to be shared by both the > > >> fixed/floating table inits. This was another thing my patch achieved: > > >> only doing the more expensive double table init once across > > >> float/fixed, and then doing the cheap conversion to uint32_t via > > >> av_float2int or lrint(x*8192). Please change; it could go into a > > >> separate patch if you prefer. > > > > > > IMHO you really need to argue why that would be desirable. > > > The only case I can see this as useful is if someone > > > runs at the same time fixed-point AAC decode and AAC encode, > > > where it saves a bit of startup time. > > > In all other cases you waste time and memory initializing > > > a table that will never be used. > > > > I don't understand the waste; the double init anyway needs to be done, > > all tables are derived from it. This dates to an approach I did in > > commit: 07a11ebcab9b31e9fc784029e5d24e6fbf486ff3. > > The waste is in writing to the table that will never be used. > As long as it is left as 0, it will not use memory, as soon > as you touch it it uses up memory. > But see my patch, if people think it's better it can be added.
And looking at that commit, I actually realize now that the cbrt_tab_dbl will also permanently waste 64 kB of memory despite never being used again. Using malloc/free for it would potentially be better (though in general I have some doubts about the wisdom of optimizing for initialization time at the detriment of runtime performance or memory usage). _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
