[FFmpeg-devel] pre discussion around Blackfin dct_quantize_bfin routine

Siarhei Siamashka siarhei.siamashka
Tue Jun 12 13:52:29 CEST 2007


On 6/12/07, Michael Niedermayer <michaelni at gmx.at> wrote:
> Hi
>
> On Tue, Jun 12, 2007 at 05:49:19AM -0400, Marc Hoffman wrote:
> > Does these allow me to ignore the DCT permutation?
>
> no it would still break if the user selected the other integer idct

Is it possible to add a configure option to be able to compile ffmpeg
only with IDCT that do not need permutation (and do not allow the user
to select other idct)? At least it would eliminate table lookups in
many places (replace table lookups with a macro which expands either
to table lookup or the value itself). The point is that ARM devices
are heavily CPU limited and ARMv5TE optimized IDCT does not use
permutation. Blackfin powered devices may be CPU limited too (Marc can
probably privide more information about blackfin performance). I'll
try to do some benchmarks on ARM and post some results later.

> >
> > yoda:~/ffmpeg-svn/libavcodec/bfin mmh$ svn diff dsputil_bfin.c
> > Index: dsputil_bfin.c
> > ===================================================================
> > --- dsputil_bfin.c      (revision 9231)
> > +++ dsputil_bfin.c      (working copy)
> > @@ -285,6 +285,7 @@
> >       c->put_no_rnd_pixels_tab[0][2] = bfin_put_pixels16_y2_nornd;
> >       c->put_no_rnd_pixels_tab[0][3] = ff_bfin_put_pixels16_xy2_nornd;
> > +    c->idct_permutation_type = FF_NO_IDCT_PERM;
> >       c->fdct               = ff_bfin_fdct;
> >       c->idct               = ff_bfin_idct;
> >       c->idct_add           = bfin_idct_add;
>
> [...]




More information about the ffmpeg-devel mailing list