[FFmpeg-devel] [PATCH] fix --enable-runtime-cpudetect --disable-amd3dnow compilation

[Michael Niedermayer]

On Tue, Sep 07, 2010 at 06:48:24AM -0400, Alex Converse wrote:
> On Sat, Sep 4, 2010 at 7:08 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> > On Fri, Sep 03, 2010 at 06:06:11PM -0400, Alexander Strange wrote:
> >> CC ? ? ?libswscale/swscale.o
> >> ...
> >> libswscale/swscale.c: In function ?ff_getSwsFunc?:
> >> libswscale/swscale.c:1268: warning: implicit declaration of function ?sws_init_swScale_3DNow?
> >> libswscale/swscale.c:1269: error: ?swScale_3DNow? undeclared (first use in this function)
> >> libswscale/swscale.c:1269: error: (Each undeclared identifier is reported only once
> >> libswscale/swscale.c:1269: error: for each function it appears in.)
> >>
> >> Alternatively, it could declare prototypes for sws_init_swScale_3DNow / swScale_3DNow even if they aren't being compiled.
> >> That would let us use "if (COMPILE_TEMPLATE_AMD3DNOW && flags & SWS_CPU_CAPS_3DNOW)" instead of #ifdefs. But it might make some of the other templating more complex.
> >>
> >
> > the code was designed for 2 cases
> > 1. runtime cpu detection (for distros) to support whatever cpu the user has
> > 2. compiletime detection (for an individual user) to support his cpu
> >
> 
> Is there substantial overhead in using runtime cpudetect (1) for an
> individual users CPU (2)? dsputil and av_fft don't support compiletime
> CPU detect on x86 and everyone seems ok with that.

I think that for video codecs that call things per 4x4 or 8x8 block the
overhead is big enough for alternatives to the current function ptr system
to be considered
for swscale that calls per line it probably doesnt matter much

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

No great genius has ever existed without some touch of madness. -- Aristotle
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