[FFmpeg-devel] [PATCH] configure: enable runtime cpu detect by default.
michaelni at gmx.at
Mon Sep 24 13:42:51 CEST 2012
On Sun, Sep 23, 2012 at 03:49:28PM +0200, Michael Niedermayer wrote:
> On Sun, Sep 23, 2012 at 10:32:33AM +0800, Xidorn Quan wrote:
> > On Sun, Sep 23, 2012 at 9:57 AM, Michael Niedermayer <michaelni at gmx.at>wrote:
> > > On Fri, Sep 21, 2012 at 06:15:39PM +0200, Michael Niedermayer wrote:
> > > > with the exception of libpostproc runtime_cpudetect = no is not
> > > > supported thus having no as default really is quite odd, it results in
> > > > a libpostproc where HAVE_MMX* have very different meaning from the
> > > > rest of ffmpeg and it breaks any x86 cpu that doesnt support mmx2
> > > > because mmx2 is hardcoded as a result
> > > >
> > > > Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
> > >
> > > if there are no objections i will apply this tomorrow, it fixes
> > > libpostproc on pre MMX2 cpus
> > >
> > Most people should prefer to compile for their own cpu which is
> > hardly changed. Only those who distribute binary packages would like
> > to enable runtime cpu detection.
> no strong disagreement here in principle but
> > So I think it is better to disable
> > it by default, and notice the distributors to enable it themselves.
> The problem is currently ffmpeg does not support "no cpu detection
> at runtime", only libpostproc supports this mode
> so when you disable runtime detect (as its default now) it really
> disables it just for 2% of the code, 98% still does runtime_cpudetect
> The second problem is that the build system has no support to detect
> the cpu features of your cpu at all so when runtime_cpudetect is
> disabled it will not compile libpostproc with a feature set matching
> your cpu but it will compile with a random feature set. And this
> breaks on pre MMX2 cpus as described previously.
> or to say it differently a ./configure && make will not create a
> working libpostproc on pre MMX2 cpus, this patch fixes this
> Ill apply it later today or tomorrow unless i hear objections
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Opposition brings concord. Out of discord comes the fairest harmony.
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