[FFmpeg-cvslog] r28500 - trunk/libswscale/swscale-example.c

[Aurelien Jacobs]

Ivan Kalvachev wrote:

> On 2/9/09, Diego Biurrun <diego at biurrun.de> wrote:
> > On Mon, Feb 09, 2009 at 08:13:55PM +0000, M?ns Rullg?rd wrote:
> >> Diego Biurrun <diego at biurrun.de> writes:
> >>
> >> > On Mon, Feb 09, 2009 at 08:53:27PM +0100, Michael Niedermayer wrote:
> >> >> On Mon, Feb 09, 2009 at 07:04:19PM +0100, diego wrote:
> >> >> >
> >> >> > Log:
> >> >> > Add config.h #include for ARCH_X86 definition.
> >> >>
> >> >> config.h is not a public header there is no way how swscale-example
> >> >> could
> >> >> include it.
> >> >> Please keep in mind this is a example on how people should use swscale
> >> >> from
> >> >> their code, you wouldnt want them to include our config.h would you?
> >> >
> >> > Unfortunately this example program was broken in multiple ways.  I fixed
> >> > compilation so that at least 'make tests' can run, but yes, it still has
> >> > issues.  It contains
> >> >
> >> >   #if ARCH_X86
> >> >
> >> > which implicitly relies on config.h being available.
> >>
> >> Then that should be fixed, not more breakage added.
> >
> > Do you have bright suggestions?  Is there a way to avoid the
> >
> > #if ARCH_X86
> >     __asm__ volatile ("emms\n\t");
> > #endif
> 
> This instruction clears the fpu registers after they have been used by mmx.
> The real question is:
> Is this really necessary? Does swscale leave the fpu registers in mmx
> state to boost speed on K6?
> From quick look in the template it looks like - no.
> 
> I guess this is ancient workaround for bug fixed long time ago.

It seems to be so.
It indeed looks like swscale already does the appropriate emms, so
they could be removed from swscale-example.c.
Anyway, it don't seem reasonable to require calling apps to do an
emms after calling swscale. So in case this emms in swscale-example.c
is really required, I would consider this a bug in swscale.
So what about attached patch ?

Aurel
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