[FFmpeg-devel] [HOWTO] Building FFmpeg for iPhone

Reimar Döffinger Reimar.Doeffinger
Sat Oct 3 19:23:46 CEST 2009


On Sat, Oct 03, 2009 at 07:03:00PM +0200, Reimar D?ffinger wrote:
> On Fri, Oct 02, 2009 at 11:05:43PM +0100, M?ns Rullg?rd wrote:
> > "Ronald S. Bultje" <rsbultje at gmail.com> writes:
> > >> 4a. For iPhone 3GS or iPod Touch 3G 32GB/64GB, use this command:
> > >> 4b. For other iPhone or iPod Touch models, use this command:
> > >
> > > What if I want one that is cross-compatible with both?
> > 
> > Binaries for the old devices will work on the new ones.  However,
> > FFmpeg will be *much* faster if built for the 3GS since it supports
> > NEON.
> 
> Is there some way to do runtime detection of NEON?

Seems like ARM is one of those instructions sets that didn't consider it
necessary to include a (userspace-)instruction for this.
With the usual effect of making runtime detection a broken mess.
I hereby declare my very firm wish that anyone who designs an instruction
will in the future also try to make it practical to use also for those
who care about backwards compatibility.



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