[Ffmpeg-devel] Problem building ffmpeg on G3 PPC without altivec unit

[Aurelien Jacobs]

On Mon, 27 Feb 2006 14:44:50 +0100
Diego Biurrun <diego at biurrun.de> wrote:

> On Mon, Feb 27, 2006 at 01:34:59AM +0100, Aurelien Jacobs wrote:
> > On Sun, 26 Feb 2006 22:41:34 +0100
> > Diego Biurrun <diego at biurrun.de> wrote:
> > > 
> > > Just read through configure, look at lines 866-888 and try to find out
> > > why it enables AltiVec.  Maybe add
> > 
> > I don't think that autodetection fails. It only check if cpu is a
> > powerpc, and if gcc is able to build altivec code. Both should be
> > true even when running on a G3.
> > So I guess that the altivec code as always been built on G3, and the
> > current problem is not specific to G3 build.
> 
> Yes, the current code is quite bogus.  We should simply check if the
> machine supports AltiVec by making it run some sort of AltiVec
> instruction.

Hum... I might be wrong, but IIRC, libavcodec contains a kind of
runtime CPU detection, so it should really be safe to compile the
altivec code on a G3. Altivec simply wouldn't be used at runtime.
And the produced binary will target G3 and G4 at the same time,
which is great and desirable.
I tend to think that it's the altivec code itself which need some
fixing (but again, I know nothing about altivec).

Aurel