[MPlayer-dev-eng] RE: MPlayer-dev-eng Digest, Vol 43, Issue 72

[Bas Hulsken]

>Date: Sat, 15 Jul 2006 17:53:05 +0200
>From: "Emanuele Giaquinta" <emanuele.giaquinta at gmail.com>
>On 7/15/06, Romain Dolbeau <romain at dolbeau.org> wrote:
>
> > There's an assumption not mentioned  in the code : that both parameters
> > to the function a52_resample_STEREO_to_2_altivec are akligned on a
> > 16-bytes boundary. You might want to check that dynamically, I'm not
> > sure if it's really guaranteed or if it happens to "just work".
>
>They are if the system has a working memalign, which should be the
>case on glibc.
>
>--
>Emanuele Giaquinta

ok, this memalign stuff might be the problem, I'll test it as soon as I can 
find some time (might take a few days). Anyway, parse.c from liba52 
dynamically tests if it could get a memaligned malloc, if using SSE with 
these lines (at lines 77 to 80):

if(((int)state->samples%16) && (mm_accel&MM_ACCEL_X86_SSE)){
    mm_accel &=~MM_ACCEL_X86_SSE;
    fprintf(stderr, "liba52: unable to get 16 byte aligned memory disabling 
usage of SSE instructions\n");
}

I guess we should at least add the same for PPCs altivec:

if(((int)state->samples%16) && (mm_accel&MM_ACCEL_PPC_ALTIVEC)){
    mm_accel &=~MM_ACCEL_PPC_ALTIVEC;
    fprintf(stderr, "liba52: unable to get 16 byte aligned memory disabling 
usage of ALTIVEC instructions\n");
}

btw. mplayer configure detects a working memalign for the mini on linux, but 
I guess memalign can always go wrong.. do you agree Emanuele?

Romain, Emanuele, I see in another mail ( do not define MEMALIGN_HACK on 
OSX) some problems with memalign on OSX? Is it possible that the altivec 
resampler works on OSX, but not on linux because of some side effect of 
this? Just a thought....

thanks& best regards,
Bas Hulsken