[vlc-devel] commit: contrib: ffmpeg optimizations for N900: ( Rémi Denis-Courmont )

[Måns Rullgård]

git at videolan.org (git version control) writes:

> vlc | branch: master | Rémi Denis-Courmont <remi at remlab.net> | Sat Aug  8 22:05:23 2009 +0300| [f9dc97504787faeec490918c6e30ae7f7a5a93b1] | committer: Rémi Denis-Courmont 
>
> contrib: ffmpeg optimizations for N900:
>
> * assume Cortex-A8 ARM core,
>  * enable NEON instructions,
>  * disable run-time CPU detection.
>
>> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=f9dc97504787faeec490918c6e30ae7f7a5a93b1
> ---
>
>  extras/contrib/src/Makefile |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/extras/contrib/src/Makefile b/extras/contrib/src/Makefile
> index edbe95c..606a876 100644
> --- a/extras/contrib/src/Makefile
> +++ b/extras/contrib/src/Makefile
> @@ -163,6 +163,9 @@ endif
>
>  ifdef HAVE_LINUX
>  ifdef HAVE_MAEMO
> +ifneq ($(filter -m%=cortex-a8, $(EXTRA_CFLAGS)),)
> +FFMPEGCONF += --disable-runtime-cpudetect --enable-neon --cpu=cortex-a8
> +endif

This won't work the way you think.  You need to somehow pass
-mfpu=neon to gcc, and NEON will be automatically enabled.  Without
-mfpu=neon, NEON will be disabled regardless of the configure command
line, simply because without this flag, gcc will not permit any NEON
instructions.

-- 
Måns Rullgård
mans at mansr.com