[FFmpeg-devel] [PATCH][RFC] Lagarith Decoder.

[Måns Rullgård]

Michael Niedermayer <michaelni at gmx.at> writes:

> On Wed, Aug 12, 2009 at 08:25:41PM +0100, M?ns Rullg?rd wrote:
>> Michael Niedermayer <michaelni at gmx.at> writes:
>> 
>> > On Wed, Aug 12, 2009 at 07:47:45PM +0100, M?ns Rullg?rd wrote:
>> >> Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
>> >> 
>> >> > On Wed, Aug 12, 2009 at 06:59:42PM +0100, M?ns Rullg?rd wrote:
>> >> >> Michael Niedermayer <michaelni at gmx.at> writes:
>> >> >> 
>> >> >> > On Wed, Aug 12, 2009 at 06:31:36PM +0200, Reimar D?ffinger wrote:
>> >> >> >> On Wed, Aug 12, 2009 at 05:10:36PM +0100, M?ns Rullg?rd wrote:
>> >> >> >> > Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
>> >> >> >> > 
>> >> >> >> > > On Wed, Aug 12, 2009 at 04:12:25PM +0100, M?ns Rullg?rd wrote:
>> >> >> >> > >> Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
>> >> >> >> > >> 
>> >> >> >> > >> > Well, you still have to teach the compiler at least to
>> >> >> >> > >> > use clz for av_log2, I think you haven't yet ;-)
>> >> >> >> > >> 
>> >> >> >> > >> I can't because it's in common.h, which is installed.  We really
>> >> >> >> > >> should find a way to fix that.
>> >> >> >> > >
>> >> >> >> > > Just put the optimizations under HAVE_AV_CONFIG_H like
>> >> >> >> > > everything else in there that is messy?
>> >> >> >> > 
>> >> >> >> > And keep adding to the mess?  That's not the way to do things.
>> >> >> >> 
>> >> >> >> Then how about adding a new internal header with that function and
>> >> >> >> putting the version in the installed header under
>> >> >> >> #ifndef HAVE_AV_CONFIG_H
>> >> >> >> i.e. just to keep API compatibility?
>> >> >> >> Possibly even deprecating that version?
>> >> >> >> Would that be clean enough?
>> >> >> >
>> >> >> > It would be nice if applications using libav* could also use
>> >> >> > the optimized version
>> >> >> 
>> >> >> I can't see a way to make that happen.
>> >> >
>> >> > Actually... You could install a pseudo-config.h that contains the
>> >> > necessary CPU settings...
>> >> > There is not really a reason we can't install generated headers...
>> >> > Or am I missing something?
>> >> 
>> >> Doing so would require all FFmpeg-using apps to use the same compiler
>> >> and flags as were used when configuring FFmpeg.  This is not
>> >> reasonable.
>> >
>> > a few #ifdefs in the header would solve that,
>> > same compiler -> all optims
>> > other compiler -> fallback to plain C
>> 
>> That is not very nice.  Besides, it is impossible to implement.
>
> could you elaborate on why it is impossible?

It is impossible to determine with #ifdefs what compiler flags are
being used.

-- 
M?ns Rullg?rd
mans at mansr.com