[FFmpeg-cvslog] r23095 - in trunk/libavcodec: Makefile allcodecs.c mpegaudio.h mpegaudio_tablegen.h mpegaudiodec.c mpegaudiodec_float.c

Måns Rullgård mans
Thu May 13 17:40:27 CEST 2010

Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:

> On Wed, May 12, 2010 at 09:27:43PM +0100, M?ns Rullg?rd wrote:
>> Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
>> > Btw. going back to the original commit, what are your thoughts about an
>> > "automp3" codec that automatically selects whichever codec should be faster
>> > (could be compile-time for now)?
>> Compiling both doesn't really make much sense IMO.  I would suggest
>> making float-only the default and providing configure option for
>> switching to integer.  This could be done automatically for CPUs known
>> to lack an FPU (or have a slow one).
> Well, compiling both makes testing and comparison benchmarks easier

Easier testing and comparing is not reason enough to bloat the build
two copies of essentially the same code for everybody.

> and allows runtime-switching if we want to support devices where
> which one is faster might depend on which CPU extensions are
> available.

This is a valid point.  However, using different codec names is not a
good way to achieve this.  We should have one AVCodec selecting the
best implementation internally.

> I don't mind much either way, it just seemed like the more flexible
> solution, particularly since I don't know the speed difference
> between both.

The float version is 4x slower on Cortex-A8 not counting post-conversion.
Float and int are about the same speed on Intel i7.

M?ns Rullg?rd
mans at mansr.com

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