[Ffmpeg-devel] [PATCH] fix mpegaudiodec on ARM and benchmark

[Måns Rullgård]

Siarhei Siamashka <siarhei.siamashka at gmail.com> writes:

> On Thursday 24 August 2006 01:08, Aurelien Jacobs wrote:
>
> ...
>
>> > and another idea, try to set -mcpu -march -mtune correctly for the cpu
>>
>> When setting -march=armv4 or armv4t or armv5 or armv5t it don't even
>> compile:
>>
>> arm-linux-gnu-gcc -DHAVE_AV_CONFIG_H -I.. -I../libavutil
>> -Wdeclaration-after-statement -march=armv5t -D_REENTRANT -I/usr/include
>> -I/usr/src/DVB/ost/include -I/usr/include/dxr2 -I/usr/local/include/cdda
>> -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_ISOC9X_SOURCE    -c -o
>> armv4l/dsputil_arm_s.o armv4l/dsputil_arm_s.S armv4l/dsputil_arm_s.S:
>> Assembler messages:
>> armv4l/dsputil_arm_s.S:77: Error: selected processor does not support `pld
>> [r1]' armv4l/dsputil_arm_s.S:88: Error: selected processor does not support
>> `pld [r1]' [...]
>
> Hmm, that's interesting. The use of 'pld' instruction means that ffmpeg
> already  unconditionally requires armv5te instruction set support.
>
> And it can possibly mean that there are no armv4 users left already
> as nobody complained. Is it ok to assume that armv5te code can be
> added without any special configuration option necessary?
>
> Also it is not quite related to ffmpeg, but mplayer can't be
> configured to use HAVE_IWMMXT, so it does not use full optimizations
> on xscale cpu such as yours, maybe it is a good idea to fix it?
>
>> Setting -march=armv5te (which is exactly what my Xscale is) is quite
>> slower, I don't understand why:
>> BENCHMARKs: VC:   0.000s VO:   0.000s A: 206.553s Sys:   0.438s =  206.991s
>> BENCHMARK%: VC:  0.0000% VO:  0.0000% A: 99.7882% Sys:  0.2118% = 100.0000%
>
> ...
>
> If I get it right, armv5te is instruction set and xscale is cpu architecture
> which supports this instruction set.
>
> For example my cpu also supports armv5te and its description is here (along
> with the information about instruction timings):
> http://www.arm.com/pdfs/DVI0035B_926_PO.pdf

I have one of those too (in a Nokia 770).  Are you planning to do some
optimizations?

-- 
M?ns Rullg?rd
mru at inprovide.com