[FFmpeg-devel] [PATCH 00/15] replace pow(10, x) by exp10(x) across FFmpeg

[Michael Niedermayer]

On Wed, Dec 23, 2015 at 10:47:20AM -0800, Ganesh Ajjanagadde wrote:
> exp10(x) is superior to pow(10,x).
> Note that in some cases, this may affect integers derived from pow calls. When
> spotted, this remark has been added to the relevant commit message.
> 
> Note that if such a thing is troublesome, one can do one of two things:
> 1. leave the pow(10,x) call as is in such places.
> 2. replace the lavu/libm fallback by the correct pow(10,x) as opposed to the
> sloppy exp2(M_LOG2_10 * x).
> 
> Patches tested with FATE on x86-64, GNU/Linux.

some of these fail on arm

i suspect thats because exp10 is only available with GNU_SOURCE
and we dont define that nor do we want to define that
-DGNU_SOURCE often leaks in from pkg_config files though
my arm setup doesnt include many external libs so GNU_SOURCE doesnt
get enabled

i didnt think deeply abot it but would it make sense to always enable
the fallback even if exp10 is available? that is assuming the fallback
is faster everywhere



ffmpeg/libavfilter/af_volume.c: In function ‘filter_frame’:
ffmpeg/libavfilter/af_volume.c:379:13: error: implicit declaration of function ‘exp10’
ffmpeg/libavfilter/af_compand.c: In function ‘config_output’:
ffmpeg/libavfilter/af_compand.c:509:9: error: implicit declaration of function ‘exp10’
CC      libavcodec/cngdec.o
make: *** [libavfilter/af_compand.o] Error 1
make: *** [libavfilter/af_volume.o] Error 1
CC      libavcodec/dcaenc.o
ffmpeg/libavfilter/f_ebur128.c: In function ‘get_histogram’:
ffmpeg/libavfilter/f_ebur128.c:451:9: error: implicit declaration of function ‘exp10’
make: *** [libavfilter/f_ebur128.o] Error 1
CC      libavcodec/imc.o
ffmpeg/libavfilter/vsrc_testsrc.c: In function ‘test_fill_picture’:
ffmpeg/libavfilter/vsrc_testsrc.c:618:23: error: implicit declaration of function ‘exp10’
make: *** [libavfilter/vsrc_testsrc.o] Error 1
CC      libavcodec/on2avc.o
CC      libavcodec/opus.o
ffmpeg/libavcodec/acelp_pitch_delay.c: In function ‘ff_amr_set_fixed_gain’:
ffmpeg/libavcodec/acelp_pitch_delay.c:135:9: error: implicit declaration of function ‘exp10f’
CC      libavcodec/wmadec.o
make: CC        libavcodec/wmaenc.o
*** [libavcodec/acelp_pitch_delay.o] Error 1
CC      libavcodec/wmaprodec.o
CC      libavutil/eval.o
ffmpeg/libavcodec/aacpsy.c: In function ‘psy_3gpp_init’:
ffmpeg/libavcodec/aacpsy.c:352:13: error: implicit declaration of function ‘exp10’
make: *** [libavcodec/aacpsy.o] Error 1
ffmpeg/libavcodec/cngdec.c: In function ‘cng_decode_frame’:
ffmpeg/libavcodec/cngdec.c:116:9: error: implicit declaration of function ‘exp10’
make: *** [libavcodec/cngdec.o] Error 1
ffmpeg/libavcodec/dcaenc.c: In function ‘encode_init’:
ffmpeg/libavcodec/dcaenc.c:183:13: error: implicit declaration of function ‘exp10’
make: *** [libavcodec/dcaenc.o] Error 1
ffmpeg/libavcodec/opus.c: In function ‘ff_opus_parse_extradata’:
ffmpeg/libavcodec/opus.c:337:9: error: implicit declaration of function ‘exp10’
make: *** [libavcodec/opus.o] Error 1
ffmpeg/libavcodec/imc.c: In function ‘iac_generate_tabs’:
ffmpeg/libavcodec/imc.c:140:13: error: implicit declaration of function ‘exp10’
make: *** [libavcodec/imc.o] Error 1
ffmpeg/libavcodec/wmadec.c: In function ‘wma_decode_block’:
ffmpeg/libavcodec/wmadec.c:630:13: error: implicit declaration of function ‘exp10’
make: *** [libavcodec/wmadec.o] Error 1
ffmpeg/libavcodec/on2avc.c: In function ‘on2avc_decode_init’:
ffmpeg/libavcodec/on2avc.c:938:9: error: implicit declaration of function ‘exp10’
make: *** [libavcodec/on2avc.o] Error 1
ffmpeg/libavcodec/wmaenc.c: In function ‘init_exp’:
ffmpeg/libavcodec/wmaenc.c:136:9: error: implicit declaration of function ‘exp10’
make: *** [libavcodec/wmaenc.o] Error 1
ffmpeg/libavutil/eval.c: In function ‘av_strtod’:
ffmpeg/libavutil/eval.c:109:13: error: implicit declaration of function ‘exp10’
make: *** [libavutil/eval.o] Error 1
ffmpeg/libavcodec/wmaprodec.c: In function ‘decode_subframe’:
ffmpeg/libavcodec/wmaprodec.c:1354:17: error: implicit declaration of function ‘exp10’
make: *** [libavcodec/wmaprodec.o] Error 1
make: Target `all' not remade because of errors.



[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

He who knows, does not speak. He who speaks, does not know. -- Lao Tsu
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