On Sat, Dec 26, 2015 at 06:37:31PM -0800, Ganesh Ajjanagadde wrote: > On Sat, Dec 26, 2015 at 6:19 PM, Michael Niedermayer > <mich...@niedermayer.cc> wrote: > > On Sat, Dec 26, 2015 at 05:23:55PM -0800, Ganesh Ajjanagadde wrote: > >> On Sat, Dec 26, 2015 at 4:20 PM, Ganesh Ajjanagadde <gajja...@mit.edu> > >> wrote: > >> > On Sat, Dec 26, 2015 at 4:08 PM, James Almer <jamr...@gmail.com> wrote: > >> >> On 12/23/2015 3:47 PM, Ganesh Ajjanagadde wrote: > >> >>> exp10, introduced recently, is superior for the purpose. > >> >>> > >> >>> Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com> > >> >>> --- > >> >>> libavcodec/on2avc.c | 5 +++-- > >> >>> 1 file changed, 3 insertions(+), 2 deletions(-) > >> >>> > >> >>> diff --git a/libavcodec/on2avc.c b/libavcodec/on2avc.c > >> >>> index 04c8e41..0409b3e 100644 > >> >>> --- a/libavcodec/on2avc.c > >> >>> +++ b/libavcodec/on2avc.c > >> >>> @@ -22,6 +22,7 @@ > >> >>> > >> >>> #include "libavutil/channel_layout.h" > >> >>> #include "libavutil/float_dsp.h" > >> >>> +#include "libavutil/libm.h" > >> >>> #include "avcodec.h" > >> >>> #include "bytestream.h" > >> >>> #include "fft.h" > >> >>> @@ -934,9 +935,9 @@ static av_cold int > >> >>> on2avc_decode_init(AVCodecContext *avctx) > >> >>> "Stereo mode support is not good, patch is welcome\n"); > >> >>> > >> >>> for (i = 0; i < 20; i++) > >> >>> - c->scale_tab[i] = ceil(pow(10.0, i * 0.1) * 16) / 32; > >> >>> + c->scale_tab[i] = ceil(exp10(i * 0.1) * 16) / 32; > >> >>> for (; i < 128; i++) > >> >>> - c->scale_tab[i] = ceil(pow(10.0, i * 0.1) * 0.5); > >> >>> + c->scale_tab[i] = ceil(exp10(i * 0.1) * 0.5); > >> >>> > >> >>> if (avctx->sample_rate < 32000 || avctx->channels == 1) > >> >>> memcpy(c->long_win, ff_on2avc_window_long_24000, > >> >> > >> >> This apparently broke ICC > >> >> > >> >> http://fate.ffmpeg.org/report.cgi?time=20151226215846&slot=x86_64-linux-gnu-icc-2011.4.191 > >> >> http://fate.ffmpeg.org/report.cgi?time=20151226235348&slot=x86_64-linux-gnu-icc-2011_sp1.13.367 > >> >> http://fate.ffmpeg.org/report.cgi?time=20151226203729&slot=x86_64-archlinux-icc-2013 > >> > > >> > Thanks for the report. A couple of questions: > >> > 1. Is there an easy way to acquire icc so that I can reproduce? > >> > GCC/Clang are perfectly fine with it. > >> > 2. Do you know what the ICC platforms use for exp2? > >> > > >> > In the absence of remarks and my own inability to fix this, I will > >> > revert tonight. > >> > BTW, please let me know the general policy for this kind of breakage: > >> > i.e, how quickly do such regressions need to be fixed. > >> > >> Different fix pushed that also speeds up things. > > > > but speed doesnt really matter for this code while maintainability > > IMHO matters more > > Definitely, I did not do it for speed actually, speed was a side > effect - this is also why the first line of the message does not > mention speed effect. I did this because it improved accuracy on > clang/gcc (as also mentioned in the commit message). In any case, I > was looking for a quick fix since I assumed ICC regression is serious, > and wanted to do so in a way that improves numerical accuracy. > > > > > either way, the code is numerically unstable as some of the arguments > > to ceil() fall exactly on the mid point between different outputs > > this is still so after the change and would be in case of a revert too > > Yes. I think something needs to be done to FATE to fix this, but I have no > idea.
patch posted [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB It is dangerous to be right in matters on which the established authorities are wrong. -- Voltaire
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