On Wed, Oct 08, 2014 at 09:46:56AM +0000, Nedeljko Babic wrote: > Hi again, > > >> but I do agree that it is more maintainable to have one float emulation > >> and I > >> am willing to integrate our emulation in softfloat. > >> > >> However, there is a difference in some conventions used (for example is it > >> more > >> important to represent exactly 0.5 or 1, order of fields in struct that > >> represents emulated float, etc.) and our aac implementation is tailored to > >> use > >> our float emulation. > > > >i dont understand what you mean by 0.5 vs 1 ? > >floats are base 2 so both 0.5 and 1 can be represented exactly > > > > I was a little unclear here, sorry. > > It is true that both 0.5 and 1 can be represented exactly. > > I was referring to a range of normalized mantissas. > > We are using [0.5 - 1) and softfloat uses different range. > We do not have 1 in our range. > > Please look at difference between av_normalize1_sf that is used in softfloat > version of mul and normalization used in our float_mul for example.
softfloat uses "if (a.mant + 0x40000000 < 0)" to normalize 0x40000000U + 0x40000000U is < 0 for int32 and thus not part of the range though -1 would be, is that a problem ? we could use a.mant + 0x40000000 <= 0 in that case the main difference i see to aac is that it shifts up if its too small while softfloat shift down when its too large both dont implement rounding correctly > > If we need to use range from softfloat, all calculations in aac fixed point > implementation that depend on it need to be changed, so I am in favor of using > our range (of course :)), especially since softfloat is not being used > anywhere > currently and changing the range of mantissas in it would not cause any > disturbance in ffmpeg. > > - Nedeljko > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel > -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Those who are best at talking, realize last or never when they are wrong.
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