On Thu, Oct 09, 2014 at 12:02:26PM +0000, Nedeljko Babic wrote: > > > >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 > > The main problem is exactly in difference of handling too large and too small > values. > If we must use code from softfloat as is, it will demand a lot of changes in > aac implementation. > > And there are other problems with softfloat: > - Normalization done for av_add_sf (and av_sub_sf), av_normalize1_sf, is not > ok. > It's the same normalization used in multiplication and it will not handle > normalization of mantissa and exponent correctly after addition. > On the other hand, av_normalize_sf can not be used as is since it would > have > infinite loop for a.mant == 0. > - I guess we would have a problem with av_div_sf since it needs for b to be > normalized and it doesn't handle division by zero (also I am not sure about > precision). > > We need functions that are implemented just in our emulation (like sincos > for example) and not in softfloat and I guess (but am not sure atm) that some > of them would also need to be changed if we need to use assumptions from > softfloat. > > > > >both dont implement rounding correctly > > We use this rounding for simplicity. On our test cases we do not have > significant problems with it (overall max 3 bit difference with floating > point code), although we can change it if it proves to be necessary. >
> My question still remains: should we use our float emulation and just > integrate it in softfloat adjusting it where necessary, or should we use > softfloat and adjust our aac implementation? its ok to integrate your code in sf / change sf as long as it doesnt remove optimizations or make future optimizations hard thanks [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Avoid a single point of failure, be that a person or equipment.
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