On Fri, Nov 13, 2015 at 11:19:44PM +0100, Andreas Cadhalpun wrote: > On 13.11.2015 04:21, Michael Niedermayer wrote: > > On Thu, Nov 12, 2015 at 08:51:28PM +0100, Andreas Cadhalpun wrote: > >> On 11.11.2015 23:19, Michael Niedermayer wrote: > >>> On Wed, Nov 11, 2015 at 09:31:18PM +0100, Andreas Cadhalpun wrote: > >>>> I'm not sure, but it can happen, when q_mapped is very small, which can > >>>> be > >>>> caused by noise_facs becoming tiny in sbr_dequant. > >>>> That's kind of the opposite problem of 'envelope scalefactors > >>>> overflowing'. > >>> > >>> sbr_dequant() does not look like it can set noise_facs to 0 > >>> except by underflow of the exponent range > >> > >> That's exactly what happens. > >> > >>> that "has" to be invalid as this depends on the implementation > >> > >> So should sbr_dequant error out instead? > >> If so, what's the minimal value it should accept? > > > > I dont know the valid range, and i doubt the spec lists this > > so picking what causes a problem (0) would be the easy solution > > thats what i would suggest in absence of other suggestions > > Well, unfortunately just rejecting 0 in sbr_dequant is no solution, > because, as you noticed, that only happens via underflow.
a value that has underflowed should be 0, so underflow affecting anything implies 0 as result and so a check for 0 would cover all underflows I think i misunderstand somehow > One could check for exponents smaller than MIN_EXP, but since exponents must not be smaller than MIN_EXP. no *_sf function should set such an exponent. code directly writing exponents has to check for exp < MIN_EXP that could in principle be done by using a _sf function which allows such exponents on input and clears it up on output > the exponent can get smaller during the calculations in sbr_gain_calc, > that wouldn't necessarily avoid the division by 0. > > Additionally both sbr_dequant and sbr_gain_calc are void functions, > so can't easily return errors. iam not sure i understand your concern ? the resturn type is easy changeable or flag could be added to the context indicating an error or a simpler hack could be used to fix this in the releases with a more complete cleanup in master but maybe iam missing something why you consider this to be a bad solution ? [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Freedom in capitalist society always remains about the same as it was in ancient Greek republics: Freedom for slave owners. -- Vladimir Lenin
signature.asc
Description: Digital signature
_______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
