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. One could check for exponents smaller than MIN_EXP, but since 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. So the only simple way to avoid the division by zero is adapting sbr_gain_calc to handle this case gracefully. Best regards, Andreas _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
