[FFmpeg-devel] [libav-devel] [PATCH] aacpsy: avoid norm_fac becoming NaN

Andreas Cadhalpun andreas.cadhalpun at googlemail.com
Tue Apr 21 18:50:20 CEST 2015


On 21.04.2015 02:20, Claudio Freire wrote:
> On Mon, Apr 20, 2015 at 9:13 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> On Mon, Apr 20, 2015 at 09:07:14PM -0300, Claudio Freire wrote:
>>> On Mon, Apr 20, 2015 at 8:59 PM, Claudio Freire <klaussfreire at gmail.com> wrote:
>>>> On Mon, Apr 20, 2015 at 8:32 PM, Andreas Cadhalpun
>>>> <andreas.cadhalpun at googlemail.com> wrote:
>>>>>>>> The long version:
>>>>>>>>
>>>>>>>> ath should approximate the shape of the absolute hearing threshold, so
>>>>>>>> yes, it's best if it really uses the minimum, since that will prevent
>>>>>>>> clipping of the ath curve and result in a more accurate threshold
>>>>>>>> computation.
>>>>>>>
>>>>>>> So you agree with my patch fixing minath?
>>>>>>> Or would you prefer a version with:
>>>>>>>     minath = ath(3410 - 0.733 * ATH_ADD, ATH_ADD)
>>>>>>
>>>>>> Well, that's not really closer to the minimum (a few tests with gnuplot say).
>>>>>
>>>>> Are you sure your plots were done correctly?
>>>>> Because I'm quite sure this is the correct first order approximation
>>>>> of the minimum.
>>>>>
>>>>> For ATH_ADD = 4 this gives 3407.068, which is quite close to Michael's value
>>>>> (3407.080774800152).
>>>>
>>>> I checked the formula several times, but still, I could have made a mistake.
>>>
>>>
>>> This is what I did if you want to check it out (maybe you spot the mistake)
>>>
>>> gnuplot> ath(f,a) = _ath(f/1000.0, a)
>>> gnuplot> _ath(f,a) = 3.64 * f**(-0.8) - 6.8 * exp(-0.6 * (f-3.4) *
>>> (f-3.4)) + 6.0 * exp(-0.15 * (f-8.7) * (f-8.7)) + (0.6 + 0.04 * a) *
>>> 0.001 * f * f * f
>>           ^^^^^^^^^^
>> missing * f
> 
> Much better now :)
> 
> So yes. I'd say it's a good change.

OK, patch attached.

Best regards,
Andreas

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