>===== Original Message From [EMAIL PROTECTED] =====
>Menno wrote:
>> While implementing M/S threshold calculations for FAAC, I noticed some
>> things that could be improved in GPSYCHO.
>>
>> The formula for the BMLD protection ratios you reverse engineered should
>> look like this:
>> mld[b] = pow(10, -3*(0.5+0.5*(M_PI*(min(bval[b], 15.5)/15.5))));
>> I took this from the 14496-3 ISO document.
>> If you want to see what the rest of the calculations should look like, you
>> should take a look at psy_step11andahalf() in psych.c from FAAC 0.55beta.
>> Also the paper advises to use the more tonal tonality values from the left
>> and right channels for the mid and side channels. And the minimum of
>> unpredictability from the left and right channels for both the mid and side
>> channels.
>> I haven't tried this in LAME myself, but in FAAC it works very good.
>>
>> Bye, Menno
>
>Hi Menno,
>I just compared your mld with the one implemented in Lame, and they
>are totaly different, even in the tendency.
>With your mld = -3*(0.5+0.5*(M_PI*(min(bval[b], 15.5)/15.5)))
>and Lames mld = 1.25*(1-cos(PI*b/SBPSY_s))-2.5
>the one in Lame increases monoton, yours falls monoton.
>Here are the mlds for short blocks:
>
> Lame mld your mld difference
> -2.5 -1.5 -1
> -2.45741 -2.02384 -0.433572
> -2.33253 -2.54737 0.214835
> -2.13388 -3.03745 0.903571
> -1.875 -3.45245 1.57745
> -1.57352 -3.81333 2.2398
> -1.25 -4.14806 2.89806
> -0.926476 -4.43749 3.51101
> -0.625 -4.69682 4.07182
> -0.366117 -4.93336 4.56724
> -0.167468 -5.15104 4.98357
> -0.0425927 -5.33832 5.29572
>
>So, what is going on here?
>
>And where can I find the sources for FAAC 0.55beta? I only found
>the sources for FAAC 0.42.
>
>Robert
>
>--
>MP3 ENCODER mailing list ( http://geek.rcc.se/mp3encoder/ )
Hi,
That's right. therefore in FAAC you will see this:
if ((nb[0][b] <= 1.58*nb[1][b])||(nb[1][b] <= 1.58*nb[0][b]))
and in LAME:
if ((ratio[0][b] >= 1.58*ratio[1][b])||(ratio[1][b] >= 1.58*ratio[0][b]))
Or the other way around, I don't have access to my source code where I am now.
Also I think that LAME is doing these calculations with the final ratios,
while I in FAAC use the nb values (can't remember how they were called in
LAME, sorry).
The beta source code is available on the developers page, I hope you can find
them, it will make this a lot clearer.
Bye, Menno
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