[WM]: Re: Asking help about Psychoacoustic Model.

["Krishnakumar S." <krishku@erdcitvm.org>]

Hi,

The equation that you are referring to is

LTg(i)=3D10log10[10^(LTq(i)/10))+sumj(10^LTtm(z(j),z(i))/10)+sumj(10^LTnm=
(z(j)
,z(i))/10)]

(where 'a^b' is read as 'a raised to the power b').

I am not sure wether you missed the two summations or it got deleted in =
the formatting or soome thing of that sort. There is
nothing wrong with the equation. What it does is,to sum the =
contributions of the threshold in quite, contributions of tonal
maskers and that of the non-tonal maskers. Since all the masking =
thresholds are expressed in dB, before summing one has to convert
it to linear quantities. That is why the 10^((LT)/10) operations are =
used. And the outer 10log10[] converts the result back into a
dB value.

Hope that answers your question.

KK

----- Original Message -----
From: "Benrong" <brchen@ee.cuhk.edu.hk>
To: <watermarking@watermarkingworld.org>
Sent: Tuesday, March 25, 2003 9:52 AM
Subject: [WM]: Asking help about Psychoacoustic Model.


> Dear all,
>
> In the MPEG standard 11172-3, Coding of Moving Pictures and Associated
Audio for Digital Storage Media at up to about 1.5 MBIT/S
> Part 3, Audio.
>
> ANNEX D (informative)
> Psychoacoustic Model I,
>
> While in the Step 7, Calculation of the global masking threshold LTg.
>
> There is a equation like this:
>
> LTg(i) =3D 10 log (10 LTq(i) / 10 ++);
>
> It is said to find the global masking threshold by summing the powers
corresponding to the individual masking threshold and threshold in =
quiet.
>
> But I am confused  about this equation. Is there anything wrong? Or=20
> can anybody help me to express this problem.
>
> Thanks in advance.
>
> Regards
> Ben


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