Dear Ytchang,
i saw ur posting on Mp3 Encode Mailing List as under.
" Dear all:
I'm working on a MP3-encoder and I have some question about PQMF
encoding. I don't understand the meaning of global variable
"enwindow[]" in 3.91 version. It seems to be the coefficients C_i of the
analysis windows multiply constant_1 and divide constant_2. But I don't
understand the meaning of constant_1 and constant_2
the enwindow[] is defined as followed.
-4.77e-07,1.03951e-04, 9.53674e-04, 2.841473e-03, 3.5758972e-02 is
coefficients C_i of analysis windows (spec p69 Table c.1)
but I don't understand the meaning of 0.740951125354959 and 2.384e-06
static const FLOAT8 enwindow[] =
{
-4.77e-07*0.740951125354959/2.384e-06,
1.03951e-04*0.740951125354959/2.384e-06,
9.53674e-04*0.740951125354959/2.384e-06,
2.841473e-03*0.740951125354959/2.384e-06,
3.5758972e-02*0.740951125354959/2.384e-06,
...........
}
Thanks in advance.
ytchang
"
I am also working on Mp3 Encoder and wanted to know how LAME has got the
table enwindow[]?
I have figured out that in each
enwindow_entry = C_i of the analysis windows *constant_1 /constant_2
constant_1 = filter_coeffecient
but i am not able to figure out what is constant_2
at some points LAME is multiplyimg C_i by SQRT2*0.5 i.e. nothing but 1/SQRT
2
i.e. again a filer coeff cos pi/4 etc..
but what is 2.384e-06?
Please help me on this.
Since the posting was in 2004.
Hope u must have figured it out.
Looking forward to your response.
Thanks in advance,
Sonal Gupta.
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