Hi Jaffino, the term "octave" as applied to the DWT is just referring to the dyadic scales. So you take all the coefficients at that scale. For example:
x = randn(1024,1);
[C,L] = wavedec(x,3,'db4');
d3 = detcoef(C,L,3);
d3 is the vector of coefficients at scale 3 (3rd octave). I think octave is a bit outdated now in the wavelet literature, better to refer to them as just scales.
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