From: Clay on 19 Mar 2010 10:29 On Mar 18, 6:23 pm, robert bristowjohnson <r...(a)audioimagination.com> wrote: > On Mar 18, 11:52 am, dbd <d...(a)ieee.org> wrote: > > > > > > > On Mar 18, 6:09 am, "Junglist" <vasily.karpenko(a)n_o_s_p_a_m.gmail.com> > > wrote: > > > > Hello! > > > > I have read article "Optimum Masking Levels and Coefficient Sparseness for > > > Hilbert Transformers and HalfBand Filters Designed Using the > > > FrequencyResponse Masking Technique", Yong Ching Lim, NOVEMBER 2005. > > > > There're in example two filters Hb(z) and H1(z). I guess they derived by > > > multiplication classical hilbert impulse function h(n)=[1cos(Pi*n)]/Pi*n > > > on different windows. What kind of windows is using there? > .. > > Why do you suggest the use of windows here? The frequency response > > masking literature takes advantage of a variety of filter design > > methods, but usually optimizing techniques. > > an implied window can come from any design technique as long as you > can avoid dividing a nonzero numerator by a zero denominator. > > because halfband symmetry let's us ditch the evennumbered taps, any > design that imposes halfband symmetry can have its (properly aligned) > impulse response divided by the ideal > > h[n] = (1  (1)^n)/(pi*n) (h[0]=0) > > for odd n, and you have an implied window. > > r bj Hide quoted text  > >  Show quoted text  True, but the article refers to Chebyshev approximation and the effect the masking has on its ripple, so I assume he's using a Remez method to obtain his original filters. And then "sharpening" them from there. My 2 cents worth anyway. Clay
From: robert bristowjohnson on 20 Mar 2010 17:06 On Mar 19, 10:29 am, Clay <c...(a)claysturner.com> wrote: > On Mar 18, 6:23 pm, robert bristowjohnson <r...(a)audioimagination.com> > wrote: > > > > > On Mar 18, 11:52 am, dbd <d...(a)ieee.org> wrote: > > > > On Mar 18, 6:09 am, "Junglist" <vasily.karpenko(a)n_o_s_p_a_m.gmail.com> > > > wrote: > > > > > Hello! > > > > > I have read article "Optimum Masking Levels and Coefficient Sparseness for > > > > Hilbert Transformers and HalfBand Filters Designed Using the > > > > FrequencyResponse Masking Technique", Yong Ching Lim, NOVEMBER 2005. > > > > > There're in example two filters Hb(z) and H1(z). I guess they derived by > > > > multiplication classical hilbert impulse function h(n)=[1cos(Pi*n)]/Pi*n > > > > on different windows. What kind of windows is using there? > > .. > > > Why do you suggest the use of windows here? The frequency response > > > masking literature takes advantage of a variety of filter design > > > methods, but usually optimizing techniques. > > > an implied window can come from any design technique as long as you > > can avoid dividing a nonzero numerator by a zero denominator. > > > because halfband symmetry let's us ditch the evennumbered taps, any > > design that imposes halfband symmetry can have its (properly aligned) > > impulse response divided by the ideal > > > h[n] = (1  (1)^n)/(pi*n) (h[0]=0) > > > for odd n, and you have an implied window. > .... > > True, but the article refers to Chebyshev approximation and the effect > the masking has on its ripple, so I assume he's using a Remez method > to obtain his original filters. And then "sharpening" them from there. still, an implied window can be derived from the data as long as there are no 1/0 kind of division. even when using ParksMcClellan, you can enforce halfband symmetry, which will make the even samples zero. then the conditions are met and an implied window can be observed. r bj
From: Clay on 22 Mar 2010 13:00 On Mar 20, 5:06 pm, robert bristowjohnson <r...(a)audioimagination.com> wrote: > On Mar 19, 10:29 am, Clay <c...(a)claysturner.com> wrote: > > > > > > > On Mar 18, 6:23 pm, robert bristowjohnson <r...(a)audioimagination.com> > > wrote: > > > > On Mar 18, 11:52 am, dbd <d...(a)ieee.org> wrote: > > > > > On Mar 18, 6:09 am, "Junglist" <vasily.karpenko(a)n_o_s_p_a_m.gmail..com> > > > > wrote: > > > > > > Hello! > > > > > > I have read article "Optimum Masking Levels and Coefficient Sparseness for > > > > > Hilbert Transformers and HalfBand Filters Designed Using the > > > > > FrequencyResponse Masking Technique", Yong Ching Lim, NOVEMBER 2005. > > > > > > There're in example two filters Hb(z) and H1(z). I guess they derived by > > > > > multiplication classical hilbert impulse function h(n)=[1cos(Pi*n)]/Pi*n > > > > > on different windows. What kind of windows is using there? > > > .. > > > > Why do you suggest the use of windows here? The frequency response > > > > masking literature takes advantage of a variety of filter design > > > > methods, but usually optimizing techniques. > > > > an implied window can come from any design technique as long as you > > > can avoid dividing a nonzero numerator by a zero denominator. > > > > because halfband symmetry let's us ditch the evennumbered taps, any > > > design that imposes halfband symmetry can have its (properly aligned) > > > impulse response divided by the ideal > > > > h[n] = (1  (1)^n)/(pi*n) (h[0]=0) > > > > for odd n, and you have an implied window. > > ... > > > True, but the article refers to Chebyshev approximation and the effect > > the masking has on its ripple, so I assume he's using a Remez method > > to obtain his original filters. And then "sharpening" them from there. > > still, an implied window can be derived from the data as long as there > are no 1/0 kind of division. even when using ParksMcClellan, you can > enforce halfband symmetry, which will make the even samples zero. > then the conditions are met and an implied window can be observed. > > r bj Hide quoted text  > >  Show quoted text  I wasn't saying you can't do it this way, but rather I was reflecting on the OP's question about what window or how the particular filters in the article were created. Clay
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