On Mon, 31 Mar 2008 16:03:42 -0600, jim <".sjedgingN0sp"@m@mwt.net> wrote:>Jerry Avins wrote: >> >> It's all semantics, then. The alteration comes about not from the >> downsampling, but from the filtering that precedes it. > > >> When there is no >> energy above the new Fs/2, there will be no change in the samples. > > The statement was when a anti-alias filter was "required". But even if >you used one where it was not required there would be no change in samples >only if you know how to make an anti-alias filter that removes absolutely >no energy from below the new Fs/2. > >-jimIt's not necessarily the shape of the filter frequency response, but the presence and distribution of energy in the signal. One would hope that something like a solitary tone in the passband would survive any unity-gain filter largely unchanged if the samples weren't moved in time (i.e., interpolated). If there was energy that got removed then the difference should be related only to the energy removed, ideally. Eric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org
Re: Interpolation
Started by ●March 31, 2008
Reply by ●March 31, 20082008-03-31
On Mon, 31 Mar 2008 16:03:42 -0600, jim <".sjedgingN0sp"@m@mwt.net> wrote:>Jerry Avins wrote: >> >> It's all semantics, then. The alteration comes about not from the >> downsampling, but from the filtering that precedes it. > > >> When there is no >> energy above the new Fs/2, there will be no change in the samples. > > The statement was when a anti-alias filter was "required". But even if >you used one where it was not required there would be no change in samples >only if you know how to make an anti-alias filter that removes absolutely >no energy from below the new Fs/2. > >-jimIt's not necessarily the shape of the filter frequency response, but the presence and distribution of energy in the signal. One would hope that something like a solitary tone in the passband would survive any unity-gain filter largely unchanged if the samples weren't moved in time (i.e., interpolated). If there was energy that got removed then the difference should be related only to the energy removed, ideally. Eric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org
Reply by ●March 31, 20082008-03-31
On Mon, 31 Mar 2008 16:03:42 -0600, jim <".sjedgingN0sp"@m@mwt.net> wrote:>Jerry Avins wrote: >> >> It's all semantics, then. The alteration comes about not from the >> downsampling, but from the filtering that precedes it. > > >> When there is no >> energy above the new Fs/2, there will be no change in the samples. > > The statement was when a anti-alias filter was "required". But even if >you used one where it was not required there would be no change in samples >only if you know how to make an anti-alias filter that removes absolutely >no energy from below the new Fs/2. > >-jimIt's not necessarily the shape of the filter frequency response, but the presence and distribution of energy in the signal. One would hope that something like a solitary tone in the passband would survive any unity-gain filter largely unchanged if the samples weren't moved in time (i.e., interpolated). If there was energy that got removed then the difference should be related only to the energy removed, ideally. Eric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org
Reply by ●April 1, 20082008-04-01
Eric Jacobsen wrote:> > On Mon, 31 Mar 2008 16:03:42 -0600, jim <".sjedgingN0sp"@m@mwt.net> > wrote: > > >Jerry Avins wrote: > >> > >> It's all semantics, then. The alteration comes about not from the > >> downsampling, but from the filtering that precedes it. > > > > > >> When there is no > >> energy above the new Fs/2, there will be no change in the samples. > > > > The statement was when a anti-alias filter was "required". But even if > >you used one where it was not required there would be no change in samples > >only if you know how to make an anti-alias filter that removes absolutely > >no energy from below the new Fs/2. > > > >-jim > > It's not necessarily the shape of the filter frequency response, but > the presence and distribution of energy in the signal.This is true. It is also irrelevant. The statement that was called "incorrect" was that when a AA filter is required that the samples will change. For you to bring up what happens when an AA filter isn't required does nothing but muddy the water. -jim> One would > hope that something like a solitary tone in the passband would > survive any unity-gain filter largely unchanged if the samples weren't > moved in time (i.e., interpolated). If there was energy that got > removed then the difference should be related only to the energy > removed, ideally. > > Eric Jacobsen > Minister of Algorithms > Abineau Communications > http://www.ericjacobsen.org----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.pronews.com The #1 Newsgroup Service in the World! >100,000 Newsgroups ---= - Total Privacy via Encryption =---
Reply by ●April 1, 20082008-04-01
Eric Jacobsen wrote:> > On Mon, 31 Mar 2008 16:03:42 -0600, jim <".sjedgingN0sp"@m@mwt.net> > wrote: > > >Jerry Avins wrote: > >> > >> It's all semantics, then. The alteration comes about not from the > >> downsampling, but from the filtering that precedes it. > > > > > >> When there is no > >> energy above the new Fs/2, there will be no change in the samples. > > > > The statement was when a anti-alias filter was "required". But even if > >you used one where it was not required there would be no change in samples > >only if you know how to make an anti-alias filter that removes absolutely > >no energy from below the new Fs/2. > > > >-jim > > It's not necessarily the shape of the filter frequency response, but > the presence and distribution of energy in the signal.This is true. It is also irrelevant. The statement that was called "incorrect" was that when a AA filter is required that the samples will change. For you to bring up what happens when an AA filter isn't required does nothing but muddy the water. -jim> One would > hope that something like a solitary tone in the passband would > survive any unity-gain filter largely unchanged if the samples weren't > moved in time (i.e., interpolated). If there was energy that got > removed then the difference should be related only to the energy > removed, ideally. > > Eric Jacobsen > Minister of Algorithms > Abineau Communications > http://www.ericjacobsen.org----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.pronews.com The #1 Newsgroup Service in the World! >100,000 Newsgroups ---= - Total Privacy via Encryption =---
Reply by ●April 5, 20082008-04-05
On Tue, 01 Apr 2008 06:52:52 -0500, "cpshah99" <cpshah99@rediffmail.com> wrote: (Snipped by Lyons)> >Hello Guys > >This thread was started by my question on 'Interpolation'. And this >discussion has become more interesting and I have almost forgotten my >fundamentals!!!!!! But finally I solved my problem, thanks to Randy who >gave one nice link > >http://ccrma.stanford.edu/~jos/pasp/Linear_Interpolation.html >Hi, If I'm not mistaken, it looks like the coefficients have been incorrectly swapped in Figure 3.2 of the above link. [-Rick-]
Reply by ●April 5, 20082008-04-05
Rick Lyons <R.Lyons@_BOGUS_ieee.org> writes:> On Tue, 01 Apr 2008 06:52:52 -0500, "cpshah99" > <cpshah99@rediffmail.com> wrote: > > (Snipped by Lyons) >> >>Hello Guys >> >>This thread was started by my question on 'Interpolation'. And this >>discussion has become more interesting and I have almost forgotten my >>fundamentals!!!!!! But finally I solved my problem, thanks to Randy who >>gave one nice link >> >>http://ccrma.stanford.edu/~jos/pasp/Linear_Interpolation.html >> > > Hi, > If I'm not mistaken, it looks like the > coefficients have been incorrectly swapped in > Figure 3.2 of the above link.I see what you mean - I agree. Also, due to the way he wrote the difference equation, the whole thing is delayed by one sample, which is good since his original architecture required predicting the future. -- % Randy Yates % "Remember the good old 1980's, when %% Fuquay-Varina, NC % things were so uncomplicated?" %%% 919-577-9882 % 'Ticket To The Moon' %%%% <yates@ieee.org> % *Time*, Electric Light Orchestra http://www.digitalsignallabs.com
