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Real-time wavelet denoising

Started by Poj December 27, 2007
On Dec 27, 5:56 pm, Jerry Avins <j...@ieee.org> wrote:
> John wrote: > > On Dec 27, 12:59 pm, Vladimir Vassilevsky <antispam_bo...@hotmail.com> > > wrote: > >>>> If you are using a linear filter to resolve the frequencies, then the > >>>> incurred delay can't be less then about 1/transition band. > >>> Baseline wander removal is difficult in a realtime system for all the > >>> reasons you cite. > >> The only way to trick the nature is using parametric models of the > >> signal and the drift. The parameters should be estimated as ML. However > >> the results are going to be wild if the models do not match. > > >> VLV > > > The drift is difficult to model. In the case of a Galvanic Skin > > Response (GSR), sometimes the baseline can be holding flat for many > > seconds, then all of a sudden it plunges downward. > > That isn't baseline, it's an as-yet unaccounted-for phenomenon that > you're measuring. There's information in that thar noise. Can you find a > way to use it? > > Jerry > -- > Engineering is the art of making what you want from things you can get. > &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Baseline is the standard term for it. Baseline wander is caused by perspiration, body movement, etc. The actual response that is being measured is summed with the wandering baseline. Google "baseline wander" for more information. John
John <sampson164@gmail.com> writes:

> On Dec 27, 5:56 pm, Jerry Avins <j...@ieee.org> wrote: >> John wrote: >> > On Dec 27, 12:59 pm, Vladimir Vassilevsky <antispam_bo...@hotmail.com> >> > wrote: >> >>>> If you are using a linear filter to resolve the frequencies, then the >> >>>> incurred delay can't be less then about 1/transition band. >> >>> Baseline wander removal is difficult in a realtime system for all the >> >>> reasons you cite. >> >> The only way to trick the nature is using parametric models of the >> >> signal and the drift. The parameters should be estimated as ML. However >> >> the results are going to be wild if the models do not match. >> >> >> VLV >> >> > The drift is difficult to model. In the case of a Galvanic Skin >> > Response (GSR), sometimes the baseline can be holding flat for many >> > seconds, then all of a sudden it plunges downward. >> >> That isn't baseline, it's an as-yet unaccounted-for phenomenon that >> you're measuring. There's information in that thar noise. Can you find a >> way to use it? >> >> Jerry >> -- >> Engineering is the art of making what you want from things you can get. >> &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095; > > Baseline is the standard term for it. Baseline wander is caused by > perspiration, body movement, etc. The actual response that is being > measured is summed with the wandering baseline. Google "baseline > wander" for more information.
Isn't this just a fancy term for DC offset, or "slowly time-varying DC offset"? If so, then couldn't it be removed with a DC notch filter? The IIR form doesn't have too much of a delay. -- % Randy Yates % "Ticket to the moon, flight leaves here today %% Fuquay-Varina, NC % from Satellite 2" %%% 919-577-9882 % 'Ticket To The Moon' %%%% <yates@ieee.org> % *Time*, Electric Light Orchestra http://www.digitalsignallabs.com
On Dec 27, 7:17 pm, Randy Yates <ya...@ieee.org> wrote:
> John <sampson...@gmail.com> writes: > > On Dec 27, 5:56 pm, Jerry Avins <j...@ieee.org> wrote: > >> John wrote: > >> > On Dec 27, 12:59 pm, Vladimir Vassilevsky <antispam_bo...@hotmail.com> > >> > wrote: > >> >>>> If you are using a linear filter to resolve the frequencies, then the > >> >>>> incurred delay can't be less then about 1/transition band. > >> >>> Baseline wander removal is difficult in a realtime system for all the > >> >>> reasons you cite. > >> >> The only way to trick the nature is using parametric models of the > >> >> signal and the drift. The parameters should be estimated as ML. However > >> >> the results are going to be wild if the models do not match. > > >> >> VLV > > >> > The drift is difficult to model. In the case of a Galvanic Skin > >> > Response (GSR), sometimes the baseline can be holding flat for many > >> > seconds, then all of a sudden it plunges downward. > > >> That isn't baseline, it's an as-yet unaccounted-for phenomenon that > >> you're measuring. There's information in that thar noise. Can you find a > >> way to use it? > > >> Jerry > >> -- > >> Engineering is the art of making what you want from things you can get. > >> &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095; > > > Baseline is the standard term for it. Baseline wander is caused by > > perspiration, body movement, etc. The actual response that is being > > measured is summed with the wandering baseline. Google "baseline > > wander" for more information. > > Isn't this just a fancy term for DC offset, or "slowly time-varying DC offset"? > If so, then couldn't it be removed with a DC notch filter? The IIR form doesn't > have too much of a delay. > -- > % Randy Yates % "Ticket to the moon, flight leaves here today > %% Fuquay-Varina, NC % from Satellite 2" > %%% 919-577-9882 % 'Ticket To The Moon' > %%%% <ya...@ieee.org> % *Time*, Electric Light Orchestrahttp://www.digitalsignallabs.com
The wandering baseline can sometimes move quickly, as in a rapid plunge, and a simple filter will probably attenuate the features that the analyst is trying to measure. That's why one turns to fairly exotic techniques for this problem, but holding down the delay in a real time instrument is difficult, as the OP obviously knows. John
On Dec 27, 3:16 pm, "Poj" <netsir...@hotmail.com> wrote:
> Hi John, > > Thanks for message. > > Yes, you are right. Lag between input and output is too much. Do you have > any articles, links or other information related to sliding DWT? >
I only have what can be found with a search on IEEE Xplore or Google Scholar. John
John <sampson164@gmail.com> writes:

> On Dec 27, 7:17 pm, Randy Yates <ya...@ieee.org> wrote: >> John <sampson...@gmail.com> writes: >> > On Dec 27, 5:56 pm, Jerry Avins <j...@ieee.org> wrote: >> >> John wrote: >> >> > On Dec 27, 12:59 pm, Vladimir Vassilevsky <antispam_bo...@hotmail.com> >> >> > wrote: >> >> >>>> If you are using a linear filter to resolve the frequencies, then the >> >> >>>> incurred delay can't be less then about 1/transition band. >> >> >>> Baseline wander removal is difficult in a realtime system for all the >> >> >>> reasons you cite. >> >> >> The only way to trick the nature is using parametric models of the >> >> >> signal and the drift. The parameters should be estimated as ML. However >> >> >> the results are going to be wild if the models do not match. >> >> >> >> VLV >> >> >> > The drift is difficult to model. In the case of a Galvanic Skin >> >> > Response (GSR), sometimes the baseline can be holding flat for many >> >> > seconds, then all of a sudden it plunges downward. >> >> >> That isn't baseline, it's an as-yet unaccounted-for phenomenon that >> >> you're measuring. There's information in that thar noise. Can you find a >> >> way to use it? >> >> >> Jerry >> >> -- >> >> Engineering is the art of making what you want from things you can get. >> >> &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095; >> >> > Baseline is the standard term for it. Baseline wander is caused by >> > perspiration, body movement, etc. The actual response that is being >> > measured is summed with the wandering baseline. Google "baseline >> > wander" for more information. >> >> Isn't this just a fancy term for DC offset, or "slowly time-varying DC offset"? >> If so, then couldn't it be removed with a DC notch filter? The IIR form doesn't >> have too much of a delay. >> -- >> % Randy Yates % "Ticket to the moon, flight leaves here today >> %% Fuquay-Varina, NC % from Satellite 2" >> %%% 919-577-9882 % 'Ticket To The Moon' >> %%%% <ya...@ieee.org> % *Time*, Electric Light Orchestrahttp://www.digitalsignallabs.com > > The wandering baseline can sometimes move quickly, as in a rapid > plunge, and a simple filter will probably attenuate the features that > the analyst is trying to measure. That's why one turns to fairly > exotic techniques for this problem, but holding down the delay in a > real time instrument is difficult, as the OP obviously knows.
Hi John, If the bandwidth of the interference intersects with the bandwidth of the signal, then no linear filter technique (including wavelets) will suffice. It seems in that case that the best possible solution is to model the interference and design a canceller, as Vladimir pointed out. -- % Randy Yates % "Ticket to the moon, flight leaves here today %% Fuquay-Varina, NC % from Satellite 2" %%% 919-577-9882 % 'Ticket To The Moon' %%%% <yates@ieee.org> % *Time*, Electric Light Orchestra http://www.digitalsignallabs.com
I think packing all DWT-noise elimination-IDWT into a single sliding kernel
is the best idea. Does anyone know how to do it?

Happy New Year!




>On Dec 27, 3:16 pm, "Poj" <netsir...@hotmail.com> wrote: >> Hi John, >> >> Thanks for message. >> >> Yes, you are right. Lag between input and output is too much. Do you
have
>> any articles, links or other information related to sliding DWT? >> > > >I only have what can be found with a search on IEEE Xplore or Google >Scholar. > >John >
I was able to extract the sliding wavelet denoising kernel by injecting an
impulse to the entire DWT-noise elimination-IDWT process. The impulse
response in time-domain is in fact the kernel I want. And, the kernel can
represent the entire denoising process. So, the problem is resolved. The
case now is closed.

-poj



>I think packing all DWT-noise elimination-IDWT into a single sliding
kernel
>is the best idea. Does anyone know how to do it? > >Happy New Year! > > > > >>On Dec 27, 3:16 pm, "Poj" <netsir...@hotmail.com> wrote: >>> Hi John, >>> >>> Thanks for message. >>> >>> Yes, you are right. Lag between input and output is too much. Do you >have >>> any articles, links or other information related to sliding DWT? >>> >> >> >>I only have what can be found with a search on IEEE Xplore or Google >>Scholar. >> >>John >> >