From: <dan...@br...> - 2004-06-21 09:35:45
|
Hi Scott > A little while ago Daniel talked about replacing the FHT with another scheme to generate the impulse response, which appears to have been done. Can you confirm that it is as fast as the FHT? I don't know if it's as fast as FHT, it's certainly fast enough for desktop computers. I have no idea how they do it, but fftw doesn't seem to be that much slower for n^2-1 fft lengths than n^2 lengths. >Does the correlation still create a perfect unit response as it should with the MLS? I'm not sure what you mean with a perfect unit response. But I'm sure the new scheme is much more accurate than the FHT. I have compared the results from the sweep mode with the MLS mode and they are the same. The problem with FHT MLS is that you assume that the soundcard doesn't degrade the signal at all. It's in fact even more sensitive to this than you might think. Even with an almost perfectly flat freqency response you will still not get good results with the FHT. I think the FHT should be viewed as a last resort, only to be used when speed is top priority and not accuracy. Although some of the FHT problems could be solved with calibration I still don't think you will get as good results as when you correlate in the frequency domain. I'm not sure that the FHT errors are static enough to be effectivly removed with calibration. > I must get started on a test/demo app. I have almost finished a waveform viewer/library that can be used from other appplications, so you might want to wait for that. I will make it public as soon as I figure out where to put it. > One final thing. If we have upgraded the project name to level 1 then I think we need to upgrade the major revision number to 1 as well. Perhaps 1.0. I agree on this, although I don't think we should go 1.0 until the library is stable. /Daniel |
From: Daniel S. <ds...@ho...> - 2004-06-23 14:55:33
|
>=20 >>I have two questions: what is FHT? Fast Hamahard Transform? >=20 >=20 > Fast Hadamard Transform, I think. >=20 >=20 >>Daniel: did libmls use FHT before and now uses FFT? >=20 >=20 > Yes, I basically replaced the FHT transform routines from Anders Torger= with FFTW. > I'm not sure if it would be more correct to call it DFT or FFT though, = since it's not N^2 length. > But FFTW must use some kind of FFT method anyway since it's so fast. >=20 Well, I just realized I have studied this in a signal processing=20 course... I actually have access to very detailed theory on this=20 subject...:-) >=20 > The above also means that the information in the README file is=20 > longer correct. There is no mic calibration mode anymore, and > there must be a loop from the output to the left (reference > channel) and the right channel must be used for measurements. > If this is the case we really need some updated documentation, could you=20 please patch the README and we will make an updated release. > And then to my attachment: > I have attached the loudspeaker library that I'm working on. > I plan to put it on savannah.gnu.org or sourceforge soon, but I would l= ike to have some comments on the code before I do that. > I will try to take a look at this and of course comment if I feel the=20 need to... > My goal with this library, is that it, together with libmls, should be > complete enough to replace CALSOD, MLSSA etc. with open source tools. > I also want to keep it as portable as possible. >=20 It's all about the GUI today, you know...:-) Regards Daniel Sundberg > The intended audience is: > Developers of measurement or loudspeaker software like e.g. gspeakers. > Advanced users that would like complete freedom in choosing design meth= odology. >=20 > So it is both a library, to satisfy the first group. > And a set of command line utilities using the above library, to satisfy= the second group. >=20 > To make it both as portable and as easily scriptable/customizable as po= ssible the command line utilities should only do one operation each and t= he only thing requiring potentially hard to port or compile GUI code shou= ld be the waveform viewer. >=20 > Implemented at the moment is: > *FRD/ZMA file I/O > *Import of ddb speaker data base. > As generated and used by: > http://www.danbbs.dk/~ko/ubmodel.htm > *Partial implementation of the loudspeaker model in: > http://www.hal-pc.org/~bwhitejr/btsmodel.zip > found here: > http://www.geocities.com/loudspeakerguru/Speaker_Design_Equations.htm= l > *Standard filter generator > *Ladder filter simulator with file I/O > *FRD waveform viewer >=20 > The waveform viewer can use plotutils or gnuplot and it can display the= results from mra/sra. > It doesn't require plotutils to compile and it should be very easy to p= ort to other platforms or to embed in other applications. >=20 > So most of the boring infrastructure things are at least usable and lot= s of fun remains: > Filter/box optimization, spice like simulator and other box types (tl, = horn, etc.). >=20 > When mra/sra has been updated with a bit more options (getopt) it would= be very easy to create a graphical front end that would just launch mra = and pass the results to resgraph (the waveform viewer). >=20 > There are some example scripts in the script directory, > both for using plotutils and gnuplot. >=20 > Regards, > Daniel W >=20 >=20 >>From: Daniel Sundberg <ds...@ho...> >>Date: 2004/06/22 ti AM 11:11:57 GMT+02:00 >>To: lib...@li... >>=C4mne: Re: [Libmls0-developers] RE: libmls-0.3 released >> >>Hi! >> >>I have two questions: what is FHT? Fast Hamahard Transform? >> >>Daniel: did libmls use FHT before and now uses FFT? I am afraid I have=20 >>not been looking very close at the source code lately (mostly since I d= o=20 >>not own a decent measurement microphone). >> >>Also, when some of you start to work on a sample application it might b= e=20 >>a good idea to create a separate module in the cvs or create a new proj= ect. >> >>Regards >> >>Daniel Sundberg >> >> >>dan...@br... wrote: >> >>>Hi Scott >>> >>> >>> >>>>A little while ago Daniel talked about replacing the FHT with another= scheme to generate the impulse response, which appears to have been done= . Can you confirm that it is as fast as the FHT? >>> >>> >>>I don't know if it's as fast as FHT, it's certainly fast enough for de= sktop computers. I have no idea how they do it, but fftw doesn't seem to = be that much slower for n^2-1 fft lengths than n^2 lengths. >>> >>> >>> >>>>Does the correlation still create a perfect unit response as it shoul= d with the MLS? >>> >>> >>>I'm not sure what you mean with a perfect unit response. But I'm sure = the new scheme is much more accurate than the FHT. I have compared the re= sults from the sweep mode with the MLS mode and they are the same. >>> >>>The problem with FHT MLS is that you assume that the soundcard doesn't= degrade the signal at all. It's in fact even more sensitive to this than= you might think. Even with an almost perfectly flat freqency response yo= u will still not get good results with the FHT. I think the FHT should be= viewed as a last resort, only to be used when speed is top priority and = not accuracy. >>>Although some of the FHT problems could be solved with calibration I s= till don't think you will get as good results as when you correlate in th= e frequency domain. I'm not sure that the FHT errors are static enough to= be effectivly removed with calibration. >>> >>> >>> >>>>I must get started on a test/demo app. >>> >>> >>>I have almost finished a waveform viewer/library that can be used from= other appplications, so you might want to wait for that. >>>I will make it public as soon as I figure out where to put it. >>>=20 >>> >>> >>>>One final thing. If we have upgraded the project name to level 1 then= I think we need to upgrade the major revision number to 1 as well. Perha= ps 1.0. >>> >>> >>>I agree on this, although I don't think we should go 1.0 until the lib= rary is stable. >>> >>>/Daniel >>> >>> >>> >>> >>>------------------------------------------------------- >>>This SF.Net email is sponsored by The 2004 JavaOne(SM) Conference >>>Learn from the experts at JavaOne(SM), Sun's Worldwide Java Developer >>>Conference, June 28 - July 1 at the Moscone Center in San Francisco, C= A >>>REGISTER AND SAVE! http://java.sun.com/javaone/sf Priority Code NWMGYK= ND >>>_______________________________________________ >>>Libmls0-developers mailing list >>>Lib...@li... >>>https://lists.sourceforge.net/lists/listinfo/libmls0-developers >>> >>> >> >> >> >>------------------------------------------------------- >>This SF.Net email sponsored by Black Hat Briefings & Training. >>Attend Black Hat Briefings & Training, Las Vegas July 24-29 -=20 >>digital self defense, top technical experts, no vendor pitches,=20 >>unmatched networking opportunities. Visit www.blackhat.com >>_______________________________________________ >>Libmls0-developers mailing list >>Lib...@li... >>https://lists.sourceforge.net/lists/listinfo/libmls0-developers >> |
From: Daniel S. <ds...@ho...> - 2004-06-23 15:09:07
|
Hi again! As always, one more thing. Daniel: it would be really nice if you could=20 provide a very short summary of what the different programs in you=20 lsputils actually does. "FRD to ZMA transformer" is not very useful information if you do not=20 know what frd and zma is. Of course I might look at the source, which I=20 will do anyway, and find out for myself, but a very short and quick=20 description will get me started a little quicker...:-) /Daniel Daniel Sundberg wrote: >> >>> I have two questions: what is FHT? Fast Hamahard Transform? >> >> >> >> Fast Hadamard Transform, I think. >> >> >>> Daniel: did libmls use FHT before and now uses FFT? >> >> >> >> Yes, I basically replaced the FHT transform routines from Anders=20 >> Torger with FFTW. >> I'm not sure if it would be more correct to call it DFT or FFT though,= =20 >> since it's not N^2 length. >> But FFTW must use some kind of FFT method anyway since it's so fast. >> >=20 > Well, I just realized I have studied this in a signal processing=20 > course... I actually have access to very detailed theory on this=20 > subject...:-) >=20 >> >> The above also means that the information in the README file is=20 >=20 > > longer correct. There is no mic calibration mode anymore, and > > there must be a loop from the output to the left (reference > > channel) and the right channel must be used for measurements. > > >=20 > If this is the case we really need some updated documentation, could yo= u=20 > please patch the README and we will make an updated release. >=20 >> And then to my attachment: >> I have attached the loudspeaker library that I'm working on. >> I plan to put it on savannah.gnu.org or sourceforge soon, but I would=20 >> like to have some comments on the code before I do that. >> >=20 > I will try to take a look at this and of course comment if I feel the=20 > need to... >=20 >> My goal with this library, is that it, together with libmls, should be >> complete enough to replace CALSOD, MLSSA etc. with open source tools. >> I also want to keep it as portable as possible. >> >=20 > It's all about the GUI today, you know...:-) >=20 > Regards >=20 > Daniel Sundberg >=20 >=20 >> The intended audience is: >> Developers of measurement or loudspeaker software like e.g. gspeakers. >> Advanced users that would like complete freedom in choosing design=20 >> methodology. >> >> So it is both a library, to satisfy the first group. >> And a set of command line utilities using the above library, to=20 >> satisfy the second group. >> >> To make it both as portable and as easily scriptable/customizable as=20 >> possible the command line utilities should only do one operation each=20 >> and the only thing requiring potentially hard to port or compile GUI=20 >> code should be the waveform viewer. >> >> Implemented at the moment is: >> *FRD/ZMA file I/O >> *Import of ddb speaker data base. >> As generated and used by: >> http://www.danbbs.dk/~ko/ubmodel.htm >> *Partial implementation of the loudspeaker model in: >> http://www.hal-pc.org/~bwhitejr/btsmodel.zip >> found here: >> http://www.geocities.com/loudspeakerguru/Speaker_Design_Equations.ht= ml >> *Standard filter generator >> *Ladder filter simulator with file I/O >> *FRD waveform viewer >> >> The waveform viewer can use plotutils or gnuplot and it can display=20 >> the results from mra/sra. >> It doesn't require plotutils to compile and it should be very easy to=20 >> port to other platforms or to embed in other applications. >> >> So most of the boring infrastructure things are at least usable and=20 >> lots of fun remains: >> Filter/box optimization, spice like simulator and other box types (tl,= =20 >> horn, etc.). >> >> When mra/sra has been updated with a bit more options (getopt) it=20 >> would be very easy to create a graphical front end that would just=20 >> launch mra and pass the results to resgraph (the waveform viewer). >> >> There are some example scripts in the script directory, >> both for using plotutils and gnuplot. >> >> Regards, >> Daniel W >> >> >>> From: Daniel Sundberg <ds...@ho...> >>> Date: 2004/06/22 ti AM 11:11:57 GMT+02:00 >>> To: lib...@li... >>> =C4mne: Re: [Libmls0-developers] RE: libmls-0.3 released >>> >>> Hi! >>> >>> I have two questions: what is FHT? Fast Hamahard Transform? >>> >>> Daniel: did libmls use FHT before and now uses FFT? I am afraid I=20 >>> have not been looking very close at the source code lately (mostly=20 >>> since I do not own a decent measurement microphone). >>> >>> Also, when some of you start to work on a sample application it might= =20 >>> be a good idea to create a separate module in the cvs or create a new= =20 >>> project. >>> >>> Regards >>> >>> Daniel Sundberg >>> >>> >>> dan...@br... wrote: >>> >>>> Hi Scott >>>> >>>> >>>> >>>>> A little while ago Daniel talked about replacing the FHT with=20 >>>>> another scheme to generate the impulse response, which appears to=20 >>>>> have been done. Can you confirm that it is as fast as the FHT? >>>> >>>> >>>> >>>> I don't know if it's as fast as FHT, it's certainly fast enough for=20 >>>> desktop computers. I have no idea how they do it, but fftw doesn't=20 >>>> seem to be that much slower for n^2-1 fft lengths than n^2 lengths. >>>> >>>> >>>> >>>>> Does the correlation still create a perfect unit response as it=20 >>>>> should with the MLS? >>>> >>>> >>>> >>>> I'm not sure what you mean with a perfect unit response. But I'm=20 >>>> sure the new scheme is much more accurate than the FHT. I have=20 >>>> compared the results from the sweep mode with the MLS mode and they=20 >>>> are the same. >>>> >>>> The problem with FHT MLS is that you assume that the soundcard=20 >>>> doesn't degrade the signal at all. It's in fact even more sensitive=20 >>>> to this than you might think. Even with an almost perfectly flat=20 >>>> freqency response you will still not get good results with the FHT.=20 >>>> I think the FHT should be viewed as a last resort, only to be used=20 >>>> when speed is top priority and not accuracy. >>>> Although some of the FHT problems could be solved with calibration I= =20 >>>> still don't think you will get as good results as when you correlate= =20 >>>> in the frequency domain. I'm not sure that the FHT errors are static= =20 >>>> enough to be effectivly removed with calibration. >>>> >>>> >>>> >>>>> I must get started on a test/demo app. >>>> >>>> >>>> >>>> I have almost finished a waveform viewer/library that can be used=20 >>>> from other appplications, so you might want to wait for that. >>>> I will make it public as soon as I figure out where to put it. >>>> >>>> >>>> >>>>> One final thing. If we have upgraded the project name to level 1=20 >>>>> then I think we need to upgrade the major revision number to 1 as=20 >>>>> well. Perhaps 1.0. >>>> >>>> >>>> >>>> I agree on this, although I don't think we should go 1.0 until the=20 >>>> library is stable. >>>> >>>> /Daniel >>>> >>>> >>>> >>>> >>>> ------------------------------------------------------- >>>> This SF.Net email is sponsored by The 2004 JavaOne(SM) Conference >>>> Learn from the experts at JavaOne(SM), Sun's Worldwide Java Develope= r >>>> Conference, June 28 - July 1 at the Moscone Center in San Francisco,= CA >>>> REGISTER AND SAVE! http://java.sun.com/javaone/sf Priority Code=20 >>>> NWMGYKND >>>> _______________________________________________ >>>> Libmls0-developers mailing list >>>> Lib...@li... >>>> https://lists.sourceforge.net/lists/listinfo/libmls0-developers >>>> >>>> >>> >>> >>> >>> ------------------------------------------------------- >>> This SF.Net email sponsored by Black Hat Briefings & Training. >>> Attend Black Hat Briefings & Training, Las Vegas July 24-29 - digital= =20 >>> self defense, top technical experts, no vendor pitches, unmatched=20 >>> networking opportunities. Visit www.blackhat.com >>> _______________________________________________ >>> Libmls0-developers mailing list >>> Lib...@li... >>> https://lists.sourceforge.net/lists/listinfo/libmls0-developers >>> >=20 >=20 >=20 > ------------------------------------------------------- > This SF.Net email sponsored by Black Hat Briefings & Training. > Attend Black Hat Briefings & Training, Las Vegas July 24-29 - digital=20 > self defense, top technical experts, no vendor pitches, unmatched=20 > networking opportunities. Visit www.blackhat.com > _______________________________________________ > Libmls0-developers mailing list > Lib...@li... > https://lists.sourceforge.net/lists/listinfo/libmls0-developers >=20 >=20 |
From: Daniel S. <ds...@ho...> - 2004-06-30 08:13:41
|
> =20 > I have however had the time to look at the released version of libmls1,= =20 > and I have some comments.=20 > First, that it compiles under Mandrake 10.0 and Gentoo Linux.=20 > But, I'm having trouble compiling the code in cvs.=20 > Is it just me or should it work?=20 > What kind of errors do you get? Of course it should compile, it does=20 compile without problems on my fc1 system. > I also think the mra/sra applications are a little bit more than=20 > examples, at least when I'm done with them, and should be compiled and=20 > installed as default.=20 I see libmls as a library. I think that only simple applications should=20 be distributed with the library. If you decide to extend the sra and mra applications I think that you=20 should put them in a separate module in the cvs and release them as a=20 separate tarball on the libmls website. Also, I really think we need a=20 very simple example since the example is the only documentation available. /Daniel --- http://sumpan.com > I will change the command line parameter processing to getopt once I=20 > can compile the code in cvs. Then mra/sra should support everything=20 > libmls supports.=20 > =20 > I also now think that the impedance measurement tools frd2zma/zma2rlc=20 > should be removed, as these are generic tools, and can be used with any= =20 > response measurement software. I have already incorporated these in my=20 > lsp library and I think they fit better there.=20 > =20 > /Daniel=20 > =20 >=20 >>=20 >>From: Daniel Sundberg <ds...@ho...>=20 >>Date: 2004/06/23 on PM 05:07:55 GMT+02:00=20 >>CC: lib...@li...=20 >>=C4mne: Re: [Libmls0-developers] RE: libmls-0.3 released=20 >>=20 >>Hi again!=20 >>=20 >>As always, one more thing. Daniel: it would be really nice if you=20 >=20 > could =20 >=20 >>provide a very short summary of what the different programs in you =20 >>lsputils actually does.=20 >>=20 >>"FRD to ZMA transformer" is not very useful information if you do not =20 >>know what frd and zma is. Of course I might look at the source, which=20 >=20 > I =20 >=20 >>will do anyway, and find out for myself, but a very short and quick =20 >>description will get me started a little quicker...:-)=20 >>=20 >>/Daniel=20 >>=20 >>=20 >>Daniel Sundberg wrote:=20 >> >>>>>I have two questions: what is FHT? Fast Hamahard Transform?=20 >>>> >>>> >>>> >>>>Fast Hadamard Transform, I think.=20 >>>> >>>> >>>> >>>>>Daniel: did libmls use FHT before and now uses FFT?=20 >>>> >>>> >>>> >>>>Yes, I basically replaced the FHT transform routines from Anders =20 >>>>Torger with FFTW.=20 >>>>I'm not sure if it would be more correct to call it DFT or FFT=20 >=20 > though, =20 >=20 >>>>since it's not N^2 length.=20 >>>>But FFTW must use some kind of FFT method anyway since it's so=20 >=20 > fast.=20 >=20 >>>=20 >>>Well, I just realized I have studied this in a signal processing =20 >>>course... I actually have access to very detailed theory on this =20 >>>subject...:-)=20 >>>=20 >>> >>>>The above also means that the information in the README file is =20 >>> >>>=20 >>> > longer correct. There is no mic calibration mode anymore, and=20 >>> > there must be a loop from the output to the left (reference=20 >>> > channel) and the right channel must be used for measurements.=20 >>> >=20 >>>=20 >>>If this is the case we really need some updated documentation,=20 >=20 > could you =20 >=20 >>>please patch the README and we will make an updated release.=20 >>>=20 >>> >>>>And then to my attachment:=20 >>>>I have attached the loudspeaker library that I'm working on.=20 >>>>I plan to put it on savannah.gnu.org or sourceforge soon, but I=20 >=20 > would =20 >=20 >>>>like to have some comments on the code before I do that.=20 >>>> >>> >>>=20 >>>I will try to take a look at this and of course comment if I feel=20 >=20 > the =20 >=20 >>>need to...=20 >>>=20 >>> >>>>My goal with this library, is that it, together with libmls,=20 >=20 > should be=20 >=20 >>>>complete enough to replace CALSOD, MLSSA etc. with open source=20 >=20 > tools.=20 >=20 >>>>I also want to keep it as portable as possible.=20 >>>> >>> >>>=20 >>>It's all about the GUI today, you know...:-)=20 >>>=20 >>>Regards=20 >>>=20 >>>Daniel Sundberg=20 >>>=20 >>>=20 >>> >>>>The intended audience is:=20 >>>>Developers of measurement or loudspeaker software like e.g.=20 >=20 > gspeakers.=20 >=20 >>>>Advanced users that would like complete freedom in choosing design =20 >>>>methodology.=20 >>>> >>>>So it is both a library, to satisfy the first group.=20 >>>>And a set of command line utilities using the above library, to =20 >>>>satisfy the second group.=20 >>>> >>>>To make it both as portable and as easily scriptable/customizable=20 >=20 > as =20 >=20 >>>>possible the command line utilities should only do one operation=20 >=20 > each =20 >=20 >>>>and the only thing requiring potentially hard to port or compile=20 >=20 > GUI =20 >=20 >>>>code should be the waveform viewer.=20 >>>> >>>>Implemented at the moment is:=20 >>>>*FRD/ZMA file I/O=20 >>>>*Import of ddb speaker data base.=20 >>>> As generated and used by:=20 >>>> http://www.danbbs.dk/~ko/ubmodel.htm=20 >>>>*Partial implementation of the loudspeaker model in:=20 >>>> http://www.hal-pc.org/~bwhitejr/btsmodel.zip=20 >>>> found here:=20 >>>> =20 >=20 > http://www.geocities.com/loudspeakerguru/Speaker_Design_Equations.html=20 >=20 >>>>*Standard filter generator=20 >>>>*Ladder filter simulator with file I/O=20 >>>>*FRD waveform viewer=20 >>>> >>>>The waveform viewer can use plotutils or gnuplot and it can=20 >=20 > display =20 >=20 >>>>the results from mra/sra.=20 >>>>It doesn't require plotutils to compile and it should be very easy=20 >=20 > to =20 >=20 >>>>port to other platforms or to embed in other applications.=20 >>>> >>>>So most of the boring infrastructure things are at least usable=20 >=20 > and =20 >=20 >>>>lots of fun remains:=20 >>>>Filter/box optimization, spice like simulator and other box types=20 >=20 > (tl, =20 >=20 >>>>horn, etc.).=20 >>>> >>>>When mra/sra has been updated with a bit more options (getopt) it =20 >>>>would be very easy to create a graphical front end that would just =20 >>>>launch mra and pass the results to resgraph (the waveform viewer).=20 >>>> >>>>There are some example scripts in the script directory,=20 >>>>both for using plotutils and gnuplot.=20 >>>> >>>>Regards,=20 >>>>Daniel W=20 >>>> >>>> >>>> >>>>>From: Daniel Sundberg <ds...@ho...>=20 >>>>>Date: 2004/06/22 ti AM 11:11:57 GMT+02:00=20 >>>>>To: lib...@li...=20 >>>>>=C4mne: Re: [Libmls0-developers] RE: libmls-0.3 released=20 >>>>> >>>>>Hi!=20 >>>>> >>>>>I have two questions: what is FHT? Fast Hamahard Transform?=20 >>>>> >>>>>Daniel: did libmls use FHT before and now uses FFT? I am afraid I =20 >>>>>have not been looking very close at the source code lately=20 >=20 > (mostly =20 >=20 >>>>>since I do not own a decent measurement microphone).=20 >>>>> >>>>>Also, when some of you start to work on a sample application it=20 >=20 > might =20 >=20 >>>>>be a good idea to create a separate module in the cvs or create a=20 >=20 > new =20 >=20 >>>>>project.=20 >>>>> >>>>>Regards=20 >>>>> >>>>>Daniel Sundberg=20 >>>>> >>>>> >>>>>dan...@br... wrote:=20 >>>>> >>>>> >>>>>>Hi Scott=20 >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>>A little while ago Daniel talked about replacing the FHT with =20 >>>>>>>another scheme to generate the impulse response, which appears=20 >=20 > to =20 >=20 >>>>>>>have been done. Can you confirm that it is as fast as the FHT?=20 >>>>>> >>>>>> >>>>>> >>>>>>I don't know if it's as fast as FHT, it's certainly fast enough=20 >=20 > for =20 >=20 >>>>>>desktop computers. I have no idea how they do it, but fftw=20 >=20 > doesn't =20 >=20 >>>>>>seem to be that much slower for n^2-1 fft lengths than n^2=20 >=20 > lengths.=20 >=20 >>>>>> >>>>>> >>>>>>>Does the correlation still create a perfect unit response as it =20 >>>>>>>should with the MLS?=20 >>>>>> >>>>>> >>>>>> >>>>>>I'm not sure what you mean with a perfect unit response. But I'm =20 >>>>>>sure the new scheme is much more accurate than the FHT. I have =20 >>>>>>compared the results from the sweep mode with the MLS mode and=20 >=20 > they =20 >=20 >>>>>>are the same.=20 >>>>>> >>>>>>The problem with FHT MLS is that you assume that the soundcard =20 >>>>>>doesn't degrade the signal at all. It's in fact even more=20 >=20 > sensitive =20 >=20 >>>>>>to this than you might think. Even with an almost perfectly flat =20 >>>>>>freqency response you will still not get good results with the=20 >=20 > FHT. =20 >=20 >>>>>>I think the FHT should be viewed as a last resort, only to be=20 >=20 > used =20 >=20 >>>>>>when speed is top priority and not accuracy.=20 >>>>>>Although some of the FHT problems could be solved with=20 >=20 > calibration I =20 >=20 >>>>>>still don't think you will get as good results as when you=20 >=20 > correlate =20 >=20 >>>>>>in the frequency domain. I'm not sure that the FHT errors are=20 >=20 > static =20 >=20 >>>>>>enough to be effectivly removed with calibration.=20 >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>>I must get started on a test/demo app.=20 >>>>>> >>>>>> >>>>>> >>>>>>I have almost finished a waveform viewer/library that can be=20 >=20 > used =20 >=20 >>>>>>from other appplications, so you might want to wait for that.=20 >>>>>>I will make it public as soon as I figure out where to put it.=20 >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>>One final thing. If we have upgraded the project name to level=20 >=20 > 1 =20 >=20 >>>>>>>then I think we need to upgrade the major revision number to 1=20 >=20 > as =20 >=20 >>>>>>>well. Perhaps 1.0.=20 >>>>>> >>>>>> >>>>>> >>>>>>I agree on this, although I don't think we should go 1.0 until=20 >=20 > the =20 >=20 >>>>>>library is stable.=20 >>>>>> >>>>>>/Daniel=20 >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>-------------------------------------------------------=20 >>>>>>This SF.Net email is sponsored by The 2004 JavaOne(SM)=20 >=20 > Conference=20 >=20 >>>>>>Learn from the experts at JavaOne(SM), Sun's Worldwide Java=20 >=20 > Developer=20 >=20 >>>>>>Conference, June 28 - July 1 at the Moscone Center in San=20 >=20 > Francisco, CA=20 >=20 >>>>>>REGISTER AND SAVE! http://java.sun.com/javaone/sf Priority Code =20 >>>>>>NWMGYKND=20 >>>>>>_______________________________________________=20 >>>>>>Libmls0-developers mailing list=20 >>>>>>Lib...@li...=20 >>>>>>https://lists.sourceforge.net/lists/listinfo/libmls0-developers=20 >>>>>> >>>>>> >>>>> >>>>> >>>>> >>>>>-------------------------------------------------------=20 >>>>>This SF.Net email sponsored by Black Hat Briefings & Training.=20 >>>>>Attend Black Hat Briefings & Training, Las Vegas July 24-29 -=20 >=20 > digital =20 >=20 >>>>>self defense, top technical experts, no vendor pitches, unmatched =20 >>>>>networking opportunities. Visit www.blackhat.com=20 >>>>>_______________________________________________=20 >>>>>Libmls0-developers mailing list=20 >>>>>Lib...@li...=20 >>>>>https://lists.sourceforge.net/lists/listinfo/libmls0-developers=20 >>>>> >>> >>>=20 >>>=20 >>>=20 >>>-------------------------------------------------------=20 >>>This SF.Net email sponsored by Black Hat Briefings & Training.=20 >>>Attend Black Hat Briefings & Training, Las Vegas July 24-29 -=20 >=20 > digital =20 >=20 >>>self defense, top technical experts, no vendor pitches, unmatched =20 >>>networking opportunities. Visit www.blackhat.com=20 >>>_______________________________________________=20 >>>Libmls0-developers mailing list=20 >>>Lib...@li...=20 >>>https://lists.sourceforge.net/lists/listinfo/libmls0-developers=20 >>>=20 >>>=20 >> >>=20 >>=20 >>=20 >>-------------------------------------------------------=20 >>This SF.Net email sponsored by Black Hat Briefings & Training.=20 >>Attend Black Hat Briefings & Training, Las Vegas July 24-29 -=20 >>digital self defense, top technical experts, no vendor pitches,=20 >>unmatched networking opportunities. Visit www.blackhat.com=20 >>_______________________________________________=20 >>Libmls0-developers mailing list=20 >>Lib...@li...=20 >>https://lists.sourceforge.net/lists/listinfo/libmls0-developers=20 >>=20 >=20 >=20 >=20 >=20 |
From: Daniel S. <ds...@ho...> - 2004-06-22 09:12:04
|
Hi! I have two questions: what is FHT? Fast Hamahard Transform? Daniel: did libmls use FHT before and now uses FFT? I am afraid I have not been looking very close at the source code lately (mostly since I do not own a decent measurement microphone). Also, when some of you start to work on a sample application it might be a good idea to create a separate module in the cvs or create a new project. Regards Daniel Sundberg dan...@br... wrote: > Hi Scott > > >>A little while ago Daniel talked about replacing the FHT with another scheme to generate the impulse response, which appears to have been done. Can you confirm that it is as fast as the FHT? > > > I don't know if it's as fast as FHT, it's certainly fast enough for desktop computers. I have no idea how they do it, but fftw doesn't seem to be that much slower for n^2-1 fft lengths than n^2 lengths. > > >>Does the correlation still create a perfect unit response as it should with the MLS? > > > I'm not sure what you mean with a perfect unit response. But I'm sure the new scheme is much more accurate than the FHT. I have compared the results from the sweep mode with the MLS mode and they are the same. > > The problem with FHT MLS is that you assume that the soundcard doesn't degrade the signal at all. It's in fact even more sensitive to this than you might think. Even with an almost perfectly flat freqency response you will still not get good results with the FHT. I think the FHT should be viewed as a last resort, only to be used when speed is top priority and not accuracy. > Although some of the FHT problems could be solved with calibration I still don't think you will get as good results as when you correlate in the frequency domain. I'm not sure that the FHT errors are static enough to be effectivly removed with calibration. > > >>I must get started on a test/demo app. > > > I have almost finished a waveform viewer/library that can be used from other appplications, so you might want to wait for that. > I will make it public as soon as I figure out where to put it. > > >>One final thing. If we have upgraded the project name to level 1 then I think we need to upgrade the major revision number to 1 as well. Perhaps 1.0. > > > I agree on this, although I don't think we should go 1.0 until the library is stable. > > /Daniel > > > > > ------------------------------------------------------- > This SF.Net email is sponsored by The 2004 JavaOne(SM) Conference > Learn from the experts at JavaOne(SM), Sun's Worldwide Java Developer > Conference, June 28 - July 1 at the Moscone Center in San Francisco, CA > REGISTER AND SAVE! http://java.sun.com/javaone/sf Priority Code NWMGYKND > _______________________________________________ > Libmls0-developers mailing list > Lib...@li... > https://lists.sourceforge.net/lists/listinfo/libmls0-developers > > |