From: Daniel S. <ds...@ho...> - 2004-06-23 14:55:33
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>=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. 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