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From: Steve H. <S.W...@ec...> - 2003-10-29 21:39:45
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Thanks to Mark for running the impulses through the filters, sadly there isn't enough inforamtion in the impulse (maybe due to some noise that crept in somewhere, maybe due to some non linearity in the filter, to be honest I dont know why) to analyse them, eg here are 4 traces from the lowpass filters: http://www.ecs.soton.ac.uk/~swh/gst-impulses/ They are the highest resonance settings, 4 different frequencies, which are the clearest, but still dont have much information in them. Mark, if possible could run run a very good whitenoise source (I can provide a WAV if you need one) into the same filters, runnning them a couple of seconds at each setting? Sorry, I didnt realise the signal would be so noisy. Just at minimum resonance settings with the 4 cutoffs you used before will be great for starters. As a note for me, and incase anyone wants to try it, you can produce spectrum plots in octave easily: 1) chop out the signal into sections to analyse (preferably just over 1 sec) with no other signal in them. save as 16bit mono WAV (eg. 01.wav) 2) convert to raw PCM file (eg. sox 01.wav 01.raw) 3) octave stuff: $ octave octave:1> # produce an fft of the raw file octave:1> f = fft(loadaudio('01', 'raw'), 44100); octave:2> # plot the freq response octave:2> plot(abs(f(1:22050)/max(abs(f)))); the plot is frequency (Hz) on the x-axis and normalised amplitude on the y-axis. plot(20.0 * log(abs(f(1:22050)/max(abs(f))))/log(10)); will show amplitude in dB's, which can be helpful. - Steve |
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From: Mark K. <mar...@co...> - 2003-10-29 22:32:06
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On Wed, 2003-10-29 at 13:39, Steve Harris wrote: > Mark, if possible could run run a very good whitenoise source (I can > provide a WAV if you need one) into the same filters, runnning them a > couple of seconds at each setting? Sorry, I didnt realise the signal > would be so noisy. Steve, This would be no problem at all. I would just take a white noise wave file and then build a new gig file using it. Now that I know how, that would take only 30 minutes or so, and running the recording only takes a few seconds really, so it's no big deal at all for me. I can record a wave file using the white noise generator in Pro Tools. I do not know if it qualifies as 'a very good white noise source.' If you provided a wave file that you are happy with, then we wouldn't have this uncertainly. Are you sure this noise you're seeing is *not* caused by me messing up somehow in the way I constructed the gig file? If you provided a well-known (to you anyway) noise source file would you be more likely to see me making a mistake? If so, then I think it makes the most sense for you to supply it. Please remember, I have done very few gig files, and none of them for 'scientific' purposes! ;-) > > Just at minimum resonance settings with the 4 cutoffs you used before will > be great for starters. Sure. Get that much, make sure it's right, and then move on to the other settings? Do you want all the filter types initially, or should we just do the low pass and see if it is working? Can you put a wave file you are interested in on your web site somewhere and point me at it? I'll download it and do it soon. BTW - Should i do this next set of recordings in mono? Mark |
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From: ian e. <de...@cu...> - 2003-10-30 15:32:24
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the impulse response of a filter completely describes its frequency response... what other information do you need? On Wed, 2003-10-29 at 16:39, Steve Harris wrote: > Thanks to Mark for running the impulses through the filters, sadly there > isn't enough inforamtion in the impulse (maybe due to some noise that > crept in somewhere, maybe due to some non linearity in the filter, to be > honest I dont know why) to analyse them, eg here are 4 traces from the > lowpass filters: > > http://www.ecs.soton.ac.uk/~swh/gst-impulses/ > > They are the highest resonance settings, 4 different frequencies, which > are the clearest, but still dont have much information in them. > > Mark, if possible could run run a very good whitenoise source (I can > provide a WAV if you need one) into the same filters, runnning them a > couple of seconds at each setting? Sorry, I didnt realise the signal > would be so noisy. > > Just at minimum resonance settings with the 4 cutoffs you used before will > be great for starters. > > As a note for me, and incase anyone wants to try it, you can produce > spectrum plots in octave easily: > > 1) chop out the signal into sections to analyse (preferably just over 1 > sec) with no other signal in them. save as 16bit mono WAV (eg. 01.wav) > > 2) convert to raw PCM file (eg. sox 01.wav 01.raw) > > 3) octave stuff: > > $ octave > octave:1> # produce an fft of the raw file > octave:1> f = fft(loadaudio('01', 'raw'), 44100); > octave:2> # plot the freq response > octave:2> plot(abs(f(1:22050)/max(abs(f)))); > > the plot is frequency (Hz) on the x-axis and normalised amplitude on the > y-axis. > > plot(20.0 * log(abs(f(1:22050)/max(abs(f))))/log(10)); > will show amplitude in dB's, which can be helpful. > > - Steve > > > ------------------------------------------------------- > This SF.net email is sponsored by: SF.net Giveback Program. > Does SourceForge.net help you be more productive? Does it > help you create better code? SHARE THE LOVE, and help us help > YOU! Click Here: http://sourceforge.net/donate/ > _______________________________________________ > Linuxsampler-devel mailing list > Lin...@li... > https://lists.sourceforge.net/lists/listinfo/linuxsampler-devel |
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From: <be...@ga...> - 2003-10-30 16:16:45
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Scrive ian esten <de...@cu...>: > the impulse response of a filter completely describes its frequency > response... what other information do you need? I agree. What noise are you refering to ? Mark said he recorded the output via digital audio link (Protools) and the original sample (non filtered) show all samples zero except one. So don't understand where the noise source could lie (except perhaps in a wrong GSt setting ?). Steve please show the iFFT of the impulses in a logarithmic scale. ( at least the y-axis (in dB) The graphs you posted are impossible to read. Perhaps it looks much better in the log scale ? Let us know please. Benno > > > On Wed, 2003-10-29 at 16:39, Steve Harris wrote: > > Thanks to Mark for running the impulses through the filters, sadly there > > isn't enough inforamtion in the impulse (maybe due to some noise that > > crept in somewhere, maybe due to some non linearity in the filter, to be > > honest I dont know why) to analyse them, eg here are 4 traces from the > > lowpass filters: ------------------------------------------------- This mail sent through http://www.gardena.net |
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From: Mark K. <mar...@co...> - 2003-10-30 16:48:14
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On Thu, 2003-10-30 at 08:16, be...@ga... wrote: > Scrive ian esten <de...@cu...>: > > > the impulse response of a filter completely describes its frequency > > response... what other information do you need? > > I agree. > What noise are you refering to ? > Mark said he recorded the output via digital audio link (Protools) > and the original sample (non filtered) show all samples zero except one. > So don't understand where the noise source could lie (except perhaps in > a wrong GSt setting ?). Clearly a possibility. > > Steve please show the iFFT of the impulses in a logarithmic scale. ( > at least the y-axis (in dB) > The graphs you posted are impossible to read. > Perhaps it looks much better in the log scale ? > I have built the white noise wave file and discussed it with Steve. I can now run sox and octave locally, so if there are commands in those programs people know of to analyze the work I'm doing, please send them along and I'll do more work up front before spewing out too much stuff. (I don't have time to try and read octave manuals, nor much interest.) I am building the gig file based on this today. If I solve my MIDI problem that cropped up last night I will certainly be able to get some data of the noise source going through the filters, so we'll have both versions of filter data to look at. I would expect that if I made a wrong turn in GSt with the impulses, then I'll make the same wrong turn using the white noise and we'll see that, so stay tuned. More data later this evening or tomorrow some time. - Mark |
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From: Steve H. <S.W...@ec...> - 2003-10-30 16:49:17
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On Thu, Oct 30, 2003 at 05:16:53 +0100, be...@ga... wrote: > Scrive ian esten <de...@cu...>: > > > the impulse response of a filter completely describes its frequency > > response... what other information do you need? > > I agree. > What noise are you refering to ? > Mark said he recorded the output via digital audio link (Protools) > and the original sample (non filtered) show all samples zero except one. > So don't understand where the noise source could lie (except perhaps in > a wrong GSt setting ?). Well, something was wrong. Maybe it will become clear after I've seen the noise plots. The plots quite clearly contained a sinewave of some kind and some harmonics. Either the impulse wasnt clean or there is some kind of non-linearity in there. - Steve |
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