Ask
Also, please don't loose my request to see the actual source and receive time signals as this is very valuable information when debugging a setup (you never mentioned this).
I had trouble with level issues as one other poster commented, but it took a while to track this down. If I could have seen the signals being used then I would have known immediately what the problem was. I simply do not trust any measurement where I can't see the raw data being used.
The program does look like a very good start - it could be great.
Also, please don't loose my request to see the actual source and receive time signals as this is very valuable information when debugging a setup (you never mentioned this).
I had trouble with level issues as one other poster commented, but it took a while to track this down. If I could have seen the signals being used then I would have known immediately what the problem was. I simply do not trust any measurement where I can't see the raw data being used.
The program does look like a very good start - it could be great.
Hey Earl,
How did you resolve your level issues? My issue as previously posted is that I can't get a loud enough output from the program. Is there a setting somewhere in there that I'm missing? Another program drives me out of the room at the level I have my Windows mixer set to. I can hear the sweep, just very faintly.
John
How did you resolve your level issues? My issue as previously posted is that I can't get a loud enough output from the program. Is there a setting somewhere in there that I'm missing? Another program drives me out of the room at the level I have my Windows mixer set to. I can hear the sweep, just very faintly.
John
No ASIO support yet.. + Levels
Now HOLMImpulse does not have ASIO support - only MME
The audio library (PortAudio) can support ASIO, but I see no need for that yet. (The increased latency in MME is no problem for such an application)
ASIO
- Do you have soundcards, that have ASIO, but not MME?
- How much do you prioritize ASIO support?
Levels
The logsweep send via MME has full level and HOLMImpulse does not do anything for the MME volume settings. In XP the master and wave volume must be adjusted. In Vista the application level and recording level.
Audacity
Audacity also uses PortAudio with MME-support.
In Audacity you can see the out->in waveforms, so until HOLMImpulse shows the out->in waveform, you can use this application for troubleshooting the MME sound-levels.
(In audacity you can generate waveforms)
Now HOLMImpulse does not have ASIO support - only MME
The audio library (PortAudio) can support ASIO, but I see no need for that yet. (The increased latency in MME is no problem for such an application)
ASIO
- Do you have soundcards, that have ASIO, but not MME?
- How much do you prioritize ASIO support?
Levels
The logsweep send via MME has full level and HOLMImpulse does not do anything for the MME volume settings. In XP the master and wave volume must be adjusted. In Vista the application level and recording level.
Audacity
Audacity also uses PortAudio with MME-support.
In Audacity you can see the out->in waveforms, so until HOLMImpulse shows the out->in waveform, you can use this application for troubleshooting the MME sound-levels.
(In audacity you can generate waveforms)
Showing the Waveforms is not a simple task
Thanks for the feedback
Don't misunderstand me... you do like to 
NB: I if you haven't smilies enabled above does not make sense.
Maybe you are right, but showing the Waveforms is not a simple taskgedlee said:
- How to integrate in GUI
- Performance, Performance, don't slow measuring down
- Performance, zooming, latency, ...
Thanks for the feedback
Don't misunderstand me... you do like to
NB: I if you haven't smilies enabled above does not make sense.
And Ask,
pls don't forget a DUT response IMPORT option, for offline-processing and "raw" use of the convolver, since I intend to preprocess the DUT response if needed (you can see, I just want to abuse your programming skills to get around programming my own freq-domain convolver with partitioning and all the frills needed to make it run efficiently, ha-ha).
And take your time, no need to hurry.
- Klaus
pls don't forget a DUT response IMPORT option, for offline-processing and "raw" use of the convolver, since I intend to preprocess the DUT response if needed (you can see, I just want to abuse your programming skills to get around programming my own freq-domain convolver with partitioning and all the frills needed to make it run efficiently, ha-ha).
And take your time, no need to hurry.
- Klaus
KSTR said:
Is the inverse really of any value if you have the stimulus? Does anyone besides Farina really bother to convolve with the inverse rather than simply do regularised division by the FFT in the frequency domain?
Wouldn't float do the job as well as double, and at half the file size? Your sweep would need to run for hours (days? weeks?
) to exceed the dynamic range of floats.
Good point, I indeed intended to try other convolvers to look at the IR they would come up with and compare with Ask's result. From a practial standpoint FFT division would do for FR mag, for correct phase info we'd need to align the response first (or let the SW do that, like ie spectralab does). Also I could just derive the inverse from the stimulus (reversed and with the 6dB/oct mag correction) but there is some uncertainity and guesswork involved.JohnPM said:
float WAVs would suffice in term of precision, thats true. But I have SW's which only accept headerless raw double for input...Wouldn't float do the job as well as double, and at half the file size? Your sweep would need to run for hours (days? weeks?
- Klaus
KSTR said:
Just do it in the frequency domain, FFT, element-wise reciprocal (regularised if stimulus content is band limited), IFFT, and the guesswork and magnitude corrections disappear. The whole reversal/magnitude correction thing is only the time domain approximation to the frequency division after all, but without the precision.
BUG: Don't set signal length to 21.
Yes you are right! It also crashes for me at signal length = 21
Thank you for reporting
I'll put it on the list. I'm making an updated list of bugs / feature requests. Below file is updated.
http://www.holmacoustics.com/downloads/HOLMImpulse/Issues.txt
/Ask
lazycatken said:
Yes you are right! It also crashes for me at signal length = 21
Thank you for reporting
I'll put it on the list. I'm making an updated list of bugs / feature requests. Below file is updated.
http://www.holmacoustics.com/downloads/HOLMImpulse/Issues.txt
/Ask
Regulized IFFT - bandpassed IFFT
Now please don't make this complicated
ref page 14 in:
http://pcfarina.eng.unipr.it/Public/Papers/238-NordicSound2007.pdf
The computation of the inverse filter is done in
frequency domain:
C[f] = Conj(H[f])/(Conj(H[f])H[f]+ε[f])
Where ε(f) is a small regularization parameter,
which can be frequency-dependent, so that the
inversion does not operates outside the frequency
range covered by the sine sweep
Without ε[f] we would simply have: C[f] = 1/H[f]
Applying ε[f] is nothing else than a bandpass of the resulting response. Like when Klaus is sweeping from 1000 Hz, then he knows that the response below 1000 Hz is not valid.
I'm in doubt if I should adopt this bandpass for the log-sweep - If I did Klaus and Earl would require that it could be disabled, so they could get the raw impulse
Now please don't make this complicated
ref page 14 in:
http://pcfarina.eng.unipr.it/Public/Papers/238-NordicSound2007.pdf
The computation of the inverse filter is done in
frequency domain:
C[f] = Conj(H[f])/(Conj(H[f])H[f]+ε[f])
Where ε(f) is a small regularization parameter,
which can be frequency-dependent, so that the
inversion does not operates outside the frequency
range covered by the sine sweep
Without ε[f] we would simply have: C[f] = 1/H[f]
Applying ε[f] is nothing else than a bandpass of the resulting response. Like when Klaus is sweeping from 1000 Hz, then he knows that the response below 1000 Hz is not valid.
I'm in doubt if I should adopt this bandpass for the log-sweep - If I did Klaus and Earl would require that it could be disabled, so they could get the raw impulse