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Old 2nd November 2012, 01:48 AM   #51
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Food for filter thought.

If response contains a moderately high Q peak at low frequency, the time domain may go on for thousands of samples before dieing to below dynamic range of CD. A true correction filter will be the same length.

Example:

120Hz peak of 6dB with Q=5, with sampling rate be 48kHz looks like:

120Hz peak 6db Q10 fs48.png

With time domain that runs on for more than 6k samples at 16bits and beyond 10k samples to get into noise floor of 24bit samples:

120Hz peak 6db Q10 fs48 wave.png

Getting great control down to 20Hz I find 32k-65k taps fills the bill, and for >60Hz 8k-16k taps.
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Old 2nd April 2013, 03:27 AM   #52
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Default Trying to get PORC working...

I have installed (I think) all the components of PORC, and it now runs, but I'm not seeing the results I expect.

Firstly, the graph that pops up only shows the uncorrected graph. Secondly, the .wav file that is created is not loadable by REW or the convolver in JRiver Media Center (I'm running the rather new Mac version).

Here's a snapshot of the graph produced, along with the results of running "play" on the file created.

JRiver shows a file status of "Not valid" when I load the output file. I've tried it in mono and in stereo (using sox to merge two copies of the original file to stereo).

Neither works.

Any suggestions?

Thanks,
Tim
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File Type: png Voila_Capture166.png (92.4 KB, 238 views)
File Type: jpg Voila_Capture167.jpg (26.4 KB, 233 views)
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Old 2nd April 2013, 03:33 AM   #53
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Quote:
Originally Posted by timbarnes View Post
Firstly, the graph that pops up only shows the uncorrected graph.
Just looking at the graph, you're definitely not getting the correct output. PM me, and send me your impulse responses, and I'll see if I get the same result on my end.
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Old 2nd April 2013, 04:26 AM   #54
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Quote:
Originally Posted by greenm01 View Post
Just looking at the graph, you're definitely not getting the correct output. PM me, and send me your impulse responses, and I'll see if I get the same result on my end.
Thanks - I just sent a link to the file via PM.

tim
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Old 2nd April 2013, 10:53 AM   #55
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Quote:
Originally Posted by timbarnes View Post
Thanks - I just sent a link to the file via PM.
Works on my end. I sent you a link to the filters in a PM. See below attached screen shot. I assume the stereo file you sent me was left/right channels (which I labeled the filenames), although they both look exactly the same to me.
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Last edited by greenm01; 2nd April 2013 at 10:54 AM. Reason: editorial
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Old 2nd April 2013, 03:15 PM   #56
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Quote:
Originally Posted by greenm01 View Post
Works on my end. I sent you a link to the filters in a PM. See below attached screen shot. I assume the stereo file you sent me was left/right channels (which I labeled the filenames), although they both look exactly the same to me.
Thanks - it was originally a mono recording. I think I have it working too - there must have been something wrong with my installation. I went crazy with macports trying to reinstall lots of the packages, and now I'm seeing results.

If I want to reduce the amount of gain in the bass, I need to modify the house curve file - is that right? I suspect my (non-measurement) mic. is a bit weak in the bass. In any case, the results are causing clipping and boominess, so I need to cut back the low bass.

Thanks again,
Tim
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Old 6th April 2013, 05:53 PM   #57
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Default Working with target files

I'm trying to modify my response so I don't get huge gain in the bass - my system is going into clipping. So I created a target response with attenuation in the bass. For some reason I'm not seeing the target response change as I'd expect. I've attached the graph from porc, and the contents of the target file.

My command line is as follows:

Code:
python porc.py -t target.txt -n 6144 FebImpulseOffice.wav OfImp2.wav
I would expect the output curve to somewhat follow the target...

Did I configure the target curve incorrectly?

Thanks for your help,

tim
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File Type: png figure_1.png (113.5 KB, 192 views)
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File Type: txt target.txt (102 Bytes, 11 views)
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Old 10th April 2013, 07:49 AM   #58
jlo is offline jlo  France
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Quote:
I'm not seeing the target response change as I'd expect.
I tried same target with http://www.ohl.to/audio/downloads/align2.zip and no problem, result follows target. As I did some minor changes about target in porc.py, you may check this file.

By the way, I noticed that Mason added a new function about mixed phase compensation. Could we get some details ?
Thanks, Mason.
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Old 12th April 2013, 06:27 AM   #59
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Hmm. I tried Align2 and I can't get any output at all. I get a window of zero size and no files. I do see command windows go by, but they close before I can read the error message.

I guess there's something wrong with my installation, but I don't know how to work out what it is

tim
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Old 12th April 2013, 02:58 PM   #60
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Quote:
Originally Posted by jlo View Post
By the way, I noticed that Mason added a new function about mixed phase compensation. Could we get some details ?
Mixed-phase equalizers can correct the non-minimum-phase part of the Room Transfer Function (impulse response), in the time domain. The method I'm using is based on the paper ""Mixed Time-Frequency approach for Multipoint Room Response Equalization," by Alberto Carini, et al.

This white paper, published by Dirac Research, is a good, high-level, summary of mixed-phase equalization.

Quote:
Originally Posted by timbarnes View Post
I guess there's something wrong with my installation, but I don't know how to work out what it is
I'm the first to admit that PORC's installation process is tedious. I plan to make it a lot more user friendly: 1st by reducing some of the Python dependencies, and 2nd porting the code to C to create a stand-alone command line executable. Folks can use something like Align2 if they want a nice GUI on top (neither which I have time nor patience to create myself).
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