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https://github.com/bstegmaier75/porc

Python Open Room Correction (PORC)
https://github.com/bstegmaier75/porc

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Python Open Room Correction (PORC)

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README 

        
Python Open Room Correction (PORC)

==================================



PORC now includes mixed-phase compensation (see below)!



DSP Loudspeaker-Room correction filter wizard; transfer function modeling and equalization 

by fixed-pole parallel filters. Algorithm ported to Python by Mason A. Green, based on the work 

of Dr. Balazs Bank: http://home.mit.bme.hu/~bank/parfilt/



More details about Dr. Bank's parallel filter can be found in the papers:



    Balazs Bank, "Perceptually Motivated Audio Equalization Using Fixed-Pole Parallel

    Second-Order Filters," IEEE Signal Processing Letters, 2008.



http://www.acoustics.hut.fi/go/spl08-parfilt



    Balazs Bank, "Direct Design of Parallel Second-order Filters for

    Instrument Body Modeling," International Computer Music Conference,

    Copenhagen, Denmark, Aug. 2007.



http://www.acoustics.hut.fi/go/icmc07-parfilt

    

Mixed-Phase Compensation references:



	Alberto Carini, et al, "Mixed Time-Frequency approach for Multipoint

	Room Response Equalization," AES 45th International Conference, 2012

	

	Defrance & Polak, "Measuring the mixing time in auditoria," Acoustics

	Paris 2008

	

Required Python dependencies:



    1) Python 2.7

    2) Scientific Python: SciPy, Numpy, & Matplotlib



The easiest install method on Windows is simply to install the continuum.io Anaconda package.



Measurement

===========



One needs to measure the log-frequency impulse response of your speakers with a 

calibrated Electret Measurement Microphone, e.g. Dayton Audio EMM-6. Software 

such as Room EQ Wizard (REQ), Holm Impulse, or Arta may be used for this purpose:

http://www.hometheatershack.com/roomeq/



Usage

=====



porc.py [-h] [--mixed] [-t FILE] [-n NTAPS] [-o OPFORMAT] input_file output_file



    python porc.py -t tact30f.txt -n 6144 -o bin l48.wav leq48.bin



Use the -h flag for help!



PORC has been tested successfully on both Linux and Windows 7 with Python 2.7. Linux depenency 

install is fairly straightforward. Windows install packages are available for all dependencies.



Target Response

===============



The default target curve for PORC is flat. Included in the data directory are a number 

of target curves. Experiment to suit your listening preferences. Use the [-t] flag to load 

a target curve file.



Per default the target curve is interpolated using logarithmic interpolation. 

E.g., two data points 1000/0.0 and 10000/-6.0 will produce a straight rolloff of 6dB from 

1000Hz to 10kHz in a bode plot.

Logarithmic interpolation can be disabled using the --nologint flag.

Target curves do not have to include an entry for 0Hz and Fs/2. 



One may also target a flat curve, and then use separate parametric equalization for bass 

boosting and other pschoaccoustic preferences. 



For further reference, the B&K House Curve is a good place to start. Read "Relevant 

loudspeaker tests in studios in Hi-Fi dealers' demo rooms in the home etc.," Figure 5:

http://www.bksv.com/doc/17-197.pdf



Mixed-Phase Compensation

==============



To use mixed-phase compensation, one needs to specify the [--mixed] flag. One also needs to modify

the Room Impulse Response (RIR) to remove leading silence (zeros) before the main impulse. You can

easily do this with Audacity or REQ.



Example:



	python porc.py --mixed -t tact30f.txt -n 6144 -o bin l48.wav leq48.wav

	

Have some patience with this method. The convolution takes a few CPU cycles.



PC Convolution

==============



Suggestions:



Windows (foobar2000 convolver)

Linux (jconvolver w/ jcgui & Jack)



You may need to merge left and right channels into a single stereo .wav 



    sox -M le148.wav req48.wav equalizer.wav



OpenDRC Convolution

===================



Use -o bin flag to set binary 32bit IEEE floating point mono file format output for OpenDRC.



TODO

====



	Implement algo to automatically remove leading silence (zeros) from RIR.

	Add a GUI Frontend (pretty interactive graphs, drawing target curve, etc...)

	Update this page with better documentation!



Contact

=======



Complaints, suggestions, bugfixes: mason dot green at gmail