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Digital room correction with DRC and BruteFIR
04-07-2015, 09:55
Post: #1
Digital room correction with DRC and BruteFIR
MinimStreamer makes it possible to do room correction on Linux quite easily with DRC and BruteFIR

To make it work, avconv need to be warped so that i calls the BruteFIR convolver. This can be done with the following script:

Code:
#!/bin/bash
avconv "$@" | brutefir /opt/drc/brutefir/brutefir.cfg 2> /opt/drc/brutefir/brutefir.log

I have placed MinimServer, wrapper scripts and configuration files in the following structure:

/opt/drc/brutefir/ -> BruteFIR conf and log folder
/opt/drc/bin -> avconv wrapper script folder
/opt/drc/minimserver -> minimserver folder

Of course BruteFIR and avconv must be installed. Do the following on Ubuntu:

Code:
sudo apt-get install brutefir
sudo apt-get install libav-tools

MinimStreamer should then be configured to use the wrapper avconv script. In MinimWatch configure the following:

stream.converter = /opt/drc/bin/avconv
stream.transcoder = flac:wav24;96

This presupposes that your are using flac files and that BruteFIR is configured to use a sample rate of 96000.

Now for the hard part, a sweep must be record, a correction filter must be generated and BruteFIR must be configured.

I have used DrcDesigner to generate the sweep, but DrcDesigner will not directly create correction filters that can be use with BruteFIR.

To make the correction filter (for the left channel) with DrcDesigner installed on Windows do the following:

Code:
cd c:\DRCDesigner\drc-3.2.0\sample
drc.exe --PSPointsFile="c:\DRCDesigner\drc-3.2.0\sample\DRCDesignerCustomizedPoints.txt" --BCInFile=LeftSpe
akerImpulseResponse96000.pcm --PSOutFile=LeftSpeaker96000ERB.pcm erb96000.drc

Sample rate should be changed depending on how the sweep was recorded. Do the same for the right channel.

If you try to generate a correction filter with DrcDesigner, it will create a bat file starting with the name drcWrapperRunDRC . You can also use the DRC command in these files for generating correction filters.

Now you have two correction filter files LeftSpeaker96000ERB.pcm and RightSpeaker96000ERB.pcm these can be used in BruteFIR.

I suggest using the following guide for configuring BruteFIR:

http://wiki.slimdevices.com/index.php/Brutefir_Filter

Also, the test configuration (the one that delay the right channel relative to the left) is really helpful for verifying that the setup works.
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