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The JSFX SoX Plugins software package provides plugins for being used in digital audio workstations (DAW); they implement some of the audio processing effects from SoX. It is also possible to use them in any VST compatible DAW using the freely available ReaJS VST plugin that is able to interpret JSFX files.
SoX is a command line audio processing tool for Unix, Windows and Mac OS that transforms source audio files in several formats into other audio files. It provides several standard audio effects (like e.g. filters or reverb) in good quality and with a transparent, open-source implementation. Currently a project called SoX_ng and led by Martin W. Guy is modernizing all those effects and hence serves as the reference for this project.
The effects provided here are a complete rewrite in JSFX of the SoX algorithms for producing (bit-exact) identical renderings in the DAW. This can easily be checked by rendering some audio externally with SoX and internally with the plugins and subtracting the results. Apart from roundoff errors (SoX often uses 32bit integer processing, while the SoXPlugins always uses double floating point processing) the results cancel out with typically a residual noise of -140dBFS.
The main motivation for this package is to be able to play around with effects in a DAW and be sure that the external rendering by SoX will produce exactly the same results. Although SoX does not always provide the "best" effects, it still is a reliable and well-defined audio tool.
Only a selection of SoX effects has been reimplemented as plugins, but those are the ones that are - in my opinion - the more prominent effects in that suite.
Because SoX very often uses rich command line options for its effects, not every effect configuration from SoX can be fully transported into the slider oriented GUI for a plugin. E.g. the compander of SoX allows the definition of a transfer function having multiple segments. Although the internal engine of the SoXPlugins compander implements exactly the same internal segment logic, the user interface only allows the typical definition of a threshold and a compression ratio (with three segments).
Note also that a spiffy user interface is not at all a priority in this project. Also their parameter ranges are somewhat debatable, but they simply reflect the wide parameter ranges of the SoX command-line effect.
The redesign and restructuring has also been done for easier maintenance, because there is some redundancy and unnecessary complexity in the original sources due to their several contributors. Nevertheless - as pointed out - the effects provided here faithfully model the SoX command-line processing.
The following effects are available in this package:
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allpass: a biquad allpass filter two-poled with filter frequency and the filter bandwith (in several units)
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band: a biquad bandpass filter with center filter frequency and the filter bandwith (in several units) and an option for unpitched audio
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bandpass: a biquad filter for bandpass with center filter frequency and the filter bandwith (in several units)
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bandreject: a biquad filter for bandreject with center filter frequency and the filter bandwith (in several units)
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bass: a biquad filter for boosting or cutting bass with a shelving characteristics with settings for filter frequency and the filter bandwith (in several units)
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biquad: a generic biquad (iir) filter with 6 coefficients b0, b1, b2, a0, a1 and a2
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chorus: a chorus effect with multiple parallel echos modulated either by sine or triangle signals,
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compand: a compander with attack, release, input gain shift, threshold and compression and soft knee; this is a reduced version of SoX compand with only a simple transfer function
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echo: a tapped delay with several absolute delay times and signal decays,
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echos: a sequential delay with delay stages with absolute delay times and signal decays fed with signals from the previous stages,
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equalizer: a biquad filter for equalizing with settings for the pole count, the filter frequency and the filter bandwith (in several units)
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gain: a volume changer by exact decibels...
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highpass: a biquad filter for highpass with settings for the pole count, the filter frequency and the filter bandwith (in several units)
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lowpass: a biquad filter for lowpass with settings for the pole count, the filter frequency and the filter bandwith (in several units)
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mcompand: a multiband compander with a Linkwitz-Riley crossover filter and for each band a compander with attack, release, input gain shift, threshold and compression and soft knee; again the companders only allow a simple transfer function
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overdrive: a simple tanh distortion with gain and colour specification
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phaser: a phaser effect with sine or triangle modulation
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reverb: a reverb effect (based on Freeverb) with several parameters for the room (like size and HF damping) as well as a possible predelay
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treble: a biquad filter for boosting or cutting treble with a shelving characteristics with settings for filter frequency and the filter bandwith (in several units)
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tremolo: a tremolo effect with sine modulation using a double-sideband suppressed carrier modulation
As an analysis tool (e.g. for comparing the tool outputs with reference audio clips) a multilane oscilloscope is also available.
The installation is as follows:
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Close the Reaper application or your DAW using ReaJS (if open).
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Make a subdirectory "Dr_TT" in either the "Effects" directory of the Reaper installation (typically in "\Program Files\Reaper\Effects") or - if your DAW uses some different directory for JSFX files - in that directory.
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Copy over all *.jsfx and *.jsfx-inc files from the distribution into this directory. If helpful, also add the documentation from the root directory.
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Restart Reaper (or your other DAW). You should now be able to select the plugins from the JSFX folder (they are all prefixed with "SoX").
Alternatively - and much easier! - you can use the
[ReaPack][reference:reapack] plugin and do an automatic install via
the index.xml file in this repository.
After the installation via ReaPack all the effects can be found in the effects list of the Reaper installation.
The above diagram gives an example for one of the plugins: this is the UI for the phaser effect.
Here In Gain is the amplification factor for the input in decibels.
Delay gives the delay in milliseconds, Decay a factor for the
decay within the phaser and Frequency gives the modulation frequency
in Hz. The Waveform of the modulation is either sinusoidal or
triangular. Out Gain is the volume of the output.
If you are acquainted with the SoX command-line effects, you can see
that this is a direct representation of the parameter list in the
phaser effect.
If you want to run the test, you also have to have a SoX installation. The test script "makeTestFiles.bat" or "makeTestFiles.sh" in the test directory assumes that SoX is available in the program search path.
The test script produces several sound and noise files and applies SoX audio effects to produces result audio files.
Since there are so many DAWs available, it is hard to provide a test project for each of those. The distribution contains a Reaper project referencing those audio test files and result files in autonomous tracks. Adaption to other DAW should be straightforward.
The project file "testSoXPlugins.rpp" for the Reaper DAW references those test and result files and applies the corresponding effect plugins. Ideally (because the result files have inverted phase), everything should cancel out as shown here:
The detailed user manual can be found here.
This project is a derivative work based on the foundations laid by the SoX community. Although the algorithms used were modified and redesigned, this project would been much more complicated and tedious without this basis.
Hence my thanks go to Chris Bagwell, Nick Bailey, Martin W. Guy, Daniel Pouzzner, Måns Rullgård, Rob Sewell and all the other contributors of the SoX project: without your effort this would not have been possible!