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TITLE:: FluidBufMelBands
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SUMMARY:: A Perceptually Spread Spectral Contour Descriptor on a Buffer
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CATEGORIES:: Libraries>FluidDecomposition
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RELATED:: Guides/FluCoMa, Guides/FluidDecomposition, Classes/FluidBufMFCC
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DESCRIPTION::
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This class implements a spectral shape descriptor where the amplitude is given for a number of equally spread perceptual bands. The spread is based on the Mel scale (https://en.wikipedia.org/wiki/Mel_scale) which is one of the first attempt to mimic pitch perception scientifically. This implementation allows to select the range and number of bands dynamically. It is part of the Fluid Decomposition Toolkit of the FluCoMa project.FOOTNOTE:: This was made possible thanks to the FluCoMa project ( http://www.flucoma.org/ ) funded by the European Research Council ( https://erc.europa.eu/ ) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 725899).::
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The process will return a single multichannel buffer of STRONG::numBands:: per input channel. Each frame represents a value, which is every hopSize.
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CLASSMETHODS::
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METHOD:: process
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This is the method that calls for the spectral shape descriptors to be calculated on a given source buffer.
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ARGUMENT:: server
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The server on which the buffers to be processed are allocated.
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ARGUMENT:: source
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The index of the buffer to use as the source material to be described through the various descriptors. The different channels of multichannel buffers will be processing sequentially.
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ARGUMENT:: startFrame
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Where in the srcBuf should the process start, in sample.
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ARGUMENT:: numFrames
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How many frames should be processed.
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ARGUMENT:: startChan
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For multichannel srcBuf, which channel should be processed first.
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ARGUMENT:: numChans
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For multichannel srcBuf, how many channel should be processed.
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ARGUMENT:: features
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The destination buffer for the STRONG::numBands:: amplitudes describing the spectral shape.
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ARGUMENT:: numBands
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The number of bands that will be perceptually equally distributed between STRONG::minFreq:: and STRONG::maxFreq::. It will decide how many channels are produce per channel of the source.
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ARGUMENT:: minFreq
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The lower boundary of the lowest band of the model, in Hz.
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ARGUMENT:: maxFreq
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The highest boundary of the highest band of the model, in Hz.
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ARGUMENT:: windowSize
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The window size. As spectral description relies on spectral frames, we need to decide what precision we give it spectrally and temporally, in line with Gabor Uncertainty principles. http://www.subsurfwiki.org/wiki/Gabor_uncertainty
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ARGUMENT:: hopSize
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The window hop size. As spectral description relies on spectral frames, we need to move the window forward. It can be any size but low overlap will create audible artefacts.
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ARGUMENT:: fftSize
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The inner FFT/IFFT size. It should be at least 4 samples long, at least the size of the window, and a power of 2. Making it larger allows an oversampling of the spectral precision.
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ARGUMENT:: action
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A Function to be evaluated once the offline process has finished and all Buffer's instance variables have been updated on the client side. The function will be passed [features] as an argument.
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RETURNS::
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Nothing, as the destination buffer is declared in the function call.
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EXAMPLES::
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code::
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// create some buffers
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(
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b = Buffer.read(s,File.realpath(FluidBufMelBands.class.filenameSymbol).dirname.withTrailingSlash ++ "../AudioFiles/Nicol-LoopE-M.wav");
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c = Buffer.new(s);
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)
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// run the process with basic parameters
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(
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Routine{
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t = Main.elapsedTime;
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FluidBufMelBands.process(s, b, features: c, numBands:10);
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(Main.elapsedTime - t).postln;
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}.play
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)
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// listen to the source and look at the buffer
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b.play;
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c.plot
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::
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STRONG::A stereo buffer example.::
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CODE::
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// load two very different files
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(
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b = Buffer.read(s,File.realpath(FluidBufSpectralShape.class.filenameSymbol).dirname.withTrailingSlash ++ "../AudioFiles/Tremblay-SA-UprightPianoPedalWide.wav");
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c = Buffer.read(s,File.realpath(FluidBufSpectralShape.class.filenameSymbol).dirname.withTrailingSlash ++ "../AudioFiles/Tremblay-AaS-AcousticStrums-M.wav");
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)
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// composite one on left one on right as test signals
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FluidBufCompose.process(s, c, numFrames:b.numFrames, startFrame:555000,destStartChan:1, destination:b)
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b.play
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// create a buffer as destinations
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c = Buffer.new(s);
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//run the process on them
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(
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Routine{
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t = Main.elapsedTime;
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FluidBufMelBands.process(s, b, features: c, numBands:10);
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(Main.elapsedTime - t).postln;
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}.play
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)
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// look at the buffer: 10 bands for left, then 10 bands for right
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c.plot(separately:true)
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:: |