flucoma-sc/release-packaging/HelpSource/Classes/FluidBufOnsetSlice.schelp

TITLE:: FluidBufOnsetSlice
SUMMARY:: Spectral Difference-Based Audio Buffer Slicer
CATEGORIES:: Libraries>FluidDecomposition
RELATED:: Guides/FluCoMa, Guides/FluidDecomposition

DESCRIPTION::
This class implements many spectral-based onset detection functions, most of them taken from the literature. (http://www.dafx.ca/proceedings/papers/p_133.pdf) Some are already available in SuperCollider's LINK::Classes/Onsets:: object yet not as offline processes. 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).::

The process will return a buffer which contains indices (in sample) of estimated starting points of different slices.

CLASSMETHODS::

METHOD:: process
	This is the method that calls for the slicing to be calculated on a given source buffer.

ARGUMENT:: server
	The server on which the buffers to be processed are allocated.

ARGUMENT:: source
	The index of the buffer to use as the source material to be sliced through novelty identification. The different channels of multichannel buffers will be summed.

ARGUMENT:: startFrame
	Where in the srcBuf should the slicing process start, in sample.

ARGUMENT:: numFrames
	How many frames should be processed.

ARGUMENT:: startChan
	For multichannel sources, which channel should be processed.

ARGUMENT:: numChans
	For multichannel sources, how many channel should be summed.

ARGUMENT:: indices
	The index of the buffer where the indices (in sample) of the estimated starting points of slices will be written. The first and last points are always the boundary points of the analysis.

ARGUMENT:: function
	The function used to derive a difference curve between spectral frames. It can be any of the following:
		TABLE::
		##0 || Energy || thresholds on (sum of squares of magnitudes / nBins) (like Onsets \power)
		##1 || HFC || thresholds on (sum of (squared magnitudes * binNum) / nBins)
		##2 || SpectralFlux || thresholds on (diffence in magnitude between consecutive frames, half rectified)
		##3 || MKL || thresholds on (sum of log of magnitude ratio per bin) (or equivalent: sum of difference of the log magnitude per bin) (like Onsets \mkl)
		##4 || IS || (WILL PROBABLY BE REMOVED) Itakura - Saito divergence (see literature)
		##5 || Cosine || thresholds on (cosine distance between comparison frames)
		##6 || PhaseDev || takes the past 2 frames, projects to the current, as anticipated if it was a steady state, then compute the sum of the differences, on which it thresholds (like Onsets \phase)
		##7 || WPhaseDev || same as PhaseDev, but weighted by the magnitude in order to remove chaos noise floor (like Onsets \wphase)
		##8 || ComplexDev || same as PhaseDev, but in the complex domain - the anticipated amp is considered steady, and the phase is projected, then a complex subtraction  is done with the actual present frame. The sum of magnitudes is used to threshold (like Onsets \complex)
		##9 || RComplexDev || same as above, but rectified (like Onsets \rcomplex)
		::

ARGUMENT:: threshold
The thresholding of a new slice. Value ranges are different for each function, from 0 upwards.

ARGUMENT:: debounce
	The minimum duration of a slice in number of hopSize.

ARGUMENT:: filterSize
	The size of a smoothing filter that is applied on the novelty curve. A larger filter filter size allows for cleaner cuts on very sharp changes.

ARGUMENT:: frameDelta
		For certain functions (HFC, SpectralFlux, MKL, Cosine), the distance does not have to be computed between consecutive frames. By default (0) it is, otherwise this sets the distane between the comparison window in samples.

ARGUMENT:: winSize
	The window size. As spectral differencing 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

ARGUMENT:: hopSize
	The window hope size. As spectral differencing relies on spectral frames, we need to move the window forward. It can be any size but low overlap will create audible artefacts. The -1 default value will default to half of winSize (overlap of 2).

ARGUMENT:: fftSize
	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. The -1 default value will default to windowSize.

ARGUMENT:: action
		A Function to be evaluated once the offline process has finished and indices instance variables have been updated on the client side. The function will be passed indices as an argument.

RETURNS::
	Nothing, as the various destination buffers are declared in the function call.

EXAMPLES::

CODE::
(
//prep some buffers
b = Buffer.read(s,File.realpath(FluidBufOnsetSlice.class.filenameSymbol).dirname.withTrailingSlash ++ "../AudioFiles/Nicol-LoopE-M.wav");
c = Buffer.new(s);
)

(
// with basic params
Routine{
	t = Main.elapsedTime;
	FluidBufOnsetSlice.process(s,b.bufnum, indices: c.bufnum, threshold:0.5);
	s.sync;
	(Main.elapsedTime - t).postln;
}.play
)

//check the number of slices: it is the number of frames in the transBuf minus the boundary index.
c.query;

//loops over a splice with the MouseX
(
{
	BufRd.ar(1, b.bufnum,
		Phasor.ar(0,1,
			BufRd.kr(1, c.bufnum,
				MouseX.kr(0, BufFrames.kr(c.bufnum) - 1), 0, 1),
			BufRd.kr(1, c.bufnum,
				MouseX.kr(1, BufFrames.kr(c.bufnum)), 0, 1),
			BufRd.kr(1,c.bufnum,
				MouseX.kr(0, BufFrames.kr(c.bufnum) - 1), 0, 1)), 0, 1);
		}.play;
)
::