control curves
v1.0 [pdf]
As a last step for making iDAFx, when the effects and the feature extractions are already existing, counts the control curve. The best work already made on it is from the hand of Verfaille and Arfib.
The feature extraction stage ends with a curve of values that change. Before entering the parameter curve/values of the effect a few adaptations must be made:
- combine
One can choose (it's optional) to combine several features. These can be added as a linear combination, each with their specific weight. Also must the signal be normalized. A block is made for this: combine. - map
Several mapping strategies have to be provided, depending on the features and the effect parameter one wants to control. A lot of experimenting may be done with all possibilities. Different blocks are made for this, they all have one input and one output, both normalized: mapLinear, mapSine, mapTrunc, mapTime,...
Also other mappings can be used. mapping is nothing more than applying a function. More window-like functions can be used too: hamming, hann, gauss,... and also non-symmetrical windows come in handy. View the documentation in the document mapWindow. Some other techniques are also presented is this documentation (eg bpm2time ) - scale
In the last step the curve must be shifted and scaled to the appropriate range of the effect parameter: scale.
Hereunder follows the documentation of the blocks used for the technique described in the above mentioned paper.
combine
This block makes a linear combination of the inlets. The factors can be chosen from the display. The inlets must be normalized before entering the block. The output is normalized too.version
v1.0: built 29/04/2007 with Pd v0.40-2 [pd]interface
Input 1, 2 and 3: control signals to combine. They have to be normalized before entering the block. One can also use only two inlets.Output 1: a normalized control signal that is the linear combination as chosen from the display.
Controls:
number box 1, 2 and 3: The factors a, b and c in the equation y = ax1 + bx2 + cx3.
implementation
The equation used here is:y = (ax1 + bx2 + cx3)/(a+b+c)The bang blocks make sure that it doesn't matter which inlets are used or not used. Either way the sum will be updated, even though a cold inlet might be used (that normally would not update that sum). If the inlets are normalized (and this is assumed), the division by the sum of all coefficients will normalize the output too.
scale, scaleS
This block scales a normalized input to a range that is specified in the controls on a display or at the inlets.version
v1.0: built 29/04/2007 with Pd v0.40-2 [scale.pd][scaleS.pd]interface
Input 1: Input control signal ranging between 0 and 1Input 2, number box m: lower boundary of the target range
Input 3, number box M: upper boundary of the target range
Output 1: a scaled version of the input signal
implementation
For both instances the following mathematical formula is performed:y = (M-m)*x+m
mapLinear/mapLin
This block performs a linear mapping between a normalized input and a normalized output. That constraint is not even necessary, the only real constraint is that the curve starts at zero. But for mapping purposes the signal is mostly normalized. Include an argument number!version
v1.0: built 29/04/2007 with Pd v0.40-2 [mapLinear][mapLin]interface
mapLinear:Input 1: control signal
Input 2, 3, 4: knee of the curve: x1, x2, x3. These knees correspond with thresholds in dynamics processing
Input 5, 6, 7, 8: slopes of each line: a1, a2, a3, a4. The slopes correspond eg with compression factors: 2:1 would give a slope of 1/2 or 0.5
Output 1: the normalized result of the linear curve
mapLin:
Input 1: control signal
Input 2: slope of the line a
Input 3: y-intercept of the line b
implementation
This patch does nothing more than performing the formulas you find in the graphs in the section interface. To check where x is situated, moses blocks are used.
mapSine
This block maps the normalized input according to a sinusoidal curve (as one can see in the figure in the preamble).version
v1.0: built 29/04/2007 with Pd v0.40-2 [pd]interface
Input 1: a normalized input control signalOutput 1: a mapped signal output according to the given curve. It ranges from 0 to 1.
implementation
The given formula is performed with Pure Data blocks. The sin~ block is a phase shifted version of the cos~ block. View the documentation of sin~ if needed. Because it outputs an audio signal, the bang object bangs a snapshot~ object that samples and holds the value of that moment. Because the bang block is connected with the output of the calculation, each change will result in a new sample at the output of the snapshot~ block.
mapTrunc/mapTruncS
This block maps a chosen part of the normalized input to the output (as one can see in the figure in the preamble). This mapping curve is a very basic limiter and noise gate. The threshold of the noise gate would be tm and the threshold of the limiter would be tM. Include an argument number!version
v1.0: built 29/04/2007 with Pd v0.40-2 [mapTrunc][mapTruncS]interface
Input 1: a normalized input control signalInput 2, number box tm: lower boundary of truncation
Input 3, number box tM: upper boundary of truncation
Output 1: a mapped signal output according to the given curve. It ranges from 0 to 1.
implementation
In comparison with other implementations in this document, nothing new is done, only another formula. The formula performed here with Pure Data blocks is:y = [tm (if x<tm) + tM (if x>tM) + x (if tm<x<tM)]/(tM-tm)
mapTime/mapTimeS
This block time stretches the original control signal. The time-stretched parameter alpha divides the original range into two parts: the lowest will be contracted to sm, the upper dilated to sM (as one can see in the figure in the preamble). Include an argument number!version
v1.0: built 29/04/2007 with Pd v0.40-2 [mapTime.pd][mapTimeS.pd]interface
Input 1: a normalized input control signalInput 2, number box alpha: time-stretched parameter that realizes the boundary between contraction and dilatation.
Input 3, number box sm: contraction factor smaller than or equal to 1
Input 4, number box sM: dilatation factor greater than or equal to 1
Output 1: a mapped signal output according to the given curve. It ranges from 0 to 1.
implementation
As with the other blocks in this document a formula is calculated with PureData blocks. Care is taking to include dollar arguments to ensure multiple and correct use in the same patch. The formula calculated is:y = sm^((alpha-x)/alpha) (if x < alpha) + sM^(x.alpha/(1-alpha)) (if x > alpha))
bpm2time
This block calculates the period between two beats or any division of it. It can be used to calculate a certain delay time parameter.version
v1.0: built 29/04/2007 with Pd v0.40-2 [pd]interface
Input 1: a bpm value. Best somewhere between 40bpm and 250bpm, but it works for every value given.Input 2: the division (DIV) parameter specifies how to divide the period between two beats. Here's a list with values that can be used on instruments like the Korg Microkorg and Roland SH32. The ones with an asterisk are whole divisions of a period. The others need several periods to synchronise again with the first count of a measure. A block is made for this purpose: measure. It has buttons for every possibility.
1/1 DIV=1 *
3/4 DIV=0.75
2/3 DIV=0.66666
1/2 DIV=0.5 *
3/8 DIV=0.375
1/3 DIV=0.333333 *
1/4 DIV=0.25 *
3/16 DIV=0.1875
1/6 DIV=0.16666 *
1/8 DIV=0.125 *
3/32 DIV=0.09375
1/12 DIV=0.08333 *
1/16 DIV=0.0625 *
3/64 DIV=0.04687
1/24 DIV=0.04166 *
1/32 DIV=0.03125 *
Output 1: a time parameter in msec. 60bpm=1000msec
implementation
This is the measure block implementation. All in the red box is part of the display (by a graph-on-parent).
The mathematical formula for this calculation is:DLY = DIV*60000/BPMThis formula come from 60sec/minute and 1000msec/second. The bang block is provided to make sure that the output is also updated when only the DIV inlet is changed, although it is attached to the cold inlet of the multiplication block.
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