Effectparameter Scaling

On This page we collect all issue and ideas about Scaling of Effect Parameter.

Controls

Hardware Solutions

Stomp Boxes / DJ Mixer

Rotary Potentiometer
Slider Potentiometer
Rotary Step Switch
Rocker Switch (2 or 3 steps)
Slider Switch
Pushbuttons

DJ Consoles

Rotary Knobs with Midi or higher resolution
Endless Rotary Knobs (Up/Down commands)
LED Row for Feedback
Pushbuttons

Parameter Examples

Gain
Center/Cut-off Frequency
Mode Switch
Periods
Bits
Rate

Desired Scales / Behaviors

Linear
Logarithmic
Audio-Taper
Steps
Split Scale
Pushbutton
Togglebutton
Latching button
Powerwindow button

Requirements

Value Feedback including units
Control a quantization Value with a continuous Knob
* Feedback of the Snapped value
Controllable by Super knob

LV2

http://lv2plug.in/ns/lv2core/

Parameters are "Class lv2:ControlPort" they have a value of c type float.

Example of a ControlPort:

[
  a lv2:ControlPort, lv2:InputPort;
  lv2:index 1;
  lv2:symbol "balance";
  lv2:name "Balance";
  lv2:minimum -1;
  lv2:maximum 1;
  lv2:default 0;
  lv2:scalePoint [ rdfs:label "Left"; rdf:value -1 ];
  lv2:scalePoint [ rdfs:label "Right"; rdf:value 1 ];
],

Additions for Mode Switches:

lv2:enumeration

" Indicates that a port's only reasonable values are the scale points defined for that port. A host SHOULD NOT allow a user to set the value of such a port to anything other than a scale point. However, a plugin MUST operate reasonably even if such a port has an input that is not a scale point, preferably by simply choosing the largest enumeration value less than or equal to the actual input value (i.e. round the input value down). "

lv2:integer

" Indicates that a port's reasonable values are integers (eg. a user interface would likely wish to provide a stepped control allowing only integer input). A plugin MUST operate reasonably even if such a port has a non-integer input. "

lv2:toggled

" Indicates that the data item should be considered a Boolean toggle. Data less than or equal to zero should be considered "off" or "false", and data above zero should be considered "on" or "true". "

lv2:sampleRate

" Indicates that any bounds specified should be interpreted as multiples of the sample rate. For instance, a frequency range from 0Hz to the Nyquist frequency (half the sample rate) could be requested by this property in conjunction with lv2:minimum 0.0 and lv2:maximum 0.5. Hosts that support bounds at all MUST support this property. "

VST

VST uses C Float parameter.

They workon the float range of 0.0f to 1.0f for the value of the parameter. Required scaling should be done inside the PlugIn

/* this struct taken from http://asseca.com/vst-24-specs/efGetParameterProperties.html */
struct _VstParameterProperties
{
   float stepFloat;
   float smallStepFloat;
   float largeStepFloat;
   char label[64];
   int32_t flags;
   int32_t minInteger;
   int32_t maxInteger;
   int32_t stepInteger;
   int32_t largeStepInteger;
   char shortLabel[8];
};

/* this enum taken from http://asseca.com/vst-24-specs/efGetParameterProperties.html */
enum VstParameterFlags
{
  kVstParameterIsSwitch = 1 << 0, /* parameter is a switch (on/off) */
  kVstParameterUsesIntegerMinMax = 1 << 1, /* minInteger, maxInteger valid */
  kVstParameterUsesFloatStep = 1 << 2, /* stepFloat, smallStepFloat, largeStepFloat valid */
  kVstParameterUsesIntStep = 1 << 3, /* stepInteger, largeStepInteger valid */
  kVstParameterSupportsDisplayIndex = 1 << 4, /* displayIndex valid */
  kVstParameterSupportsDisplayCategory = 1 << 5, /* category, etc. valid */
  kVstParameterCanRamp = 1 << 6 /* set if parameter value can ramp up/down */
};