HoaNFProx | SuperCollider 3.13.0 Help

Description

Higher Order Ambisonic signal (HOA) near-field effect (NFE) proximity transformer.

Class Methods

.ar

Arguments:

in	The input signal.
order	Ambisonic order.

Discussion:

HoaNFProx translates an input HOA signal where refRadius = AtkHoa.refRadius to refRadius = inf.

This transform offers an HOA equivalent to FoaProximity where distance = AtkHoa.refRadius, in the first order case.

NOTE: This operation may be used to decode signals encoded as HOA with NFE to FOA or third party Ambisonic signal sets.

WARNING: The near-field effect proximity transformer is inherently numerically unstable and requires the use of signal pre-conditioned input to avoid overflow. In many cases, the use of HoaNFCtrl is advised, instead.

Examples

Decode from HOA1 with NFE to FOA

// Inspect the ATK's speed of sound reference
"Speed of sound: % m/s".format(AtkHoa.speedOfSound);

// Inspect the ATK's reference radius
"Reference radius: % m".format(AtkHoa.refRadius);

// Inspect the ATK's channel/coefficient ordering
"Coefficient ordering: %".format(AtkHoa.ordering);

// Inspect the ATK's channel/coefficient ordering
"Coefficient normalisation: %".format(AtkHoa.normalisation);

// simple test...

// boot rt server
s.boot;

// choose Ambisonic order
~order = 1  // match FOA, first order!

// choose an outbus, if need be
~outbus = 0

// open scope
s.scope(~order.asHoaOrder.size, ~outbus);

// encoding angles
// azimuth & elevation
~theta = 0.0;
~phi = 0.0;

// explicitly set encoding radius
// i.e., radius != AtkHoa.refRadius
~encRadius = 2.0;  // > AtkHoa.refRadius
~encRadius = 1.5;  // = AtkHoa.refRadius
~encRadius = 1.0;  // < AtkHoa.refRadius

// audition
(
{
    // saw params
    var freq = 110.0;
    var gain = -12;

var sig;
    var hoa;

sig = Saw.ar(freq, gain.dbamp);  // saw
    // sig = SinOsc.ar(freq, mul: gain.dbamp);  // sine

// HOA encoding, refRadius = AtkHoa.refRadius (= 1.5)
    hoa = HoaEncodeDirection.ar(sig, ~theta, ~phi, ~encRadius, ~order);  // no need to precondition sig!

// FOA decoding, refRadius = inf
    HoaDecodeMatrix.ar(
        HoaNFProx.ar(
            HPF.ar(hoa, freq/3),  // precondition sig, i.e., "make safe" for proximity (HOA1)
            ~order
        ),
        HoaMatrixDecoder.newFormat(\fuma, ~order)  // from atk to fuma
    );

}.play(outbus: ~outbus)
)

// quit rt server
s.quit

helpfile source: HelpSource/Classes/HoaNFProx.schelp
link::atk-sc3/Classes/HoaNFProx::

HoaNFProxExtension