HOA Tutorial Exercise 09

Extension

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This Tutorial shows how to use Binaural Rendering in combination with VBAP and Ambisonics.

You can use HOABinaural in combination with the HOAEncLebedev50 in order to listen to VBAP spatializations: First extract the Lebedevnode grid positions (azimuth and elevation), pack them in pairs and convert them to degrees. Use these positions as speaker positions in your VBAPSpeakerArray and prepare the necessary buffer for VBAP triangulation.a = VBAPSpeakerArray.new(3, HOAEncLebedev50.grid.flop.raddeg); // the next command might take a while for 50 speaker positions. b = Buffer.loadCollection(s, a.getSetsAndMatrices); // load the buffers for the Binaural HOABinaural.loadbinauralIRs(s); HOABinaural.loadHeadphoneCorrections(s); HOABinaural.binauralIRs; HOABinaural.headPhoneIRs; // watch the scope window for you binaural results s.scope(2);

Now encode a Noise source over VBAP with the Lebedev speaker positions and feed this 50 channels into the HOAEncLebedev50 e.g. for the 5th order. Then, binauralize the resulting b-format.( x = { |azi = 0, ele = 0, spr = 0| var source, lbedev50, order5Sig ; source = PinkNoise.ar(10); // source = SinOsc.ar(440.0); lbedev50 = VBAP.ar(50, source, b.bufnum, MouseX.kr(-180, 180), MouseY.kr(-90, 90), spr); order5Sig = HOAEncLebedev50.ar(5, lbedev50, gain: 0, filters:0); HOABinaural.ar(5, order5Sig, headphoneCorrection: nil); }.play; ) // play with the VBAP spread x.set(\spr, 5) x.set(\spr, 10) x.set(\spr, 15) x.set(\spr, 20) x.set(\spr, 25) x.set(\spr, 50)

The next example is for comparison with the Lebedev50BinauralDecoder. first we need the HRIRs:Lebedev50BinauralDecoder.loadHrirFilters(s);

Then we can encode again directly into a Lebedev 50 VBAP grid and convolve the grid positions directly with the HRIRs.( x = { |azi = 0, ele = 0, spr = 0| var source, lbedev50, order5Sig ; source = PinkNoise.ar(10); // source = SinOsc.ar(440.0); lbedev50 = VBAP.ar(50, source, b.bufnum, MouseX.kr(180, -180), MouseY.kr(-90, 90), spr); Lebedev50BinauralDecoder.ar(lbedev50 * 0.1); }.play; ) // play with the VBAP spread x.set(\spr, 5) x.set(\spr, 10) x.set(\spr, 15) x.set(\spr, 20) x.set(\spr, 25) x.set(\spr, 50)

If you want to encode any array of virtual speakers into the b-format assuming distant static sound sources as plane waves you can use the class HOASphericalHarmonics, which returns for a given order the coefficients for each combination of azimuth and elevation.( ~order = 1; // change order here HOASphericalHarmonics.coefN3D(~order, 0, 0).postcs; HOASphericalHarmonics.coefSN3D(~order, 0, 0).postcs; )

Encoding of sources using HOASphericalHarmonics listened to via binaural rendering would then work like that:( { var order = 5; var source = WhiteNoise.ar(0.1) ; //var source = SoundIn.ar(0.1) ; var bform = HOASphericalHarmonics.coefN3D(order, MouseX.kr(-pi, pi, 0).poll, MouseY.kr(-0.5pi, 0.5pi, 0).poll ) * source; var binaural = HOABinaural.ar(order, bform, headphoneCorrection:~headphoneModel); binaural }.play; )

Now we can implememt the Lebedev VBAP grid from above circumventing HOAEncLebedev50. This in turn means that you can replace these VBAP positions with any positions of your choice.(// first we get the source positions in radians ~postions = HOAEncLebedev50.grid.flop; // then we calculate the spherical Harmonics for each position ~order = 5; ~sh = ~postions.collect({|item,i| HOASphericalHarmonics.coefN3D(~order, item[0], item[1] )}); )

The next example is exactly as the first one but we remove the HOAEncLebedev50 encoder and replace the encoding step with the spherical harmonics from above from above.( x = { |azi = 0, ele = 0, spr = 0| var source, lbedev50, order5Sig ; // source = PinkNoise.ar(0.01); source = SinOsc.ar(440.0, 0, 0.1); lbedev50 = VBAP.ar(50, source, b.bufnum, MouseX.kr(-180, 180), MouseY.kr(-90, 90), spr); // lbedev50 = VBAP.ar(50, source, b.bufnum, SinOsc.ar(0.1, 0, 180), SinOsc.ar(0.15, 0, 90), spr); // This is the Ugen we are replacing with the hand made VBAP positions // order5Sig = HOAEncLebedev50.ar(5, lbedev50, gain: 0, filters:0); order5Sig = (~sh * lbedev50).sum; // this is a matrix multiplication HOABinaural.ar(5, order5Sig, headphoneCorrection: nil); }.play; ) // play with the VBAP spread x.set(\spr, 5) x.set(\spr, 10) x.set(\spr, 15) x.set(\spr, 20) x.set(\spr, 25) x.set(\spr, 50)

In the next example we encode the VBAP sources with the HOAEncoder.( ~order = 1; x = { |azi = 0, ele = 0, spr = 0| var source, lbedev50, order5Sig ; source = PinkNoise.ar(0.1); // source = SinOsc.ar(440.0); lbedev50 = VBAP.ar(50, source, b.bufnum, MouseX.kr(-180, 180), MouseY.kr(-90, 90), spr); // lbedev50 = VBAP.ar(50, source, b.bufnum, SinOsc.ar(0.1, 0, 180), SinOsc.ar(0.15, 0, 90), spr); order5Sig = ~postions.collect({|item,i| HOAEncoder.ar(~order, lbedev50[i], item[0], item[1], 1, 1, 10 ) }).sum; HOABinaural.ar(~order, order5Sig, headphoneCorrection: nil); }.play; ) // play with the VBAP spread x.set(\spr, 5) x.set(\spr, 10) x.set(\spr, 15) x.set(\spr, 20) x.set(\spr, 25) x.set(\spr, 50)

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