HOA Tutorial Exercise 05

Extension

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Below are some simple examples that show how to play back a multichannel soundfile in HOA b-format and listen to it through headphones. The 3rd order field recordings have been made with the Eigenmike https://mhacoustics.com/products with the kind support ofthe Centre for Interdisciplinary Research in Music Media and Technology, housed at the Schulich School of Music at McGill University (CIRMMT) http://www.cirmmt.org/ a microphone array with 32 capsules.

In case you have not done so yet: let's start the sound server, which we configure first to get more audio buses and to have 36 output channels.s.quit; // quit the server first if it is still running with another configuration. ( ServerOptions.devices; s = Server.local; Server.local = Server.default; o = Server.local.options; // Get the local server's options o.numInputBusChannels = 2; // Set Input to number of Inputs o.numOutputBusChannels = 36; // lets start after chan 36 so as not to see the mic input o.numAudioBusChannels = 2048; o.blockSize = 512; o.numWireBufs = 1024 * 16; o.memSize = 2.pow(18); o.sampleRate = 48000; s.makeWindow; s.boot; )

Start the oscilloscope showing all the channels for the selected order of the B-format.( ~order = 3; ~hoaNumChannels = (~order+1).pow(2); s.scope(2); // let's use only two channels as we will monitor it with headphones )

Let's load some 16 channels 3rd order soundfiles, the filenames indicate the channel ordering as well as the normalization (ACN, N3D):~hoaSoundFile = Buffer.read(s, HOA.soundsDir++"/eigen_ACN_N3D_Montreal_Metro_cello.wav"); ~hoaSoundFile = Buffer.read(s, HOA.soundsDir++"/eigen_ACN_N3D_Montreal_Metro.wav"); ~hoaSoundFile = Buffer.read(s, HOA.soundsDir++"/eigen_ACN_N3D_CIRMMT_Foyer_short.wav"); ~hoaSoundFile = Buffer.read(s, HOA.soundsDir++"/eigen_ACN_N3D_Montreal_LePlateau_Backyard_short.wav"); ~hoaSoundFile.numChannels;

Let's make a node that can play back the 3rd order HOA sound file.( ~hoaSignal = NodeProxy.new(s, \audio, ~hoaNumChannels); ~hoaSignal.source = { HPF.ar(PlayBuf.ar( ~hoaSoundFile.numChannels, ~hoaSoundFile, loop:1 ), 100) }; ~hoaSignal.fadeTime = 1; )

Let's make the decoder:HOADecLebedev26.loadHrirFilters(s); HOADecLebedev26.hrirFilters.size; ( ~decoderOrder = 2; // let's reduce the order ~decoderNumChannels = (~decoderOrder+1).pow(2); ~decoder = NodeProxy.new(s, \audio, 26); ~decoder.source = {var in; in = \in.ar(0!~decoderNumChannels); HOADecLebedev26.ar(~decoderOrder, in, hrir_Filters:1) }; ~decoder.fadeTime = 1; ~decoder.play(0, 26); )

And then we connect them:~hoaSignal <>> ~decoder;

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