An efficient binaural spatializer

The "binauralModeled-ircam" object is a pure-vanilla implementation of the binaural model created at IRCAM.. An example of its capabilities can be found at this page.

The object is found at my repository: https://github.com/andresbrocco/binauralModeled-pd

Main concept

Basically, it applies ITD and approximates the HRTF to a series of biquad filters, whose coefficients are avaliable here.

Sample Rate limitation: those coefficients work for audio at 44100Hz only!

Space interpolation

There is no interpolation in space (between datapoints): the chosen set of coefficients for the HRTF is the closest datapoint to the given azimuth and elevation (by euclidean distance).

Time interpolation

There is interpolation in time (so that a moving source sound smooth): two binauralModels run concurrently, and the transition is made by alternating which one to use (previous/current). That transition occurs in 20ms, whenever a new location is received.

Interface

You can control the Azimuth and Elevation through the interface, or pass them as argument to the first inlet.

Performace

Obs.: If the Azimuth and elevation does not match exactly the coordinates of a point in the dataset of HRTFs, the object will perform a search by distance, which is not optimal. Therefore, if this object is embedded in a higher level application and you are concerned about performance, you should implement a k-d tree search in order to find the exact datapoint before passing it to the "binauralModeled-ircam" object.

Ah, maybe this statement is obvious, but: it only works with headphones!

Thanks for sharing this! BTW, is the [!-~ 1] object inside the [pd crossfader] subpatch a typo? Should this be [!=~ 1] instead?

Hey @alexandros. that's not a typo! That's short for [expr(1-$f1)]: the exclamation point reverses the order of the inlets when preceding basic math operators + - * /

@andresbrocco Isn't it a cyclone object?

Ahh, indeed! I forgot to mention that
The goal is to be pure vanilla, so I'll replace it with:

[*~ -1]
|
[+~ 1]

Thanks @FFW and @alexandros

i wonder how you came up with the filter topology and settings and how you were deciding/balancing the filter curve precision vs the LR runtime difference/phase shift.

HRTF FIRs are a beast, and in my experience it already sounds terrible when you take it over to an fft filter.

@Obineg sorry for the delay!

Actually I'm not the one that designed the filters. I just copied the coefficients from a research published by IRCAM! That is mentioned at the readme file.

Regarding the LR phase difference, that's also a parameter provided by IRCAM (ITD), which I implemented using 2 delay~ lines, one for each channel.

Have you tested out? What do you think of the performance? Does it sound good for your ears?