Hi all, Just thought I'd chime in as the author of the mentioned toolkit <https://www.princeton.edu/3D3A/SABREToolkit.html> - I'm happy to answer any questions anyone might have and to try to help you get it up and running if needed.
Regarding the spherical harmonic HRTF (SH-HRTF) approach described by Archontis, we've implemented this as the default in the toolkit. If you don't specify a desired virtual "speaker" grid, then the entire HRTF measurement set is used, and a "compact" decoder is created. This process is exactly what Archontis described: the decoder matrix becomes the identity matrix, and each ambisonic signal is filtered by corresponding the spherical-harmonic term of the HRTF (see Sec. 3.3 of the manual <https://github.com/PrincetonUniversity/3D3A-SABRE-Toolkit/blob/master/doc/SABRE_Manual.pdf>). Hopefully, the toolkit should streamline and simplify this process for the ambiX plug-in. In my experience, however, the SH-HRTF approach can sometimes yield a "blurry" 3D image (for example, compared to an only slightly oversampled virtual speaker grid - e.g., 36 speakers for 4th order decoding). I haven't fully sorted out why this happens yet, so I'd be interested to hear anyone's thoughts on it; my guess is that this has to do with the time alignment of the measured HRIRs. (Since the SH-HRIRs are linear combinations of the measured HRIRs, improper time alignment of the measurements will just spread out the resulting IR.) Also, HRTF sets with only partial coverage of the sphere might not give very good SH-HRTFs (depending on the order, of course) due to the poor conditioning in the SH matrix. In those cases, it might actually be better to use a subset of the measured HRIRs for most of the sphere, and then interpolate a few extra directions (e.g., below the listener) where no measurements exist. Then localization in at least the measured directions should be good. Anyways, those are just my two cents, and it's why I kept the toolkit flexible since I felt like these issues might be worth exploring. I'd be curious to hear anyone else's thoughts on them. Thanks, Joe On 23 November 2017 at 09:50, Politis Archontis <archontis.poli...@aalto.fi> wrote: Hi Gernot, > I haven?t used the toolkit, but I don?t see the reason for HRTF > interpolation in a predefined grid - if you generate the spherical harmonic > filters for whatever HRTF set you have without interpolation, then all you > need in AmbiX is a binaural decoding configuration file with a (N+1)^2 x > (N+1)^2 decoding matrix that is a unity matrix (zeros everywhere and ones > in the diagonal), along with the (N+1)^2 stereo WAV files of the filters > you generated (where N is the order you are going for). > Regards, > Archontis Politis > > On 23 Nov 2017, at 01:13, Gernot von Schultzendorff < > g.schultzendo...@saalakustik.de<mailto:g.schultzendo...@saalakustik.de>> > wrote: > Looking through IDA informations there seem to be two different ways to >> perform the individual scans: >> - "Using their smartphone?s camera, users will be able to scan >> themselves, gathering sufficient data for IDA Audio and Genelec to >> accurately 3D model and then create the unique HRTF filter set for personal >> rendering of 3D audio." [https://www.genelec.com/genelec-and-ida-audio- >> redefine-immersive-3d-audio-professional-headphone-users < >> https://www.genelec.com/genelec-and-ida-audio- >> redefine-immersive-3d-audio-professional-headphone-users>] >> - "An IDA 3D scan can be performed at a licensed IDA ScanStation on a >> variety of scanners, including structured light, laser, and photogrammetry >> scanners." [http://idaaudio.com/professionals/<http://idaaudio.com/ >> professionals/>] > > > > Regarding the import of SOFA files into the ambiX binaural player the >> Princeton University 3-D Audio & Applied Acoustics Lab has developed the >> SABRE toolkit specifically for this task (https://www.princeton.edu/ >> 3D3A/SABREToolkit.html <https://www.princeton.edu/3D3A/SABREToolkit.html>). >> Requires MATLAB knowledge and decisions about interpolation "when measured >> HRTFs are not available at the desired grid positions". Anyone having >> experiences with this toolkit? > > > > -- >> Gernot > > > -- Joseph G. Tylka Doctoral Candidate in Mechanical and Aerospace Engineering 3-D Audio & Applied Acoustics Laboratory Princeton University josep...@princeton.edu -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20171124/322dac3f/attachment.html> _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
