Interesting thread! At the risk of accusations of marketing (the shame, the shame!)*, I thought I'd provide a few details on how Blue Ripple Sound approaches binaural HOA decoders. We DO use an approach which shares quite a bit with Archontis' suggestions. I prefer this to the "virtual speaker" approach, but (as with many things HOA) there are lots of ways to get it badly wrong, and some of the maths/processing involved in the approach we settled on is some of the scariest I've done. The original Rapture3D binaural decoders (Orange, Yellow, Red, Blue, Green) were generated with our third generation of this tech (IIRC - something like that). Amber came out of our fourth generation (a rewrite) quite a few years later.
As of Rapture3D Advanced v2.7.0, we've been supporting import of AES69 personal HRTF files. This is our fifth generation - hopefully we now have this working sufficiently robustly to let it run automatically. That said, we've not publicised it widely - I'm not even sure I've posted anything here - that is because this is very definitely an "experimental" feature right now. AES69 is based on SOFA, which is a flexible (i.e. complex) file format - you need to be using HDF5 and NetCDF4 (not earlier versions) to get to the real data, and then there are a number of optional geometric transforms - we currently can't be 100% sure we've handled all cases correctly. Then there's our scary processing, which obviously has a sensitivity to data quality - and we don't know what will be thrown at this code in the future. And finally, and probably most importantly, the current pool of testers is rather small because personal HRTF data is rare - we'd LOVE more feedback in this area - one day we'd lik e to remove the "experimental" tag. So, if you're measuring HRTFs, or estimating HRTFs (and I think that's the future) and are interested in HOA and/or Rapture3D Advanced, we'd love to hear from you. On orders: doing this "perfectly" requires very high orders indeed, but if you do things right then results just get better as the order increases. At first order, the effect is there, and reasonably natural - but not strong (and head-tracking is easy enough, as Archontis mentions). Third order is nice and solid. Rapture3D Advanced internally spits out decoders up to seventh order, although the VST only supports first to third order. (We actually have an in-house version of all our VST plugins at seventh order but currently have no plans to release it - third order is PLENTY for content right now IMHO.) You can render at up to fifth order using our old Rapture3D Advanced OpenAL game engine. The new Rapture3D VR/game engine will not support AES69 import initially, for simplicity during deployment - although temporarily the beta is including my personal HRTF, which was imported from AES69, and we've included some hooks for the future... Best wishes, --Richard [*] More seriously - please let me know off-list if I've misjudged this - I'm never sure about this sort of thing... _______________________________________________ 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.
