Jun, Sounds like a great project. I have long been playing with Teensy's and ambisonics including porting both encoding and decoding there. My code won't directly help you since one of the first things I did was convert the whole audio chain in the Teensy Audio Library to use floats instead of integers. Not only was my own code already in floats but I find DSP programming in floats much easier than in integers. And since the Teensy's have hardware single precision floating point, it all works fine.
A Teensy 4 will certainly be able to run a basic decoder. The most basic version is nothing but sums and differences. The next step up might be to add shelf filters. However, for the application you envision, most people would want to do a conversion to binaural and there I expect you will run into trouble. Binaural conversions normally require running multiple convolutions. The filters are usually short but I suspect even eight 512 point convolutions are beyond the Teensy 4's ability but perhaps you could manage if you use integer math and truncate the filters. That said, I'm sure you can create a basic decoder and run a simple XY stereo output. I have seen this used for VR playback with head tracking and the results were quite usable. You will also need an ambisonic rotate unit, ideally with smoothing to avoid zipper noise. The rotate itself would then be an interpolation between two 4x4 matrix multiplies, but I expect you will need to set up table driven trig functions to build the matrices. I'd love to hear more about how your project develops. You can contact me at dmcgri...@vvaudio.com if the discussion gets too detailed for this forum. Thanks, David On Wed, Jan 5, 2022 at 7:58 PM byungjun kwon <byung...@gmail.com> wrote: > Hello, > > I'm a media artist and have been playing around with headphones with > custom-built circuitry > < > https://drive.google.com/drive/folders/1C2FX65AsQ9YsBrL4eVJvjhEDyWnPpXSt?usp=sharing > >. > > It's similar topic with on-going Air-pods but I opened a new thread > since it involves new hardware. > > The circuit is based on Teensy 4.0 > <https://www.pjrc.com/store/teensy40.html> with audio codec(sgtl5000), > SD card, indoor positioning(DW1000), GPS, accel/gyro(LSM6DS33), on-board > mic and etc. > > Combined with Teensy audio library > <https://www.pjrc.com/teensy/gui/index.html> , I was using it in various > art projects which offer quite accurate site-specific audio in the space > and user-interaction based on the distance and head-tracking. > > FOA playback with headtracking has long been on my list and I'd like to > have your opinion. > > It may play multichannel audio from SD card and is fast enough(600Mhz) > to run decoder, I think. > > Can anyone guide me how to develop FOA decoder in Teensy Audio > environment to achieve self-contained headphones with head tracking? > > Any comments would be appreciated! > > Regards, Jun > > > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > https://mail.music.vt.edu/mailman/private/sursound/attachments/20220106/9755ea74/attachment.htm > > > _______________________________________________ > 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. > -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20220106/f9d3812b/attachment.htm> _______________________________________________ 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.
