Thank you for all the encouraging comments and feedback from you, I do appreciate it. The reason that I chose Teensy is because it's open-source, easy to add more and has a good community to ask around. Since I'm not developing commercial products, it's my best fit although there's a limitation. For those whom are interested, here's schematic of the circuit. https://drive.google.com/drive/folders/1QNsF_T_vU45BRMgzj9-kIxvA4my_8nar?usp=sharing (I didn't open it yet to public since there are still things to be done.) I'll get back to you with more results, hopefully soon. Jun
On Fri, Jan 7, 2022 at 6:22 AM Colin Ritchie <colin@voyage.audio> wrote: > Cool project! I built something similar that sounded really great, although > it was a bit cumbersome to use on a regular basis with cables running here > and there from my head. Actually building it into the headphones is key and > I like how you have accomplished this! > > The convolution required to decode FOA to binaural will most likely be too > much for the Teensy. The 38 mm X 78 mm device I created used an XMOS > XU216-512-TQ128 processor that worked quite well. > > Since this processor offers 16 deterministic "cores", I could > simultaneously: > 1. Stream multichannel uncompressed 24-bit audio over USB 2.0. > 2. Asynchronously stream quaternion data from a 9-axis IMU. > 3. Create the rotation matrix. > 4. Use overlap-add convolution to decode to binaural using the Google > Resonance HRTF filters. 512 taps if I remember correctly. > 5. Stream 4 audio channels of FOA via USB or stereo audio that was encoded > using the "super-stereo" technique. Stereo audio worked either via USB or a > line-in jack. > 6. Change modes and give IMU calibration feedback with a simple push > button and LED interface. > > Yes, I did this using fixed-point but it really wasn't that bad with the > XMOS DSP library. I think this would be a good platform to develop on since > the audio quality will be better than the Teensy. > > I might still have some extra boards floating around - feel free to reach > out if you would like any help or information: colin@voyage.audio > > Regards, > Colin > > > > -- > *Colin Ritchie* > Co-Founder > Voyage Audio > > > On Thu, Jan 6, 2022 at 8:25 AM David McGriffy <da...@mcgriffy.com> wrote: > > > 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. > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > https://mail.music.vt.edu/mailman/private/sursound/attachments/20220106/aa08aefe/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... 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