Having quickly skimmed through the discussion, I'm not sure if I missed something, so apologies if I have.
HRTF derived binaural is never going to completely work unless you use your own, personalised HRTFs. Using generic HRTF datasets, the problems usually manifest as front-back reversals (which head tracking ought to disambiguate) and lack of externalisation. (especially, I seem to remember, directly in front of the head). The externalisation problem can be extended to the range-perception problem - and range perception is very largely to do with indirect sound - just as, for instance, range perception does not work well in an anechoic room. I thought full HRTFs did take into account shoulder and torso reflections - though it seems likely that it's usually measured with shoulders parallel to the line running through the ears? Dr Peter Lennox School of Technology, Faculty of Arts, Design and Technology University of Derby, UK e: p.len...@derby.ac.uk t: 01332 593155 ________________________________________ From: Sursound [sursound-boun...@music.vt.edu] On Behalf Of Bo-Erik Sandholm [bo-erik.sandh...@ericsson.com] Sent: 20 November 2014 09:30 To: Surround Sound discussion group Subject: Re: [Sursound] Oculus Rift Visual Demo + Ambisonic Audio Available? Some of the current subject was vitalized by me trying to be ironic about how non ambisonic guys are trying to solve the sound field recording problem. Originally there was not, and I am not sure there currently exist a solution for sound and picture having a coherent scene movement (controlled by head direction) for Oculus Rift and like VR viewer in video and sound environments other than those controlled by game engines. I want to listen to realistic FOA tetramic recordings over headphones if possible. My thinking is strongly impacted by the current availability of a < 20 USD 3D direction sensors and low cost processing power. Pointer on howto implement low cost head tracker including headtracking binaural software http://www.matthiaskronlachner.com/?p=2091 Low cost processing: M805 1.5GHz (Cortex-A5) android 4.4 stick for < 40 USD. http://www.geekbuying.com/item/MK808B-Plus-Amlogic-M805-Quad-Core-Android-4-4-Mini-TV-Dongle-1G-8G-WIFI-H-265-HW-Decode-Bluetooth-DLNA-Miracast---Black-337068.html note to self does this ARM v5 version support NEON answer = Yes. I believe there are at least a few glaring problems in the way binaural is generated via HRTF's currently. I think head tracking is part of the solution. That is that the sound field decoding parameters to binaural change when you move your head. - the goal of adding head tracking with binaural listening is to get to the status that the sound field is stationary and externalized . - Personally for me listening to others binaural recordings with inear microphones there can an experience like listening to a vertical sound field slice/surface trough the ears, that is a bit externalization to the sides and up and down but no depth! - Introducing head tracking controlled rotation of the sound field before ambisonic to binaural conversion enables the sound field to stay in the "initial position" when the listener moves the head in all directions. Things having potential for improvement are in my opinion: - HRTF's are not individual, maybe not such large problem can appearently be adapted to during listening, is the ear to ear distance most important? - In current state of art all HRTF's are created with the live victim locked in a head brace and the whole body stationary as sound source is rotated horizontally / vertically in relation to the subject or in worst case the subject is a decapitated kunstkopf! - Maybe we should add a separate info channel for "torso tracing" in addition to the head tracing. See Note 1 - Note 1 I took a look in the mirror :-) When turning the head or nodding, the distance from my shoulders to the ear channels stay the same, more or less. When nodding sideways (is that english?) the distance to the shoulders changes drastically. Today on my walk to work through a park, I walked past a distant white noise point source (a large fan in an air cooling installation). I decided to do a small psychoacoustic experiment with my HRTF's :-). - 1- I rotated my whole body in relation to the sound source as if I had a head brace. - 2- I rotated my whole torso in relation to the sound source with my head directed towards the sound source. - 3- I rotated my head in relation to the sound source with stationary torso. - 4- I forgot to nod sideways :-) The only sound change I could notice was for case -2-, there was a large noticable impact on the white noise spectra, as I am not a musician I am not able to specify the frequency range that was mostly impacted. I think this is a strong indication that head movement in relation to the Torso should be added to HRTF processing for binaural sound! Maybe it can be implemented and tested for a special case, that is: - HRTF's created for a fixed torso with the head turned instead of the whole person? - Can this be created with the best resolution in the forwards listening sphere for optimization? Best Regards Bo-Erik Sandholm Stockholm Sweden -----Original Message----- From: Sursound [mailto:sursound-boun...@music.vt.edu] On Behalf Of dw Sent: den 20 november 2014 00:02 To: sursound@music.vt.edu Subject: Re: [Sursound] Oculus Rift Visual Demo + Ambisonic Audio Available? On 19/11/2014 22:49, Paul Doornbusch wrote: > Can you give us some links to this please? > > Thanks, > Paul I'll give you a couple. If you record a sound in front of a dummy head, you would expect to hear it in front on replay through headphones. If you tilt your head backwards while listening, you would expect the auditory image to rotate with the head/ears/torso. Neither happens in all cases.. And then there is the 'externalization' problem. > > On 20 Nov 2014, at 9:46 AM, dw <d...@dwareing.plus.com> wrote: > >> There are numerous examples where the predictions of HRTF localisation are >> falsified by observations. What is one to think of the science? >> >> _______________________________________________ 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. The University of Derby has a published policy regarding email and reserves the right to monitor email traffic. If you believe this was sent to you in error, please select unsubscribe. Unsubscribe and Security information contact: info...@derby.ac.uk For all FOI requests please contact: f...@derby.ac.uk All other Contacts are at http://www.derby.ac.uk/its/contacts/ _______________________________________________ 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.
