The sync issue to video raises a number of questions, for which the question of 
a tracker and reaper HOA decoder are secondary to me. 

First, is the video individual or projected? Is this HMD/GoogleCardboard type 
situation? If the first, what are the audio/video sync latency tolerances for 
the piece? 

Second, is the sound scene a "shared" experience, in that do the actions of one 
person affect the sound heard by another? Is the scene dynamically 
generated/rendered in real-time or is this basic off-line rendered audio HOA 
playback? Single point of view in the sound scene, or does each listener have 
their own view, and it is fixed or moving with the user's position? 

If the audio is pre-rendered, without data upload from the user to the server, 
then a local HOA player started by a sync signal should suffice. This is far 
easier then hosting the audio on a server (REAPER) for which the tracker info 
needs to get from the user to the server, decoded, then sent back. Having more 
than just a few wireless streams can be difficult, and broadcast streaming of 
HOA has issues, as true "broadcast" doesn't exist in WiFi the same as it does 
for Wired LAN (i.e. don't bet on it being able to send audio with low latency). 

We had some similar questions on a project almost a decade ago now (see 
references below) where a shared sound-scene was to be shared to multiple users 
in a common (gallery) setting. The solution was local mini-PCs decoding the 
Ambisonic stream with the local head-tracker. If there is no upstream data, and 
only "play" commands, this would be a better solution in my mind.  

- N. Mariette, B. Katz, K. Boussetta, and O. Guillerminet, “SoundDelta : a 
study of audio augmented reality using WiFi-distributed Ambisonic cell 
rendering,” in Audio Eng Soc Conv 128, (London), pp. 1–15, 2010.
- N. Mariette and B. Katz, “SoundDelta - Largescale, multi-user audio augmented 
reality,” in EAA Symp. on Auralization, (Espoo), pp. 1–6, 2009.
- http://remu.fr/remu/realisations/sound-delta/  

For the plug-in, if the tracking is coming in via OSC, or midi, or most other 
means, I would think that you could redirect this control signal to different 
HOA-binaural converters (if you use a client-server architecture and send the 
binaural audio from the server). 

Of course, if you want to go beyond HOA and do dynamic binaural rendering, I 
offer a small bit of promo for Anaglyph, our research developed binaural VST 
plug-in:      http://anaglyph.dalembert.upmc.fr/ 

Best of luck,
--
Brian FG Katz, Ph.D, HDR
Research Director, CNRS
Groupe Lutheries - Acoustique - Musique 
Sorbonne Université, CNRS, UMR 7190, Institut Jean Le Rond ∂'Alembert
bureau 510, 5ème, allé des tours 55-65
4, Place Jussieu 
75005 Paris 
Tel: (+33) 01 44 27 80 34
web_perso: http://www.dalembert.upmc.fr/home/katz  
web_lab: http://www.dalembert.upmc.fr     
web_group: http://www.dalembert.upmc.fr/lam


-----Original Message-----

From: Simon Connor <sico...@gmail.com>
To: sursound@music.vt.edu
Subject: Re: [Sursound] Multi-user head tracked binaural ambisonics
        query
Message-ID:
        <cacmg1nmqdv0cjdzrzho0t6ragqt5fovpok4i37et_pffjf9...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Thanks for the swift reply Lorenzo! This is a great start.

I shall check these out, one key thing I should have mentioned is that the 
audio feed needs to be synced to video (hence the Reaper functionality - as 
this will simultaneously run the audio and video). So the audio will need to be 
streamed to all users synchronously. I'm not sure if this has an implication on 
the use of mobile phones or not?
Cheers
Simon


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