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Ambisonics is a fascinating technology. It's basically the same concept as differential stereo encoding (where you record an R+L and R-L channel and use them to derive R and L, or just play the R+L channel for mono) extended to all three axis to create surround sound (so you have a sum channel, a horizontal difference channel, a vertical difference channel, and a depth difference channel). This was all developed in the 70s (and thus out of patent today) but abandoned for more direct means of encoding surround since it was more complex to process the signals for not much gain. Of course now with DSPs the signal processing is much easier and with VR there's suddenly a niche for it to fill since it fully preserves the 3D soundscape (unlike e.g. 7.1 surround which only records 7 point sources at fixed positions).

On a side note, the upcoming 1.3 release of the Opus codec is adding support for Ambisonics-encoded surround sound.




Amazed to see it's still going, I haven't heard mention of it for decades. It was going to be the next big thing around the same time that quadrophonics was failing to take off. Obviously that didn't happen. :)

It was developed by the long defunct UK National Research Corporation that also brought us carbon fibre and the hovercraft.


When I studied recording in college in the early 1990s, I got to play with a Calrec Soundfield ambisonic mic. It was astoundingly cool. We were working with all sorts of other stereo mic techniques (XY, Blumlein, etc), and it just smoked them all for "realness".


Oh Calrec <3. I used to do work as an audio engineer and assisted on a lot of orchestral recordings in concert halls. Among many others, we often used a calrec stereo mic and was just such a great sounding mic.


This would only be 3 axis sound right? I don't think you can get full 6 axis reproduction with this, can you?


What do you mean 6-axis? We're talking about directional pressure at a point, so 3 dimensions is sufficient.


6-axis as in not just directional, but positional. You can both be looking towards or away from a source, as well as looking forward but moving your listening position in such a way that the source is either on the left or right side of listener. In full roomscale VR you'll ideally want to handle positional tracking as well.


You can figure out the shape of the wavefront if you are stubborn enough.


The Opus ambisonics stuff is cool, I think it would be interesting to use ambisonics for emitters in 3D environments, but I have no idea how computationally complex this would need to be before it produced good effects.

Inverse ambisonic recording (i.e. measuring emitted sound from outside the focal point, rather than attempting to record from the focal point) is considerably easier than real ambisonic recording.




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