[microsound] video and surround

[Trond Lossius]

Hi,

Bruce Wiggins did a PhD some years ago working on a method to find optimal decoding coefficients for each of the speakers to use when decoding 2nd order ambisonics for ITU 5.1. The thesis is available for download, and should be easy to google for.

The SoundField SPS200 microphone is doing ambisonics recordings, and the accompanying VST and AU plugins are able to decode for a number of formats, including 5.1. I've tested it a bit at the studio at BEK, and it works, but my initial impression is that the sound image is fairly unstable once you move outside of the sweet spot. If you were to use video with ambisonics decoded for 5.1 in e.g. a video screening program, I would test this thoroughly in order to have a better idea of how/to what degree it's working. One option might be to use this to create a surrounding backdrop, and then position additional sources using standard DAW surround panning techniques on top of it for more exact locations.

I have listend to some of the 6 channel sounds that comes with Logic/SoundTrack/FinalCut that can be used as ambiences in sound design, and it strikes me that they are pulling lots of tricks to make it sound the best. E.g. there is one or more sound recordings "at the bay", with the sound of waves breaking as they hit the quay. This sound actually seems to be made up from 5 totally independent mono channel signals. The result is that water seems to be splashing at all sides, but if you listen more carefully it is actually only splashing at the locations of the speakers.

I have used ambisonics in combination with video and other media in several of my installations, e.g. Stages Bodies:

http://trondlossius.no/works/29-staged-bodies-2005-06-

Here video was rendered in real time using max/Jitter/OpenGL using two projectors. Likewise sound was generated in realtime using Max, and played back using 9 loudspeakers in a kind of horse show formation.

Another example is Elektropoesia from 2004 in collaboration with Kurt Ralske. Again a wide panoramic video image, and this time 16 loudspeakers on a line just below the video:

http://trondlossius.no/works/17-elektropoesia-2004

One of the limitations (for me) of ambisonics in installations is that it is pretty strict about loudspeaker positioning if it is to work optimal. That might not always be straight forward to combine with how I want or am able to position the speakers in an installation context. So, often I instead end up breaking the rules, but still getting some interesting spatial results. On the other hand Natasha Barrett has found ways of using ambisonics in installations that has used it very efficient.

Cheers,
Trond


On Dec 7, 2010, at 10:46 AM, Davide Oliveri wrote:

> Hello and many thanks for sharing and speaking about your opinion.
> 
> Did you record ambisonic sound or it's a matter of editing ? And what did you use to edit ?
> 
> I tried to do something in UHJ about one year ago and I used Max/Msp externals Ambiencode/Ambidecode, 
> but I didn't like the result because I wanted to achieve the effect of "flying" sound over the head 
> and I guess it's not so easy to do with just two channels...
> 
> You can listen an excerpt of the result here. 
> 
> So one can use ambisonic in surround system and get a better surround effect, it sounds interesting.
> I wonder if ambisonc is actually used in newest sourround productions.
> 
> Don't you think that surround could be an "invasion" of the space of the (film/video) audience ?
> I mean, we see something "over there" but we hear something "here".
> 
> However i didn't find the sound of "the adder's bite" so present to be considered "here" and i think it's a good thing. 
> By the way, what is the best configuration for the speakers to liste the UHJ format, in front or at side ?
> 
> 
> Davide Oliveri
> 
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