Thanks for all the answers. Since I really looking for a method I could use more or less blindly, I guess for the moment I will not dive more into it. I would be interested the tools that Eric mentions when they are released.
Would an automated “blind" search algorithm possibly give worse results then just using the equations for the symmetrical case ? I know many people using ambisonics for eletroacoustic music and I think all of them use the equations for the symmetrical case in whatever system they are playing in, which most often is not symmetrical. And it kind of works. How much improvement do you get from using proper coefficient sets ? best, Miguel A 29/02/2012, às 20:13, Eric Benjamin escreveu: > I second everything that Fons wrote, most especially that "(n)either method > can > be used 'blindly', in the sense that you just > throw a set of speaker coordinates at it and get a guaranteed result" > > This has been a very difficult problem for us. For regular arrays it's easy > to > say that a certain result (group of decoder coefficients) is optimum in some > sense. When the array is irregular then you have to make a determination as > to > which direction is most important for you. Then you can decide on a > trade-off > between making the performance good in the better directions (directions with > the greatest density of loudspeakers) without making it bad in the poor > directions (directions with the lowest density of loudspeakers). > > From one point of view the solution would be to only use regular arrays, and > that's fine for research institutions and facilities where the room can be > built > with the intention of housing the regular array. But for many or most > applications there is a real limit to what one can practically do. The > challenge is to do as well as possible within the real-world constraints. > And > that's what Aaron Heller, Richard Lee and I are trying to do. > > Our toolkit (really, it's Aaron's) will be available at about the time of the > Linux Audio Conference and it uses open source tools that operate on a > variety > of computing platforms. But there's a lot more to be done, particularly in > the > area of providing indications as to which of several compromised solutions is > better. > > Eric > > > > ----- Original Message ---- > From: Fons Adriaensen <f...@linuxaudio.org> > To: sursound@music.vt.edu > Sent: Wed, February 29, 2012 6:28:55 AM > Subject: Re: [Sursound] Decoding coefficients for non symmetrical setups > > On Wed, Feb 29, 2012 at 01:15:40PM +0000, Miguel Negrao wrote: > >> I’ve been a bit disconnected from the ambisonics world. From my past reading >> on >> this list it is my understanding that there isn’t an explicit formula for >> decoding coefficients for non-symmetrical setups. Are there currently >> available >> tools to generate decoding coefficients for non-symmetrical setups or an >> iterative algorithm that I could implement on my own ? > > > Two possible methods have been published. > > The first is Franz Zotter's work, using an 'almost regular' virtual layout > based > on > t-designs for which a decoder can be designed in closed form. Then the > virtual > set > of speakers is mapped onto the real one using VBAP. As far as I know there is > no > 'ready to use' toolset for this method. > > The second is the subject of BLaH paper #4, and is based on using a non-linear > optimisation toolset to find a solution, given the error constraints and > weights > for a set of performance metrics. I developed more or less the same (even > using > the same freely available non-linear library), but wasn't allowed to publish > the > results, so I can confirm this can work rather well. What looks like a > practical > implementation (by B,L & H) of this method is scheduled for presentation at > the > next Linux Audio Conference at CCRMA. > > I don't think either method can be used 'blindly', in the sense that you just > throw a set of speaker coordinates at it and get a guaranteed result. You > will have to evaluate the results, and you may have to decide on tradeoffs > and iterate the procedure using modified parameter sets. At this point you > will need some familiarity with the internals in order to be able to proceed. > > Ciao, > > > -- > FA > > Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl. > > _______________________________________________ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound > > _______________________________________________ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound -- Miguel Negrão // ZLB http://www.friendlyvirus.org/artists/zlb/ _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
