On Fri, May 03, 2013 at 03:18:47PM -0300, Iain Mott wrote: > If I do implement moving virtual sources - what I think I'd do, would be > to make 4 nearfield IRs in north, south, east, west locations for > example and an additional 4 IRs at a greater distance. Spatialisation of > virtual sources would be done via ambisonic encoding with something like > "iem_ambi" in puredata. In addition, a single IR would be chosen on the > basis of its general proximity to the movement of the object, convolved > with the sound (eg. using jconvolver) and mixed with the ambi-encoded > signal to give it some ambience. Without ruling out moving sources > however, and if the interpolation and the modelling of IRs are out of > the question, perhaps the nearest IRs can be selected as the virtual > source moves from one region to another, and the convolved signal, > cross-faded to provide a smooth transition. > > Perhaps this is the most practical approach?
It certainly is a practical approach. There is one more refinement you could use to limit the amount of CPU use. Of course the IRs for different source directions will be different. But the *signficant* differences are only in the first 100 ms or so. In many cases the 'tail' of the reverb will sound just the same even if the IR is 100% decorrelated with one for another direction. That means you need to do the direction-dependent convolution only for the initial 100 ms or of the IR. For the rest you can share a single IR for all sources. Practically that means you have two post-fader aux sends, one feeding a convolution for the early reflections (dependend on source direction) and the second feeding the reverb tail. You could also experiment with changing the relative delay of the direct sound and the reverb sends (no standard mixer will allow you to do that easily, but if you use Pd or a similar tool it is entirely possible. Since you mention jconvolver, there are two preset files in the source distribution that are designed to do this: sala-concerti-cdm and santa-elisabetta. Both use ambisonic IRs which you can download from my website. For the concert hall there are IRs corresponding to various on-stage source position, and for santa-elisabetta (a small church) there are 8 early reflection IRs spaced 45 degrees apart. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
