Hmm - catching up with this conversation rather late... I guess the question is whether the reverb is 1x4 or 4x4. 1x4 is easy enough to measure and use with standard techniques, but 4x4 is trickier as you'd need to collect impulse responses from a range of source locations in the room (effectively the 4x says that you want the reverb to vary with the input direction(/distance?), which needs measurement). Entirely possible though - if anyone has such a set of responses I'd be very interested in a play... (?)
The reverb in the Rapture3D game engine is written from the ground up for Ambisonics and uses a 4x4 form, though the late reflections are actually only 1x4. But it's not a convolution reverb because the controls all have to be dynamic, and games use several of them so the CPU budget is small. I could probably generate some 4x4 IRs from it with some contortion, but I suspect it'd always be much more efficient to just run it, for all but very short decays. I keep meaning to find time to put some things like this in VST plugins, but it's hard to justify the time when DAWs still make Ambisonics hard to work with... Anyone aware of any progress/potential partners there? I've not really looked for a while. Best wishes, --Richard -----Original Message----- From: sursound-boun...@music.vt.edu [mailto:sursound-boun...@music.vt.edu] On Behalf Of Sampo Syreeni Sent: 18 December 2010 04:34 To: Surround Sound discussion group Subject: Re: [Sursound] Another plugin inquiry... On 2010-12-03, Ronald C.F. Antony wrote: > How would the IR reverb have to be "optimized" for ambisonics? > Convolution is convolution is convolution, right? No, it ain't. Nobody does full 4x4 convolution; even the simplest case. We optimize both using simple statistics, and the more powerful psychoacoustics. > The key question is what IR files you feed the reverb as a basis to do > its convolution, and these have to be made with ambisonics in mind, > e.g. created from B-format recording of starter pistol shots, or > equivalent synthetic B-format "events". Which ever means you use, those files as well will be pretty much random. Not something you can simplify easily. So then you will have to employ some magic to make them easily computable -- or parallize neatly enough, which is also an option nowadays. We do have lots of cheap, low-power, low-heat, and fast-as-parallel-only workhorse going for us. -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-50-5756111, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 _______________________________________________ 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
