I'd just add here that a sensible approach would be to use (or design) a 'tinted' decoder. That is, a decoder that includes frequency (& or time) domain filtering to color the soundfield on playback.
Blue Ripple Sound <http://www.blueripplesound.com/> includes tinted decoders <http://www.blueripplesound.com/products/poa-decoding-vst> in their technology portfolio. (Furse describes this in a patent <http://www.google.com/patents/US20120014527>.) For the ATK <http://www.ambisonictoolkit.net/wiki/tiki-index.php>, I've thought about including a help page in the SuperCollider documentation <http://doc.sccode.org/Browse.html#Libraries%3EAmbisonic%20Toolkit> on how to go about implementing a tinted decoder, but haven't done so at this time. The basic idea of 'tinting' is very simple: process the reproduced soundfield in a way that 'enhances' or further achieves some effect you'd like. To enhance elevation, we may choose to color the soundfield in a way that exaggerates this sense. We have two choices in the processing: 1. process the soundfield before decoding 2. process the soundfield after decoding A combination of both gives the most flexible results, and the best choice really depends on what kind of decoding array you're working with. If you have a full 3D array, choice 2 makes sense. Whereas, with a 2D layout, processing the soundfield before decoding (option 1) is probably the best idea. Option 1 is implemented like this: - decode soundfield to array of equally distributed 'virtual loudspeakers' - filter 'virtual loudspeakers', depending on direction - re-encode soundfield Option 2 is this: - decode soundfield to array of real loudspeakers - filter these, depending on direction Choosing the correct filtering to enhance elevation is the tricky part. You'll want these to be phase matched. (Linear FIR, is an easy choice. Phase matched 2nd-order IIR shelfs also work well.) There are many papers about modeling HRTFs, a simple choice is to just review the suggested filtering for simple spherical head modeling. A very quick search turns up a paper from Duda and Brown <http://www.ece.ucdavis.edu/cipic/files/2015/04/cipic_Brown_Duda98.pdf>. With listening in an Ambisonic soundfield, you need to remember that the listener's head already applies the listener's own HRTF. The trick will be to enhance without unduly distorting. Something also useful to note: if you're a creative artist, you can 'tint' the soundfield for creative purposes. A simple example is what might be what we call 'soundfield highlight'. The idea here is that we'd low-pass all of the soundfield, except our 'highlight'. And notably, we can steer where the 'highlight' is located. (E.g., highlight different parts of the soundfield.) We can think of this as 'directional masking', but with a frequency dependence. I won't go into the exact details of implementing a signal flow to generate this effect, but the ATK <http://www.ambisonictoolkit.net/wiki/tiki-index.php> includes all the parts needed to do so. My kind regards, *Joseph Anderson* *http://www.ambisonictoolkit.net/ <http://www.ambisonictoolkit.net/>* On Thu, Dec 10, 2015 at 9:29 AM, Jörn Nettingsmeier < netti...@stackingdwarves.net> wrote: > On 12/10/2015 04:59 PM, Peter Lennox wrote: > >> It does imply that an ambisonic panner plugin that incorporates spectral >> manipulation would be more efficacious >> > > noooooo! > > if it's an ambisonic panner, it doesn't change the spectrum. if it changes > the spectrum, it's not an ambisonic panner :) > > > > -- > Jörn Nettingsmeier > Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487 > > Meister für Veranstaltungstechnik (Bühne/Studio) > Tonmeister VDT > > http://stackingdwarves.net > > _______________________________________________ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, > edit account or options, view archives and so on. > -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20151210/d099a481/attachment.html> _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
