Hi Sampo, > On 09 Jan 2017, at 06:27, Sampo Syreeni <de...@iki.fi> wrote: > > The critique I'd have for such panning laws is that they don't really respect > the ambisonic/Gerzon theory, especially at the low frequencies. In essence, > they work, and necessarily would *have* to work in the high frequency, > (ambisonically speaking) high order,sparse array limit. Which is why they > mostly work for common music and speech signals.
I am a bit baffled by the idea that VBAP is not compatible with Ambisonics theory (?) Thinking in terms of velocity and energy vectors, as far as I understand, VBAP with the (classic) amplitude panning formulation has zero angular error for the (Makita) velocity vectors for all directions. If you take the energy formulation of VBAP for high frequencies (solving for energies instead of amplitudes) then it results in the maximum (Gerzon) energy vectors that the setup can achieve with zero directional error again. Of course at low frequencies you cannot achieve the “perfect” pressure reconstruction that a mode-matching decoder can achieve, but then you see what are the gains that such a decoder imposes on not ideal regular setups to realize that perfect reconstruction should be compromised anyway with some more practical solution. > However, they fail to work general speaker arrays fully. Especially at the > lower frequencies. Ambisonically speaking, where we'd go with a holistic, > whole array, directionally averaged velocity decode. Again I think it depends how you mean it - VBAP will just work for any speaker array with a performance limited by the setup in a quite intuitive understandable way (large spread for large triangle apertures, full concentration at a speaker direction, nothing for regions outside a partial setup etc..). Ambisonic decoding for any array is not designed as easily as computing VBAP gains, and it seems for irregular setups, one of the most straightforward and practical ways to do it is to combine the properties of VBAP and Ambisonic decoding (as the work of Zotter, Batke, and Epain have shown). Considering panning specifically, I think it depends on the application what works best, for VR or interactive-audio stuff for example, where normally sound objects would be rendered with maximum sharpness VBAP would work better. If however some and more even directional spreading is preferred, then ambisonic panning should be better, or some VBAP variant with spreading as has been presented by Ville and others. So I find Augustine's comments reasonable on panning sounds, but not in general: VBAP vs Ambisonics. > On 09 Jan 2017, at 12:33, Augustine Leudar <augustineleu...@gmail.com> wrote: > > Yes i just mean - when making a 3D sound installation you can use various > types of panning round a sphere (or whatever of speaker array). You seemed > to be saying ambisonics had a clear advantage over other types of panning > for 3D audio - I was just wondering what you saw as ambisonics' advantages > over VBAP. I've actually found Ambisonics to be worse compared to VBAP in > many situations and better in others - but generally I use Vbap or Dbap . > The only real advantage I can see of ambisonics is having one file that can > be up or down mixed - but you can do that to a degree with Vbap files as > well. (What is a VBAP file?) That’s if you have actually access to the sound objects with their parametric information, in which case sure you can pan them however you like, you can even switch between different panners on the fly and pick the one you prefer. However, the generality of Ambisonics becomes clear if you have real sound-scene recordings, or you don’t have access to the objects due to bandwidth limitations, and it makes sense to downmix them to a format that preserves their directional properties as good as possible. This last case becomes especially important if decoding of some HOA channels (or even FOA with parametric decoding) becomes perceptually indistinguishable with respect to spatializing many of sound objects separately.. Regards, Archontis _______________________________________________ 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.
