I have skimmed through it too. Nothing on curvature, but it’s very interesting non the less.
It needs a thorough read through
One of the many encoding and decoding solutions at grabbed my attention (it’s very comprehensive) is:
'‘D’ Channel (as in WXYZD)
The ‘D’ channel will encode as a normalized distance which can as one example be recovered as value of 0 (being in the head at the origin), 0.25 being exactly in the near-field, and up to 1 for a source rendered fully in the far-field. This encoding can be achieved by using an absolute value reference such as 0 dBFS or by relative magnitude and/or phase vs one or more of the other channels such as the “W” channel. Any actual distance attenuation resulting from being beyond the far-field is handled by the B-Format part of the mix as it would in legacy solutions
By treating distance m this way, the B-Format channels are functionally backwards compatible with normal decoders by dropping the D channel(s), resulting in a distance of 1 or “far-field” being assumed.
One method of encoding the D channel is to use relative magnitude of the W channel at each frequency. If the D channel's magnitude at a particular frequency is exactly the same as the magnitude as the W channel at that frequency, then the effective distance at that frequency is 1 or “far-field.” If the D channel's magnitude at a particular frequency is 0, then the effective distance at that frequency is 0, which corresponds to the middle of the listener's head. In another example, if the D channel's magnitude at a particular frequency is 0.25 of the W channel's magnitude at that frequency, then the effective distance is 0.25 or “near-field.” The same idea can be used to encode the D channel using relative power of the W channel at each frequency.'
It’s a DTS patent application too, so it also covers loads of options for matrix-ing.
Happy Monday
Steve
> On 29 Jan 2018, at 10:41, Augustine Leudar <***@gmail.com> wrote:
>
> Thanks for the list Markus,
> I read the conclusions and abstracts for these papers and skimmed through
> them - I am also quite busy ! However none of them seem to investigate or
> suggest that the curvature of the wavefront and this curvatures interaction
> with pinna folds is a potential distance and size cue in the nearfiled. I
> did find this though which mentions it but doesnt really investigate (or
> reference a source unfortunately) :
>
> https://pdfs.semanticscholar.org/0664/8964b53ac8f812b0068088caa4838c3ba7ce.pdf
>
> On 24 January 2018 at 14:35, Markus Noisternig (IRCAM) <
> ***@ircam.fr> wrote:
>
>> Dear All,
>>
>> Here are some references:
>>
>> Brungart and Rabinowitz [1] showed that HRTF vary significantly for
>> sources in the proximity region (i.e. at distances less than 1m from the
>> head).
>> Lentz et al. [2] perceptually evaluated measured HRTFs at different
>> distances from the head, showing limits of noticeable differences between
>> near-field and far-field HRTFs.
>> Romblom and Cook [3] proposed near-field compensation filters.
>> Duraiswami et al. [4], Zhang et al. [5], and Pollow et al. [6] compute
>> HRTFs for arbitrary field points using spherical harmonics decomposition
>> (as an extension of the work of Evans et al. [7]).
>> Duda and Martens [8] evaluated simulation results on a spherical head model
>>
>> Have fun reading!
>>
>> Very best,
>>
>> Markus
>>
>> [1] D.S.Brungart,W.M.Rabinowitz:Auditorylocalizationof nearby sources.
>> head-related transfer functions. J. Acoust. Soc. Am. 106 (1999) 1465–1479.
>> [2] T. Lentz, I. Assenmacher, M. Vorländer, T. Kuhlen: Precise
>> near-to-head acoustics with binaural synthesis. Journal of Virtual Reality
>> and Broadcasting 3 (2006).
>> [3] D. Romblom, B. Cook: Near-field compensation for hrtf processing.
>> 125th Conv. Audio Eng. Soc., San Francisco, USA, 2008, no. 7611.
>> [4 ]R. Duraiswami, D. N. Zotkin, N. A. Gumerov: Interpola- tion and range
>> extrapolation of HRTFs. IEEE ICASSP, Montreal, Canada, 2004, 45–48.
>> [5] W. Zhang, T. D. Abhayapala, R. A. Kennedy, R. Du- raiswami: Modal
>> expansion of HRTFs: Continuous repre- sentation in frequency-range-angle.
>> ICASSP, Los Alami- tos, USA: IEEE Computer Society, 2009, 285–288.
>> [6] Pollow, M., Nguyen, K.-V., Warusfel, O., Carpentier, T.,
>> Müller-Trapet, M., Vorländer, M., and Noisternig, M. (2012). “Calculation
>> of Head-Related Transfer Functions for Arbitrary Field Points Using
>> Spherical Harmonics Decomposition,” Acta Acust United Ac, 98, 72–82.
>> doi:10.3813/AAA.918493
>> [7] M. J. Evans, J. A. S. Angus, A. I. Tew: Analyzing head- related
>> transfer function measurements using surface spher- ical harmonics. J.
>> Acoust. Soc. Am. 104 (1998) 2400– 2411
>> [8] R. O. Duda, W. L. Martens: Range dependence of the re- sponse of a
>> spherical head model. J. Acoust. Soc. Am. 104 (1998) 3048–3058.
>>
>>
>>> On 24 Jan 2018, at 15:01, John Merchant <***@mtsu.edu> wrote:
>>>
>>> Tom Smurdon and Peter Stirling of Oculus presented research on
>> near-field HRTF for VR at last fall's OC4. The video of that talk is
>> available here:
>>> https://www.youtube.com/watch?v=l7mhXRB9PA4
>>>
>>> ________________________________________
>>> From: Sursound <sursound-***@music.vt.edu> on behalf of
>> ***@mail.telepac.pt <***@mail.telepac.pt>
>>> Sent: Tuesday, January 23, 2018 8:12 PM
>>> To: Surround Sound discussion group
>>> Subject: Re: [Sursound] A submittal for a patent on Ambisonics?
>>>
>>> Citando Augustine Leudar <***@gmail.com>:
>>>
>>>> Hi Jack,
>>>>
>>>> Aside from ILDs, ITDs, I also wondered if the pinna was able to
>> distinguish
>>>>
>>>> very close sound sources due to the fact the wavefront would be much
>> more
>>>>
>>>> curved almost spherical to the degree that it would be different
>> pressure
>>>>
>>>> present at different folds of the pinna (ie very close up sound slike
>> a
>>>>
>>>> mosquito) . I dont think theres been much done on that...
>>>
>>> Hi Augustine,
>>>
>>> I think "there has been done quite a lot on that"... 😉
>>>
>>> (Reproduction of near-field audio sources)
>>>
>>> Beside of spherical waves (and their consequences) we should not
>>> overlook that any high-frequency emitting (annoying) mosquito next to
>>> your left ear would be heard much softer at your right ear, the head
>>> shadow being even more relevant at close distances.
>>>
>>> BR
>>>
>>> Stefan
>>>
>>> P.S.: It is important to know about the "depth" of a mosquito audio
>>> object relative to your head, both in VR and in real life...
>>>
>>>> On 23 January 2018 at 11:58, jack reynolds <***@gmail.com>
>>>>
>>>> wrote:
>>>>
>>>>> It looks like a method for binaural rendering with multiple distance
>> HRTFs.
>>>>>
>>>>>
>>>>>
>>>>> Ambisonics could be one of the inputs, but it seems to be aimed more at
>>>>>
>>>>> object based virtual reality, where the listener is more likely to come
>>>>>
>>>>> very close to an audio source.
>>>>>
>>>>>
>>>>>
>>>>> Most HRTFs are currently measured at 1m distance, so any objects closer
>>>>>
>>>>> than 1m are not currently rendered correctly.
>>>>>
>>>>>
>>>>>
>>>>> Far field HRTFs are closer to plane waves, whereas close up audio
>> objects
>>>>>
>>>>> emit more spherical waves, creating greater differences in interaural
>> time
>>>>>
>>>>> difference (ITD).
>>>>>
>>>>>
>>>>>
>>>>> Jack
>>>>>
>>>>>
>>>>>
>>>>> On 23 January 2018 at 11:18, Bearcat Şándor <***@gmail.com>
>>>>>
>>>>> wrote:
>>>>>
>>>>>
>>>>>
>>>>> I don't know a lot about patent law, but is this an attempt to tie up
>> our
>>>>>
>>>>> beloved Ambisonics?
>>>>>
>>>>>
>>>>>
>>>>> http://www.freepatentsonline.com/y2017/0366912.html
>>>>>
>>>>>
>>>>>
>>>>> ....
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>
>
>
> --
> Dr. Augustine Leudar
> Artistic Director Magik Door LTD
> Company Number : NI635217
> Registered 63 Ballycoan rd,
> Belfast BT88LL
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