Forgot the URL...
http://www.ai.sri.com/~heller/ambisonics/index.html#test-files
On Wed, Jul 5, 2017 at 6:15 PM, Aaron Heller <hel...@ai.sri.com> wrote:
> I have some first-order test files that you can try. They're FuMa
> order/normalization. There's "eight directions" and some pink noise pans.
> With a good decoder, localization should be pretty good with these --
> better in the front than the back in my experience.
>
> Aaron
>
> On Wed, Jul 5, 2017 at 5:53 PM, Aaron Heller <hel...@ai.sri.com> wrote:
>
>> Hi Martin,
>>
>> A few things...
>>
>> 1. You should use a first-order decoder to play first-order sources.
>> That's not the same as playing a first-order file into the first-order
>> inputs of a third-order decoder.
>>
>> 2. 1st-order periphonic (3D) ambisonics on a full 3D loudspeaker array
>> gets the energy correct, and hence the sense of envelopment; localization
>> is not that precise. The magnitude of the energy localization vector, rE,
>> in this situation is only sqrt(3)/3, which Gerzon noted is “perilously
>> close to being unsatisfactory." [1]
>>
>> 3. The decoders in the AmbiX plugins are single-band rE_max decoders, a
>> dual-band decoder will improve localization for central listeners a bit.
>> Both Ambdec and the FAUST decoders produced by the ADT (the ".dsp" files)
>> support 2-band decoding.
>>
>> 4. If you really want more precise localization, consider parametric
>> decoding using Harpex or the Harpex-based upmixer plugin from Blue Ripple
>> Sound. In my experience, it works very well with panned sources and
>> acoustic recordings in dry environments (outdoors, dry hall). For
>> recordings in very reverberant halls (like my recordings), the improvement
>> is not that great.
>>
>> Aaron (hel...@ai.sri.com)
>> Menlo Park, CA US
>>
>>
>> [1] Michael A. Gerzon. Practical Periphony: The Reproduction of
>> Full-Sphere Sound. Preprint 1571
>> from the 65th Audio Engineering Society Convention, London, February
>> 1980. AES E-lib http://www.aes.org/e-lib/browse.cfm?elib=3794.
>>
>> 1.
>>
>>
>> On Wed, Jul 5, 2017 at 3:10 PM, Martin Dupras <martindup...@gmail.com>
>> wrote:
>>
>>> I've deployed a 21-speaker near spherical array a few days ago, which
>>> I think is working ok, but I'm having difficulty with playing back
>>> some first order A-format recordings on it. They sound really very
>>> diffuse and not very localised at all. I figured that some of you good
>>> people on here might have some idea of where I might be going wrong or
>>> what is not right.
>>>
>>> At the moment I'm using Reaper, and for decoding I'm using Matthias
>>> Kronlachner's Ambix decoder plug-in, with a configuration that I've
>>> calculated with Aaron Heller's Ambisonics Decoder Toolbox. I think the
>>> decoder configuration is right. I've calculated it with ambix ordering
>>> and scaling, and third order in H and V. The speaker array has six
>>> speakers at floor level (-22 degrees elevation), eight at ear level at
>>> 1m70 (0 degrees elevation), six at 45 degrees elevation and one at the
>>> apex.
>>>
>>> Now: if I pan monophonic sources using a panner (e.g. o3a panner, 3rd
>>> order), the localisation is pretty good. I've tested that with several
>>> people by panning to random places and asking to blindly point out to
>>> where they hear the source. Generally, they're in about the right
>>> place (say within 45 degrees on average.)
>>>
>>> On the other hand, if I play 1st order A-format recordings (mostly
>>> that I've made using our Core TetraMic), the localisation of sources
>>> is pretty poor. I also tried with the "xyz.wav" example file from Core
>>> (https://www.vvaudio.com/downloads) with the same results. To convert
>>> from A-format to B-format, I've tried using Core's VVtetraVST plugin
>>> with the calibration files for the mic (followed by the o3a FuMa to
>>> Ambix converter), and the Senneheiser Ambeo plugin (which does the
>>> same job, but in Ambix form already.)
>>>
>>> So what am I doing wrong? I've spent the last couple of days checking
>>> everything thoroughly. I've calibrated all the speakers to within 1dB
>>> SPL for the same signal received with an omni mic at the centre of the
>>> sphere. I've triple-checked that the encoder is in the right channel
>>> numbering:
>>>
>>> //------- decoder information -------
>>> // decoder file =
>>> ../decoders/BSU_Array_6861_RAE1_3h3v_allrad_5200_rE_max_2_band.config
>>> // speaker array name = BSU_Array_6861_RAE1
>>> // horizontal order = 3
>>> // vertical order = 3
>>> // coefficient order = acn
>>> // coefficient scale = SN3D
>>> // input scale = SN3D
>>> // mixed-order scheme = HV
>>> // input channel order: W Y Z X V T R S U Q O M K L N P
>>> // output speaker order: S01 S02 S03 S04 S05 S06 S07 S08 S09 S10 S11
>>> S12 S13 S14 S15 S16 S17 S18 S19 S20 S21
>>>
>>> I'll welcome any suggestion or advice!
>>>
>>> Thanks,
>>>
>>> - martin
>>> _______________________________________________
>>> Sursound mailing list
>>> Sursound@music.vt.edu
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>>>
>>
>>
>
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