Re: [Sursound] Conversion from FOA to TOA ? How to and why or not?

[Politis Archontis]

Hi Stefan,

No it is not only you :-), I thought I was clear that these references are 
totally synthetic. We just try to make sure that they are reproducible, they do 
sound natural, they are physically-based and they do not rely on any perceptual 
spatialization methods themselves (ambisonic, panning or anything else). Then 
we consider that as a plausible reference. As I said we do not have access to 
an original soundfield, so synthetic is our next best call. 

This relates to the difficult question, I believe, of what is the best way to 
assess transparency in a reproduction method of spatial recordings (compared, 
for example, to transparency of spatial audio coding with playback of 5.0 
material and its spatially compressed version, which is a much easier task 
since there is a clear reference). For most cases transparency is not of 
interest, and an overall perceptual quality is more important. However we have 
done these comparisons in the way I described, published the results and 
somebody interested can extract their own conclusions. And if they're good for 
DirAC decoding, then maybe they're good for other decoding approaches.

Regards,
Archontis



> On 05 Jul 2016, at 21:23, Stefan Schreiber  wrote:
> 
> Politis Archontis wrote:
> 
>> 
>> We start by setting up a large dense 3D loudspeaker setup in a fully 
>> anechoic chamber (usually between 25~35 speakers at a distance of ~2.5m), so 
>> that there is no additional room effect at reproduction. Then we decide on 
>> the composition of the sound scene (e.g. band, speakers, environmental 
>> sources), their directions of arrival and the surrounding room 
>> specifications. We then generate room impulse responses (RIR) using a 
>> physical room simulator for the specified room and source positions. We end 
>> up with one RIR for each speaker and for each source in the scene. 
>> Convolving these with our tests signals and combining the results we end up 
>> with an auralization of the intended scene. This part uses no spatial sound 
>> method at all, no panning for example - if a reflection falls between 
>> loudspeakers it is quantized to the closest one. The final loudspeaker 
>> signals we consider as the reference case (after listening to it and 
>> checking if it sounds ok).
>> 
> 
> Is it only me to notice that these "original scenes" look highly synthetical?
> 
> Maybe good for DirAC encoding/decoding, but a natural recording this is not...
> 
> BR
> 
> Stefan
> 
> P.S.: (Richard Lee )
> 
>> Some good examples of 'natural' soundfield recordings with loadsa stuff
>> happening from all round are Paul Doombusch's Hampi, JH Roy's schoolyard &
>> John Leonard's Aran music.
>> 
> 
> --
> 
> 
>> Then we generate our recordings from that reference. either by encoding 
>> directly to ambisonic signals, by simulating a microphone array recording, 
>> or by putting a Soundfield or other microphone at the listening spot and 
>> re-recording the playback. These have been dependent on the study.
>> 
>> Finally the recordings are processed, and decoded back to the loudspeakers, 
>> usually to a subset of the full setup (e.g. horizontal, discrete surround, 
>> small 3D setup), or even to the full setup. That allows us to switch 
>> playback between the reference and the method.
>> 
>> The tests have been usually MUSHRA style, where the listeners are asked to 
>> judge perceived distance from the reference and various randomized playback 
>> methods (including a hidden reference and a low quality anchor, used to 
>> normalize the perceptual scale for each subject). The criteria are a 
>> combination of timbral distance/colouration, spatial distance, and artifacts 
>> if any.
>> 
>> I’ve left out various details from the above, but this is the general idea. 
>> Some publications that have used this approach are:
>> 
>> 
>> Vilkamo, J., Lokki, T., & Pulkki, V. (2009). Directional Audio Coding: 
>> Virtual Microphone-Based Synthesis and Subjective Evaluation. Journal of the 
>> Audio Engineering Society, 57(9), 709–724.
>> 
>> Politis, A., Vilkamo, J., & Pulkki, V. (2015). Sector-Based Parametric Sound 
>> Field Reproduction in the Spherical Harmonic Domain. IEEE Journal of 
>> Selected Topics in Signal Processing, 9(5), 852–866.
>> 
>> Politis, A., Laitinen, MV., Ahonen, A., Pulkki, V. (2015). Parametric 
>> Spatial Audio Processing of Spaced Microphone Array Recordings for 
>> Multichannel Reproduction. Journal of the Audio Engineering Society 63 (4), 
>> 216-227
>> 
>> Vilkamo, J., & Pulkki, V. (2014). Adaptive Optimization of Interchannel 
>> Coherence. Journal of the Audio Engineering Society, 62(12), 861–869.
>> 
>> Getting the listening test samples and generating recordings or virtual 
>> recordings from the references would be a lot of work for the time being.
>> 
>> What is easier and I can definitely do is process one or some of the 
>> recordings you 

Re: [Sursound] Conversion from FOA to TOA ? How to and why or not?

[Politis Archontis]

> On 01 Jul 2016, at 18:50, Justin Bennett  wrote:
> 
> 
> that’s interesting to hear, Trond, I was also wondering about how upsampling 
> would affect the reproduction of field recordings.
> 
> best, Justin
> 

Hi Justin,

To my experience, parametric methods such as Harpex or DirAC deal greatly with 
field recordings, since there is always enough ‘activity’ and natural 
variability in the sound scene that is analyzed and reproduced reasonably by 
the method’s underlying model. This is in contrast for example to synthetic 
material, in which you can generate unnatural cases that can “confuse” the 
model, e.g. six anechoic saw-tooth waves coming from various angles 
simultaneously with the same fundamental frequency.

Also to my experience, and that doesn’t seem to be a very popular view yet in 
ambisonic community, these parametric methods do not only upsample or sharpen 
the image compared to direct first-order decoding, but they actually reproduce 
the natural recording in a way that is closer perceptually to how the original 
sounded, both spatially and in timbre. Or at least that’s what our listening 
tests have shown in a number of cases and recordings. And the directional 
sharpening is one effect, but also the higher spatial decorrelation that they 
achieve (or lower inter-aural coherence) in reverberant recordings is equally 
important.

By the way, I have always considered the term upsampling a bit inaccurate for 
this parametric FOA-to-HOA mapping., and has no relation to upsampling from a 
signal processing POV. Upmixing would be more appropriate, since this is what 
the methods are essentially doing internally, not dissimilar to the older 
parametric upmixing methods from, e.g., stereo to surround.

Regards,
Archontis

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Re: [Sursound] Conversion from FOA to TOA ? How to and why or not?

[Trond Lossius]

>> I use the Blue Ripple Harpex upsampler extensively in my installations, in 
>> fact it was me that asked Richard Furse if he could license the Harpex 
>> library and create this plugin. The benefit is that when I do installations 
>> with 16 or more speakers, distributed as two rings near the floor and high 
>> up at the wall, and use the Rspture 3D Advanced decoder, I tend to get much 
>> more stable sound field reproduction with more precise definition and 
>> localisation of sources within B-format field recordings in the space than a 
>> FOA would give on its own.
>> 
>> I got to try this briefly at BEAST FEAST in April in the venue used for 
>> presentations with 24 speakers as I demoed the ATK for Reaper plugins. That 
>> was probably the best setup that I have been able to get my hands on to date.
> 
> that’s interesting to hear, Trond, I was also wondering about how upsampling 
> would affect the reproduction of field recordings.
> 
> What microphone are you using for your recordings?

I’m using a SoundField SPS200. You’ll find documentation of two of the 
installations I’ve done in collaboration with Jeremy Welsh here:

http://trondlossius.no/works/56-the-atmospherics-ii---flags-flames-smoke-bridges
http://trondlossius.no/works/57-the-atmospherics-iii---till-it-rains-im-gonna-stay-inside

For both of these I used 16 speakers, 8 near the floor and 8 near the 
ceiling.It’s not enough vertical coverage to give full 3D (there are holes 
below and above), but I’m thinking of this approach more as a vertical 
“widening” of the horizon as compared to 2D layouts.

We’ve just opened a new installation at the art museum in Førde, Sogn & 
Fjordane. I don’t have any audio/video documentation online, but Jeremy has 
posted a number of photos from all of the “Atmospherics” installations that 
we’ve done together, including this one:

http://jewelsh.blogspot.no/p/the-atmospherics.html

The latest work was installed in a large white cube at the museum, and the 
vertical dimension of the sound really comes into its own here. At the same 
time the rectangular shape of the space, and the amount of reverb and a number 
of acoustic oddities posed major challenges, and I ended up having to build a 
number of 4 channel filter and eq JSFX effects for Reaper that I used 
extensively to adjust for this. Still, the reverberation in this space makes 
localisation in the mid and low frequency range much more blurry than in the 
previous installations.

Cheers,
Trond


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Re: [Sursound] Conversion from FOA to TOA ? How to and why or not?

[Justin Bennett]

> On 30 Jun 2016, at 18:00, sursound-requ...@music.vt.edu wrote:
> 
> Message: 1
> Date: Wed, 29 Jun 2016 23:03:43 +0200
> From: Trond Lossius <trond.loss...@bek.no>
> To: mailing list sursound <sursound@music.vt.edu>
> Subject: Re: [Sursound] Conversion from FOA to TOA ? How to and why or
>   not?
> Message-ID: <f305f76d-9811-481d-b619-d927c5700...@bek.no>
> Content-Type: text/plain; charset=us-ascii
> 
> 
> I use the Blue Ripple Harpex upsampler extensively in my installations, in 
> fact it was me that asked Richard Furse if he could license the Harpex 
> library and create this plugin. The benefit is that when I do installations 
> with 16 or more speakers, distributed as two rings near the floor and high up 
> at the wall, and use the Rspture 3D Advanced decoder, I tend to get much more 
> stable sound field reproduction with more precise definition and localisation 
> of sources within B-format field recordings in the space than a FOA would 
> give on its own.
> 
> I got to try this briefly at BEAST FEAST in April in the venue used for 
> presentations with 24 speakers as I demoed the ATK for Reaper plugins. That 
> was probably the best setup that I have been able to get my hands on to date.

that’s interesting to hear, Trond, I was also wondering about how upsampling 
would affect the reproduction of field recordings.

What microphone are you using for your recordings?

best, Justin
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Re: [Sursound] Conversion from FOA to TOA ? How to and why or not?

[Trond Lossius]

Hi,

>> What is the simplest or best way to upscale FOA to TOA.
> 
> Harpex-based upsamplers yield good results.
> 
> Horizontal-only, you can use the Harpex-B plug-in. Full sphere, the Blue 
> Ripple Sound Harpex Upsampler.
> 
> http://harpex.net
> 
> http://www.blueripplesound.com/products/toa-harpex-upsampler-vst

I use the Blue Ripple Harpex upsampler extensively in my installations, in fact 
it was me that asked Richard Furse if he could license the Harpex library and 
create this plugin. The benefit is that when I do installations with 16 or more 
speakers, distributed as two rings near the floor and high up at the wall, and 
use the Rspture 3D Advanced decoder, I tend to get much more stable sound field 
reproduction with more precise definition and localisation of sources within 
B-format field recordings in the space than a FOA would give on its own.

I got to try this briefly at BEAST FEAST in April in the venue used for 
presentations with 24 speakers as I demoed the ATK for Reaper plugins. That was 
probably the best setup that I have been able to get my hands on to date.

Cheers,
Trond
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Re: [Sursound] Conversion from FOA to TOA ? How to and why or not?

[Courville, Daniel]

Bo-Erik Sandholm wrote:

> What is the simplest or best way to upscale FOA to TOA.

Harpex-based upsamplers yield good results.

Horizontal-only, you can use the Harpex-B plug-in. Full sphere, the Blue Ripple 
Sound Harpex Upsampler.

http://harpex.net

http://www.blueripplesound.com/products/toa-harpex-upsampler-vst

- Daniel

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