Re: [Sursound] Soundfield by Rode plugin

[Jörn Nettingsmeier]

On 12/17/18 12:15 PM, Politis Archontis wrote:


Another very sensible approach was presented by Cristoff Faller and Illusonics 
in the same conference, in a simpler adaptive filter is used to align the 
microphone signals to the phase of one of the capsules, making them again in 
essence coincident.


IIRC the Super CMIT mentioned by Chris earlier uses just this algorithm 
by Christof.


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Jörn Nettingsmeier
Tuinbouwstraat 180, 1097 ZB Amsterdam, Nederland
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Re: [Sursound] Soundfield by Rode plugin

[Dave Malham]

I think that the one really important thing to do when applying any kind of
processing, but especially processing with any sort of adaptive elements is
to always LISTEN to the results because even the best will fall down with
some sounds. One problem we face these days is the shear amount of
processed (mp3, etc.) sounds younger people are exposed to - from birth in
many cases. The resulting desensitization of their hearing was something I
was really becoming concerned with towards the end of my days at the uni.
It was becoming increasingly difficult to find students that could hear
things that even with my age-degraded hearing I found profoundly disturbing
(quantsation noise, aliasing, etc.) - recoverable with training, of course,
but, even so. :-(
 Dave

On Tue, 18 Dec 2018 at 08:35, David Pickett  wrote:

> At 12:15 17-12-18, Politis Archontis wrote:
>
>  >Another very sensible approach was presented by Cristoff Faller and
>  >Illusonics in the same conference, in a simpler adaptive filter is
>  >used to align the microphone signals to the phase of one of the
>  >capsules, making them again in essence coincident.
>
> I am interested to know how this approach gets around the problem
> that with any pair of capsules, the difference in phase is a function
> of the angle of incidence and how it distinguishes between identical
> frequency components that are actually generated by different acoustic
> sources.
>
> It seems to me that some assumptions must be involved, e.g.:
>
> -- that the microphone array is stationary during the time of the
> capture window and subsequent computation.
>
> -- that the filtered frequency components used for the computation
> contain only signals from a unique direction.
>
> The first of these assumptions has been mentioned here by reference
> to the generation of spurious signals when the mic is in motion. The
> implication would be that the time taken to acquire and compute the
> data is too long to satisfy the condition.
>
> The second is demonstrably untrue when we are talking about tonal
> music in a reverberant acoustic. How does the system distinguish
> between a 1kHz partial from a source or reflecting surface on one
> side of the array and one from a different source or reflecting
> surface arriving from another direction? (A moment's thought shows
> that a C major chord, distributed among various performers would have
> a large number of Cs, Es, G, etc coming from all around.)
>
> David
>
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-- 

As of 1st October 2012, I have retired from the University.

These are my own views and may or may not be shared by the University

Dave Malham
Honorary Fellow, Department of Music
The University of York
York YO10 5DD
UK

'Ambisonics - Component Imaging for Audio'
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Re: [Sursound] Soundfield by Rode plugin

[David Pickett]

At 12:15 17-12-18, Politis Archontis wrote:

>Another very sensible approach was presented by Cristoff Faller and
>Illusonics in the same conference, in a simpler adaptive filter is
>used to align the microphone signals to the phase of one of the
>capsules, making them again in essence coincident.

I am interested to know how this approach gets around the problem 
that with any pair of capsules, the difference in phase is a function 
of the angle of incidence and how it distinguishes between identical 
frequency components that are actually generated by different acoustic sources.


It seems to me that some assumptions must be involved, e.g.:

-- that the microphone array is stationary during the time of the 
capture window and subsequent computation.


-- that the filtered frequency components used for the computation 
contain only signals from a unique direction.


The first of these assumptions has been mentioned here by reference 
to the generation of spurious signals when the mic is in motion. The 
implication would be that the time taken to acquire and compute the 
data is too long to satisfy the condition.


The second is demonstrably untrue when we are talking about tonal 
music in a reverberant acoustic. How does the system distinguish 
between a 1kHz partial from a source or reflecting surface on one 
side of the array and one from a different source or reflecting 
surface arriving from another direction? (A moment's thought shows 
that a C major chord, distributed among various performers would have 
a large number of Cs, Es, G, etc coming from all around.)


David

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Re: [Sursound] Soundfield by Rode plugin

[Politis Archontis]

Hi,

There are various ways to do it, one is to assume a sound-field model (e.g. 
direct & diffuse sound), estimate the model parameters in each frequency bin, 
and then use them to align the signals in a coincident way, such a parametric 
approach was presented by us in AES Convention in Milan last year for similar 
applications and higher-order recording.

Another very sensible approach was presented by Cristoff Faller and Illusonics 
in the same conference, in a simpler adaptive filter is used to align the 
microphone signals to the phase of one of the capsules, making them again in 
essence coincident.

Parametric approaches for playback and recording (see e.g. DirAC, HARPEX, 
countless speech enhancement methods) have gone a long way in the last decades 
in terms of quality and they’re definitely not “snake oil” :-).

Best regards,
Archontis Politis
Post-doctoral Researcher
Department of Signal Processing and Acoustics
Aalto University
Finland






On 17 Dec 2018, at 11:39, Dave Hunt 
mailto:davehuntau...@btinternet.com>> wrote:

Hi,

There is slightly more description of their A to B-format processing
(but not much) in Rode's blog:

<http://www.rode.com/blog/all/soundfield-plugin>

>From that web page.

"The SoundField by RØDE plug-in uses a new time-frequency adaptive approach for 
A to B-format conversion. This complex mathematical process means the phase 
between the A-format channels are aligned prior to application of the 
conversion matrix – essentially correcting for the non-coincidence of the 
capsules prior to any further processing."

How might they phase/time align the capsules ??

This must indeed be highly complex, as it is frequency dependent (low 
frequencies have smaller phase differences than high frequencies) as well as 
source directionally (across multiple blind sources) dependent.

Ciao,

Dave Hunt



On 16 Dec 2018, at 17:00, 
sursound-requ...@music.vt.edu<mailto:sursound-requ...@music.vt.edu> wrote:

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 1. Re: Soundfield by Rode plugin (Gary Gallagher)

From: Gary Gallagher 
Subject: Re: [Sursound] Soundfield by Rode plugin
Date: 16 December 2018 04:36:11 GMT
To: Surround Sound discussion group 


Thanks for that reference. I guess we'll just have to wait for more
information to filter out.

On Sun, Dec 16, 2018, 01:36 Paul Hodges  wrote:

There is slightly more description of their A to B-format processing
(but not much) in Rode's blog:

<http://www.rode.com/blog/all/soundfield-plugin>

Paul

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Re: [Sursound] Soundfield by Rode plugin

[Chris Woolf]

On 17/12/2018 10:10, David Pickett wrote:


A "time-frequency adaptive approach"

What?

Unless it works spectacularly well, I would suspect the application of 
snake oil.


If this is a 3D version of the sort of technique used to improve the 
directivity of an axial mic then it can sound pretty good. The Schoeps 
SuperCMIT produces excellent sound quality with gentle processing help, 
and only starts to show faint artefacts when things are pushed very hard 
indeed.


Chris Woolf


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Re: [Sursound] Soundfield by Rode plugin

[Chris Woolf]

On 17/12/2018 09:39, Dave Hunt wrote:


How might they phase/time align the capsules ??

This must indeed be highly complex, as it is frequency dependent (low 
frequencies have smaller phase differences than high frequencies) as well as 
source directionally (across multiple blind sources) dependent.

Surely this is just multiple beam-forming - taking the different signal 
levels of single events at each capsule and correcting them in the time 
domain to be aligned as closely as possible. Yes, that's frequency 
dependent so has to be done narrow band, but can be done for multiple 
events, a multiple number of times.


This seems to be an approach that's been used by at least two mic 
manufacturers that I know  of (Audio Technica and Schoeps) to improve 
directivity of axial mics. With increasing processing power the ability 
to generate more simultaneous beams allows this to be done for multiple 
directions. The ones that I know use this technique use flat arrays and 
limit the beams to a 180° arc, but I don't see any reason not to extend 
the technique to 360° or a full orb.


I should state that this is entirely supposition - I have no actual 
knowledge of doing this.


Chris Woolf


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Re: [Sursound] Soundfield by Rode plugin

[David Pickett]

At 10:39 17-12-18, Dave Hunt wrote:

>"The SoundField by RØDE plug-in uses a new time-frequency adaptive
>approach for A to B-format conversion. This complex mathematical
>process means the phase between the A-format channels are aligned
>prior to application of the conversion matrix ­ essentially correcting
>for the non-coincidence of the capsules prior to any further processing."

A "time-frequency adaptive approach"

What?

Unless it works spectacularly well, I would 
suspect the application of snake oil.


David

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Re: [Sursound] Soundfield by Rode plugin

[Dave Hunt]

Hi,

>> There is slightly more description of their A to B-format processing
>> (but not much) in Rode's blog:
>> 
>> <http://www.rode.com/blog/all/soundfield-plugin>

>From that web page.

"The SoundField by RØDE plug-in uses a new time-frequency adaptive approach for 
A to B-format conversion. This complex mathematical process means the phase 
between the A-format channels are aligned prior to application of the 
conversion matrix – essentially correcting for the non-coincidence of the 
capsules prior to any further processing."

How might they phase/time align the capsules ??

This must indeed be highly complex, as it is frequency dependent (low 
frequencies have smaller phase differences than high frequencies) as well as 
source directionally (across multiple blind sources) dependent.

Ciao,

Dave Hunt



On 16 Dec 2018, at 17:00, sursound-requ...@music.vt.edu wrote:

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> 
> ALSO EDIT THE MESSAGE BODY
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> You are receiving the digest so when replying, please remember to edit your 
> Subject line to that of the original message you are replying to, so it is 
> more specific than "Re: Contents of Sursound-list digest…" the subject should 
> match the post you are replying to.
> 
> Also, please EDIT the quoted post so that it is not the entire digest, but 
> just the post you are replying to - this will keep the archive useful and not 
> polluted with extraneous posts.
> 
> This is the responsibility of digest subscribers. the community and list 
> subscribers care about the integrity of the threads and archives so this is 
> important.Today's Topics:
> 
>   1. Re: Soundfield by Rode plugin (Gary Gallagher)
> 
> From: Gary Gallagher 
> Subject: Re: [Sursound] Soundfield by Rode plugin
> Date: 16 December 2018 04:36:11 GMT
> To: Surround Sound discussion group 
> 
> 
> Thanks for that reference. I guess we'll just have to wait for more
> information to filter out.
> 
> On Sun, Dec 16, 2018, 01:36 Paul Hodges  wrote:
> 
>> There is slightly more description of their A to B-format processing
>> (but not much) in Rode's blog:
>> 
>> <http://www.rode.com/blog/all/soundfield-plugin>
>> 
>> Paul
>> 
>> --
>> Paul Hodges
>> 
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Re: [Sursound] Soundfield by Rode plugin

[Gary Gallagher]

Thanks for that reference. I guess we'll just have to wait for more
information to filter out.

On Sun, Dec 16, 2018, 01:36 Paul Hodges  wrote:

> There is slightly more description of their A to B-format processing
> (but not much) in Rode's blog:
>
> 
>
> Paul
>
> --
> Paul Hodges
>
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