Re: [Sursound] ST450 capsule assembly
Definitely that one, so it's the same as the 350 (it was the 250 I couldn't make out properly without dissembling) Dave On 29/02/2012 15:23, Richard Lee wrote: Svein Berge shows the ST350 capsule assembly at http://harpex.net/ My thanks to him. I want to know if this "new" stronger assembly, with the capsules secured by screw on rings, is used in the ST450 or if they have gone back to the "old" assembly using screws as in the Mk4, Mk5, ST250, SP422. David, your Mk3A may have an even more skeletal version of the Mk4. http://www.soundfield.com/soundfield/soundfield.php -- next part -- A non-text attachment was scrubbed... Name: not available Type: application/ms-tnef Size: 1970 bytes Desc: not available URL:<https://mail.music.vt.edu/mailman/private/sursound/attachments/20120229/5f3e4d8f/attachment.bin> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound -- These are my own views and may or may not be shared by my employer /*/ /* Dave Malham http://music.york.ac.uk/staff/research/dave-malham/ */ /* Music Research Centre */ /* Department of Music"http://music.york.ac.uk/"; */ /* The University of York Phone 01904 322448*/ /* Heslington Fax 01904 322450*/ /* York YO10 5DD */ /* UK 'Ambisonics - Component Imaging for Audio' */ /*"http://www.york.ac.uk/inst/mustech/3d_audio/"; */ /*/ ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Decoding coefficients for non symmetrical setups
Hi list, I’ve been a bit disconnected from the ambisonics world. From my past reading on this list it is my understanding that there isn’t an explicit formula for decoding coefficients for non-symmetrical setups. Are there currently available tools to generate decoding coefficients for non-symmetrical setups or an iterative algorithm that I could implement on my own ? best regards, Miguel Negrão ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
On Wed, Feb 29, 2012 at 01:15:40PM +, Miguel Negrao wrote: > I’ve been a bit disconnected from the ambisonics world. From my past reading > on this list it is my understanding that there isn’t an explicit formula for > decoding coefficients for non-symmetrical setups. Are there currently > available tools to generate decoding coefficients for non-symmetrical setups > or an iterative algorithm that I could implement on my own ? Two possible methods have been published. The first is Franz Zotter's work, using an 'almost regular' virtual layout based on t-designs for which a decoder can be designed in closed form. Then the virtual set of speakers is mapped onto the real one using VBAP. As far as I know there is no 'ready to use' toolset for this method. The second is the subject of BLaH paper #4, and is based on using a non-linear optimisation toolset to find a solution, given the error constraints and weights for a set of performance metrics. I developed more or less the same (even using the same freely available non-linear library), but wasn't allowed to publish the results, so I can confirm this can work rather well. What looks like a practical implementation (by B,L & H) of this method is scheduled for presentation at the next Linux Audio Conference at CCRMA. I don't think either method can be used 'blindly', in the sense that you just throw a set of speaker coordinates at it and get a guaranteed result. You will have to evaluate the results, and you may have to decide on tradeoffs and iterate the procedure using modified parameter sets. At this point you will need some familiarity with the internals in order to be able to proceed. Ciao, -- FA Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl. ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
I think IRCAM Spat is doing that quite well. I do not know what algorithm lies behind. Maybe Thibaut Carpentier I sometimes see on this list could tell us something more about that... Ciao simonefontana On 2/29/12 3:28 PM, "Fons Adriaensen" wrote: >On Wed, Feb 29, 2012 at 01:15:40PM +, Miguel Negrao wrote: > >> I¹ve been a bit disconnected from the ambisonics world. From my past >>reading on this list it is my understanding that there isn¹t an explicit >>formula for decoding coefficients for non-symmetrical setups. Are there >>currently available tools to generate decoding coefficients for >>non-symmetrical setups or an iterative algorithm that I could implement >>on my own ? > > >Two possible methods have been published. > >The first is Franz Zotter's work, using an 'almost regular' virtual >layout based on >t-designs for which a decoder can be designed in closed form. Then the >virtual set >of speakers is mapped onto the real one using VBAP. As far as I know >there is no >'ready to use' toolset for this method. > >The second is the subject of BLaH paper #4, and is based on using a >non-linear >optimisation toolset to find a solution, given the error constraints and >weights >for a set of performance metrics. I developed more or less the same (even >using >the same freely available non-linear library), but wasn't allowed to >publish the >results, so I can confirm this can work rather well. What looks like a >practical >implementation (by B,L & H) of this method is scheduled for presentation >at the >next Linux Audio Conference at CCRMA. > >I don't think either method can be used 'blindly', in the sense that you >just >throw a set of speaker coordinates at it and get a guaranteed result. You >will have to evaluate the results, and you may have to decide on >tradeoffs >and iterate the procedure using modified parameter sets. At this point you >will need some familiarity with the internals in order to be able to >proceed. > >Ciao, > > >-- >FA > >Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl. > >___ >Sursound mailing list >Sursound@music.vt.edu >https://mail.music.vt.edu/mailman/listinfo/sursound > ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
There's a third method - Bruce Wiggins' Heuristic algorithm based methodology (http://www2.derby.ac.uk/sparg-content/pdfs/bw_aes31_paper.pdf). This is, I believe, available in his "Wigware" decoder plugins.There is also some work from China on genetic algorithm based design, but I don't know what the current state of play is on that. Dave On 29/02/2012 14:28, Fons Adriaensen wrote: On Wed, Feb 29, 2012 at 01:15:40PM +, Miguel Negrao wrote: I’ve been a bit disconnected from the ambisonics world. From my past reading on this list it is my understanding that there isn’t an explicit formula for decoding coefficients for non-symmetrical setups. Are there currently available tools to generate decoding coefficients for non-symmetrical setups or an iterative algorithm that I could implement on my own ? Two possible methods have been published. The first is Franz Zotter's work, using an 'almost regular' virtual layout based on t-designs for which a decoder can be designed in closed form. Then the virtual set of speakers is mapped onto the real one using VBAP. As far as I know there is no 'ready to use' toolset for this method. The second is the subject of BLaH paper #4, and is based on using a non-linear optimisation toolset to find a solution, given the error constraints and weights for a set of performance metrics. I developed more or less the same (even using the same freely available non-linear library), but wasn't allowed to publish the results, so I can confirm this can work rather well. What looks like a practical implementation (by B,L& H) of this method is scheduled for presentation at the next Linux Audio Conference at CCRMA. I don't think either method can be used 'blindly', in the sense that you just throw a set of speaker coordinates at it and get a guaranteed result. You will have to evaluate the results, and you may have to decide on tradeoffs and iterate the procedure using modified parameter sets. At this point you will need some familiarity with the internals in order to be able to proceed. Ciao, -- These are my own views and may or may not be shared by my employer /*/ /* Dave Malham http://music.york.ac.uk/staff/research/dave-malham/ */ /* Music Research Centre */ /* Department of Music"http://music.york.ac.uk/"; */ /* The University of York Phone 01904 322448*/ /* Heslington Fax 01904 322450*/ /* York YO10 5DD */ /* UK 'Ambisonics - Component Imaging for Audio' */ /*"http://www.york.ac.uk/inst/mustech/3d_audio/"; */ /*/ ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
Ah - I withdraw that about the Wigware decoders as the versions on Bruce's website are probably not sufficiently flexible for your purposes, though the actual heuristic methodology probably is. Dave On 29/02/2012 14:47, Dave Malham wrote: There's a third method - Bruce Wiggins' Heuristic algorithm based methodology (http://www2.derby.ac.uk/sparg-content/pdfs/bw_aes31_paper.pdf). This is, I believe, available in his "Wigware" decoder plugins.There is also some work from China on genetic algorithm based design, but I don't know what the current state of play is on that. Dave On 29/02/2012 14:28, Fons Adriaensen wrote: On Wed, Feb 29, 2012 at 01:15:40PM +, Miguel Negrao wrote: I’ve been a bit disconnected from the ambisonics world. From my past reading on this list it is my understanding that there isn’t an explicit formula for decoding coefficients for non-symmetrical setups. Are there currently available tools to generate decoding coefficients for non-symmetrical setups or an iterative algorithm that I could implement on my own ? Two possible methods have been published. The first is Franz Zotter's work, using an 'almost regular' virtual layout based on t-designs for which a decoder can be designed in closed form. Then the virtual set of speakers is mapped onto the real one using VBAP. As far as I know there is no 'ready to use' toolset for this method. The second is the subject of BLaH paper #4, and is based on using a non-linear optimisation toolset to find a solution, given the error constraints and weights for a set of performance metrics. I developed more or less the same (even using the same freely available non-linear library), but wasn't allowed to publish the results, so I can confirm this can work rather well. What looks like a practical implementation (by B,L& H) of this method is scheduled for presentation at the next Linux Audio Conference at CCRMA. I don't think either method can be used 'blindly', in the sense that you just throw a set of speaker coordinates at it and get a guaranteed result. You will have to evaluate the results, and you may have to decide on tradeoffs and iterate the procedure using modified parameter sets. At this point you will need some familiarity with the internals in order to be able to proceed. Ciao, -- These are my own views and may or may not be shared by my employer /*/ /* Dave Malham http://music.york.ac.uk/staff/research/dave-malham/ */ /* Music Research Centre */ /* Department of Music"http://music.york.ac.uk/"; */ /* The University of York Phone 01904 322448*/ /* Heslington Fax 01904 322450*/ /* York YO10 5DD */ /* UK 'Ambisonics - Component Imaging for Audio' */ /*"http://www.york.ac.uk/inst/mustech/3d_audio/"; */ /*/ ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Periphonic problems
Good evening all, I am a currently looking into Ambisonic periphonic systems. This is my first post so please go easy on me. I am currently using a 16 speaker rig which includes a cube and an octagon set up. I understand that this is not a regular shape so is not optimal. The question i have at the moment is that i am trying to implement a 2nd order encoder/decoder in Matlab, however at the moment I am running into problems. I am using the method described in Hollerwegers paper “Periphonic Sound Spatialization in Multiuser Virtual Environments” using the SN3D equations, utilising the pseudo inverse method to derive my decoding matrix. I currently have a 1st and 3rd order encoder/decoder giving sensible answers with respect to Gerzons diametric decoder theorem. The problem with the 2nd order decoder is that the final gains given do not give negative phase for the diametrically opposed speaker. I have also tried using a regular shaped speaker set up, but this still does not give me negative phase in the diametrically opposed speaker. Could someone tell me where I am going wrong? Thank you, Paul -- next part -- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20120229/3675d289/attachment.html> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Periphonic problems
On 02/29/2012 08:16 PM, Paul Power wrote: The problem with the 2nd order decoder is that the final gains given do not give negative phase for the diametrically opposed speaker. I have also tried using a regular shaped speaker set up, but this still does not give me negative phase in the diametrically opposed speaker. Could someone tell me where I am going wrong? off the top of my head, you aren't. the second-order clover-shape has the same polarity on opposite lobes, and inverse polarity on both orthogonal ones. a second-order hypercardioid will have an in-phase rear lobe, and an out-of-phase "ring". -- Jörn Nettingsmeier Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487 Meister für Veranstaltungstechnik (Bühne/Studio) Tonmeister VDT http://stackingdwarves.net ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
I second everything that Fons wrote, most especially that "(n)either method can be used 'blindly', in the sense that you just throw a set of speaker coordinates at it and get a guaranteed result" This has been a very difficult problem for us. For regular arrays it's easy to say that a certain result (group of decoder coefficients) is optimum in some sense. When the array is irregular then you have to make a determination as to which direction is most important for you. Then you can decide on a trade-off between making the performance good in the better directions (directions with the greatest density of loudspeakers) without making it bad in the poor directions (directions with the lowest density of loudspeakers). From one point of view the solution would be to only use regular arrays, and that's fine for research institutions and facilities where the room can be built with the intention of housing the regular array. But for many or most applications there is a real limit to what one can practically do. The challenge is to do as well as possible within the real-world constraints. And that's what Aaron Heller, Richard Lee and I are trying to do. Our toolkit (really, it's Aaron's) will be available at about the time of the Linux Audio Conference and it uses open source tools that operate on a variety of computing platforms. But there's a lot more to be done, particularly in the area of providing indications as to which of several compromised solutions is better. Eric - Original Message From: Fons Adriaensen To: sursound@music.vt.edu Sent: Wed, February 29, 2012 6:28:55 AM Subject: Re: [Sursound] Decoding coefficients for non symmetrical setups On Wed, Feb 29, 2012 at 01:15:40PM +, Miguel Negrao wrote: > I’ve been a bit disconnected from the ambisonics world. From my past reading > on >this list it is my understanding that there isn’t an explicit formula for >decoding coefficients for non-symmetrical setups. Are there currently >available >tools to generate decoding coefficients for non-symmetrical setups or an >iterative algorithm that I could implement on my own ? Two possible methods have been published. The first is Franz Zotter's work, using an 'almost regular' virtual layout based on t-designs for which a decoder can be designed in closed form. Then the virtual set of speakers is mapped onto the real one using VBAP. As far as I know there is no 'ready to use' toolset for this method. The second is the subject of BLaH paper #4, and is based on using a non-linear optimisation toolset to find a solution, given the error constraints and weights for a set of performance metrics. I developed more or less the same (even using the same freely available non-linear library), but wasn't allowed to publish the results, so I can confirm this can work rather well. What looks like a practical implementation (by B,L & H) of this method is scheduled for presentation at the next Linux Audio Conference at CCRMA. I don't think either method can be used 'blindly', in the sense that you just throw a set of speaker coordinates at it and get a guaranteed result. You will have to evaluate the results, and you may have to decide on tradeoffs and iterate the procedure using modified parameter sets. At this point you will need some familiarity with the internals in order to be able to proceed. Ciao, -- FA Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl. ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
Thanks for all the answers. Since I really looking for a method I could use more or less blindly, I guess for the moment I will not dive more into it. I would be interested the tools that Eric mentions when they are released. Would an automated “blind" search algorithm possibly give worse results then just using the equations for the symmetrical case ? I know many people using ambisonics for eletroacoustic music and I think all of them use the equations for the symmetrical case in whatever system they are playing in, which most often is not symmetrical. And it kind of works. How much improvement do you get from using proper coefficient sets ? best, Miguel A 29/02/2012, às 20:13, Eric Benjamin escreveu: > I second everything that Fons wrote, most especially that "(n)either method > can > be used 'blindly', in the sense that you just > throw a set of speaker coordinates at it and get a guaranteed result" > > This has been a very difficult problem for us. For regular arrays it's easy > to > say that a certain result (group of decoder coefficients) is optimum in some > sense. When the array is irregular then you have to make a determination as > to > which direction is most important for you. Then you can decide on a > trade-off > between making the performance good in the better directions (directions with > the greatest density of loudspeakers) without making it bad in the poor > directions (directions with the lowest density of loudspeakers). > > From one point of view the solution would be to only use regular arrays, and > that's fine for research institutions and facilities where the room can be > built > with the intention of housing the regular array. But for many or most > applications there is a real limit to what one can practically do. The > challenge is to do as well as possible within the real-world constraints. > And > that's what Aaron Heller, Richard Lee and I are trying to do. > > Our toolkit (really, it's Aaron's) will be available at about the time of the > Linux Audio Conference and it uses open source tools that operate on a > variety > of computing platforms. But there's a lot more to be done, particularly in > the > area of providing indications as to which of several compromised solutions is > better. > > Eric > > > > - Original Message > From: Fons Adriaensen > To: sursound@music.vt.edu > Sent: Wed, February 29, 2012 6:28:55 AM > Subject: Re: [Sursound] Decoding coefficients for non symmetrical setups > > On Wed, Feb 29, 2012 at 01:15:40PM +, Miguel Negrao wrote: > >> I’ve been a bit disconnected from the ambisonics world. From my past reading >> on >> this list it is my understanding that there isn’t an explicit formula for >> decoding coefficients for non-symmetrical setups. Are there currently >> available >> tools to generate decoding coefficients for non-symmetrical setups or an >> iterative algorithm that I could implement on my own ? > > > Two possible methods have been published. > > The first is Franz Zotter's work, using an 'almost regular' virtual layout > based > on > t-designs for which a decoder can be designed in closed form. Then the > virtual > set > of speakers is mapped onto the real one using VBAP. As far as I know there is > no > 'ready to use' toolset for this method. > > The second is the subject of BLaH paper #4, and is based on using a non-linear > optimisation toolset to find a solution, given the error constraints and > weights > for a set of performance metrics. I developed more or less the same (even > using > the same freely available non-linear library), but wasn't allowed to publish > the > results, so I can confirm this can work rather well. What looks like a > practical > implementation (by B,L & H) of this method is scheduled for presentation at > the > next Linux Audio Conference at CCRMA. > > I don't think either method can be used 'blindly', in the sense that you just > throw a set of speaker coordinates at it and get a guaranteed result. You > will have to evaluate the results, and you may have to decide on tradeoffs > and iterate the procedure using modified parameter sets. At this point you > will need some familiarity with the internals in order to be able to proceed. > > Ciao, > > > -- > FA > > Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl. > > ___ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound > > ___ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound -- Miguel Negrão // ZLB http://www.friendlyvirus.org/artists/zlb/ ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Periphonic problems
On Wed, Feb 29, 2012 at 07:16:18PM +, Paul Power wrote: > I am a currently looking into Ambisonic periphonic systems. > This is my first post so please go easy on me. I am currently using a 16 > speaker rig which includes a cube and an octagon set up. I understand that > this > is not a regular shape so is not optimal. > > The question i have at the moment is that i am trying to > implement a 2nd order encoder/decoder in Matlab, however at the > moment I am running into problems. > > I am using the method described in Hollerwegers paper “Periphonic > Sound Spatialization in Multiuser Virtual Environments” using the SN3D > equations, utilising the pseudo inverse method to derive my decoding matrix. I > currently have a 1st and 3rd order encoder/decoder giving > sensible answers with respect to Gerzons diametric decoder theorem. The > problem > with the 2nd order decoder is that the final gains given do not give > negative phase for the diametrically opposed speaker. I have also tried using > a > regular shaped speaker set up, but this still does not give me negative phase > in the diametrically opposed speaker. Your setup does not support periphonic 3rd order, so the results you get for that should be taken with some big grains of salt. Regarding 2nd order, the driving functions for a regular layout would be 2nd order hypercardioids which have a positive back lobe. There is *no* reason to expect that the opposing speaker should be in antiphase. You are applying first-order theory to higher order, and that doesn't work. Ciao, -- FA Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl. ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Periphonic problems
On Wed, Feb 29, 2012 at 08:36:45PM +0100, Jörn Nettingsmeier wrote: > On 02/29/2012 08:16 PM, Paul Power wrote: >> The problem >> with the 2nd order decoder is that the final gains given do not give >> negative phase for the diametrically opposed speaker. I have also tried >> using a >> regular shaped speaker set up, but this still does not give me negative phase >> in the diametrically opposed speaker. >> >> Could someone tell me where I am going wrong? > > off the top of my head, you aren't. the second-order clover-shape has > the same polarity on opposite lobes, and inverse polarity on both > orthogonal ones. a second-order hypercardioid will have an in-phase rear > lobe, and an out-of-phase "ring". Perfect ! -- FA Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl. ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
I think the problems of using less-than-perfect decoders are easily overshadowed in the concert situation by the fact that almost all listeners are sitting quite outside the sweet spot; precision in imagery just isn't going to be there. Using higher orders with sub optimal decoders would yield better results than lower orders with optimal decoders. Note that this isn't necessarily true for sweetspot listeners - probably the reverse - but it goes for most listeners Dr Peter Lennox School of Technology, Faculty of Arts, Design and Technology University of Derby, UK e: p.len...@derby.ac.uk t: 01332 593155 From: sursound-boun...@music.vt.edu [sursound-boun...@music.vt.edu] On Behalf Of Miguel Negrao [miguel.negrao-li...@friendlyvirus.org] Sent: 29 February 2012 20:55 To: Surround Sound discussion group Subject: Re: [Sursound] Decoding coefficients for non symmetrical setups Thanks for all the answers. Since I really looking for a method I could use more or less blindly, I guess for the moment I will not dive more into it. I would be interested the tools that Eric mentions when they are released. Would an automated “blind" search algorithm possibly give worse results then just using the equations for the symmetrical case ? I know many people using ambisonics for eletroacoustic music and I think all of them use the equations for the symmetrical case in whatever system they are playing in, which most often is not symmetrical. And it kind of works. How much improvement do you get from using proper coefficient sets ? best, Miguel A 29/02/2012, às 20:13, Eric Benjamin escreveu: > I second everything that Fons wrote, most especially that "(n)either method > can > be used 'blindly', in the sense that you just > throw a set of speaker coordinates at it and get a guaranteed result" > > This has been a very difficult problem for us. For regular arrays it's easy > to > say that a certain result (group of decoder coefficients) is optimum in some > sense. When the array is irregular then you have to make a determination as > to > which direction is most important for you. Then you can decide on a trade-off > between making the performance good in the better directions (directions with > the greatest density of loudspeakers) without making it bad in the poor > directions (directions with the lowest density of loudspeakers). > > From one point of view the solution would be to only use regular arrays, and > that's fine for research institutions and facilities where the room can be > built > with the intention of housing the regular array. But for many or most > applications there is a real limit to what one can practically do. The > challenge is to do as well as possible within the real-world constraints. And > that's what Aaron Heller, Richard Lee and I are trying to do. > > Our toolkit (really, it's Aaron's) will be available at about the time of the > Linux Audio Conference and it uses open source tools that operate on a variety > of computing platforms. But there's a lot more to be done, particularly in > the > area of providing indications as to which of several compromised solutions is > better. > > Eric > > > > - Original Message > From: Fons Adriaensen > To: sursound@music.vt.edu > Sent: Wed, February 29, 2012 6:28:55 AM > Subject: Re: [Sursound] Decoding coefficients for non symmetrical setups > > On Wed, Feb 29, 2012 at 01:15:40PM +, Miguel Negrao wrote: > >> I’ve been a bit disconnected from the ambisonics world. From my past reading >> on >> this list it is my understanding that there isn’t an explicit formula for >> decoding coefficients for non-symmetrical setups. Are there currently >> available >> tools to generate decoding coefficients for non-symmetrical setups or an >> iterative algorithm that I could implement on my own ? > > > Two possible methods have been published. > > The first is Franz Zotter's work, using an 'almost regular' virtual layout > based > on > t-designs for which a decoder can be designed in closed form. Then the virtual > set > of speakers is mapped onto the real one using VBAP. As far as I know there is > no > 'ready to use' toolset for this method. > > The second is the subject of BLaH paper #4, and is based on using a non-linear > optimisation toolset to find a solution, given the error constraints and > weights > for a set of performance metrics. I developed more or less the same (even > using > the same freely available non-linear library), but wasn't allowed to publish > the > results, so I can confirm this can work rather well. What looks like a > practical > implementation (by B,L & H) of this method is scheduled for presentation at > the > next Linux Audio Conference at CCRMA. > > I don't think either method can be used 'blindly', in the sense that you just > throw a set of speaker coordinates at it and get a guaranteed result. You > will have to evaluate the results, and you may hav
Re: [Sursound] Decoding coefficients for non symmetrical setups
On Wed, Feb 29, 2012 at 08:55:05PM +, Miguel Negrao wrote: > Would an automated “blind" search algorithm possibly give worse > results then just using the equations for the symmetrical case ? > I know many people using ambisonics for eletroacoustic music and > I think all of them use the equations for the symmetrical case in > whatever system they are playing in, which most often is not > symmetrical. And it kind of works. * From a purely artistic P.O.V. that is quite OK. In particular if the signal is adjusted interactively to the (theoretically) wrong decoding. Accuracy is required if the production and reproduction environments are independent. If they are not there's a lot of headroom. Ciao, -- FA Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl. ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
On Wed, Feb 29, 2012 at 3:55 PM, Miguel Negrao wrote: > Would an automated “blind" search algorithm possibly Speaking of that, you probably want to search the list archives for a thread I started in 2009 titled: "A stupid optimizer for irregular ambisonic layouts" In it I provide the source for a simplistic decoder that uses a generic open source blackbox non-linear optimizer library with a simple objective to make matrixes. I like the generic optimization approaches _more_ than more mathematically elegant closed form solutions because it's easy to play around with the objective functions— and usually any change to the objective makes your closed form solutions need to start from scratch. The URL I gave is dead, but I found what I _believe_ is the same file and put it a location which should be a bit longer lasting. https://people.xiph.org/~greg/ambisonics/ambi_opt.c (compilation is just "gcc -std=c99 -O3 -o ambi_opt ./ambi_opt.c -lm -lnlopt") Giving a brief glance at the code, now with several more years of experience with optimization— and I see that my objective function appears differentiable. If I were to do this again I'd probably use a C++ reverse mode automatic differentiation library, so that I could get a version of the objective with gradients. My email archives indicate that Aaron Heller made a version with a bunch of improvements like RME rE optimization, and adding direction mismatch between rE and rV as part of the objective. Somewhere I had some version with support for higher orders and 3d but I don't know where that is right now. There are a lot of things you can do starting from a simple framework like this. ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
On 2012-02-29, Gregory Maxwell wrote: Would an automated “blind" search algorithm possibly Speaking of that, you probably want to search the list archives for a thread I started in 2009 titled: "A stupid optimizer for irregular ambisonic layouts" In it I provide the source for a simplistic decoder that uses a generic open source blackbox non-linear optimizer library with a simple objective to make matrixes. Before They point it out themselves, I think the fourth installment of Blah does very much the same. And of course Bruce Wiggins's (I hope) research was what started this fray out in the first place. So, yes, this is something that seems to be recommended from more than one corner, with regard to irregular layouts. But still... Personally what I find a bit worrisome is that this sort of optimization retains the blackbox leanings of machine learning as a general discipline. None of the ambisonic specific, closed form optimization literature, or the derived specifics of the base optimization problem, are being utilized. Instead the two (sometimes simultaneous, sometimes even not that) Gerzonian equations are being fed into one or another optimization framework, with no regard to what happens then, and without feeding in all of the age-old mathematical-physical knowhow of how those systems of equations behave. Like for instance psychoacoustical sensitivity estimates from the BBC era. In addition to being a fan of black box algorithms, including all of the stuff that goes under the rubric of "data mining" (professionally I make my living as a database guy), I'm also a little bit of a skeptic towards the stuff. At least as far as the math I know and love suggests I should be. For example, when using support vector machines to fit polynomial bases, how many people actually care to evaluate the Vapnik-Cervonekis bound intrinsic to the problem, and then bound it in a principled fashion before commencing to optimize numerically? That after all is the most principled framework in which to bound overfitting by the machine -- i.e. the very same thing which leads to speaker detent within the ambisonic framework, even after simple dimensional constraints have already been dealt with. And how many actually take a look at the early bispectral model of Gerzon? Or the third one which name I don't remember right now? Even if those aren't backed up by psychoacoustics, they are still very, *very* relevant as (easily, formally, in-principled-fashion) saturable optimization criteria (in the usual ambisonic L^2 sense no less). I don't think going with the easy route and just using blackbox optimizers does the job best, here. Instead, I would think we have to find a way to inject more and more current, analytically purified, psychoacoustic knowledge into the system, before we even start to optimize. Even if numerical optimization still remains the key in reaching a local optimum in this kind of a very difficult nonlinear optimization problem. Once again, Robert Greene, please help me if I'm falling short on the hard math, somehow. I like the generic optimization approaches _more_ than more mathematically elegant closed form solutions because it's easy to play around with the objective functions— and usually any change to the objective makes your closed form solutions need to start from scratch. So to reiterate, numerical optimization is a must, because the most general problem seems to be analytically intractable. I'm even pretty sure that certain rig configurations could be shown to be impossible to solve using analytic means, and even instable around their steepest, global optimum if that was ever found. At the same time, though, I think a more well-thought out optimization criterion, with some intelligent, psychoacoustically minded regularization built in, and perhaps utilizing not only the L^2 norm but also the L^1 at the same time, could still cut the mustard. That's only going to happen if we push more and more of the post-Gerzon psychoacoustic research into the optimization criterion and then use an optimization engine capable of dealing with that sort of thing. That isn't being done now. Even to accelerate convergence, or to give a global, smooth starting point for the optimization procedure(s), or to regularize the eventual outcome. Why not? Are we really that lazy (well I am, but are the researchers in the feel as lazy as me as well?) https://people.xiph.org/~greg/ambisonics/ambi_opt.c Under xiph.org? Ooh! Please, more of that. And then more reseach plus application in how to optimally code/decode even first order using Vorbis (or some derivative?). Giving a brief glance at the code, now with several more years of experience with optimization— and I see that my objective function appears differentiable. If I were to do this again I'd probably use a C++ reverse mode automatic differentiation library, so that I could get a
Re: [Sursound] Decoding coefficients for non symmetrical setups
Hi there - at the risk of performing a plug: The irregular decoder problem has been a bit of an obsession of mine over the years. Folk may have played with my ancient and somewhat naïve (but not awful) "ambidec". (Not to be confused with Fons' excellent software of course!) I dread to think how many months of effort I've spent on this now. The current generation of this thread of thought works rather nicely IMHO - in fact that realisation was the driver to set up the company "Blue Ripple Sound" - and naming it that way - maybe one day I'll be able to make a living out of this sort of thing! If you've seen the website, you may be aware that there are two editions of the software - the "User" and "Advanced" editions - the main difference is the availability of a decoder generator that supports fairly arbitrary layouts at fairly arbitrary orders. We're very happy with it :-) Anyway, apologies for the plug, and being closed source (boo hiss) - I'll go lurk again now... --Richard -Original Message- From: sursound-boun...@music.vt.edu [mailto:sursound-boun...@music.vt.edu] On Behalf Of Miguel Negrao Sent: 29 February 2012 13:16 To: Surround Sound discussion group Subject: [Sursound] Decoding coefficients for non symmetrical setups Hi list, Ive been a bit disconnected from the ambisonics world. From my past reading on this list it is my understanding that there isnt an explicit formula for decoding coefficients for non-symmetrical setups. Are there currently available tools to generate decoding coefficients for non-symmetrical setups or an iterative algorithm that I could implement on my own ? best regards, Miguel Negrão ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
> Bruce Wiggins's (I hope) research was what started this fray out in the first >place Yup. And several others. But the point is that there is a good deal more to be done, especially as you point out that: > this sort of optimization retains the blackbox leanings of machine learning > as >a general discipline Which would be OK, if the black box could give a meaningful rating of which decoders are good and which are bad, or more to the point, which is better than another. But we're not to that point yet. > how many actually take a look at the early bispectral model of Gerzon? Took a look at. But that's not the same thing as implementing it! On the side of improving the psychoacoustic models I've been working on using spherical head models to predict the localization cues achieved and making in situ measurements of the ear signals of a real listener when listening to Ambisonic reproduction. Some of this is available in: "Why Ambisonics Does Work ", Benjamin, Lee and Heller, AES preprint 8242 (2010) a paper which was semi-humorous but which also contains some good stuff. I was partly unsuccessful at showing the relationship between Gerzon's Energy vector and ILDs and that is something which I will devote some further serious attention to soon. > a more well-thought out optimization criterion, with some intelligent, >psychoacoustically minded regularization built in could still cut the >mustard Ah, if only we could find some intelligence to apply to the problem. Eric - Original Message From: Sampo Syreeni To: Surround Sound discussion group Sent: Wed, February 29, 2012 2:19:46 PM Subject: Re: [Sursound] Decoding coefficients for non symmetrical setups On 2012-02-29, Gregory Maxwell wrote: >> Would an automated “blind" search algorithm possibly > > Speaking of that, you probably want to search the list archives for a thread > I >started in 2009 titled: > > "A stupid optimizer for irregular ambisonic layouts" > > In it I provide the source for a simplistic decoder that uses a generic open >source blackbox non-linear optimizer library with a simple objective to make >matrixes. Before They point it out themselves, I think the fourth installment of Blah does very much the same. And of course Bruce Wiggins's (I hope) research was what started this fray out in the first place. So, yes, this is something that seems to be recommended from more than one corner, with regard to irregular layouts. But still... Personally what I find a bit worrisome is that this sort of optimization retains the blackbox leanings of machine learning as a general discipline. None of the ambisonic specific, closed form optimization literature, or the derived specifics of the base optimization problem, are being utilized. Instead the two (sometimes simultaneous, sometimes even not that) Gerzonian equations are being fed into one or another optimization framework, with no regard to what happens then, and without feeding in all of the age-old mathematical-physical knowhow of how those systems of equations behave. Like for instance psychoacoustical sensitivity estimates from the BBC era. In addition to being a fan of black box algorithms, including all of the stuff that goes under the rubric of "data mining" (professionally I make my living as a database guy), I'm also a little bit of a skeptic towards the stuff. At least as far as the math I know and love suggests I should be. For example, when using support vector machines to fit polynomial bases, how many people actually care to evaluate the Vapnik-Cervonekis bound intrinsic to the problem, and then bound it in a principled fashion before commencing to optimize numerically? That after all is the most principled framework in which to bound overfitting by the machine -- i.e. the very same thing which leads to speaker detent within the ambisonic framework, even after simple dimensional constraints have already been dealt with. And how many actually take a look at the early bispectral model of Gerzon? Or the third one which name I don't remember right now? Even if those aren't backed up by psychoacoustics, they are still very, *very* relevant as (easily, formally, in-principled-fashion) saturable optimization criteria (in the usual ambisonic L^2 sense no less). I don't think going with the easy route and just using blackbox optimizers does the job best, here. Instead, I would think we have to find a way to inject more and more current, analytically purified, psychoacoustic knowledge into the system, before we even start to optimize. Even if numerical optimization still remains the key in reaching a local optimum in this kind of a very difficult nonlinear optimization problem. Once again, Robert Greene, please help me if I'm falling short on the hard math, somehow. > I like the generic optimization approaches _more_ than more mathematically >elegant closed form solutions because it's easy to play around wi
Re: [Sursound] Decoding coefficients for non symmetrical setups
Dang. Have written all that, I should add that though the code works at higher orders, the player only supports formats up to third order (the game engine actually goes up to fourth right now). And rather fatally for Miguel's purposes, the decoder generator doesn't allow the coefficients to be exported. It's well worth a listen though, honest! --Richard -Original Message- From: Richard Furse [mailto:rich...@muse440.com] Sent: 29 February 2012 22:25 To: 'Surround Sound discussion group' Subject: RE: [Sursound] Decoding coefficients for non symmetrical setups Hi there - at the risk of performing a plug: The irregular decoder problem has been a bit of an obsession of mine over the years. Folk may have played with my ancient and somewhat naïve (but not awful) "ambidec". (Not to be confused with Fons' excellent software of course!) I dread to think how many months of effort I've spent on this now. The current generation of this thread of thought works rather nicely IMHO - in fact that realisation was the driver to set up the company "Blue Ripple Sound" - and naming it that way - maybe one day I'll be able to make a living out of this sort of thing! If you've seen the website, you may be aware that there are two editions of the software - the "User" and "Advanced" editions - the main difference is the availability of a decoder generator that supports fairly arbitrary layouts at fairly arbitrary orders. We're very happy with it :-) Anyway, apologies for the plug, and being closed source (boo hiss) - I'll go lurk again now... --Richard -Original Message- From: sursound-boun...@music.vt.edu [mailto:sursound-boun...@music.vt.edu] On Behalf Of Miguel Negrao Sent: 29 February 2012 13:16 To: Surround Sound discussion group Subject: [Sursound] Decoding coefficients for non symmetrical setups Hi list, Ive been a bit disconnected from the ambisonics world. From my past reading on this list it is my understanding that there isnt an explicit formula for decoding coefficients for non-symmetrical setups. Are there currently available tools to generate decoding coefficients for non-symmetrical setups or an iterative algorithm that I could implement on my own ? best regards, Miguel Negrão ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
A 29/02/2012, às 21:24, Fons Adriaensen escreveu: > On Wed, Feb 29, 2012 at 08:55:05PM +, Miguel Negrao wrote: > >> Would an automated “blind" search algorithm possibly give worse >> results then just using the equations for the symmetrical case ? >> I know many people using ambisonics for eletroacoustic music and >> I think all of them use the equations for the symmetrical case in >> whatever system they are playing in, which most often is not >> symmetrical. And it kind of works. > > * From a purely artistic P.O.V. that is quite OK. In particular if the > signal is adjusted interactively to the (theoretically) wrong decoding. And how would that adjustment be done ? > Accuracy is required if the production and reproduction environments > are independent. If they are not there's a lot of headroom. Yes, my intended use is for real-time encode and decode on the spot. All the spatial information is stored parametrically, i.e. mono sounds + x,y,z coordinates. Also, forgot to say, the rig is 3D with 34 speakers, 26 above ground and 8 below ground forming a kind of sphere, but it’s not really symmetrical to the center listening position (it’s the sonic lab of SARC). best, Miguel ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
On Wed, Feb 29, 2012 at 5:19 PM, Sampo Syreeni wrote: > Personally what I find a bit worrisome is that this sort of optimization > retains the blackbox leanings of machine learning as a general discipline. > None of the ambisonic specific, closed form optimization literature, or the > derived specifics of the base optimization problem, are being utilized. > Instead the two (sometimes simultaneous, sometimes even not that) Gerzonian > equations are being fed into one or another optimization framework, with no > regard to what happens then, and without feeding in all of the age-old > mathematical-physical knowhow of how those systems of equations behave. Like > for instance psychoacoustical sensitivity estimates from the BBC era. Indeed. But in 100 lines of fairly simple code or so — you have something that produces usable matrixes. > I'm also a little bit of a skeptic towards the > stuff. At least as far as the math I know and love suggests I should be. It's not magic, for sure— but the problems we solve here are small (few dimensions), and relatively smooth (except where they aren't as you note there are singularities)... and you can usually afford throw billions of cycles at them. While we weren't looking computers got _fast_. > I don't think going with the easy route and just using blackbox optimizers > does the job best, here. Absolutely not. But it gets you something right away. Theorizing about the best psychoacoustic criteria doesn't— and it seems like most of the people who have invested a lot of time thinking about this problem go the closed source opaque route thus failing to advance the public science... even many people who do proper research in this space only output papers, which while informative often don't do much to advance the _practice_ of surround listening (perhaps the closed source folks implement their techniques). > That isn't being done now. Even to accelerate convergence, or to give a > global, smooth starting point for the optimization procedure(s), or to > regularize the eventual outcome. Why not? Are we really that lazy (well I > am, but are the researchers in the feel as lazy as me as well?) Dunno about you, but I'm pretty darn lazy! >> https://people.xiph.org/~greg/ambisonics/ambi_opt.c > > Under xiph.org? Ooh! Please, more of that. And then more reseach plus > application in how to optimally code/decode even first order using Vorbis > (or some derivative?). Back in 2007 I created a special Vorbis mode for coupled first order b-format. I thought I posted about it here, but I can't find the message with a quick search. I don't have a surround reproduction rig so I was unable to listen to it, and I just wanted feedback about how it sounded. IIRC I didn't get any feedback. ::shrugs:: I doubt I still have the modes or files anymore. My general belief is that (with carefully constructed formats and encoders) fairly modest bitrate perceptually compressed audio can sound excellent— and if we want to increase quality further with more bits what we should be doing is going to (increasingly high fidelity) surround before decreasing lossyness.Unfortunately, high quality surround content and playback rigs are still scarce. ... and the ITU/MPEG crowds approach to lossy surround coding appears to be excessively parametric— very few bits but its mostly only good for creating ping-pongy effects and motion sickness. (probably a catch 22 with the non-existence of good content and playback rigs, why make lossy codecs for acoustic holography when people are only doing quadrophonic-redux pingpongy stuff?) In any case, the lack of practical deployment of really surround systems has made surround coding stuff stay low on my priority list even though I care about it personally— work in that area, for me, has fairly little improve-the-world bang for the buck. ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
The code that goes with the LAC2012 conference paper does 3D and higher orders. In fact we used it to make a new 3rd-order Ambdec config for CCRMA's 22 speaker array. Its written in MATLAB/Gnu Octave, and it's not a lot of code. So plenty of opportunity for tinkering with the goal functions. One comment that is not in the LAC paper is that with less than 50-70 parameters, the non-linear optimizer works quite well and converges quickly (less than a few minutes). 5 speaker first-order 2-D is 15 parameters. 22 speakers, 3rd-order is 352 parameters so some strategy is needed to guide it. The decoder for CCRMA took about 2 hours. Constraints and exploiting symmetries to reduce the number of parameters would help, but we haven't experimented with that yet. The bulk of the computation is matrix multiplies, so it would be amenable to a Cuda/GPU implementation. Aaron (hel...@ai.sri.com) Menlo Park, CA US ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
On Wed, Feb 29, 2012 at 6:04 PM, Aaron Heller wrote: > 22 speakers, 3rd-order is 352 parameters so some strategy > is needed to guide it. It wouldn't work for a 3D array of 22 speakers— but for an irregular layout with the same number of speakers as a regular one (easy in 2D, fewer choices in 3D): I'd add a single term to the optimization which controls a morphing between your desired layout and a regular one. Then start the optimizer with 1 in that position and the analytic solution for the rest of the matrix. The geometry error term could then just be included in the error function. A local optimizer should be able to then walk to a reasonable solution (if not the best one). (similarly, you may be able to add or eliminate speakers from a solution in a similar way, having a gain parameter for the extra speakers— though I'm more sceptical of that working well— it's not as obvious to me that the solutions should be all that smooth with extra speakers with infinitesimal gain) ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Decoding coefficients for non symmetrical setups
On Wed, Feb 29, 2012 at 3:36 PM, Gregory Maxwell wrote: > On Wed, Feb 29, 2012 at 6:04 PM, Aaron Heller wrote: >> 22 speakers, 3rd-order is 352 parameters so some strategy >> is needed to guide it. > > It wouldn't work for a 3D array of 22 speakers— but for an irregular > layout with the same number of speakers as a regular one (easy in 2D, > fewer choices in 3D): > > I'd add a single term to the optimization which controls a morphing > between your desired layout and a regular one. Then start the > optimizer with 1 in that position and the analytic solution for the > rest of the matrix. The geometry error term could then just be > included in the error function. A local optimizer should be able to > then walk to a reasonable solution (if not the best one). > > (similarly, you may be able to add or eliminate speakers from a > solution in a similar way, having a gain parameter for the extra > speakers— though I'm more sceptical of that working well— it's not as > obvious to me that the solutions should be all that smooth with extra > speakers with infinitesimal gain) Good ideas. In fact, for the 3rd-order solution for the CCRMA array (352 parameters) I had to switch to a local optimizer, PRAXIS, with initial values from the pseudoinverse modified by the rE-max per order gains to get it to converge. This is what one would do for a regular array. 1st-order (88 parameters) was fine with a global optimizer (CRS). ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
