Mikelib

I am currently attempting .amb file playback using Graham Wakefield's Ambi.decode external. I am using this test file as my source 

http://www.ambisonia.com/Members/ajh/ambisonicfile.2007-05-29.7251031563

I am opening the test file in audacity which splits the file into 4 mono tracks (which I assume are wxyz). I am then feeding these individual tracks into Ambi.decode~ for playback. Ambi decode is set with the arguments 3d 1st Default 4 as the .amb file is in 1st order 3D. However on playback the sounds don't appear in the correct positions. I am currently playing back on a quad setup. When using ambiencode with decode a mono input everything is positioned as it should be. Am I right in thinking I should be able to feed w x y z into ambi decode and get correct ambisonic playback? If so does anyone know what could be causing my problem?

Hi,
  I am currently attempting .amb file playback using Graham Wakefield's Ambi.decode external. I am using this test file as my source http://www.ambisonia.com/Members/ajh/ambisonicfile.2007-05-29.7251031563

I am opening the test file in audacity which splits the file into 4 mono tracks (which I assume are wxyz). I am then feeding these individual tracks into Ambi.decode~ for playback. Ambi decode is  set with the arguments 3d 1st Default 4 as the .amb file is in 1st order 3D. However on playback the sounds don't appear in the correct positions. I am currently playing back on a quad setup. When using ambiencode with decode a mono input everything is positioned as it should be. Am I right in thinking I should be able to feed w x y z into ambi decode and get correct ambisonic playback? If so does anyone know what could be causing my problem?

ambi-decode-ambisonic-playbackhelp

You're absolutely right, you should be able to play back w x y z 

channels into an [ambi.decode~ 3d 1st] for ambsionic playback, but 

there's a few possible gotchas: Ambisonics is a theory in which a 

variety of conventions have been used and no particular set is 

standard (though there has been quite a lot of activity on the 

Sursound list recently to tackle this issue, see [1]; note that my 

externals and the ICST ones are predate and do not currently follow 

Besides the 2d/3d and 1st, 2nd etc. order (or in the proposed new 

terminology, degree), there are multiple 'flavors' or coefficients 

that may or may not be assumed to apply to the ambisonic domain 

signals, various different sequences in which the domain signals are 

arranged in the domain (not necessarily intuitive, again see [1] 

which suggests W Y Z X for example) The channel order is easy to 

remedy, if it doesn't match, by patch cabling (The inlet/outlet 

assist messages (mouse over -> status bar) shows the channel names in 

all the ambi. objects). The importance channel coefficients however 

Another standards gotcha that applies to both my externals and the 

ICST ones also is the use of left-hand rule for axes (i.e. azimuth 

90' is to the right, whereas much ambisonic software uses right-hand 

rule). If your spatial image is flipped in the Y axis, it can be 

remedied by reversing the sign of your speaker configuration azimuth 

coordinates (or at 1st order, flipping the sign of the Y signal).

I don't know what conventions were used in this test file, it is not 

documented. Could you describe the 'unexpected' results?

On Oct 17, 2008, at 7:49 AM, Mike Andrews wrote:

> I am currently attempting .amb file playback using Graham 

> Wakefield's Ambi.decode external. I am using this test file as my 

http://www.ambisonia.com/Members/ajh/ambisonicfile.

> I am opening the test file in audacity which splits the file into 4 

> mono tracks (which I assume are wxyz). I am then feeding these 

> individual tracks into Ambi.decode~ for playback. Ambi decode is 

> set with the arguments 3d 1st Default 4 as the .amb file is in 1st 

> order 3D. However on playback the sounds don't appear in the 

> correct positions. I am currently playing back on a quad setup. 

> When using ambiencode with decode a mono input everything is 

> positioned as it should be. Am I right in thinking I should be able 

> to feed w x y z into ambi decode and get correct ambisonic 

> playback? If so does anyone know what could be causing my problem?

You're absolutely right, you should be able to play back w x y z  
channels into an [ambi.decode~ 3d 1st] for ambsionic playback, but  
there's a few possible gotchas: Ambisonics is a theory in which a  
variety of conventions have been used and no particular set is  
standard (though there has been quite a lot of activity on the  
Sursound list recently to tackle this issue, see [1]; note that my  
externals and the ICST ones are predate and do not currently follow  
this standard).

Besides the 2d/3d and 1st, 2nd etc. order (or in the proposed new  
terminology, degree), there are multiple 'flavors' or coefficients  
that may or may not be assumed to apply to the ambisonic domain  
signals, various different sequences in which the domain signals are  
arranged in the domain (not necessarily intuitive, again see [1]  
which suggests W Y Z X for example)  The channel order is easy to  
remedy, if it doesn't match, by patch cabling (The inlet/outlet  
assist messages (mouse over -> status bar) shows the channel names in  
all the ambi. objects). The importance channel coefficients however  
is often overlooked.

Another standards gotcha that applies to both my externals and the  
ICST ones also is the use of left-hand rule for axes (i.e. azimuth  
90' is to the right, whereas much ambisonic software uses right-hand  
rule). If your spatial image is flipped in the Y axis, it can be  
remedied by reversing the sign of your speaker configuration azimuth  
coordinates (or at 1st order, flipping the sign of the Y signal).

I don't know what conventions were used in this test file, it is not  
documented. Could you describe the 'unexpected' results?

>
> Hi,
>   I am currently attempting .amb file playback using Graham  
> Wakefield's Ambi.decode external. I am using this test file as my  
> source http://www.ambisonia.com/Members/ajh/ambisonicfile. 
> 2007-05-29.7251031563
>
> I am opening the test file in audacity which splits the file into 4  
> mono tracks (which I assume are wxyz). I am then feeding these  
> individual tracks into Ambi.decode~ for playback. Ambi decode is   
> set with the arguments 3d 1st Default 4 as the .amb file is in 1st  
> order 3D. However on playback the sounds don't appear in the  
> correct positions. I am currently playing back on a quad setup.  
> When using ambiencode with decode a mono input everything is  
> positioned as it should be. Am I right in thinking I should be able  
> to feed w x y z into ambi decode and get correct ambisonic  
> playback? If so does anyone know what could be causing my problem?
>
> Thanks for any help in advance.
>
> Mike. mandrews04@qub.ac.uk
>
>

The results seem to be pretty much random with the only constant being the centre front position. Unfortunately I will not have access to the system until tomorrow so I can not check in more detail until then. I have also tried patch cable re-ordering and have tried all possible combinations but with no luck. I have also tried this file 

http://www.ambisonia.com/Members/michael/ambisonicfile.2008-07-05.2994956247

 and am having similar problems. When you say "If your spatial image is flipped in the Y axis, it can be 

coordinates (or at 1st order, flipping the sign of the Y signal)." How would I do this? Do you mean by reversing the polarity of the Y axis? The 8 position .amb file I am trying to use was created using a perl script (

 with ambisuite so I don't know if that gives any clue on the conventions used?

Hi Graham I appreciate the reply,
         The results seem to be pretty much random with the only constant being the centre front position. Unfortunately I will not have access to the system until tomorrow so I can not check in more detail until then. I have also tried patch cable re-ordering and have tried all possible combinations but with no luck. I have also tried this file http://www.ambisonia.com/Members/michael/ambisonicfile.2008-07-05.2994956247 and am having similar problems. When you say "If your spatial image is flipped in the Y axis, it can be 
remedied by reversing the sign of your speaker configuration azimuth 
coordinates (or at 1st order, flipping the sign of the Y signal)." How would I do this? Do you mean by reversing the polarity of the Y axis? The 8 position .amb file I am trying to use was created using a perl script (http://mchapman.com/amb/soft/positions/) with ambisuite so I don't know if that gives any clue on the conventions used?
Thanks again, Mike.


Quote: lists@grahamwakefield wrote on Fri, 17 October 2008 12:50

----------------------------------------------------

> You're absolutely right, you should be able to play back w x y z 

> channels into an [ambi.decode~ 3d 1st] for ambsionic playback, but 

> there's a few possible gotchas: Ambisonics is a theory in which a 

> variety of conventions have been used and no particular set is 

> standard (though there has been quite a lot of activity on the 

> Sursound list recently to tackle this issue, see [1];

No, the situation on standards is not nearly as confused 

as you suggest. All the files on Ambisonia.com are in 

the ".amb" standard. This is fairly old and is very 

stable. The details of the standard can be found at: 

http://www.ambisonia.com/Members/mleese/file-format-for-b-format/

This document contains links to pictures and stuff which 

The standard in your ref [1] is a new standard under 

development, so is not yet stable. Unlike ".amb", the 

new one will be able to go above third-order (16 channels). 

But it is not finished yet, so ignore it.

Unfortunately, I have never used plug-in decoders, so 

can't really help the original poster other than to 

point them at the ".amb" standard document.

Quote: lists@grahamwakefield wrote on Fri, 17 October 2008 12:50
----------------------------------------------------
> Hi
>
> You're absolutely right, you should be able to play back w x y z  
> channels into an [ambi.decode~ 3d 1st] for ambsionic playback, but  
> there's a few possible gotchas: Ambisonics is a theory in which a  
> variety of conventions have been used and no particular set is  
> standard (though there has been quite a lot of activity on the  
> Sursound list recently to tackle this issue, see [1];
...
> [1] http://ambisonics.ch/standards/

No, the situation on standards is not nearly as confused 
as you suggest.  All the files on Ambisonia.com are in 
the ".amb" standard.  This is fairly old and is very 
stable.  The details of the standard can be found at:  
http://www.ambisonia.com/Members/mleese/file-format-for-b-format/

This document contains links to pictures and stuff which 
should help.

The standard in your ref [1] is a new standard under 
development, so is not yet stable.  Unlike ".amb", the 
new one will be able to go above third-order (16 channels).  
But it is not finished yet, so ignore it.

Unfortunately, I have never used plug-in decoders, so 
can't really help the original poster other than to 
point them at the ".amb" standard document.

On Oct 17, 2008, at 9:48 PM, Martin Leese wrote:

> No, the situation on standards is not nearly as confused

> as you suggest. All the files on Ambisonia.com are in

> the ".amb" standard. This is fairly old and is very

> stable. The details of the standard can be found at:

Sorry, I didn't want to suggest that there was a lack of convention 

in the .amb format, which as you say is clear and well established. 

I was talking about the literature and implementations of ambisonics 

in the wider community over the past decades, and the recent Sursound 

Double-checking the .amb definition, the channel order and channel 

weights for .amb B-format matches [ambi.decode~ 3d 1st] with no 

modifications needed. That narrows the problem down to either axis 

conventions (or speaker configuration mismatch in the decode~ vs. the 

Flipping the sign of the Y (or any axis) at 1st order is a case of 

placing a [*~ -1] in the signal path between your playback and your 

Unfortunately I don't have a 3D speaker array to hand to test. I also 

don't have a torrent client on this machine to dl the .amb file for a 

visual test. But here's a patch - could you try this? I haven't done 

all 26 positions, I figured 14 was enough to catch whatever the 

problem is. In fact, the first 6 should be enough to get that (L, R, 

F, B, U, D): if L/R are backwards, flip the X channel, etc. If this 

is working fine but yours is still sounding strange, maybe the 

speaker locations are not well defined in your patch/system?

> No, the situation on standards is not nearly as confused
> as you suggest.  All the files on Ambisonia.com are in
> the ".amb" standard.  This is fairly old and is very
> stable.  The details of the standard can be found at:
> http://www.ambisonia.com/Members/mleese/file-format-for-b-format/

Sorry, I didn't want to suggest that there was a lack of convention  
in the .amb format, which as you say is clear and well established.   
I was talking about the literature and implementations of ambisonics  
in the wider community over the past decades, and the recent Sursound  
discussions.

Double-checking the .amb definition, the channel order and channel  
weights for .amb B-format matches [ambi.decode~ 3d 1st] with no  
modifications needed.  That narrows the problem down to either axis  
conventions (or speaker configuration mismatch in the decode~ vs. the  
actual speaker layout used maybe?)

Flipping the sign of the Y (or any axis) at 1st order is a case of  
placing a [*~ -1] in the signal path between your playback and your  
ambi.decode~ inlet for that channel.

Unfortunately I don't have a 3D speaker array to hand to test. I also  
don't have a torrent client on this machine to dl the .amb file for a  
visual test. But here's a patch - could you try this?  I haven't done  
all 26 positions, I figured 14 was enough to catch whatever the  
problem is. In fact, the first 6 should be enough to get that (L, R,  
F, B, U, D): if L/R are backwards, flip the X channel, etc. If this  
is working fine but yours is still sounding strange, maybe the  
speaker locations are not well defined in your patch/system?

Thanks for taking the time to create that patch. I loaded the sound file and played it while observing the meter bars. The meter bars do not correspond to the directions for example left- back comes through each output equally. Front however on its own seems to be correct. I have also tried inverting the connections but I am still not sucessful. I modified that patch in an attempt to playback correctly on my 4 speaker set up. The speaker definitions I have used are as below. Is this correct for a 4 speaker horizontal set up?

Hi Graham,
          Thanks for taking the time to create that patch. I loaded the sound file and played it while observing the meter bars. The meter bars do not correspond to the directions for example left- back comes through each output equally. Front however on its own seems to be correct. I have also tried inverting the connections but I am still not sucessful. I modified that patch in an attempt to playback correctly on my 4 speaker set up. The speaker definitions I have used are as below. Is this correct for a 4 speaker horizontal set up?

;
decoder speaker 0 -45 0;
decoder speaker 1 45 0;
decoder speaker 2 135 0;
decoder speaker 3 -135 0;
decoder dump;


Quote: Mikelib wrote on Mon, 20 October 2008 09:05

> Thanks for taking the time to create that patch. I loaded the sound file and played it while observing the meter bars. The meter bars do not correspond to the directions for example left- back comes through each output equally. Front however on its own seems to be correct.

In Ambisonics, all speakers cooperate to localise a sound. 

So, for example, while the speakers on the left push, 

those on the right pull. Given this, looking at meters 

Quote: Mikelib wrote on Mon, 20 October 2008 09:05
----------------------------------------------------
> Hi Graham,
>           Thanks for taking the time to create that patch. I loaded the sound file and played it while observing the meter bars. The meter bars do not correspond to the directions for example left- back comes through each output equally. Front however on its own seems to be correct.
...
----------------------------------------------------

In Ambisonics, all speakers cooperate to localise a sound.  
So, for example, while the speakers on the left push, 
those on the right pull.  Given this, looking at meters 
is of limited use.


I understand this concept but surely a sound coming from 45 left for example with show a slightly higher reading on the meter of the corresponding speaker?

Hi Martin,
         I understand this concept but surely a sound coming from 45 left for example with show a slightly higher reading on the meter of the corresponding speaker?


Martin is quite correct that all speakers contribute to the 

construction of the sound field, and meters are thus not a very 

helpful way to examine the output. In the patch below you can try out 

a few cardinal directions and see what the meters show. Notice that 

all channels are active (almost) all of the time, and that although 

L, R, U, D, B, F all give helpful results for all the example 

positions, the more complex speaker positions such as ULF are often 

counter-intuitive. (This, amongst many other reasons, is why an 

irregular speaker layout can totally corrupt the spatial image!) Then 

change the decoding flavors (default, in-phase, etc.) and see how the 

Martin is quite correct that all speakers contribute to the  
construction of the sound field, and meters are thus not a very  
helpful way to examine the output. In the patch below you can try out  
a few cardinal directions and see what the meters show. Notice that  
all channels are active (almost) all of the time, and that although  
L, R, U, D, B, F all give helpful results for all the example  
positions, the more complex speaker positions such as ULF are often  
counter-intuitive. (This, amongst many other reasons, is why an  
irregular speaker layout can totally corrupt the spatial image!) Then  
change the decoding flavors (default, in-phase, etc.) and see how the  
signals change again...

Mike, if your speaker layout is horizontal only, then decoding a 3D 

encoded signal stream simply cannot reproduce positions that 

BTW, a [ambi.decode~ 2d 1st 4] object will choose exactly those 

On Oct 20, 2008, at 8:05 AM, Mike Andrews wrote:

> I modified that patch in an attempt to playback correctly on my 4 

> speaker set up. The speaker definitions I have used are as below. 

> Is this correct for a 4 speaker horizontal set up?

Mike, if your speaker layout is horizontal only, then decoding a 3D  
encoded signal stream simply cannot reproduce positions that  
incorporate vertical components!

BTW, a [ambi.decode~ 2d 1st 4] object will choose exactly those  
speaker locations as a default.

> I modified that patch in an attempt to playback correctly on my 4  
> speaker set up. The speaker definitions I have used are as below.  
> Is this correct for a 4 speaker horizontal set up?
>
> ;
> decoder speaker 0 -45 0;
> decoder speaker 1 45 0;
> decoder speaker 2 135 0;
> decoder speaker 3 -135 0;
> decoder dump;


Thanks again Graham. That patch is very helpful in explaining Martin's point. Does this mean that the eight position file 

 will not position correctly when played back on a 2d system?, even though the .amb file contains only 2d directional announcements (Front, Right-Front, Right, Right-Back, Back, Left-Back, Left, Left-Front.)

Thanks again Graham. That patch is very helpful in explaining Martin's point. Does this mean that the eight position file http://www.ambisonia.com/Members/ajh/ambisonicfile.2007-05-29.7251031563   will not position correctly when played back on a 2d system?, even though the .amb file contains only 2d directional announcements (Front, Right-Front, Right, Right-Back, Back, Left-Back, Left, Left-Front.)


That one should work on your system, as it is purely horizontal (you 

should be able to verify that the Z channel is empty).

On Oct 20, 2008, at 7:19 PM, Mike Andrews wrote:

> Thanks again Graham. That patch is very helpful in explaining 

> Martin's point. Does this mean that the eight position file 

> www.ambisonia.com/Members/ajh/ambisonicfile.2007-05-29.7251031563 

> will not position correctly when played back on a 2d system?, even 

> though the .amb file contains only 2d directional announcements 

> (Front, Right-Front, Right, Right-Back, Back, Left-Back, Left, Left- 

That one should work on your system, as it is purely horizontal (you  
should be able to verify that the Z channel is empty).

>
> Thanks again Graham. That patch is very helpful in explaining  
> Martin's point. Does this mean that the eight position file http:// 
> www.ambisonia.com/Members/ajh/ambisonicfile.2007-05-29.7251031563    
> will not position correctly when played back on a 2d system?, even  
> though the .amb file contains only 2d directional announcements  
> (Front, Right-Front, Right, Right-Back, Back, Left-Back, Left, Left- 
> Front.)

Quote: lists@grahamwakefield wrote on Tue, 21 October 2008 10:49

> That one should work on your system, as it is purely horizontal (you 

> should be able to verify that the Z channel is empty).

In a perfect world it would be empty. If the 

announcements were recorded with a soundfield mic 

(instead of being recorded in mono and panned to 

the different directions) then the Z-channel will 

contain ambiance. I haven't listened to the file, 

and its description does not make clear how it was 

Quote: lists@grahamwakefield wrote on Tue, 21 October 2008 10:49
----------------------------------------------------
> That one should work on your system, as it is purely horizontal (you  
> should be able to verify that the Z channel is empty).
...
----------------------------------------------------

In a perfect world it would be empty.  If the 
announcements were recorded with a soundfield mic 
(instead of being recorded in mono and panned to 
the different directions) then the Z-channel will 
contain ambiance.  I haven't listened to the file, 
and its description does not make clear how it was 
created.

I have now got this working. The problems was the fault of audacity and the way it bounces audio files. After I reordered them and set each one to mono the decoder now plays perfectly. The y axis also needed to be flipped. Thanks for all your help Graham and also for creating these excellent externals. Thanks also to Martin for his help.

Hi Guys,
       I have now got this working. The problems was the fault of audacity and the way it bounces audio files. After I reordered them and set each one to mono the decoder now plays perfectly. The y axis also needed to be flipped. Thanks for all your help Graham and also for creating these excellent externals. Thanks also to Martin for his help.

Im a complete newbie to the world of ambisonics and Im fairly new to max aswell. I figure this would be a good thread to ask this question as you all seem quite knowledgable on both. Im trying to set up the ICST externals on my system but make doesnt seem to be able to locate them. Ive placed the folders/content in the locations instructed but max cant see them whenever I try place them into a patch a max message stes that the object could not be found. Any suggestion or even better solutions would be much appreciated.

Hey folks,
Im a complete newbie to the world of ambisonics and Im fairly new to max aswell. I figure this would be a good thread to ask this question as you all seem quite knowledgable on both. Im trying to set up the ICST externals on my system but make doesnt seem to be able to locate them. Ive placed the folders/content in the locations instructed but max cant see them whenever I try place them into a patch a max message stes that the object could not be found. Any suggestion or even better solutions would be much appreciated.

on the off chance that this might be easy to fix:

have you restarted Max since placing the objects in the searchpath?

max 4.5 rebuilds the searchpatch only at startup...

on the off chance that this might be easy to fix:
have you restarted Max since placing the objects in the searchpath?
max 4.5 rebuilds the searchpatch only at startup...

hope this isn't silly, but isn't Ambisonics only for max 4.6.3 ?

> on the off chance that this might be easy to fix:

> have you restarted Max since placing the objects in the searchpath?

> max 4.5 rebuilds the searchpatch only at startup...

> on the off chance that this might be easy to fix:
> have you restarted Max since placing the objects in the searchpath?
> max 4.5 rebuilds the searchpatch only at startup...
>
> /*j


Ambisonics isn't just for Max 4.6.x, on the contrary:

http://www.york.ac.uk/inst/mustech/3d_audio/welcome.html

The ICST Ambisonics MSP objects work fine under Max5.

It's the [ambimonitor] external that's missing, since all GUI-objects 

We're still wainting for the release of the new SDK to complete the 

And Michael _is_ stating that he's using max 4.5 on XP SP2...

> hope this isn't silly, but isn't Ambisonics only for max 4.6.3 ?

http://www.ambisonia.com
http://www.york.ac.uk/inst/mustech/3d_audio/welcome.html
http://www.google.ch/search?q=Ambisonics

The ICST Ambisonics MSP objects work fine under Max5.
It's the [ambimonitor] external that's missing, since all GUI-objects  
have to be rewritten for Max 5.
We're still wainting for the release of the new SDK to complete the  
task.

> hope this isn't silly, but isn't Ambisonics only for max 4.6.3 ?


> Ambisonics isn't just for Max 4.6.x, on the contrary:

> The ICST Ambisonics MSP objects work fine under Max5.

> It's the [ambimonitor] external that's missing, since all GUI- 

> objects have to be rewritten for Max 5.

> We're still wainting for the release of the new SDK to complete the 

> And Michael _is_ stating that he's using max 4.5 on XP SP2...

>> hope this isn't silly, but isn't Ambisonics only for max 4.6.3 ?

> Ambisonics isn't just for Max 4.6.x, on the contrary:
>
> http://www.ambisonia.com
> http://www.york.ac.uk/inst/mustech/3d_audio/welcome.html
> http://www.google.ch/search?q=Ambisonics
>
> The ICST Ambisonics MSP objects work fine under Max5.
> It's the [ambimonitor] external that's missing, since all GUI- 
> objects have to be rewritten for Max 5.
> We're still wainting for the release of the new SDK to complete the  
> task.
>
> Thanks for your patience.
>
> /*j
>
> And Michael _is_ stating that he's using max 4.5 on XP SP2...
>
>> hope this isn't silly, but isn't Ambisonics only for max 4.6.3 ?
>


Ok so Ive gotten max to recognise the externals(by taking them out of their own folder and placing straight into the externals folder) but a new problem has arisen. Whenever i try place the ambimonitor object into a patch max closes! the same thing happens when I try access the help files for ambimonitor and ambicontrol. The encode/decode objects and their help files are fine.

in that case you're out of luck. we've never been able to pinpoint and 

Ambi.decode~ (Ambisonic playback)help