08-13-2018, 06:59 PM | #1 |
Human being with feelings
Join Date: May 2017
Posts: 3,204
|
Distinctions between the Ambisonic Orders
Distinctions between the Ambisonic Orders?
I haven't run into a good description of Orders. If I had to guess: 1st Order: Mono + L-R (AKA mid-side stereo) 2nd Order: 1st Order + Front-Back (basic surround) 3rd Order: 2nd Order + Top-Bottom (3d surround) Am I close here? Are there more higher Orders? Thanks in advance. |
08-13-2018, 10:17 PM | #2 |
Human being with feelings
Join Date: Mar 2010
Location: Adelaide, South Australia (originally from Geelong)
Posts: 5,598
|
Hi Philbo.
I'm planning on creating a topic to explain the fundamentals of Ambisonics and your question here is one of those I plan to address with that topic. For now though, basically first order Ambisonics is akin to combining three m/s techniques into one recording. A first order Ambisonic recording contains four audio channels. They are known as W, X, Y and Z. This is also commonly referred to as B-format. As you no doubt know, with a regular m/s recording, we have either a cardioid and figure 8 mic or an omni and figure 8. The omni gives us a mono signal and the figure 8 gives us the sides which when combined during m/s decoding, creates a stereo field. In Ambisonics, a complete first order configuration gives us an omni (W channel), a front/back figure 8 (the X signal), a left/right figure 8 (the Y signal) and an up/down figure 8 (the Z signal). When decoded, these four channels give us a full 3D sound field with depth, width and height information. The sound field resolution is determined by the Ambisonic order. First order gives us one lobe per direction and the lowest spacial resolution. As we increase the Ambisonic order, we add more channels which basically split the lobes into smaller lobes which gives us increasing spacial resolution. This is also referred to as spherical harmonics. A second order Ambisonic signal has nine audio channels instead of four and a third order signal has sixteen channels. They all still contain the basic mono omni (W) channel but add to the complexity of the spherical harmonics (the lobes in each direction) using pre determined mathematical formulae. The extra channels in each increasing order contain additional spacial information and greatly increase the ability for the listener to perceive accurate spacial cues. REAPER is ideal for higher order Ambisonics because it can have up to 64 audio channels per track which equates to seventh order Ambisonics. The free IEM plugin suite mentioned in various posts here supports up to seventh order Ambisonics and the man in charge of IEM development, Daniel Rudrich, is a member and contributor here as well. This is the IEM website.. https://plugins.iem.at/
__________________
|
08-14-2018, 02:14 AM | #3 |
Human being with feelings
Join Date: Jun 2011
Location: Belgium
Posts: 5,246
|
My simple-minds memory aid:
- First order: 4 mics (2D) - Second order: 8 mics (3D). Of course, this is just for basic understanding, as it leaves out 3rd order, or mics like the Zylia (that has 19 capsules, IIRC).
__________________
In a time of deceit telling the truth is a revolutionary act. George Orwell |
08-14-2018, 02:47 PM | #4 |
Human being with feelings
Join Date: Apr 2009
Location: Berlin, Germany
Posts: 1,248
|
this is incorrect. As readave says, 1st order ambisonics that can be captured with a tetrahedral mic like the soundfield can capture the 360 degree (3D) soundfield. Confusingly you can do ambisonics with only horizontal info, by omitting certain spherical harmonics. For example the Zoom H2n, can record horizontal only FOA.
Peter stitt's blog provides a nice introduction IIRC: https://spatialaudio.xyz/blog/ doesn't seem to be working right now |
08-14-2018, 03:51 PM | #5 |
Human being with feelings
Join Date: Jun 2011
Location: Belgium
Posts: 5,246
|
Thx, Oli. I was confusing mics and speakers.
Could that blog have been moved here? https://www.ssa-plugins.com/blog/category/what-is/ Mind you, there are several dead links on these pages too. Images are missing, fi. Oh, and beware, spatialaudio.com is currently serving malware.
__________________
In a time of deceit telling the truth is a revolutionary act. George Orwell |
08-14-2018, 05:00 PM | #6 |
Human being with feelings
Join Date: May 2017
Posts: 3,204
|
Thanks for that. I doubt I'll ever have enough speakers to go past 1st order though.
|
08-14-2018, 11:08 PM | #7 | |
Human being with feelings
Join Date: Mar 2010
Location: Adelaide, South Australia (originally from Geelong)
Posts: 5,598
|
Quote:
The Ambisonic order is about the spherical resolution of the recorded material. Ambisonic channels do not equal speaker channels. That is determined by your decoder.
__________________
|
|
08-15-2018, 08:28 PM | #8 |
Human being with feelings
Join Date: Feb 2014
Posts: 240
|
Perhaps this microphones doc may be helpful https://docs.google.com/spreadsheets...DinIub/pubhtml
|
08-15-2018, 10:11 PM | #9 | |
Human being with feelings
Join Date: Feb 2006
Location: France
Posts: 915
|
Quote:
But, you have written "Zoom H4n" as a 4 channel ambisonic recorder. Isn't this a mistake since it has only 2 external mic inputs ? And even the H6 which has 4 phantom powered inputs is not suitable since their level cannot be synced. To my knowledge, only the F4 (and the F8 of course) from Zoom can be used for 1st order ambisonics. Also, the LG 360 cam don't use ambisonics but a multichannel ring (which is by the way not bad at all). |
|
08-20-2018, 05:39 PM | #10 | ||
Human being with feelings
Join Date: Feb 2014
Posts: 240
|
Quote:
Quote:
Apparently it can https://www.google.com/search?q=LG+360+CAM+ambisonics |
||
08-21-2018, 12:26 AM | #11 |
Human being with feelings
Join Date: Feb 2006
Location: France
Posts: 915
|
Oh, thanks, silly me !
I had only the 5.1 option on mine, but with the update I found now there is a 3D option and gives a 4 channels soundtrack instead of the previous 6 channels one. Of course it is only horizontal, but it is a nice addition for this cheap camera. |
09-28-2018, 12:04 AM | #12 | |
Human being with feelings
Join Date: Sep 2018
Posts: 3
|
Quote:
|
|
03-06-2019, 03:49 AM | #13 |
Human being with feelings
Join Date: Jan 2017
Posts: 43
|
Wikipedia has a quite good article about Ambisonics:
https://en.wikipedia.org/wiki/Ambisonics From the picture in the "higher order Ambisonics" paragraph, you can see what the orders mean: Order 0: only omnidirectional mono signal (W) - 1 track Order 1: omni + FrontBack + sideLR + UpDown (WXYZ) - 4 tracks HOA (Higher Order Ambisonics) is like 1st Order but more precise with localization and positional information, thanks to a higher number of mic capsules. MS stereo technique is not part of an Ambisonics order; is sitting in between Order 0 and Order 1, because it carries only front and sideLR horizontal information. |
Thread Tools | |
Display Modes | |
|
|