posted 10 October 2010 08:12            

[This message has been edited by franz (edited 10 October 2010).]

[This message has been edited by franz (edited 10 October 2010).]

posted 11 October 2011 09:13            

This week I just got such microphone. I haver started doing some surround field recording with a Roland R-44 and a proper windscreen.

If you come across any information about B format and Kyma please let me know.

Regards,

posted 13 October 2011 07:02            

I wish I would be able to build something like that within Kyma. Maybe someone could give us a hint where to start?

posted 05 January 2012 16:35            

The B-format consists consists of the following four signals:

W - a pressure signal corresponding to the output from an omnidirectional microphone
X - the front-to-back directional information, a forward-pointing velocity or "figure-of-eight" microphone
Y - the side-to-side directional information, a leftward-pointing "figure-of-eight" microphone
Z - the up-to-down directional information, an upward-pointing "figure-of-eight" microphone

When you have these 4 types of signal it is possible to 'decode' Mono, Stereo, Mid-Side (MS), 5.1 and all future Surround Formats from the information in these signals.

The B-format contains the three-dimensional acoustic information and consists of 3 figure-eight patterns (X,Y, Z) and one Omni-pattern (called W) These 4 signals have all the same center-point in space what makes this format hyper phase coherent.

X: Front/Back information
Y: Left/Right information
Z: Height information
W: this Omni signal will be used to derivate the LFE-signal by Low-Pass filtering

From B-format to Stereo

The X-signal goes to one track, the Y-signal on another. Threat these two tracks as a standard MS-stereo, so put it through a MS-decoder. Add (if desired) the information from the W-signal equal to the left and right track.

In this configuration you'll listen to the left-right information, as expected in stereo. Putting the volume from track 1 & 2 at 100% you will get the equivalent of a BLUMLEIN (Stereosonic) stereo couple (two coïncident figure-8 microphones at an angle of 90° to each other). When adding the third track to the mix of 2 an 3 you will change the Figure-8 component to a cardioid component, just like when using a standard XY-stereo pair.

When cutting track 2 en leave 1 and 3 open you will just listen to the Left-component from the stereo-couple.
When cutting track A en leave 2 and 3 open you will just listen to the Right-component from the stereo-couple.

If you want to change the stereo-field like making a 90° left turn with your head, just swap the phase of the X signal (track 1) and you will listen to the Left side in Stereo.
If you want to change the stereo-field like making a 90° right turn with your head, just swap the phase of the Y signal (track 2) and you will listen to the Right side in Stereo.
If you want to listen to the stereo-field like you dit a 180° just swap the Phase from ass well the X as the Y signal and you will listen to the back in Stereo.

From B-format to 5.1

From what we have learned from the above the only component we have to handle is the Center Channel. To obtain the signal for this channel you just take the W- and the Y-signaal equally and send them to the Center (This results just like a cardioid microphone pointed to the front.

For the 0.1 or LFE channel use the W signal trough a Low-Pass filter.

For the current surround formats we can leave the Z-signal for what it is as it contains the currently not used vertical information. On the other hand the decoding of this signal can be handled as the above.

So in short, MS-decoding, Phase handling, routing and lowpass filtering are the components of your B-format decoder.

Kind regards from Belgium,

Pedro