Ambisonic Studio Ambisonic
   
Stereo UHJ to
                      B-Format with Nuendo  
 
 

The goal of this article is to provide step by stepinstructions for converting Ambisonic Stereo UHJ interleaved audio files to horizontal first order B-Format three channels audio stream and files. If you're not familiar with Ambisonic surround sound technology, we suggest you read this articleand this article or the Wikipedia entry first. You must also be familiar with Steinberg Nuendo.

DISCLAIMER: we are not satisfied with the resulting audio output of the process suggested. End results are really, really, really, not guaranteed.

The software used for this demonstration is OS X 10.4 to 10.8, Steinberg Nuendo 3/4/5, Angelo Farina UHJ to B-Format impulse responses, Dave Malham & Ambrose Field Ambisonic VST plug-ins and York University Ambisonic VST plug-ins and a Stereo Convolver VST plug-in of your choice.Apart from OS X, all the software is compatible with Windows OS

The information on this page is provided as is, without any guarantee regarding performance or end result.

People familiar with Ambisonic know about Stereo UHJ: it's a way of encoding first order B-Format into two channels for compatible playback on traditional stereo equipment and for decoding in surround sound with the appropriate Ambisonic decoder. Meridian is a manufacturer of such hardware decoders.

Ambisonic Stereo UHJ compact discs are available mainly from Nimbus Records and a few other companies.

If you don't want to construct the Stereo UHJ to B-Format Nuendo project, here's a Nuendo template.

 

1

 

UHJ to
                            B signal processing

 

This is the signal processing path for the Stereo UHJ to B-Format conversion that will be followed in Nuendo.

Signal processing path and image by Angelo Farina.

         

2

 

VST Connections

 

In Nuendo, create a New Project. In the Outputs pane of the VST Connections window, create a Stereo output bus and LRS output bus.

You can rename the output busses Stereo UHJ and B-Format.

         

3

 

Project UHJ tone

 

In the Project window, add a Stereo Audio track and three Stereo Group Channel tracks.

You can rename the Stereo Audio track Stereo UHJ and the stereo Group Channels UHJ to W, UHJ to X and UHJ to Y.

         

4

 

Mixer

 

In the Mix window, assign the Stereo UHJ Audio Track to the Stereo UHJoutput bus.

Assign the UHJ to W Group Channel to the Left channel of the B-Format output bus.

Assign the UHJ to X Group Channel to the Right channel of the B-Format output bus.

Assign the UHJ to Y Group Channel to the Center Surround channel of the B-Format output bus.

Pan the three Group Channels to the center.

Insert an instance of Nuendo TestGenerator and a Stereo Convolver in each of the Group Channels, but leave them off.

Optionally insert an instance of York's B-Proc and B-Mic in the B-Format output bus: this will give you the opportunity to manipulate the B-Format and to compare the undecoded Stereo UHJ to a straight stereo decoding of the B-Format.

         

5

 

Mixer Sends

 

In the Mix window, turn on three Sends in the Stereo UHJ Audio Track, one to each of the Group Channels. The Sends are post fader and at 0 dB level.

         

6

 

W Check

 

You can verify that the UHJ to W Group Channel is going to the W channel (Left of LRS) with the TestGenerator.

         

7

 

X Check

 

You can verify that the UHJ to X Group Channel is going to the X channel (Right of LRS) with the TestGenerator.

         

8

 

Y Check

 

You can verify that the UHJ to Y Group Channel is going to the Y channel (Center Surround of LRS) with the TestGenerator.

         

9

 

IR UHJ to Y

 

Activate the Stereo Convolver plug-ins in the three Group Channels. Load the appropriate impulse response in each (uhj_w_**.wav, uhj_x_**.wav, uhj_y_**.wav) with the sample rate corresponding to the Nuendo project.

Download the Stereo UHJ to B-Format impulses responses.

         

10

 

Tone & Pink UHJ

 

To test the conversion process, use the 200 Hz, 20000 Hz and pink noise files, encoded in UHJ, available here.

The files are two channel interleaved 16 bit FLAC file at 44.1 kHz sample rate.

         

11

 

W UHJ
                            Check

 

The first minute of the UHJ encoded test files contains W only signal. The conversion should look this.

W = 0.5*(0.982*L + 0.982*R + j*0.164*L - j*0.164*R)

 

         

12

 

X UHJ
                            Check

 

The second minute of the UHJ encoded test files contains X only signal. The conversion should look this.

X = 0.5*(0.419*L + 0.419*R - j*0.828*L + j*0.828*R)

         

13

 

Y UHJ
                            Check

 

The third minute of the UHJ encoded test files contains Y only signal. The conversion should look this.

Y = 0.5*(0.763*L - 0.763*R + j*0.385*L + j*0.385*R)

         

14

 

Project Sergei's View

 

Replace the test files in the Project window with the Stereo UHJ sound files to convert to B-Format.

         

15

 

Mixer Converting

 

At this point, you can do the following:

Activate the B-Proc in the B-Format output bus to manipulate the sound field.

Compare the Stereo UHJ outputbus to a stereo decode with the B-Mic in the B-Format output bus (don't forget to mute one output or the other).

 

   

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