Ambisonic Studio | Stereo UHJ to B-Format with Nuendo



Conversion from Stereo UHJ to B-Format with Nuendo

August 2019 • Important note

The information on this page is now obsolete.

As of version 8.2, Steinberg Nuendo is Ambisonics-aware, providing busses for B-Format up to 3rd order. Combined with some freely available ambisonic VST plug-ins, ambisonic production in Nuendo has never been so easy. We recommend upgrading to Nuendo 8.2 or later and installing the following plug-ins:

Aalto University SPARTA and COMPASS plug-ins | IEM Plug-in Suite | Matthias Kronlachner's ambiX plug-ins | Blue Ripple Sound's O3A Core suite | Nuendo 8 update

We recommend the following book as the reference on Ambisonics audio production:

Ambisonics: A Practical 3D Audio Theory for Recording, Studio Production, Sound Reinforcement, and Virtual Reality

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

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

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

9				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				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				The first minute of the UHJ encoded test files contains W only signal. The conversion should look this. W = 0.5(0.982L + 0.982R + j0.164L - j0.164*R)

12				The second minute of the UHJ encoded test files contains X only signal. The conversion should look this. X = 0.5(0.419L + 0.419R - j0.828L + j0.828*R)

13				The third minute of the UHJ encoded test files contains Y only signal. The conversion should look this. Y = 0.5(0.763L - 0.763R + j0.385L + j0.385*R)

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

15				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).