Parametric Time-Frequency Domain Spatial Audio

13 Upmixing and Beamforming in Professional Audio

Christof Faller

Illusonic GmbH, Switzerland and École Polytechnique Fédérale de Lausanne (EPFL), Switzerland

13.1 Introduction

As the earlier chapters in this book show, a wide variety of techniques has been proposed in the field of parametric time–frequency domain spatial audio. A few commercial products already exist that utilize such techniques. This chapter presents three examples, also discussing considerations of different features and quality requirements that are important in professional products. The products that are described are:

• TSL Soundfield UPM-1/X-1: A stereo to 5.1 upmix processor widely used in broadcasting.
• Schoeps SuperCMIT 2U: A professional beamformer, that is, a shotgun microphone enhanced with adaptive beamforming.
• Sennheiser Esfera: A 5.1 surround microphone using two cardioid microphone elements. The algorithm can be viewed as an upmixer optimized for the specific microphone setup.

The first product, the Soundfield UPM-1 (and its successor, the Soundfield X-1), is described with a high level of detail on the time–frequency processing. The level of detail is reduced in the descriptions of the other products, since the principles are similar. The descriptions are for illustrative purposes only. The actual products may work differently or may have been updated with modified algorithms.

13.2 Stereo-to-Multichannel Upmix Processor

13.2.1 Product Description

In stereo-to-multichannel upmixing, a stereophonic ...