Upmixing and Beamforming in Professional Audio
Christof Faller · 2017
This chapter presents examples and discusses considerations of different features and quality requirements that are important in professional products. It presents three commercial products that utilize parametric time-frequency-domain processing of spatial audio in applications of stereo upmixing, adaptive beamforming, and spatial sound reproduction. In stereo-to-multichannel upmixing, a stereophonic signal is rendered to a surround setup with typically five or seven loudspeakers in the horizontal plane around the listener. Time-frequency upmixing gives a vast improvement in the spatial audio quality when compared to time-domain matrix upmix. A discrete short-time Fourier transform (STFT) is used as the time-frequency representation. The stereo signal is decomposed into direct and ambient sound. Shotgun microphones are an acoustic implementation of a delay-and-sum beamformer, based on a single microphone element. The chapter discusses the quality considerations in professional audio that are taken into account in the development of products, such as single-channel quality and delay.