METHOD FOR RENDERING MULTI-CHANNEL AUDIO SIGNALS FOR L1 CHANNELS TO A DIFFERENT NUMBER L2 OF LOUDSPEAKER CHANNELS AND APPARATUS FOR RENDERING MULTI-CHANNEL AUDIO SIGNALS FOR L1 CHANNELS TO A DIFFERENT NUMBER L2 OF LOUDSPEAKER CHANNELS

摘要

Multi-channel audio content is mixed for a particular loudspeaker setup. However, a consumer's audio setup is very likely to use a different placement of speakers. The present invention provides a method of rendering multi-channel audio that assures replay of the spatial signal components with equal loudness of the signal. A method for obtaining an energy preserving mixing matrix (G) for mixing L1 input audio channels to L2 output channels comprises steps of obtaining (s711) a first mixing matrix G, performing (s712) a singular value decomposition on the first mixing matrix Ĝ to obtain a singularity matrix S, processing (s713) the singularity matrix S to obtain a processed singularity matrix Ŝ, determining (s715) a scaling factor a, and calculating (s716) an improved mixing matrix G according to G=a U Ŝ VT. The perceived sound, loudness, timbre and spatial impression of multi-channel audio replayed on an arbitrary loudspeaker setup practically equals that of the original speaker setup.

主权项

1. A method for rendering L1 channel-based input audio signals to L2 loudspeaker channels, where L1 is different from L2, the method comprising steps of
determining a mix type of the L1 input audio signals, wherein the mix type specifies a coordinate system used for defining speaker positions and wherein possible mix types include at least one of spherical, cylindrical and rectangular; performing a first delay and gain compensation on the L1 input audio signals according to the determined mix type, wherein a delay and gain compensated input audio signal with L1 channels and with a defined mix type is obtained; mixing the delay and gain compensated input audio signal for L2 audio channels, wherein a remixed audio signal for L2 audio channels is obtained; clipping the remixed audio signal, wherein a clipped remixed audio signal for L2 audio channels is obtained; and performing a second delay and gain compensation on the clipped remixed audio signal for L2 audio channels, wherein L2 loudspeaker channels are obtained; wherein the mixing uses an energy preserving mixing matrix G that is obtained by obtaining a first mixing matrix Ĝ from virtual source directions and target speaker directions using a panning method; performing a singular value decomposition on the first mixing matrix Ĝ according to Ĝ=U S VT, wherein U ∈ L2×L2 and V ∈ L1×L2 are orthogonal matrices and S ∈ L2×L2 is a singularity matrix and has s first diagonal elements being the singular values of G in descending order and all other elements of S are zero; processing the singularity matrix S, wherein a quantized singularity matrix Ŝ is obtained with diagonal elements that are above a threshold set to one and diagonal elements that are below a threshold set to zero; determining a number m of diagonal elements that are set to one in the quantized singularity matrix Ŝ; determining a scaling factor α according toa=L1for(L2≤L1)ora=L2for(L2>L1);and
calculating the energy preserving mixing matrix G according to G=α U ŜVT.