Spatial Audio Processing: MPEG Surround and Other Applications

9.3 Side information

The previously derived expressions for the inter-channel cues occurring when mixing the (original) source signals indicate which properties determine the inter-channel cues of the mixer output signal. The ICLD (Equation 9.6) depends on the mixing parameters (a_i, b_i) and on the short-time subband power of the sources, E{²(n)} (Equation 9.5). The normalized subband cross-correlation function Φ(n, d) (Equation 9.11), that is needed for ICTD (Equation 9.9) and ICC (Equation 9.8) computation, depends on E{²₁(n)} and additionally on the normalized sub-band autocorrelation function, Φ_i(n, e) (Equation 9.12), for each source signal. If no time adjustments are applied (i.e. c_i = d_i = 0), only subband powers are required, without autocorrelation functions. Finally, the level of the mixer output channels depends on the mixing parameters (a_i, b_i) and sub-band power of the sources E{²(n)(n)}.

Hence, given the rendering parameters (a_i, b_i, c_i, d_i), the spatial parameters of the rendered scene can be obtained based on the source subband powers E{²_i(n)} which hence have to be transmitted ...