Spatial Audio Processing: MPEG Surround and Other Applications

8.2 Binaural parameters

Binaural parameters refer to the effective spatial cues (i.e., ILD, ITD, ICC, and spectral envelopes) at the level of the eardrums that result from an auditory scene with one or more virtual sound sources. Binaural cues are the result of: (1) sound source spectral properties of each individual sound source; (2) the change in signal properties induced by HRTF convolution; and (3) the summation of signals from each sound source at the level of the ear drum. In Chapter 4, it was shown that spatial properties between audio channels can be described using spatial parameters, such as time- and frequency-dependent ICLD, ICTD/ICPD and ICC parameters. In Chapter 7, the same approach was outlined for binaural rendering, using ILD, IPD and ICC parameters between HRTF pairs.

The fact that inter-channel dependencies, as well as acoustical transfer characteristics can be described using a common repertoire of statistical (signal) properties allows for an efficient combination of spatial cecoding and binaural rendering in a single processing step, as will be outlined below. The underlying hypothesis is that spatial parameters, as well as HRTF parameters are locally stationary, which means that they are assumed to be constant within certain time/frequency tiles. In other words, it is assumed that HRTFs are parameterized according to the method described in Chapter 7.