A Multichannel Sinusoidal Model Applied to Spot Microphone Signals for Immersive Audio

In this paper, a multichannel version of the sinusoids plus noise model (also known as deterministic plus stochastic decomposition) is proposed and applied to spot microphone signals of a music recording. These are the recordings captured by the various microphones placed in a venue, before the mixing process produces the final multichannel audio mix. Coding these microphone signals makes them available to the decoder, allowing for interactive audio reproduction which is a necessary component in immersive audio applications. The proposed model uses a single reference audio signal in order to derive a noise signal per spot microphone. This noise signal can significantly enhance the sinusoidal representation of the corresponding spot signal. The reference can be one of the spot signals or a downmix, depending on the application. Thus, for a collection of multiple spot signals, only the reference is fully encoded (e.g., as an MP3 monophonic signal). For the remaining spot signals, their sinusoidal parameters and corresponding noise spectral envelopes are retained and coded, resulting in bitrates for this side information in the order of 15 kb/s for perceptual performance above the 4.0 grade on the mean opinion score (MOS) scale.