Optimal frequency-differential encoding of sinusoidal model parameters

Sinusoidal coding has proven to be efficient for low bit-rate audio coding. In this paper we consider schemes for frequency-differential (FD) encoding of the sinusoidal model parameters. For a given signal frame, the parameters of a sinusoidal component may be encoded either differentially relative to other components in the same frame, or directly, i.e., without differential encoding. Using basic tools from graph theory, two algorithms are derived for finding bit rate optimal combinations of direct and differential encoding of the sinusoidal parameters. In simulation experiments with audio signals, the algorithms showed bit-rate reductions of up to 27% relative to direct encoding. Furthermore, when compared to a commonly used FD encoding scheme, the proposed algorithms achieved bit rate reductions of up to 7%.