EE-597 Class Notes - Sub-Band Coding
Phil Schniter · 2004
Figure 1: Simplified MPEG-style audio coding system. • Fig. 2 illustrates a generic subband coder. In short, the input signal is passed through a parallel bank of analysis filters {Hi(z)} and the outputs are “downsampled” by a factor of N . Downsampling-byN is a process which passes every N th sample and ignores the rest, effectively decreasing the data rate by factor N . The downsampled outputs are quantized (using a potentially different number of bits per branch—as in transform coding) for storage or transmission. Downsampling ensures that the number of data samples to store is not any larger than the number of data samples entering the coder; in Fig. 2, N sub-band outputs are generated for every N system inputs.