Spatial Audio Processing: MPEG Surround and Other Applications

5.3 Relation to BCC

The parametric stereo algorithm is based on identical principles as BCC and spatial audio coding techniques. The differences rely in certain implementation aspects and engineering choices.

• Parametric stereo supports dynamic segmentation of the incoming audio, to enable bit-rate scalability (by modifying the parameter update rate) and improve the coding efficiency. Signal parts that are reasonably stable in terms of spatial properties can be encoded with low parameter update rates (i.e., long analysis frames), while strong spatial dynamics can be accounted for as well by a temporarily higher update rate.
• A slightly different ICC, ICTD parameterization is used to allow parameterization of out-of-phase signals. The ICTD is replaced by an inter-channel phase difference (ICPD), which has the additional advantage of a lower estimation complexity in the encoder.
• A dedicated filterbank was designed that has a lower computational complexity and memory requirement than FFT-based methods, and which allows for efficient integration with aacPlus.
• An alternative decoder-side synthesis method has a low complexity, and allows for synthesis of out-of-phase output signals.