Audio decoder with programmable downmixing of mpeg/ac-3 and method

Abstract

An audio decoder is provided with a programmable and re-configurable downmixing process. In one embodiment, the audio decoder includes a control module and a data path. The data path is configured to read, scale, add, and write audio samples to and from various audio channel frame buffers. The control module implements state diagrams which specify various control signals for directing the operations of the data path. The control module implements state diagrams for directing windowing and downmixing operations. The order in which these operations are performed may be reconfigurable, i.e. downmixing may be performed before or after windowing. This reconfigurability advantageously permits the system designer to trade a slight audio quality enhancement for a decreased memory requirement for some speaker configurations. The downmixing operation requires scaling coefficients which are provided by the control module. In one embodiment, the control module implements a standardized set of equations with a minimal number of downmixing coefficients, which advantageously allows the decoder to implement fully programmable downmix modes for both MPEG and Dolby standards while minimizing decoder complexity. The coefficients may be set according to a downmix mode and bitstream-specified parameters, or in another embodiment, the coefficients are set by the user.