Generalised candidate scheme for the stochastic codebook search of scalable CELP coders

MPEG-4 CELP speech coders configured with multiple bit rates and coding layers provide SNR scalability, and hence may be operated effectively in variable bandwidth environments. A generalised candidate (GC) scheme is proposed to reduce the computational complexity of the stochastic codebook search of CELP coders. The experimental results demonstrate that the proposed GC scheme, incorporated with the verification model (VM) of the MPEG-4 CELP coder, enables a reduction of over 50% of the computational load without suffering any subjective quality degradations. The proposed GC scheme is not only suitable for the base layer and enhancement layers, but also facilitates computational scalability, and is therefore suitable for different working platforms and integrated media source services.