Fast encoding algorithms for MPEG-4 TwinVQ audio tool

The ISO/IEC MPEG-4 audio standard includes the TwinVQ encoding tool. This tool is suitable for low-bit-rate general audio coding, but a drawback is the computational complexity of the encoder. To develop a faster TwinVQ encoder, new fast vector quantization algorithms - area localized pre-selection and hit zone masking - are introduced. These algorithms exploit the pre- and main-selection procedure scheme of the conjugate structure vector quantization which is used in the TwinVQ. The improvement is evaluated by measuring the encoding speed and the sound quality of reproduction. Finally, additionally optimized encoders are developed by making use of the 3DNow!/SSE technologies. In total, encoding times are reduced to 1/2-1/3 compared to the original TwinVQ encoder in the ISO/IEC reference encoder