Presented are modifications to the MPEG-2 AAC encoder that significantly increase computational efficiency while maintaining high sound quality. These modifications include changes to the perceptual model, block-switching control, pre-estimation of quantizer scale-factors, and changes to the quantizer rate/distortion loop. These changes result in an overall speedup (when combined with processor-specific optimizations) of approximately 250% compared to the reference Low Complexity professional MPEG-2 AAC encoder. Tests show a mean degradation of 0.2 on the ITU-R 5-point audio impairment scale.
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