Quantization bit number allocation by first selecting a subband signal having a maximum of signal to mask ratios in an input signal.

摘要

As a selected subband signal, selected is one of frequency band signals of an input signal that has a maximal signal to mask ratio. The selected subband signal is assigned, as a primary provisional bit-number, with a maximal quantization bit number allocatable thereto. A primary mask to noise ratio of the selected subband signal is calculated. Other subband signals are assigned with temporary bit numbers incremented one by one from zero with secondary mask to noise ratios of the other subband signal meanwhile calculated each time when the temporary bit numbers are incremented by one. The temporary bit numbers are allocated to the other subband signals as secondary provisional bit numbers when the secondary mask to noise ratios individually exceed the primary mask to noise ratio. Some of the secondary provisional bit numbers may be equal to zero. A sum of the primary and the secondary provisional bit numbers is compared with a total of quantization bit numbers allocatable to the frequency band signals. If the sum does not exceed the total, the primary and the secondary provisional bit numbers are allocated to the selected and the other subband signals. If the sum exceeds the total, the primary and the secondary provisional bit numbers are uniformly reduced and allocated, unless reduced to negative, to the selected and the other subband signals. Zero is used instead of at least one of the secondary provisional bit numbers that is reduced to negative. <IMAGE>