DSPによるコンプレッサ/リミッタのオーバーイージー特性の実現

概要

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Over-easy characteristic of compressor/limiter is widely used due to the fact that the ratio around a threshold level is changed slowly, and the compression process is smooth and almost inaudible even for a large compression ratio. This paper describes a new design method of over-easy characteristic of compressor/limiter on a DSP for digital audio systems. For the standard characteristic of compressor/limit, we have proposed an efficient method on DSP by calculating the polynomial expression to approximate the power transformation. Based on the approximation algorithm, we devide an over-easy characteristic curve into two parts, i.e. over-easy and standard compression ranges, then apply two polynomial expressions to realize the curves, respectively. By this method, the ideal input-output characteristic can be achieved using two seven-order polynomial expressions for a compression range control of 50 dB. The digital signal processing on DSP is about 90 steps for the compressor/limiter. Standard characteristic with higher quality can be obtained by using the same signal processjng structure.
社団法人日本音響学会の論文