| 摘要 |
PROBLEM TO BE SOLVED: To improve sound quality by exhibiting modulation and reality of an audio signal with a compressed dynamic range regardless of whether or not the audio signal is at full scale.SOLUTION: A dynamic range extension device includes: first envelope detection means 21-23 for detecting a first envelope by a maximum state of a signal; mean calculation means 25 for calculating an amplitude mean of the first envelope; maximum calculation means 26 for calculating an amplitude maximum Yof the first envelope; detection gain decision means 27 for deciding a detection gain on the basis of the amplitude mean and the amplitude maximum; and second envelope detection means for detecting a second envelope with a lower limit value at the detection gain. The detection gain decision means 27 decides the detection gain at zero when a ratio of the amplitude mean to the amplitude maximum is smaller than a first threshold, decides the detection gain at a value smaller than 10logYwhen the value of the ratio is not smaller than the first threshold nor larger than a second threshold, and decides the detection gain at a value smaller than the second threshold when the value of the ratio is larger than the second threshold. |
