| 摘要 |
PURPOSE: To attain compression coding with a high compression efficiency by making a word length variable with respect to each selected quantizer. CONSTITUTION: A masking calculation section 24 calculates a signal versus masking ratio. A border bit calculation section 25 obtains a minimum word length (border bit number) used by a mid-riser quantizer. A required bit number calculation section 26 obtains a minimum word length (required bit number) where a signal to quantization noise ratio is a signal to masking ratio or over as to a mid-tread/mid-riser quantizer and selects a word length and a quantizer. A bit distribution section 27 adjusts the word length in response to a bit number able to be distributed to one frame and decides the word length and a quantizer by referencing the border bit number. Thus, the deterioration in the compression accuracy and the compression rate is prevented and compression coding with a high compression efficiency is conducted by selecting a quantizer in use at a lower limit word length where a mid-riser quantizer is available. |
