Distortion detecting device, distortion correcting device, and distortion correcting method for digital audio signal

A digital audio signal distortion correcting method comprising the steps of:

• estimating a conversion error for an analog/digital converter that is used, from a level distribution of a digital audio signal recorded using the analog/digital converter;
• calculating, based on the estimated conversion error, a conversion table in which data bit lengths are extended to make a correction with respect to the conversion error of said analog/digital converter for all quantization levels of said digital audio signal;
• and
• performing a conversion process using said conversion table on said digital audio signal to correct a distortion generated by the conversion error of said analog/digital converter while extending bits.

A distortion correcting method comprising the steps of:

• collecting a predetermined number of samples from a digital audio signal recorded using an analog/digital converter to obtain a level distribution of the concerned samples;
• applying a low-pass filtering process on said level distribution to generate an ideal level distribution approximating an ideal case where the analog/digital converter has no error;
• dividing said level distribution, before said low-pass filtering process was applied, by said level distribution, and accumulating the divided result to set the divided result thereof as a normalized level distribution,
• carrying out accumulation based on the normalized level distribution to calculate a conversion table in which data bit lengths are extended to make a correction with respect to a conversion error of said analog/digital converter for all quantization levels of said digital audio signal;
• and substituting the quantization level of the digital audio signal with the level data according to the conversion table for output.