| 摘要 |
PROBLEM TO BE SOLVED: To suppress deterioration of an audio signal obtained by decoding an ADPCM coded signal having additional information embedded therein.SOLUTION: An additional information insertion device includes: a quantization step control part which calculates a quantization step width in ADPCM coding of an audio signal; an ADPCM encoder which generates a first encoded signal based upon a difference value between reproduced signals of the audio signal and an audio signal therebefore based upon the quantization step width; an adaptive error calculator which calculates an error between the difference value and a quantized difference value; a change control part which performs control for changing the first encoded signal, without changing the additional information, based upon the error so that an error from the difference value before the quantization becomes small; an additional information insertion part which inserts the additional information into the first encoded signal and changes an ADPCM code that the first encoded signal indicates according to the control; and a re-encoding part which generates a second encoded signal using the first encoded signal having the additional information embedded therein. A quantization step control part calculates a quantization step width based upon the second ADPCM encoded signal. |
