Method and apparatus for processing digital audio signal and related computer program

An apparatus for processing a digital audio signal having a sequence of samples, the apparatus comprising:

• means for detecting every extreme value in an audio waveform represented by the digital audio signal, the extreme value being either a maximum value or a minimum value;
• means for detecting a number of samples between samples corresponding to the first and second latest detected extreme values to get a detected inter-extreme sample number;
• means for calculating a difference between the first and second latest detected extreme values to get a calculated inter-extreme difference;
• means for generating a corrective value in response to the detected inter-extreme sample number and the calculated inter-extreme difference, the generated corrective value being updated each time a new extreme value is detected;
• means for designating ones among samples in response to the detected inter-extreme sample number as objects to be corrected, the designated samples including at least (1) a sample adjacently following the sample corresponding to the second latest detected extreme value, (2) a sample adjacently preceding the sample corresponding to the first latest detected extreme value, and (3) one of the sample corresponding to the first latest detected extreme value and the sample corresponding to the second latest detected extreme value;
• and
• means for correcting the designated samples in response to at least one of (1) the currently-generated corrective value, (2) the previously-generated corrective value, and (3) a generated corrective value next to the currently-generated corrective value.

A computer program stored in a computer readable medium for processing a digital audio signal having a sequence of samples, the computer program comprising the steps of:

• detecting every extreme value in an audio waveform represented by the digital audio signal, the extreme value being either a maximum value or a minimum value;
• detecting a number of samples between samples corresponding to the first and second latest detected extreme values to get a detected inter-extreme sample number;
• calculating a difference between the first and second latest detected extreme values to get a calculated inter-extreme difference;
• generating a corrective value in response to the detected inter-extreme sample number and the calculated inter-extreme difference, the generated corrective value being updated each time a new extreme value is detected;
• designating ones among samples in response to the detected inter-extreme sample number as objects to be corrected, the designated samples including at least (1) a sample adjacently following the sample corresponding to the second latest detected extreme value, (2) a sample adjacently preceding the sample corresponding to the first latest detected extreme value, and (3) one of the sample corresponding to the first latest detected extreme value and the sample corresponding to the second latest detected extreme value;
• and
• correcting the designated samples in response to at least one of (1) the currently-generated corrective value, (2) the previously-generated corrective value, and (3) a generated corrective value next to the currently-generated corrective value.

A method of pre-emphasizing a digital audio signal having a sequence of samples to generate a pre-emphasized digital audio signal before the pre-emphasized digital audio signal is compressed by an encoder, the pre-emphasizing being designed to compensate for audio quality degradation caused by the compression by the encoder, the method comprising the steps of:

• detecting every extreme value in an audio waveform represented by the digital audio signal, the extreme value being either a maximum value or a minimum value;
• detecting a number of samples between samples corresponding to the first and second latest detected extreme values to get a detected inter-extreme sample number;
• calculating a difference between the first and second latest detected extreme values to get a calculated inter-extreme difference;
• generating a corrective value in response to the detected inter-extreme sample number and the calculated inter-extreme difference, the generated corrective value being updated each time a new extreme value is detected;
• designating ones among samples in response to the detected inter-extreme sample number and the degree of the audio quality degradation as objects to be corrected, the designated samples including at least (1) a sample adjacently following the sample corresponding to the second latest detected extreme value, (2) a sample adjacently preceding the sample corresponding to the first latest detected extreme value, and (3) one of the sample corresponding to the first latest detected extreme value and the sample corresponding to the second latest detected extreme value;
• and
• correcting the designated samples in response to at least one of (1) the currently-generated corrective value, (2) the previously-generated corrective value, and (3) a generated corrective value next to the currently-generated corrective value.

An apparatus for pre-emphasizing a digital audio signal having a sequence of samples to generate a pre-emphasized digital audio signal before the pre-emphasized digital audio signal is compressed by an encoder, the pre-emphasizing being designed to compensate for audio quality degradation caused by the compression by the encoder, the apparatus comprising:

• means for detecting every extreme value in an audio waveform represented by the digital audio signal, the extreme value being either a maximum value or a minimum value;
• means for detecting a number of samples between samples corresponding to the first and second latest detected extreme values to get a detected inter-extreme sample number;
• means for calculating a difference between the first and second latest detected extreme values to get a calculated inter-extreme difference;
• means for generating a corrective value in response to the detected inter-extreme sample number and the calculated inter-extreme difference, the generated corrective value being updated each time a new extreme value is detected;
• means for designating ones among samples in response to the detected inter-extreme sample number and the degree of the audio quality degradation as objects to be corrected, the designated samples including at least (1) a sample adjacently following the sample corresponding to the second latest detected extreme value, (2) a sample adjacently preceding the sample corresponding to the first latest detected extreme value, and (3) one of the sample corresponding to the first latest detected extreme value and the sample corresponding to the second latest detected extreme value;
• and
• means for correcting the designated samples in response to at least one of (1) the currently-generated corrective value, (2) the previously-generated corrective value, and (3) a generated corrective value next to the currently-generated corrective value.

A computer program stored in a computer readable medium for pre-emphasizing a digital audio signal having a sequence of samples to generate a pre-emphasized digital audio signal before the pre-emphasized digital audio signal is compressed by an encoder, the pre-emphasizing being designed to compensate for audio quality degradation caused by the compression by the encoder, the computer program comprising the steps of:

• detecting every extreme value in an audio waveform represented by the digital audio signal, the extreme value being either a maximum value or a minimum value;
• detecting a number of samples between samples corresponding to the first and second latest detected extreme values to get a detected inter-extreme sample number;
• calculating a difference between the first and second latest detected extreme values to get a calculated inter-extreme difference;
• generating a corrective value in response to the detected inter-extreme sample number and the calculated inter-extreme difference, the generated corrective value being updated each time a new extreme value is detected;
• designating ones among samples in response to the detected inter-extreme sample number and the degree of the audio quality degradation as objects to be corrected, the designated samples including at least (1) a sample adjacently following the sample corresponding to the second latest detected extreme value, (2) a sample adjacently preceding the sample corresponding to the first latest detected extreme value, and (3) one of the sample corresponding to the first latest detected extreme value and the sample corresponding to the second latest detected extreme value;
• and
• correcting the designated samples in response to at least one of (1) the currently-generated corrective value, (2) the previously-generated corrective value, and (3) a generated corrective value next to the currently-generated corrective value.

A method of processing a digital audio signal having a sequence of samples, the method comprising the steps of:

• detecting every extreme value in an audio waveform represented by the digital audio signal, the extreme value being either a maximum value or a minimum value;
• repetitively detecting a local period of the audio waveform;
• repetitively detecting a local amplitude of the audio waveform;
• and
• correcting a sample corresponding to the detected extreme value, a sample adjacently preceding the sample corresponding to the detected extreme value, and a sample adjacently following the sample corresponding to the detected extreme value in response to the detected local period and the detected local amplitude.

An apparatus for processing a digital audio signal having a sequence of samples, the apparatus comprising:

• means for detecting every extreme value in an audio waveform represented by the digital audio signal, the extreme value being either a maximum value or a minimum value;
• means for repetitively detecting a local period of the audio waveform;
• means for repetitively detecting a local amplitude of the audio waveform;
• and
• means for correcting a sample corresponding to the detected extreme value, a sample adjacently preceding the sample corresponding to the detected extreme value, and a sample adjacently following the sample corresponding to the detected extreme value in response to the detected local period and the detected local amplitude.