# US 8,788,275 B2 · Decoding method and apparatus for an audio signal through high frequency compensation

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- Number: US 8,788,275 B2
- Document ID: US8788275B2
- Status: Granted
- Kind: B2
- Application number: 11/902,325
- Filed: 2007-09-20
- Published: 2008-05-29
- Granted: 2014-07-22
- Earliest claimed: 2006-11-24
- Assignees: Fujitsu Limited
- Applicants: Miyuki Shirakawa; Masanao Suzuki; Takashi Makiuchi; Yoshiteru Tsuchinaga
- Inventors: Miyuki Shirakawa; Masanao Suzuki; Takashi Makiuchi; Yoshiteru Tsuchinaga
- Web page: https://patentgrep.com/patent/US8788275B2

## CPC

- G10L 19/24: Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding
- G10L 21/0364: for improving intelligibility
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

A decoding apparatus decodes a first encoded data that is encoded from a low-frequency component of an audio signal, and a second encoded data that is used when creating a high-frequency component of an audio signal from a low-frequency component and encoded in accordance with a certain bandwidth, into the audio signal. In the decoding apparatus, a high-frequency component detecting unit divides the high-frequency component into bands with a certain interval range correspondingly to the certain bandwidth, and detects magnitude of the high-frequency components corresponding to each of the bands. A high-frequency component compensating unit compensates the high-frequency components based on the magnitude of the high-frequency components corresponding to each of the bands detected by the high-frequency component detecting unit. A decoding unit that decodes the low-frequency component decoded from the first encoded data, and the high-frequency components compensated by the high-frequency component compensating unit, into the audio signal.

## Claims

### Claim 1

A decoding apparatus that decodes a first encoded data that is encoded from a low-frequency component of an audio signal, and a second encoded data that is used when creating a high-frequency component of an audio signal from a low-frequency component and encoded in accordance with a certain bandwidth, into the audio signal, the decoding apparatus comprising:
a high-frequency component detecting unit that divides the high-frequency component into bands with a certain interval range correspondingly to the certain bandwidth, and detects magnitude of power of the high-frequency components corresponding to each of the bands;
a compensation-band determining unit that determines a band of a compensation subject which is a high-frequency component to be compensated based on an interval range of the high-frequency components divided by the high-frequency component detecting unit;
a high-frequency component compensating unit that acquires a difference value by subtracting a power corresponding to the band of the compensation subject from a power corresponding to an adjacent band, acquires a change rate by dividing the difference value by a bandwidth of the band of the compensation subject, acquires an energy of a subdivided band by dividing the power corresponding to the band of the compensation subject by the bandwidth of the band of the compensation subject, acquires a compensating power by adding the energy of the subdivided band to a value which is computed by multiplying the change rate by a frequency change within the band of the compensation subject, and compensates the compensation subject in accordance with the compensating power; and
a decoding unit that decodes the low-frequency component decoded from the first encoded data, and the high-frequency components compensated by the high-frequency component compensating unit, into the audio signal.

### Claim 2 (depends on 1)

The decoding apparatus according to claim 1, wherein the high-frequency component compensating unit acquires a difference value by subtracting a power corresponding to the band of the compensation subject from a power corresponding to an adjacent band in a time direction, acquires a change rate by dividing the difference value by a time width corresponding to the band of the compensation subject, acquires an energy of a subdivided band by dividing the power corresponding to the band of the compensation subject by the time width corresponding to the band of the compensation subject, acquires a compensating power by adding the energy of the subdivided band to a value which is computed by multiplying the change rate by a temporal change amount within the band of the compensation subject, and compensates the compensation subject in accordance with the compensating power.

### Claim 3 (depends on 1)

The decoding apparatus according to claim 1, further comprising a compensation-band determining unit that determines a band of a high-frequency component to be compensated based on a change in magnitude of an adjacent high-frequency component from among the high-frequency components divided into the bands with the certain interval range by the high-frequency component detecting unit.

### Claim 4 (depends on 1)

The decoding apparatus according to claim 1, further comprising a compensation-band determining unit that determines that a band of a high-frequency component to be compensated is a band having a difference in magnitude equal to or higher than a threshold with the magnitude of an adjacent high-frequency component from among the high-frequency components divided into the bands with the certain interval range by the high-frequency component detecting unit.

### Claim 5

A decoding method for decoding a first encoded data that is encoded from a low-frequency component of an audio signal, and a second encoded data that is used when creating a high-frequency component of an audio signal from a low-frequency component and encoded in accordance with a certain bandwidth, into the audio signal, the decoding method comprising:
high-frequency component detecting, using a microprocessor, including dividing the high-frequency component into bands with a certain interval range correspondingly to the certain bandwidth, and detecting magnitude of power of the high-frequency components corresponding to each of the bands;
determining, using a microprocessor, a band of a compensation subject which is a high-frequency component to be compensated based on an interval range of the high-frequency components divided at the high-frequency component detecting;
acquiring a difference value by subtracting a power corresponding to the band of the compensation subject from a power corresponding to an adjacent band;
acquiring a change rate by dividing the difference value by a bandwidth of the band of the compensation subject;
acquiring an energy of a subdivided band by dividing the power corresponding to the band of the compensation subject by the bandwidth of the band of the compensation subject;
acquiring a compensating power by adding the energy of the subdivided band to a value which is computed by multiplying the change rate by a frequency change within the band of the compensation subject;
compensating, using a microprocessor, the compensation subject in accordance with the compensating power; and
decoding the low-frequency component decoded from the first encoded data, and the high-frequency components compensated at the compensating, into the audio signal.

### Claim 6 (depends on 5)

The decoding method according to claim 5,
acquiring a difference value by subtracting a power corresponding to the band of the compensation subject from a power corresponding to an adjacent band in a time direction;
acquiring a change rate by dividing the difference value by a time width corresponding to the band of the compensation subject;
acquiring an energy of a subdivided band by dividing the power corresponding to the band of the compensation subject by the time width corresponding to the band of the compensation subject;
acquiring a compensating power by adding the energy of the subdivided band to a value which is computed by multiplying the change rate by a temporal change amount within the band of the compensation subject; and
compensating, using a microprocessor, the compensation subject in accordance with the compensating power.

### Claim 7 (depends on 5)

The decoding method according to claim 5, further comprising determining, using a microprocessor, a band of a high-frequency component to be compensated based on a change in magnitude of an adjacent high-frequency component from among the high-frequency components divided into the bands with the certain interval range at the high-frequency component detecting.

### Claim 8 (depends on 5)

The decoding method according to claim 5, further comprising determining, using a microprocessor, that a band of a high-frequency component to be compensated is a band having a difference in magnitude equal to or higher than a threshold with the magnitude of an adjacent high-frequency component from among the high-frequency components divided into the bands with the certain interval range at the high-frequency component detecting.