Gain control method for audio encoding device

• US 5,825,320 A
• Filed: 03/13/1997
• Issued: 10/20/1998
• Est. Priority Date: 03/19/1996
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Ueno, Masatoshi, Miyamori, Shinji
• Primary Examiner(s): Young, Brian K.
• Application Number:
  US08/816,090
• Time in Patent Office: 586 Days
• Field of Search: 341/139, 455/140, 455/234.1, 455/245.1, 375/345
• US Class Current: 341/139
• CPC Class Codes: G10L 19/0204 using subband decomposition
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 2021/02082 the noise being echo, reverberation of the speech
• CPC Class Codes: G10L 25/27 characterised by the analysis technique
• CPC Class Codes: H04B 1/665 using psychoacoustic properties of the ear, e.g. masking effect

Abstract

A method and apparatus for encoding input signals, such as digital data, by so-called high-efficiency encoding, in which pre-echo and post-echo are suppressed. A gain control position decision circuit detects an attack portion and a release portion of an audio signal entering an input terminal. An acoustic model application circuit finds a masking level based on a psychoacoustic model of the input signal. A gain control decision circuit determines the gain control value adaptively selected in accordance with the masking level. A gain control circuit controls the gain of the audio signal entering the input terminal in meeting with the gain control value.

Claims

1. A gain controlling method used in an encoding device for audio signals, comprising the steps of:

detecting an attack portion in which the signal level of waveform elements of the waveform signals rises sharply;

detecting a release portion in which the signal level of the waveform signals decays sharply;

finding a masking level based on a psychoacoustic model using the waveform signals and the detection position information of the attack portion and the release portion;

adaptively selecting a gain control value from plural gain control values using the above masking level;

gain-controlling at least the waveform elements previous to the attack portion and the waveform elements of the release portion, using the selected gain control value;

transforming the gain-controlled waveform signals into plural frequency components; and

encoding the control information for gain control and said plural frequency components.

2. The gain control method as claimed in claim 1 wherein said masking level is found from frequency components obtained on orthogonal transform of said waveform signals.

3. The gain control method as claimed in claim 1 wherein said step of finding the masking level splits the waveform signals into plural overlapped areas for analysis and finds said masking level from said plural areas for analysis.

4. The gain control method as claimed in claim 1 wherein said step of finding the masking level splits the waveform signals into plural waveform signals in each detected gain control position and finds the masking level from said plural split waveform signals.

5. The gain control method as claimed in claim 1 wherein said step of selecting the gain control value calculates the number of bits required for encoding for at least a portion of plural gain control values;

and selecting a gain control value which minimizes the required number of bits.

6. The gain control method as claimed in claim 5 wherein, for calculating, the number of bits, frequency components obtained on gain-controlling the waveform signals and orthogonally transforming the gain-controlled waveform signals are used.

7. The gain control method as claimed in claim 5 wherein, for calculating the number of bits, frequency components obtained on slitting the waveform signals into overlapped plural separate areas for analysis and orthogonally transforming the plural waveform signals obtained from said areas for analysis.

8. The gain control method as claimed in claim 5 wherein, for calculating the number of bits, frequency components obtained on splitting the waveform signals for each detected gain control position into plural waveform signals and orthogonally transforming the plural split waveform signals are used.

9. A gain controlling apparatus used in an encoding device for audio signals, comprising:

means for detecting an attack portion in which the signal level of waveform elements of the waveform signals rises sharply;

means for detecting a release portion in which the signal level of the waveform signals decays sharply;

means for finding a masking level based on a psychoacoustic model using the waveform signals and the detection position information of the attack portion and the release portion;

means for adaptively selecting a gain control value from plural gain control values using at least said masking level;

means for gain-controlling at least the waveform elements previous to the attack portion and the waveform elements of the release portion, using the selected gain control value;

means for transforming the gain-controlled waveform signals into plural frequency components; and

means for encoding the control information for gain control and said plural frequency components.

10. The gain control apparatus as claimed in claim 9 wherein said means for calculating the masking level finds the masking level from frequency components obtained on orthogonal transform of said waveform signals.

11. The gain control apparatus as claimed in claim 9 wherein said means for finding the masking level splits the waveform signals into plural overlapped areas for analysis and finds said masking level from said plural split areas for analysis.

12. The gain control apparatus as claimed in claim 9 wherein said means for finding the masking level splits the waveform signals into plural waveform signals for each detected gain control position and finds the masking level from said plural split waveform signals.

13. The gain control apparatus as claimed in claim 9 wherein said means for selecting the gain control value calculates the number of bits required for encoding for at least a portion of plural gain control values;

and selecting a gain control value which minimizes the required number of bits.

14. The gain control apparatus as claimed in claim 13 wherein, for calculating the number of bits, frequency components obtained on gain-controlling the waveform signals and orthogonally transforming the gain-controlled waveform signals are used.

15. The gain control method as claimed in claim 13 wherein, for calculating the number of bits, frequency components obtained on slitting the waveform signals into overlapped plural separate areas for analysis and orthogonally transforming the gain-controlled waveform signals obtained from said areas for analysis are used.

16. The gain control method as claimed in claim 13 wherein, for calculating the number of bits, frequency components obtained on splitting the waveform signals for each detected gain control position into plural waveform signals and orthogonally transforming the plural split waveform signals are used.