SPEECH DECODING APPARATUS AND SPEECH ENCODING APPARATUS

• US 20090326930A1
• Filed: 07/11/2007
• Published: 12/31/2009
• Est. Priority Date: 07/12/2006
• Status: Active Grant

• Current Assignee: III Holdings 12, LLC (Intellectual Ventures LLC)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Yoshida, Koji, Kawashima, Takuya, Ehara, Hiroyuki
• Granted Patent: US 8,812,306 B2
• Time in Patent Office: Days
• US Class Current: 704/207
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 2019/0011 Long term prediction filters, i.e. pitch estimation
• CPC Class Codes: G10L 25/90 Pitch determination of speech signals
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/43 Assembling or disassembling of packets, e.g. segmentation and reassembly [SAR]

Abstract

Provided is an audio decoding device capable of suppressing an information amount for a lost frame compensation process and encoding efficiency. In this device, a decoded sound source generation unit (203) generates a lost frame decoded sound source signal; a pitch pulse information decoding unit (204) decodes the pitch pulse position information and the pitch pulse amplitude information; a pitch pulse waveform learning unit (205) learns a pitch pulse learning waveform in the past frame in advance from the lost frame; a convolution unit (206) amplitude-adjusts the pitch pulse learning waveform according to the pitch pulse amplitude information, and convolutes the pitch pulse waveform into a time axis which has been amplitude-adjusted according to the pitch pulse position information; a sound source signal correction unit (207) adds or replaces the pitch pulse waveform convoluted into the time axis to the lost frame decoded sound source signal.

Claims

1. A speech decoding apparatus comprising:

a receiving section that receives frame loss information identifying a first frame that is a lost frame;

a first decoding section that decodes an encoded parameter transmitted in a second frame different from the first frame, to acquire a pitch pulse information and an excitation signal of the first frame;

a learning section that learns a pitch pulse learning waveform in a steady-state frame backward in time from the first frame; and

a compensation section that compensates the excitation signal of the first frame using the pitch pulse learning waveform and the pitch pulse information.

2. The speech decoding apparatus according to claim 1, wherein:

the pitch pulse information includes pitch pulse position information and pitch pulse amplitude information relating to a first pitch pulse in a past direction of a time domain from a rear-end of a frame; and

the compensation section performs amplitude adjustment of the pitch pulse learning waveform using the pitch pulse amplitude information to generate a first pitch pulse waveform, and adds the first pitch pulse waveform to the excitation signal based on the pitch pulse position information to generate a compensated excitation signal.

3. The speech decoding apparatus according to claim 2, further comprising:

a second decoding section that decodes an encoded parameter transmitted in the second frame different from the first frame to acquire an excitation power of the first frame as first excitation power; and

a first adjustment section that adjusts power of the compensated excitation signal to the first excitation power.

4. The speech decoding apparatus according to claim 3, wherein the first adjustment section adjusts power of the compensated excitation signal to the first excitation power while maintaining amplitude of the first pitch pulse waveform.

5. The speech decoding apparatus according to claim 4, further comprising:

a first calculation section that calculates excitation power of the first pitch pulse waveform as second excitation power;

a second calculation section that calculates a difference between the first excitation power and the second excitation power as third excitation power; and

a differential section that makes amplitude of a section corresponding to the first pitch pulse waveform zero in an excitation signal of the first frame, to generate a differential excitation signal,

wherein the first adjustment section adjusts amplitude of the differential excitation signal and adjusts excitation power of the differential excitation signal to the third excitation power.

6. The speech decoding apparatus according to claim 2, further comprising:

a detection section that eliminates the first pitch pulse waveform in a search section of predetermined length backward in time from a rear-end of the first frame and detects a pitch pulse waveform whose amplitude is greater than or equal to a threshold value as a pseudo-pitch-pulse-waveform;

a noise generation section that generates noise of a length of the pseudo-pitch-pulse-waveform; and

a replacement section that replaces the pseudo-pitch-pulse-waveform with the noise in an excitation signal of the first frame.

7. The speech decoding apparatus according to claim 6, wherein the predetermined length of the search section is equal to a pitch lag length of one frame ahead in time from the first frame.

8. The speech decoding apparatus according to claim 6, wherein the noise is generated using random noise, Gaussian noise, or a past steady-state excitation.

9. The speech decoding apparatus according to claim 2, wherein:

the pitch pulse information further includes pitch lag; and

the compensation section further generates a second pitch pulse waveform by multiplying the pitch pulse learning waveform by an attenuation coefficient, calculates an addition position of the second pitch pulse waveform using the pitch pulse position information and the pitch lag, and further adds the second pitch pulse waveform to the excitation signal to generate a compensated excitation signal.

10. The speech decoding apparatus according to claim 9, wherein the compensation section calculates a position separated by the pitch lag in a past direction of a time domain from a position indicated by the pitch pulse position information as the addition position.

11. The speech decoding apparatus according to claim 9, wherein the compensation section detects a pitch pulse position from a past frame, and calculates an equidistant position from a position indicated by the pitch pulse position information of the past frame and a position indicated by the pitch pulse position information of the lost frame as an addition position of the second pitch pulse waveform.

12. The speech decoding apparatus according to claim 2, wherein the compensation section detects a pitch pulse position from a past frame, calculates an equidistant position from a position indicated by the pitch pulse position information of the past frame and a position indicated by the pitch pulse position information of the lost frame, extracts a predetermined section from the excitation signal with the equidistant position as a center and further applies a triangular window to an extracted result, to obtain a third pitch pulse waveform, and adds the third pitch pulse waveform to the equidistant position of the excitation signal to generate a compensated excitation signal.

13. A speech encoding apparatus comprising:

a detection section that detects a pitch pulse in a first frame;

a first encoding section that encodes information relating to the pitch pulse to generate a first encoded parameter;

a second encoding section that encodes an excitation of a second frame different from the first frame to generate a second encoded parameter; and

a multiplexing section that multiplexes the first encoded parameter and the second encoded parameter.

14. The speech encoding apparatus according to claim 13, wherein:

the detection section detects the pitch pulse with maximum amplitude in a search section of predetermined length backward in time from a rear-end of the first frame;

the predetermined length of the search section is a pitch lag length of a third frame one frame ahead in time from the first frame; and

the information relating to the pitch pulse includes position information and amplitude information of the pitch pulse.

15. The speech encoding apparatus according to claim 14, further comprising a determination section that determines suitability of the pitch pulse, wherein:

the determination section determines that the pitch pulse is suitable if a correlation value between a waveform such that a waveform peripheral to the pitch pulse is delayed by a predetermined delay amount and the third frame is greater than or equal to a predetermined value; and

the predetermined delay amount is a pitch lag length of a frame one frame ahead in time from the first frame.

16. The speech encoding apparatus according to claim 14, further comprising a calculation section that calculates excitation power of the first frame,

wherein the multiplexing section further multiplexes a parameter indicating the excitation power.