IMPROVED FRAME LOSS CORRECTION WITH VOICE INFORMATION

• US 20170040021A1
• Filed: 04/24/2015
• Published: 02/09/2017
• Est. Priority Date: 04/30/2014
• Status: Active Grant

• Current Assignee: Orange S.A.
• Original Assignee: Orange S.A.
• Inventors: Faure, Julien, Ragot, Stephane
• Granted Patent: US 10,431,226 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 19/028 Noise substitution, i.e. substituting non-tonal spectral components by noisy source comfort noise for discontinuous speech transmission G10L19/012
• CPC Class Codes: G10L 19/20 using sound class specific coding, hybrid encoders or object based coding
• CPC Class Codes: G10L 2025/932 Decision in previous or following frames
• CPC Class Codes: G10L 25/81 for discriminating voice from music

Abstract

A method for processing a digital audio signal, including a series of samples distributed in consecutive frames, is implemented when decoding the signal in order to replace at least one signal frame lost during decoding. The method includes the following steps: a) searching, in a valid signal segment available when decoding, for at least one period in the signal, determined in accordance with the valid signal; b) analyzing the signal in the period, in order to determine spectral components of the signal in the period; c) synthesizing at least one frame for replacing the lost frame, by construction of a synthesis signal from: an addition of components selected among the predetermined spectral components, and a noise added to the addition of components. In particular, the amount of noise added to the addition of components is weighted in accordance with voice information of the valid signal, obtained when decoding.

Claims

1. A method for processing a digital audio signal comprising a series of samples distributed in successive frames, the method being implemented when decoding said signal in order to replace at least one lost signal frame during decoding,

the method comprising the steps of:

a) searching, in a valid signal segment available when decoding, for at least one period in the signal, determined based on said valid signal,

b) analyzing the signal in said period, in order to determine spectral components of the signal in said period,

c) synthesizing at least one replacement for the lost frame, by constructing a synthesis signal from;

an addition of components selected from among said determined spectral components, and

noise added to the addition of components,

wherein the amount of noise added to the addition of components is weighted based on voice information of the valid signal, obtained when decoding.

2. The method according to claim 1, wherein a noise signal added to the addition of components is weighted by a smaller gain in the case of voicing in the valid signal.

3. The method according to claim 2, wherein the noise signal is obtained by a residual between the valid signal and the addition of selected components.

4. The method according to claim 1, wherein the number of components selected for the addition is larger in the case of voicing in the valid signal.

5. The method according to claim 1, wherein, in step a), the period is searched for in a valid signal segment of greater length in the case of voicing in the valid signal.

6. The method according to claim 1, wherein the voice information is supplied in a bitstream received in decoding and corresponding to said signal comprising a series of samples distributed in successive frames,

and wherein, in the case of frame loss in decoding, the voice information contained in a valid signal frame preceding the lost frame is used.

7. The method according to claim 6, wherein the voice information comes from an encoder generating the bitstream and determining the voice information, and wherein the voice information is encoded in a single bit in the bitstream.

8. The method according to claim 7, wherein a noise signal added to the addition of components is weighted by a smaller gain in the case of voicing in the valid signal, and, if the signal is voiced, the gain value is 0.25, and otherwise is 1.

9. The method according to claim 6, wherein the voice information comes from an encoder determining a spectrum flatness value, obtained by comparing amplitudes of the spectral components of the signal to a background noise, said encoder delivering said value in binary form in the bitstream.

10. The method according to claim 7, wherein a noise signal added to the addition of components is weighted by a smaller gain in the case of voicing in the valid signal, and the gain value is determined as a function of said flatness value.

11. The method according to claim 9, wherein said flatness value is compared to a threshold in order to determine:

that the signal is voiced if the flatness value is below the threshold, and

that the signal is unvoiced otherwise.

12. The method according to claim 7, wherein the number of components selected for the addition is larger in the case of voicing in the valid signal, and wherein:

if the signal is voiced, the spectral components having amplitudes greater than those of the neighboring first spectral components are selected, as well as the neighboring first spectral components, and

otherwise only the spectral components having amplitudes greater than those of the neighboring first spectral components are selected.

13. The method according to claim 7, wherein, in step a), the period is searched for in a valid signal segment of greater length in the case of voicing in the valid signal, and wherein:

if the signal is voiced, the period is searched for in a valid signal segment of a duration of more than 30 milliseconds,

and if not, the period is searched for in a valid signal segment of a duration of less than 30 milliseconds.

14. A computer readable medium storing a code of a computer program, wherein said computer program comprises instructions for implementing the method according to claim 1 when the program is executed by a processor.

15. A device for decoding a digital audio signal comprising a series of samples distributed in successive frames, the device comprising a computer circuit for replacing at least one lost signal frame, by:

a) searching, in a valid signal segment available when decoding, for at least one period in the signal, determined based on said valid signal,

b) analyzing the signal in said period, in order to determine spectral components of the signal in said period,

c) synthesizing at least one frame for replacing the lost frame, by constructing a synthesis signal from;

an addition of components selected from among said determined spectral components, and

noise added to the addition of components,

the amount of noise added to the addition of components being weighted based on voice information of the valid signal, obtained when decoding.

16. A device for encoding a digital audio signal, comprising a computer circuit for providing voice information in a bitstream delivered by the encoding device, distinguishing a speech signal likely to be voiced from a music signal, and, in the case of a speech signal:

identifying that the signal is voiced or generic, in order to consider it as generally voiced, or

identifying that the signal is inactive, transient, or unvoiced, in order to consider it as generally unvoiced.