# US 2014/0207445 A1 · System and Method for Correcting for Lost Data in a Digital Audio Signal

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- Number: US 2014/0207445 A1
- Document ID: US20140207445A1
- Status: Published application
- Kind: A1
- Application number: 14/219,773
- Filed: 2014-03-19
- Published: 2014-07-24
- Earliest claimed: 2009-05-05
- Assignees: Huawei Technologies Co., Ltd.
- Applicants: Huawei Technologies Co., Ltd.
- Inventors: Yang Gao; Herve Marcel Taddei; Lei Miao
- Web page: https://patentgrep.com/patent/US20140207445A1

## CPC

- G10L 19/0017: {Lossless audio signal coding; Perfect reconstruction of coded audio signal by transmission of coding error (G10L19/24 takes precedence)}
- G10L 19/005: Correction of errors induced by the transmission channel, if related to the coding algorithm
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

In an embodiment, a method of receiving a digital audio signal, using a processor, includes generating a high band time domain signal; generating low band time domain signal; estimating an energy ratio between the high band and the low band from a last good frame; keeping the energy ratio for following frame-erased frames by applying an energy correction scaling gain to a high band signal segment by segment in the time domain; and combining the low band signal and the high band signal into a final output.

## Claims

### Claim 1

A method of receiving a digital audio signal using a processor,
generating a high band time domain signal;
generating low band time domain signal;
estimating an energy ratio between the high band and the low band from a last good frame;
keeping the energy ratio for following frame-erased frames by applying an energy correction scaling gain to a high band signal segment by segment in the time domain; and
combining the low band signal and the high band signal into a final output.

### Claim 2 (depends on 1)

The method of claim 1, wherein the scaling gain is smoothed sample by sample from one segment to a next segment of the high band signal.

### Claim 3 (depends on 1)

The method of claim 1, wherein the energy ratio is estimated as:
Ratio
=
E
HB
E
LB
=
∑
i

T
env

(
i
)

s
^
LB

(
n
)

2
,
where Tenv(i) is a temporal energy envelope of a last good high band signal,
E
HB
=
∑
i

T
env

(
i
)
is a high band energy, ELB∥ŝLB(n)∥2 is a low band energy.

### Claim 4 (depends on 1)

The method of claim 1, further comprising calculating an energy correction gain factor gi for an i-th sub-segment of following erased frames according to:
g
i
=
Ratio
·

s
^
LB
i

(
j
)

2

s
^
HB
i

(
j
)

2
if gi>1, gi=1
where ∥ŝLBi(j)∥2 represents energies of i-th sub-segments of the low band signal ŝLBi(j)=ŝLB(20·i+j) and ∥ŝHBi(j)∥2 represents energies of i-th sub-segments of the high band signal ŝHBi(j)=ŝHB(20·i+j), and j represents a sample index.

### Claim 5 (depends on 1)

The method of claim 1, further comprising calculating an energy correction gain factor gi for an i-th sub-segment of following erased frames according to:
g
i
=
Ratio
·

s
^
LB
i

(
j
)

2

s
^
HB
i

(
j
)

2
if gi>1, gi=1
where ∥ŝLBi(j)∥2 represents energies of i-th sub-segments of the low band signal ŝLBi(j)=ŝLB(L·i+j) and ∥ŝHBi(j)∥2 represents energies of i-th sub-segments of the high band signal ŝHBi(j)=ŝHB(L·i+j), L is an integer and j represents a sample index.

### Claim 6 (depends on 1)

The method of claim 1, further comprising calculating a smoothed correction gain factor gi(j) and applying the smoothed correction gain factor gi(j) to an i-th sub-segment high band signal ŝHBi(j)=ŝHB(20·i+j) according to:
gi(j)0.95· gi(j−1)+0.05·gi
ŝHBi(j)ŝHBi(j)· gi(j),
wherein gi comprises an energy correction gain factor for the an i-th sub-segment, and wherein gi(j) is smoothed from one segment to a next segment, sample by sample, and j represents a sample index.

### Claim 7 (depends on 1)

The method of claim 1, further comprising calculating a smoothed correction gain factor gi(j) and applying the smoothed correction gain factor gi(j) to an i-th sub-segment high band signal ŝHBi(j)=ŝHB(L·i+j) according to:
gi(j)λ· gi(j−1)+(1−λ)·gi
ŝHBi(j)ŝHBi(j)· gi(j),
wherein gi comprises an energy correction gain factor for the an i-th sub-segment, and wherein gi(j) is smoothed from one segment to a next segment, sample by sample, j represents a sample index, L is an integer and 0≦λ≦1.

### Claim 8

A method of correcting for missing audio data, the method comprising:
copying frequency domain coefficients of a digital audio signal from a previous frame;
using a processor, adaptively adding random noise coefficients to the copied frequency domain coefficients;
scaling the random noise coefficients and the copied frequency domain coefficients to form recovered frequency domain coefficients, wherein scaling is controlled with a parameter representing a periodicity or harmonicity of a received digital audio signal;
generating a high band time domain signal by inverse-transforming high band frequency domain coefficients of the recovered frequency domain coefficients;
generating low band time domain signal;
estimating an energy ratio between the high band and the low band from a last good frame;
keeping the energy ratio for following frame-erased frames by applying an energy correction scaling gain to a high band signal, segment by segment in the time domain; and
combining the low band signal and the high band signal to form a final output.

### Claim 9 (depends on 8)

The method of claim 8, wherein the frequency domain is a MDCT domain, DFT domain or FFT domain.

### Claim 10 (depends on 8)

The method of claim 8, wherein the parameter representing the periodicity or harmonicity comprises a voicing factor, a pitch gain, or a spectral sharpness.

### Claim 11 (depends on 8)

The method of claim 8, wherein the processor comprises an audio decoder in a voice over internet protocol (VOIP) system.

### Claim 12

A system for receiving a digital audio signal, the system comprising:
a processor; and
a computer readable storage medium storing programming for execution by the processor, the programming including instructions to
generate a high band time domain signal,
generate low band time domain signal,
estimate an energy ratio between the high band and the low band from a last good frame,
keep the energy ratio for following frame-erased frames by applying an energy correction scaling gain to a high band signal segment by segment in the time domain, and
combine the low band signal and the high band signal into a final output.

### Claim 13 (depends on 12)

The system of claim 12, wherein the scaling gain is smoothed sample by sample from one segment to a next segment of the high band signal.

### Claim 14 (depends on 12)

The system of claim 12, wherein the energy ratio is estimated as:
Ratio
=
E
HB
E
LB
=
∑
i

T
env

(
i
)

s
^
LB

(
n
)

2
,
where Tenv(i) is a temporal energy envelope of a last good high band signal,
E
HB
=
∑
i

T
env

(
i
)
is a high band energy, ELB=∥ŝLB(n)∥2 is a low band energy.

### Claim 15 (depends on 12)

The system of claim 12, wherein the programming further includes instructions to calculate an energy correction gain factor gi for an i-th sub-segment of following erased frames by determining:
g
i
=
Ratio
·

s
^
LB
i

(
j
)

2

s
^
HB
i

(
j
)

2
if gi>1, gi=1
where ∥ŝLBi(j)∥2 represents energies of i-th sub-segments of the low band signal ŝLBi(j)=ŝLB(20·i+j) and ∥ŝHBi(j)∥2 represents energies of i-th sub-segments of the high band signal ŝHBi(j)=ŝHB(20·i+j), and j represents a sample index.

### Claim 16 (depends on 12)

The system of claim 12, wherein the programming further includes instructions to calculate an energy correction gain factor gi for an i-th sub-segment of following erased frames by determining:
g
i
=
Ratio
·

s
^
LB
i

(
j
)

2

s
^
HB
i

(
j
)

2
if gi>1, gi=1
where ∥ŝLBi(j)∥2 represents energies of i-th sub-segments of the low band signal ŝLBi(j)=ŝLB(L·i+j) and ∥ŝHBi(j)∥2 represents energies of i-th sub-segments of the high band signal ŝHBi(j)=ŝHB(L·i+j), L is an integer and j represents a sample index.

### Claim 17 (depends on 12)

The system of claim 12, wherein the programming further includes instructions to calculate a smoothed correction gain factor gi(j) and apply the smoothed correction gain factor gi(j) to an i-th sub-segment high band signal ŝHBi(j)=ŝHB(20·i+j):
gi(j)0.95· gi(j−1)+0.05·gi
ŝHBi(j)ŝHBi(j)· gi(j),
wherein gi comprises an energy correction gain factor for the an i-th sub-segment, and wherein gi(j) is smoothed from one segment to a next segment, sample by sample, and j represents a sample index.

### Claim 18 (depends on 12)

The system of claim 12, wherein the programming further includes instructions to calculate a smoothed correction gain factor gi(j) and apply the smoothed correction gain factor gi(j) to an i-th sub-segment high band signal ŝHBi(j)=ŝHB(L·i+j):
gi(j)λ· gi(j−1)+(1−λ)˜gi
ŝHBi(j)ŝHBi(j)· gi(j),
wherein gi comprises an energy correction gain factor for the an i-th sub-segment, and wherein gi(j) is smoothed from one segment to a next segment, sample by sample, j represents a sample index, L is an integer and 0≦λ≦1.