US2014207445A1PendingUtilityA1
System and Method for Correcting for Lost Data in a Digital Audio Signal
Est. expiryMay 5, 2029(~2.8 yrs left)· nominal 20-yr term from priority
G10L 19/005G10L 19/0017
50
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Claims
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
exact text as granted — not AI-modifiedWhat is claimed is:
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.
2 . 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.
3 . 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 T env (i) is a temporal energy envelope of a last good high band signal,
E
HB
=
∑
i
T
env
(
i
)
is a high band energy, E LB ∥ŝ LB (n)∥ 2 is a low band energy.
4 . The method of claim 1 , further comprising calculating an energy correction gain factor g i 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 g i >1, g i =1
where ∥ŝ LB i (j)∥ 2 represents energies of i-th sub-segments of the low band signal ŝ LB i (j)=ŝ LB (20·i+j) and ∥ŝ HB i (j)∥ 2 represents energies of i-th sub-segments of the high band signal ŝ HB i (j)=ŝ HB (20·i+j), and j represents a sample index.
5 . The method of claim 1 , further comprising calculating an energy correction gain factor g i 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 g i >1, g i =1
where ∥ŝ LB i (j)∥ 2 represents energies of i-th sub-segments of the low band signal ŝ LB i (j)=ŝ LB (L·i+j) and ∥ŝ HB i (j)∥ 2 represents energies of i-th sub-segments of the high band signal ŝ HB i (j)=ŝ HB (L·i+j), L is an integer and j represents a sample index.
6 . The method of claim 1 , further comprising calculating a smoothed correction gain factor g i (j) and applying the smoothed correction gain factor g i (j) to an i-th sub-segment high band signal ŝ HB i (j)=ŝ HB (20·i+j) according to:
g i ( j ) 0.95 · g i ( j− 1)+0.05 ·g i
ŝ HB i ( j ) ŝ HB i ( j )· g i ( j ),
wherein g i comprises an energy correction gain factor for the an i-th sub-segment, and wherein g i (j) is smoothed from one segment to a next segment, sample by sample, and j represents a sample index.
7 . The method of claim 1 , further comprising calculating a smoothed correction gain factor g i (j) and applying the smoothed correction gain factor g i (j) to an i-th sub-segment high band signal ŝ HB i (j)=ŝ HB (L·i+j) according to:
g i ( j ) λ· g i ( j− 1)+(1−λ)· g i
ŝ HB i ( j ) ŝ HB i ( j )· g i ( j ),
wherein g i comprises an energy correction gain factor for the an i-th sub-segment, and wherein g i (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.
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.
9 . The method of claim 8 , wherein the frequency domain is a MDCT domain, DFT domain or FFT domain.
10 . The method of claim 8 , wherein the parameter representing the periodicity or harmonicity comprises a voicing factor, a pitch gain, or a spectral sharpness.
11 . The method of claim 8 , wherein the processor comprises an audio decoder in a voice over internet protocol (VOIP) system.
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.
13 . 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.
14 . 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 T env (i) is a temporal energy envelope of a last good high band signal,
E
HB
=
∑
i
T
env
(
i
)
is a high band energy, E LB =∥ŝ LB (n)∥ 2 is a low band energy.
15 . The system of claim 12 , wherein the programming further includes instructions to calculate an energy correction gain factor g i 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 g i >1, g i =1
where ∥ŝ LB i (j)∥ 2 represents energies of i-th sub-segments of the low band signal ŝ LB i (j)=ŝ LB (20·i+j) and ∥ŝ HB i (j)∥ 2 represents energies of i-th sub-segments of the high band signal ŝ HB i (j)=ŝ HB (20·i+j), and j represents a sample index.
16 . The system of claim 12 , wherein the programming further includes instructions to calculate an energy correction gain factor g i 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 g i >1, g i =1
where ∥ŝ LB i (j)∥ 2 represents energies of i-th sub-segments of the low band signal ŝ LB i (j)=ŝ LB (L·i+j) and ∥ŝ HB i (j)∥ 2 represents energies of i-th sub-segments of the high band signal ŝ HB i (j)=ŝ HB (L·i+j), L is an integer and j represents a sample index.
17 . The system of claim 12 , wherein the programming further includes instructions to calculate a smoothed correction gain factor g i (j) and apply the smoothed correction gain factor g i (j) to an i-th sub-segment high band signal ŝ HB i (j)=ŝ HB (20·i+j):
g i ( j ) 0.95 · g i ( j− 1)+0.05 ·g i
ŝ HB i ( j ) ŝ HB i ( j )· g i ( j ),
wherein g i comprises an energy correction gain factor for the an i-th sub-segment, and wherein g i (j) is smoothed from one segment to a next segment, sample by sample, and j represents a sample index.
18 . The system of claim 12 , wherein the programming further includes instructions to calculate a smoothed correction gain factor g i (j) and apply the smoothed correction gain factor g i (j) to an i-th sub-segment high band signal ŝ HB i (j)=ŝ HB (L·i+j):
g i ( j ) λ· g i ( j− 1)+(1−λ)˜ g i
ŝ HB i ( j ) ŝ HB i ( j )· g i ( j ),
wherein g i comprises an energy correction gain factor for the an i-th sub-segment, and wherein g i (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.Join the waitlist — get patent alerts
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