Signal processing method and device
A method for processing an audio signal, including: sound is converted to an analog audio input signal and converted into a digital audio signal; a windowed time domain signal is obtained and then a twiddled signal is obtained; the twiddled signal is pre-rotated and then an FFT is performed; an in-place fixed rotate compensation is performed on the FFT signal and then an post-rotated is performed; a quantized signal is obtained and then wrote into a bitstream for transmitting or storing.
1. A method for processing an audio signal, comprising:
converting sound into an analog audio input signal;
converting the analog audio input signal into a digital audio signal;
obtaining a windowed time domain signal by windowing the digital audio signal;
obtaining a twiddled signal based on the windowed time domain signal;
pre-rotating the twiddled signal by using a first symmetric rotation factor to obtain a pre-rotated signal, wherein the first symmetric rotation factor is a·W 4L 2p+1 , p=0, K, L/2−1, wherein a is a constant and is a real number, wherein L is the length of the input audio signal;
performing a Fast Fourier transform (FFT) of L/2 points on the pre-rotated signal to obtain an FFT signal;
performing an in-place fixed rotate compensation on the FFT signal;
post-rotating the signal that has undergone the in-place fixed rotate compensation by using a second symmetric rotation factor to obtain a post-rotated signal, wherein the second symmetric rotation factor is b·W 4L 2q+1 , q=0, K, L/2−1, and b is a constant and is a real number;
quantizing a processed signal derived from the post-rotated signal to obtain a quantized signal; and
writing the quantized signal into a bitstream for transmitting or storing.
2. The method according to claim 1 , wherein the in-place fixed rotate compensation is performed by multiplying a fixed rotate compensation factor with the FFT signal.
3. The method according to claim 2 , wherein the fixed rotate compensation factor is
1
+
j
(
3
π
4
L
)
.
4. The method according to claim 1 , wherein the twiddled signal is obtained according to z(p)= 2p)+j· L−1−2p), wherein z(p) denotes the twiddled signal, n) denotes the windowed time domain signal.
5. The method according to claim 1 , wherein W 4L 2q+1 in the first symmetric rotation factor is expressed in the following form:
W
4
L
2
p
+
1
=
cos
2
π
(
2
p
+
1
)
4
L
-
j
sin
2
π
(
2
p
+
1
)
4
L
.
6. The method according to claim 1 , wherein W 4L 2q+1 in the second symmetric rotation factor is expressed in the following form:
W
4
L
2
p
+
1
=
cos
2
π
(
2
p
+
1
)
4
L
-
j
sin
2
π
(
2
p
+
1
)
4
L
.
7. A mobile phone, comprising:
a microphone, configured to convert sound into an analog audio input signal;
an analog-to-digital converter, configured to convert the analog audio input signal into a digital audio signal;
an audio codec, configured to:
obtain a windowed time domain signal by windowing the digital audio signal,
obtain a twiddled signal based on the windowed time domain signal;
pre-rotate the twiddled signal by using a first symmetric rotation factor to obtain a pre-rotated signal, wherein the first symmetric rotation factor is a·W 4L 2p+1 , p=0, K, L/2−1, wherein a is a constant real number, wherein L is the length of the input audio signal,
perform a Fast Fourier transform (FFT) of L/2 points on the pre-rotated signal to obtain an FFT signal,
perform an in-place fixed rotate compensation on the FFT signal,
post-rotate the signal that has undergone the in-place fixed rotate compensation by using a second symmetric rotate factor to obtain a post-rotated signal, wherein the second symmetric rotation factor is b·W 4L 2q+1 , q=0, K, L/2−1, and b is a constant real number,
quantize a processed signal derived from the post-rotated signal to obtain a quantized signal, and
write the quantized signal into a bitstream for transmitting or storing.
8. The mobile phone according to claim 7 , wherein the in-place fixed rotate compensation is performed by multiplying a fixed rotate compensation factor with the FFT signal.
9. The mobile phone according to claim 8 , wherein the fixed rotate compensation factor is
1
+
j
(
3
π
4
L
)
.
10. The mobile phone according to claim 7 , wherein the twiddled signal is obtained according to z(p)= 2p)+j· L−1−2p), wherein z(p) denotes the twiddled signal, n) denotes the windowed time domain signal.
11. The mobile phone according to claim 7 , wherein W 4L 2q+1 in the first symmetric rotation factor is expressed in the following form:
W
4
L
2
p
+
1
=
cos
2
π
(
2
p
+
1
)
4
L
-
j
sin
2
π
(
2
p
+
1
)
4
L
.
12. The mobile phone according to claim 7 , wherein W 4L 2q+1 in the second symmetric rotation factor is expressed in the following form:
W
4
L
2
p
+
1
=
cos
2
π
(
2
p
+
1
)
4
L
-
j
sin
2
π
(
2
p
+
1
)
4
L
.
13. A method for processing an audio signal, the method comprising:
converting sound into an analog audio input signal;
converting the analog audio input signal into a digital audio signal;
obtaining a windowed time domain signal by windowing the digital audio signal;
obtaining a twiddled signal based on the windowed time domain signal;
pre-rotating the twiddled signal by using a first symmetric rotation factor to obtain a pre-rotated signal, wherein the first symmetric rotation factor is a·W 4L 2p+1 , p=0, K, L/2−1, wherein a is a constant and is a real number, wherein L is the length of the input audio signal;
performing a Fast Fourier transform (FFT) of L/2 points on the pre-rotated signal to obtain an FFT signal;
performing an in-place fixed rotate compensation on the FFT signal;
post-rotating the signal that has undergone the in-place fixed rotate compensation by using a second symmetric rotation factor to obtain a post-rotated signal, wherein the second symmetric rotation factor is b·W 4L 2q+1 , q=0, K, L/2−1, and b is a constant and is a real number;
obtaining a frequency domain signal based on the post-rotated signal;
quantizing a processed signal based on the frequency domain signal to obtain a quantized signal; and
writing the quantized signal into a bitstream for transmitting or storing.
14. The method according to claim 13 , wherein the in-place fixed rotate compensation is performed by multiplying a fixed rotate compensation factor with the FFT signal.
15. The method according to claim 14 , wherein the fixed rotate compensation factor is
1
+
j
(
3
π
4
L
)
.
16. The method according to claim 13 , wherein the twiddled signal is obtained according to z(p)= 2p)+j· L−1−2p), wherein z(p) denotes the twiddled signal, n) denotes the windowed time domain signal.
17. The method according to claim 13 , wherein W 4L 2q+1 in the first symmetric rotation factor is expressed in the following form:
W
4
L
2
p
+
1
=
cos
2
π
(
2
p
+
1
)
4
L
-
j
sin
2
π
(
2
p
+
1
)
4
L
.
18. The method according to claim 13 , wherein W 4L 2q+1 in the second symmetric rotation factor is expressed in the following form:
W
4
L
2
p
+
1
=
cos
2
π
(
2
p
+
1
)
4
L
-
j
sin
2
π
(
2
p
+
1
)
4
L
.
19. The method according to claim 13 , wherein the frequency domain signal is obtained by
{
y
(
2
q
)
=
Re
{
Z
_
(
q
)
}
,
y
(
L
-
1
-
2
q
)
=
-
Im
{
Z
_
(
q
)
}
,
q
=
0
,
…
,
L
/
2
-
1
;
wherein y(2q) is the real parts of the post-rotated signal and denote the odd number frequency bins of the frequency domain signal, y(L−1−2q) is the imaginary parts of the post-rotated signal and denote the even number frequency bins of the frequency domain signal, and
Z
_
(
q
)
=
(
1
+
j
3
π
/
4
L
)
*
W
4
L
2
q
+
1
∑
p
=
0
L
/
2
-
1
{
z
(
p
)
*
W
4
L
2
p
+
1
}
W
L
/
2
pq
.
20. A mobile phone, comprising:
a microphone, configured to convert sound into an analog audio input signal;
an analog-to-digital converter, configured to convert the analog audio input signal into a digital audio signal; and
an audio codec, configured to:
obtain a windowed time domain signal by windowing the digital audio signal,
obtain a twiddled signal based on the windowed time domain signal,
pre-rotate the twiddled signal by using a first symmetric rotation factor to obtain a pre-rotated signal, wherein the first symmetric rotation factor is a·W 4L 2p+1 , p=0, K, L/2−1, wherein a is a constant and is a real number, wherein L is the length of the input audio signal,
perform a Fast Fourier transform (FFT) of L/2 points on the pre-rotated signal to obtain an FFT signal,
perform an in-place fixed rotate compensation on the FFT signal,
post-rotate the signal that has undergone the in-place fixed rotate compensation by using a second symmetric rotation factor to obtain a post-rotated signal, wherein the second symmetric rotation factor is b·W 4L 2q+1 , q=0, K, L/2−1, and b is a constant and is a real number,
obtain a frequency domain signal based on the post-rotated signal,
quantize a processed signal based on the frequency domain signal to obtain a quantized signal, and
write the quantized signal into a bitstream for transmitting or storing.
21. The mobile phone according to claim 20 , wherein the in-place fixed rotate compensation is performed by multiplying a fixed rotate compensation factor with the FFT signal.
22. The mobile phone according to claim 21 , wherein the fixed rotate compensation factor is
1
+
j
(
3
π
4
L
)
.
23. The mobile phone according to claim 21 , wherein the twiddled signal is obtained according to z(p)= 2p)+j· L−1−2p), wherein z(p) denotes the twiddled signal, n) denotes the windowed time domain signal.
24. The mobile phone according to claim 21 , wherein W 4L 2q+1 in the first symmetric rotation factor is expressed in the following form:
W
4
L
2
p
+
1
=
cos
2
π
(
2
p
+
1
)
4
L
-
j
sin
2
π
(
2
p
+
1
)
4
L
.
25. The mobile phone according to claim 21 , wherein W 4L 2q+1 in the second symmetric rotation factor is expressed in the following form:
W
4
L
2
p
+
1
=
cos
2
π
(
2
p
+
1
)
4
L
-
j
sin
2
π
(
2
p
+
1
)
4
L
.
26. The mobile phone according to claim 21 , wherein the frequency domain signal is obtained by
{
y
(
2
q
)
=
Re
{
Z
_
(
q
)
}
,
y
(
L
-
1
-
2
q
)
=
-
Im
{
Z
_
(
q
)
}
,
q
=
0
,
K
,
L
/
2
-
1
;
wherein y(2q) is the real parts of the post-rotated signal and denote the odd number frequency bins of the frequency domain signal, y(L−1−2q) is the imaginary parts of the post-rotated signal and denote the even number frequency bins of the frequency domain signal, and
Z
_
(
q
)
=
(
1
+
j
3
π
/
4
L
)
*
W
4
L
2
q
+
1
∑
p
=
0
L
/
2
-
1
{
z
(
p
)
*
W
4
L
2
p
+
1
}
W
L
/
2
pq
.