Signal analyzer, signal analyzing method, signal synthesizer, signal synthesizing, windower, transformer and inverse transformer
The present disclosure relates to a signal analyzer for processing an overlapped input signal frame comprising 2N subsequent input signal values. The signal analyzer comprises: a windower adapted to window the overlapped input signal frame to obtain a windowed signal, wherein the windower is adapted to zero M+N/2 subsequent input signal values of the overlapped input signal frame, wherein M is equal or greater than 1 and smaller than N/2; and a transformer adapted to transform the remaining 3N/2−M subsequent windowed signal values of the windowed signal using N−M sets of transform parameters to obtain a transformed-domain signal comprising N−M transformed-domain signal values.
1. A signal analyzer for processing an overlapped input signal frame comprising 2N subsequent input signal values, the signal analyzer comprising:
a windower to receive the overlapped input signal frame and adapted to window the received overlapped input signal frame to obtain a windowed signal, the windower being adapted to zero M+N/2 subsequent input signal values of the received overlapped input signal frame, wherein M is equal or greater than 1 and smaller than N/2; and
a transformer configured to received the windowed signal and adapted to transform the remaining 3N/2−M subsequent windowed signal values of the received windowed signal using N−M sets of transform parameters to obtain a transformed-domain signal comprising N−M transformed-domain signal values.
2. The signal analyzer of claim 1 , wherein the window applied to the overlapped input signal frame by the windower comprises M+N/2 subsequent coefficients equal to zero, or, wherein the windower is adapted to truncate the M+N/2 subsequent input signal values.
3. The signal analyzer of claim 1 , wherein the overlapped input signal frame is formed by two subsequent input signal frames each having N subsequent input signal values.
4. The signal analyzer ( 401 ) of claim 1 , wherein each of the N−M sets of transform parameters represents an oscillation at a certain frequency, and wherein a spacing, in particular a frequency spacing, between two oscillations is dependent on N−M.
5. The signal analyzer of claim 1 , wherein the sets of transform parameters comprise a time-domain aliasing operation.
6. The signal analyzer of claim 1 , wherein the sets of transform parameters are determined by the following formula:
d
kn
=
cos
(
π
N
-
M
(
k
+
1
2
)
(
n
+
N
+
1
2
-
M
)
)
,
k
=
0
,
…
,
N
-
M
-
1
,
n
=
0
,
…
,
3
N
2
-
1
-
M
,
wherein k is a set index and defines one of the N−M sets of transform parameters, n defines one of the transform parameters of a respective set of transform parameters, and d kn , denotes the transform parameter specified by n and k.
7. The signal analyzer of claim 1 , wherein the signal analyzer has a time-domain processing mode and a transformed-domain processing mode,
wherein the windower is configured to, when switching from the transformed-domain processing mode to the time domain processing mode in response to a transition indicator, window the overlapped input signal frame using a window having N coefficients forming a rising slope, and N/2−M coefficients forming a falling slope as part of the transformed-domain processing mode; and/or
wherein the windower is configured to, when switching from the time domain processing mode to the transformed-domain processing mode in response to a transition indicator, window the overlapped input signal frame using a window having N/2−M coefficients forming a rising slope and N coefficients forming a falling slope as part of the transformed-domain processing mode.
8. The signal analyzer of claim 1 , wherein the overlapped input signal frame is formed by a current input signal frame and a previous input signal frame, each having N subsequent input signal values, wherein the signal analyzer has a time-domain processing mode and a transformed-domain processing mode, and
wherein the signal analyzer is further configured to, when switching from the transformed-domain processing mode to the time domain processing mode in response to a transition indicator, process at least a portion of the current input signal frame according to a time-domain processing mode; and/or
wherein the signal analyzer is further configured to, when switching from the time domain processing mode to the transformed-domain processing mode in response to a transition indicator, process at least a portion of the previous input signal frame according to a time-domain processing mode.
9. The signal analyzer of claim 1 , wherein the signal analyzer is an audio signal analyzer and the input signal is an audio input signal in the time-domain.
10. A signal synthesizer for processing a transformed-domain signal comprising N−M transformed-domain signal values, wherein M is greater than 1 and smaller than N/2, the signal synthesizer comprising:
an inverse transformer configured to receive the transformed-domain signal and adapted to inversely transform the N−M transformed-domain signal values using 3N/2−M sets of inverse transform parameters to obtain 3N/2−M inverse transformed-domain signal values; and
a windower configured to receive the 3N/2−M inverse transformed-domain signal values and adapted to window the received 3N/2−M inverse transformed-domain signal values using a window comprising 3N/2−M coefficients to obtain a windowed signal comprising 3N/2−M windowed signal values, wherein the 3N/2−M coefficients comprise at least N/2 subsequent nonzero window coefficients.
11. The signal synthesizer of claim 10 , wherein each of the 3N/2−M sets of inverse transform parameters represents an oscillation at a certain frequency, and wherein a spacing, in particular a frequency spacing, between two oscillations is dependent on N−M.
12. The signal synthesizer of claim 10 , wherein the sets of inverse transform parameters comprise an inverse time-domain aliasing operation.
13. The signal synthesizer of claim 10 , wherein the sets of inverse transform parameters are determined by the following formula:
g
kn
=
cos
(
π
N
-
M
(
k
+
1
2
)
(
n
+
N
+
1
2
-
M
)
)
,
n
=
0
,
…
,
3
N
2
-
1
-
M
,
k
=
0
,
…
,
N
-
M
-
1
wherein n is a set index and defines one of the 3N/2−M sets of inverse transform parameters, k defines one of the inverse transform parameters of a respective set of inverse transform parameters, and g kn denotes the inverse transform parameter specified by n and k.
14. The signal synthesizer of claim 10 , wherein the signal synthesizer further comprises:
an overlap-adder adapted to overlap and add the windowed signal and another windowed signal to obtain an output signal comprising at least N output signal values.
15. The signal synthesizer of claim 10 , wherein the signal synthesizer has a time-domain processing mode and a transformed-domain processing mode,
wherein the windower is configured to, when switching from the transformed-domain processing mode to the time domain processing mode in response to a transition indicator, window the inverse transformed domain signal using a window having N subsequent coefficients forming a rising slope, and N/2−M coefficients forming a falling slope; and/or
wherein the windower is configured to, when switching from the time domain processing mode to the transformed-domain processing mode in response to a transition indicator, window the inverse transformed-domain signal using a window having N/2−M coefficients forming a rising slope, and N coefficients forming a falling slope.
16. The signal synthesizer of claim 10 , wherein the signal synthesizer is an audio signal synthesizer, wherein the transformed-domain signal is a frequency domain signal and the inverse-transformed domain signal is a time-domain audio signal.
17. A signal analyzing method for processing an overlapped input signal frame comprising 2N subsequent input signal values, the signal analyzing method comprising:
receiving the overlapped input signal frame;
windowing the received overlapped input signal frame to obtain a windowed signal, the windowing comprising zeroing M+N/2 subsequent input signal values of the received overlapped input signal frame, wherein M is equal or greater than 1 and smaller than N/2; and
transforming the remaining 3N/2−M subsequent windowed signal values of the windowed signal using N−M sets of transform parameters to obtain a transformed domain signal comprising N−M transformed-domain signal values.
18. A signal synthesizing method for processing a transformed-domain signal comprising N−M transformed-domain signal values, wherein M is equal or greater than 1 and smaller than N/2, the signal synthesizing method comprising:
receiving the transformed-domain signal;
inversely transforming the N−M transformed-domain signal values using 3N/2−M sets of inverse transform parameters to obtain 3N/2−M inverse transformed-domain signal values; and
windowing the 3N/2−M inverse transformed-domain signal values using a window comprising 3N/2−M coefficients to obtain a windowed signal comprising 3N/2−M windowed signal values, wherein the 3N/2−M coefficients comprise at least N/2 subsequent nonzero window coefficients.
19. A method for windowing an overlapped input signal frame comprising 2N subsequent input signal values, the method comprising:
receiving the overlapped input signal frame; and
zeroing N/2+M subsequent input signal values of the overlapped input signal frame to generate a windowed signal, M being an integer equal or greater than 1 and smaller than N/2 and N being an integer greater than 1.
20. A transformer for transforming an overlapped input signal frame, the transformer configured to receive the overlapping input signal frame and transform 3N/2−M subsequent input signal values of the received overlapped input signal frame using N−M sets of transform parameters to obtain a transformed-domain signal comprising N−M transformed-domain signal values, M being an integer equal or greater than 1 and smaller than N/2 and N being an integer greater than 1.
21. An inverse transformer for inversely transforming a transformed-domain signal, the transformed-domain signal having N-M values, the inverse transformer configured to receive the transformed-domain signal and inversely transform the N-M transformed-domain signal values into 3N/2−M inversely transformed signal values using 3N/2−M sets of inverse transform parameters, M being an integer equal or greater than 1 and smaller than N/2 and N being an integer greater than 1.