METHOD AND APPARATUS FOR ESTIMATING HIGH-BAND ENERGY IN A BANDWIDTH EXTENSION SYSTEM
A method ( 100 ) includes receiving ( 101 ) an input digital audio signal comprising a narrow-band signal. The input digital audio signal is processed ( 102 ) to generate a processed digital audio signal. An estimate of the high-band energy level corresponding to the input digital audio signal is determined ( 103 ). Modification of the estimated high-band energy level is done based on an estimation accuracy and/or narrow-band signal characteristics ( 104 ). A high-band digital audio signal is generated based on the modified estimate of the high-band energy level and an estimated high-band spectrum corresponding to the modified estimate of the high-band energy level ( 105 ).
1 . A method comprising:
receiving an input digital audio signal comprising a narrow-band signal;
determining an estimated high-band energy level corresponding to the input digital audio signal; and
modifying the estimated high-band energy level based on an estimation accuracy and/or based on the narrow-band signal characteristics.
2 . The method of claim 1 wherein the step of modifying the estimated high-band energy level based on the estimation accuracy comprises the steps of:
determining a measure of unreliability in the estimation of the high-band energy level; and
biasing the estimated high-band energy level to be lower by an amount proportional to the measure of unreliability.
3 . The method of claim 2 wherein the step of determining the measure of unreliability comprises the step of determining a standard deviation of the error in the estimated high-band energy level.
4 . The method of claim 1 wherein the step of modifying the estimated high-band energy level based on the narrow-band signal characteristics comprises the step of modifying the estimated high-band energy level based on a voicing level.
5 . The method of claim 4 wherein the step of modifying the estimated high-band energy level based on the voicing level comprises the step of reducing the high-band energy level for substantially voiced speech and/or increasing the high-band energy level for substantially unvoiced speech.
6 . The method of claim 1 wherein the step of modifying the estimated high-band energy level based on the narrow-band signal characteristics comprises the step of smoothing the estimated high-band energy level.
7 . The method of claim 6 wherein the step of smoothing comprises the step of reducing an energy difference between consecutive frames.
8 . The method of claim 1 wherein the step of modifying the estimated high-band energy level based on the narrow-band signal characteristics comprises the step of modifying the estimated high-band energy level based on whether or not a frame is steady-state or transient.
9 . The method of claim 8 wherein the step of modifying the estimated high-band energy level comprises the step of reducing the high-band energy level for transient frames and/or increasing the high-band energy level for steady-state frames.
10 . The method of claim 1 wherein the step of modifying the estimated high-band energy level comprises the step of modifying the estimated high-band energy level based on an occurrence of an onset/plosive.
11 . An apparatus comprising:
an estimation and control module (ECM) receiving an input digital audio signal comprising a narrow-band signal, generating an estimated high-band energy level corresponding to the input digital audio signal, and modifying the estimated high-band energy level based on an estimation accuracy and/or based on the narrow-band signal characteristics.
12 . The apparatus of claim 11 wherein the ECM modifies the estimated high-band energy level by determining a measure of unreliability in the estimation of the high-band energy level and biasing the estimated high-band energy level to be lower by an amount proportional to the measure of unreliability.
13 . The apparatus of claim 12 wherein the measure of unreliability comprises a standard deviation.
14 . The apparatus of claim 11 wherein the ECM modifies the estimated high-band energy level by modifying the estimated high-band energy level based on a voicing level.
15 . The apparatus of claim 14 wherein the high-band energy level is reduced for substantially voiced speech and/or increased for substantially unvoiced speech.
16 . The apparatus of claim 11 wherein the ECM modifies the estimated high-band energy level by smoothing the estimated high-band energy level.
17 . The apparatus of claim 16 wherein the smoothing comprises reducing an energy difference between consecutive frames.
18 . The apparatus of claim 11 wherein the ECM modifies the estimated high-band energy level by modifying the estimated high-band energy level based on whether or not a frame is steady-state or transient.
19 . The apparatus of claim 18 wherein the high-band energy level is reduced for transient frames and/or increased for steady-state frames.
20 . A method comprising:
receiving an input digital audio signal comprising a narrow-band signal;
receiving an estimated high-band energy level corresponding to the input digital audio signal; and
modifying the estimated high-band energy level based on an estimation accuracy and/or based on the narrow-band signal characteristics.