Spectrum harmonic/noise sharpness control

• US 8,515,747 B2
• Filed: 09/04/2009
• Issued: 08/20/2013
• Est. Priority Date: 09/06/2008
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Gao, Yang
• Primary Examiner(s): JACKSON, JAKIEDA R
• Application Number:
  US12/554,675
• Publication Number:
  US 20100063803A1
• Time in Patent Office: 1,446 Days
• Field of Search: 704/234, 704/207, 704/205
• US Class Current: 704/234
• CPC Class Codes: G10L 19/0208 Subband vocoders
• CPC Class Codes: G10L 21/0364 for improving intelligibility

Abstract

A transmitted data that includes audio data and a transmitted spectral sharpness parameter representing a spectral harmonic/noise sharpness of a plurality of subbands are received. A measured spectral sharpness parameter is estimated from received audio data. The transmitted spectral sharpness parameter is compared with the measured spectral sharpness parameter. A main sharpness control parameter is formed for each of the decoded subbands. The main sharpness control parameter for each of the decoded subbands is analyzed. Ones of the decoded subbands are sharpened if the corresponding main sharpness control indicates that a corresponding subband is not sharp enough, wherein sharpened subbands are formed. Likewise, ones of the decoded subbands are flattened if the corresponding main sharpness control indicates that a corresponding subband is not flat enough, wherein flattened subbands are formed. An energy level of each sharpened subband and each flattened subband is normalized to keep an energy level of each sharpened and/or flattened subband substantially unchanged.

Claims

1. A method of receiving an encoded audio signal comprising audio data and a transmitted spectral sharpness parameter representing a spectral harmonic/noise sharpness of a plurality of spectral subbands, wherein the transmitted spectral sharpness parameter is estimated in an encoder by calculating a magnitude ratio between an average magnitude and a maximum magnitude of an original spectral subband or an energy level ratio between an average energy level and a maximum energy level of an original spectral subband, and the transmitted spectral sharpness parameter is quantized in the encoder and sent to a decoder in which it is used to control spectral sharpness of decoded spectral subbands, the method comprising:

receiving the encoded audio signal;

decoding subbands from the audio data;

estimating a measured spectral sharpness parameter from the received audio data, wherein the measured spectral sharpness parameter is estimated in the decoder by calculating a magnitude ratio between an average magnitude and a maximum magnitude of a decoded spectral subband or an energy level ratio between an average energy level and a maximum energy level of a decoded spectral subband;

comparing the transmitted spectral sharpness parameter with the measured spectral sharpness parameter;

forming a main sharpness control parameter for each of the decoded subbands, wherein the main sharpness control parameter for each decoded subband is formed by analyzing differences between the corresponding transmitted spectral sharpness parameter and the measured spectral sharpness parameter;

analyzing the main sharpness control parameter for each of the decoded subbands;

sharpening ones of the decoded subbands if the corresponding main sharpness control judges that a corresponding subband is not sharp enough based on a result of comparing the main sharpness control parameters of decoded subbands, wherein sharpened subbands are formed by reducing energy of frequency coefficients between harmonic peaks, increasing energy of the harmonic peaks, and/or reducing noise component;

flattening ones of the decoded subbands if the corresponding main sharpness control judges that a corresponding subband is not flat enough based on a result of comparing the main sharpness control parameters of decoded subbands, wherein flattened subbands are formed by increasing energy of frequency coefficients between harmonic peaks, reducing energy of the harmonic peaks, and/or increasing noise component; and

normalizing an energy level of each sharpened subband and each flattened subband to keep an energy level of each sharpened and/or flattened subband substantially unchanged.

2. The method of claim 1, further comprising transmitting a single spectral sharpness parameter estimated from a sharpest spectral subband if a number of bits to transmit spectral sharpness information is limited.

3. The method of claim 1, further comprising converting the sharpened and flattened subbands into an output audio signal.

4. The method of claim 3, further comprising driving a loudspeaker with the output audio signal.

5. The method of claim 1, wherein receiving comprises receiving over a voice over internet protocol (VOIP) network.

6. The method of claim 1, wherein receiving comprises receiving over a cellular telephone network.

7. A method of receiving an encoded audio signal, the method comprising:

receiving an encoded audio signal bitstream;

decoding subbands from the encoded audio signal bitstream;

estimating a measured spectral sharpness parameter from the encoded audio signal for each of the decoded subbands, wherein the measured spectral sharpness parameter represents a spectral harmonic/noise sharpness of the decoded subbands, and the measured spectral sharpness parameter is estimated in the decoder by calculating a magnitude ratio between an average magnitude and a maximum magnitude of a decoded spectral subband or an energy level ratio between an average energy level and a maximum energy level of a decoded spectral subband;

forming a main sharpness control parameter for each of the decoded subbands, wherein the main sharpness control parameter for each decoded subband is formed by analyzing the measured spectral sharpness parameter from decoded subbands;

sharpening ones of the decoded subbands if the corresponding main sharpness control judges that a corresponding subband is not sharp enough based on a result of comparing the main sharpness control parameters of decoded subbands, wherein sharpened subbands are formed by reducing energy of frequency coefficients between harmonic peaks, increasing energy of the harmonic peaks, and/or reducing noise component;

flattening ones of the decoded subbands if the corresponding main sharpness control judges that a corresponding subband is not flat enough based on a result of comparing the main sharpness control parameters of decoded subbands, wherein flattened subbands are formed by increasing energy of frequency coefficients between harmonic peaks, reducing energy of the harmonic peaks, and/or increasing noise component; and

normalizing an energy level of each sharpened subband and each flattened subband to keep an energy level of each sharpened and/or flattened substantially unchanged.

8. The method of claim 7, further comprising smoothing each main sharpness control parameter for each decoded subband between current subbands and/or between consecutive frames.

9. The method of claim 7, wherein sharpening further comprises:

comparing the main sharpness control parameters of the decoded subbands; and

sharpening ones of the decoded subbands if the corresponding main sharpness control parameters indicate that a corresponding subband is sharper than other decoded subbands based on the comparing.

10. A method of transmitting an input audio signal, the method comprising:

estimating a spectral sharpness parameter of each subband of the input audio signal, wherein the spectral sharpness parameter represents a spectral harmonic/noise sharpness of each subband of the input audio signal, wherein the spectral sharpness parameter is estimated in an encoder by calculating a magnitude ratio between an average magnitude and a maximum magnitude of an original spectral subband or an energy level ratio between an average energy level and a maximum energy level of an original spectral subband;

comparing the estimated spectral sharpness parameters from different subbands;

allocating more bits to subbands having a sharper spectrum based on the comparing;

allocating less bits to subbands having a flatter spectrum based on the comparing; and

transmitting the allocated bits.

11. The method of claim 10, wherein bits are further allocated to subbands according to energy level distribution of the subbands.

12. The method of claim 10, wherein bits allocated to subbands having a flatter spectrum are further reduced if a total bit budget is fixed.

13. A system for receiving an encoded audio signal, the system comprising:

a receiver configured to receive the encoded audio signal, the receiver configured to;

decode subbands from the encoded audio signal;

estimate a measured spectral sharpness parameter from the encoded audio signal for each of the decoded subbands, wherein the spectral sharpness parameter represents a spectral harmonic/noise sharpness of each decoded subband, wherein the measured spectral sharpness parameter is estimated in the decoder by calculating a magnitude ratio between an average magnitude and a maximum magnitude of a decoded spectral subband or an energy level ratio between an average energy level and a maximum energy level of a decoded spectral subband;

form a main sharpness control parameter for each of the decoded subbands, wherein the main sharpness control parameter for each decoded subband is formed by analyzing the measured spectral sharpness parameter from the decoded subbands;

sharpen ones of the decoded subbands if the corresponding main sharpness control judges that a corresponding subband is not sharp enough based on a result of comparing the main sharpness control parameters of decoded subbands, wherein sharpened subbands are formed by reducing energy of frequency coefficients between harmonic peaks, increasing energy of the harmonic peaks, and/or reducing noise component;

flatten ones of the decoded subbands if the corresponding main sharpness control judges that a corresponding subband is not flat enough based on a result of comparing the main sharpness control parameters of decoded subbands, wherein flattened subbands are formed by increasing energy of frequency coefficients between harmonic peaks, reducing energy of the harmonic peaks, and/or increasing noise component; and

normalize an energy level of each sharpened subband and each flattened subband to keep an energy level of each sharpened and/or flattened substantially unchanged.

14. The system of claim 13, wherein the receiver is further configured to convert the sharpened and flattened subbands into an output audio signal.

15. The system of claim 14, wherein the output audio signal is configured to drive a loudspeaker.

16. The system of claim 13, wherein the system is configured to operate over a voice over internet protocol (VOIP) system.

17. The system of claim 13, wherein the system is configured to operate over a cellular telephone network.