High resolution audio coding
Methods, systems, apparatuses, and computer programs encoded on computer storage media for performing linear predictive coding (LPC) are described. At least one of a differential spectrum tilt and an energy difference between a current frame and a previous frame of the audio signal is determined. A spectral stability of the audio signal is detected based on at least one of the differential spectrum tilt and an energy difference between the current frame and the previous frame of the audio signal. In response to detecting the spectral stability of the audio signal, quantized LPC parameters for the previous frame are copied into the current frame of the audio signal.
1. A computer-implemented method implemented by an audio device for performing linear predictive coding (LPC) of an audio signal, comprising:
determining at least one of a differential spectrum tilt or an energy difference between a current frame and a previous frame of the audio signal;
determining that a spectral stability of the audio signal is detected when at least one of an absolute value change of the differential spectrum tilt between the current frame and the previous frame of the audio signal or an absolute value change of the energy difference between the current frame and the previous frame of the audio signal has been within a predetermined range for at least a predetermined number of frames; and
in response to the detected spectral stability of the audio signal, copying quantized LPC parameters for the previous frame into the current frame of the audio signal.
2. The computer-implemented method of claim 1 , further comprising:
determining that the spectral stability of the audio signal is not detected based on at least one of the differential spectrum tilt or the energy difference between the current frame and the previous frame of the audio signal; and
in response to determining that the spectral stability of the audio signal is not detected, performing a quantization on LPC parameters for the current frame to generate quantized LPC parameters for the current frame.
3. The computer-implemented method of claim 2 , wherein determining that the spectral stability of the audio signal is not detected based on at least one of the differential spectrum tilt or the energy difference between the current frame and the previous frame of the audio signal comprises at least one of the following:
determining an absolute value of the differential spectrum tilt between the current frame and the previous frame for the audio signal; and determining that a change of the absolute value of the differential spectrum tilt has not been within a predetermined range for at least a predetermined number of frames; or
determining an absolute value of the energy difference between the current frame and the previous frame of the audio signal; and determining that a change of the absolute value of the energy difference has not been within a predetermined range for at least a predetermined number of frames.
4. The computer-implemented method of claim 1 , further comprising:
determining that the quantized LPC parameters has been copied for at least a predetermined number of frames prior to the current frame; and
in response to determining that the quantized LPC parameters has been copied for at least the predetermined number of frames prior to the current frame, performing a quantization on LPC parameters for the current frame to generate quantized LPC parameters for the current frame.
5. The computer-implemented method of claim 1 , further comprising:
sending a bit to a decoder indicating that the quantized LPC parameters are copied from the previous frame.
6. The computer-implemented method of claim 1 , further comprising:
in response to the spectral stability of the audio signal, performing a quantization on a differential energy level between the current frame and the previous frame to generate a quantized differential energy level; and
in response to determining that the spectral stability is not detected, performing a quantization on an energy level of the current frame to generate a quantized energy level of the current frame.
7. An electronic device, comprising:
a memory; and
one or more processors in communication with the memory, wherein the one or more processors are configured to:
determine at least one of a differential spectrum tilt or an energy difference between a current frame and a previous frame of an audio signal;
determining that a spectral stability of the audio signal is detected when at least one of an absolute value change of the differential spectrum tilt between the current frame and the previous frame of the audio signal or an absolute value change of the energy difference between the current frame and the previous frame of the audio signal has been within a predetermined range for at least a predetermined number of frames; and
in response to the detected spectral stability of the audio signal, copy quantized LPC parameters for the previous frame into the current frame of the audio signal.
8. The electronic device of claim 7 , wherein the one or more processors are further configured to:
determine that the spectral stability of the audio signal is not detected based on at least one of the differential spectrum tilt or the energy difference between the current frame and the previous frame of the audio signal; and
in response to determining that the spectral stability of the audio signal is not detected, perform a quantization on LPC parameters for the current frame to generate quantized LPC parameters for the current frame.
9. The electronic device of claim 8 , wherein determining that the spectral stability of the audio signal is not detected based on at least one of the differential spectrum tilt or the energy difference between the current frame and the previous frame of the audio signal comprises at least one of the following:
determining an absolute value of the differential spectrum tilt between the current frame and the previous frame for the audio signal; and determining that a change of the absolute value of the differential spectrum tilt has not been within a predetermined range for at least a predetermined number of frames; or
determining an absolute value of the energy difference between the current frame and the previous frame of the audio signal; and determining that a change of the absolute value of the energy difference has not been within a predetermined range for at least a predetermined number of frames.
10. The electronic device of claim 7 , wherein the one or more processors are further configured to:
determine that the quantized LPC parameters has been copied for at least a predetermined number of frames prior to the current frame; and
in response to determining that the quantized LPC parameters has been copied for at least the predetermined number of frames prior to the current frame, perform a quantization on LPC parameters for the current frame to generate quantized LPC parameters for the current frame.
11. The electronic device of claim 7 , wherein the one or more processors further configured to:
send a bit to a decoder indicating that the quantized LPC parameters are copied from the previous frame.
12. The electronic device of claim 7 , wherein the one or more processors are further configured to:
in response to the spectral stability of the audio signal, perform a quantization on a differential energy level between the current frame and the previous frame to generate a quantized differential energy level; and
in response to determining that the spectral stability is not detected, perform a quantization on an energy level of the current frame to generate a quantized energy level of the current frame.
13. A non-transitory computer-readable medium storing computer instructions for performing linear predictive coding (LPC) of an audio signal, that when executed by one or more processors, cause the one or more processors to perform operations comprising:
determining at least one of a differential spectrum tilt or an energy difference between a current frame and a previous frame of the audio signal;
determining that a spectral stability of the audio signal is detected when at least one of an absolute value change of the differential spectrum tilt between the current frame and the previous frame of the audio signal or an absolute value change of the energy difference between the current frame and the previous frame of the audio signal has been within a predetermined range for at least a predetermined number of frames; and
in response to the detected spectral stability of the audio signal, copying quantized LPC parameters for the previous frame into the current frame of the audio signal.
14. The non-transitory computer-readable medium of claim 13 , wherein the operations further comprise:
determining that the spectral stability of the audio signal is not detected based on at least one of the differential spectrum tilt or the energy difference between the current frame and the previous frame of the audio signal; and
in response to determining that the spectral stability of the audio signal is not detected, performing a quantization on LPC parameters for the current frame to generate quantized LPC parameters for the current frame.
15. The non-transitory computer-readable medium of claim 14 , wherein determining that the spectral stability of the audio signal is not detected based on at least one of the differential spectrum tilt or the energy difference between the current frame and the previous frame of the audio signal comprises at least one of the following:
determining an absolute value of the differential spectrum tilt between the current frame and the previous frame for the audio signal; and determining that a change of the absolute value of the differential spectrum tilt has not been within a predetermined range for at least a predetermined number of frames; or
determining an absolute value of the energy difference between the current frame and the previous frame of the audio signal; and determining that a change of the absolute value of the energy difference has not been within a predetermined range for at least a predetermined number of frames.
16. The non-transitory computer-readable medium of claim 13 , wherein the operations further comprise:
determining that the quantized LPC parameters has been copied for at least a predetermined number of frames prior to the current frame; and
in response to determining that the quantized LPC parameters has been copied for at least the predetermined number of frames prior to the current frame, performing a quantization on LPC parameters for the current frame to generate quantized LPC parameters for the current frame.
17. The non-transitory computer-readable medium of claim 13 , wherein the operations further comprise:
sending a bit to a decoder indicating that the quantized LPC parameters are copied from the previous frame.