Audio coding method and apparatus
An audio coding method and apparatus, where the method includes, for each audio frame in audio, when a signal characteristic of the audio frame and a signal characteristic of a previous audio frame meet a preset modification condition, determining a first modification weight according to linear spectral frequency (LSF) differences of the audio frame and the LSF differences of the previous audio frame, modifying a linear predictive parameter of the audio frame according to the determined first modification weight, and coding the audio frame according to a modified linear predictive parameter of the audio frame. According to the present disclosure, audio having a wider bandwidth can be coded while a bit rate remains unchanged or a bit rate slightly changes and a spectrum between audio frames is steadier.
1. An audio coding method comprising:
obtaining an audio signal;
performing linear prediction analysis on the audio signal to obtain a linear predictive parameter of a current frame of the audio signal;
determining a first modification weight according to linear spectral frequency (LSF) differences of the current frame of the audio signal and LSF differences of a previous frame of the current frame of the audio signal when a signal characteristic of the current frame meets a preset modification condition;
modifying the linear predictive parameter of the current frame according to the determined first modification weight; and
coding the current frame according to the modified linear predictive parameter of the current frame.
2. The method of claim 1 , wherein determining the first modification weight according to the LSF differences of the current frame of the audio signal and the LSF differences of the previous frame of the current frame of the audio signal is determined according to the formula:
w
[
i
]
=
{
lsf_new
_diff
[
i
]
/
lsf_old
_diff
[
i
]
,
lsf_new
_diff
[
i
]
<
lsf_old
_diff
[
i
]
lsf_old
_diff
[
i
]
/
lsf_new
_diff
[
i
]
,
lsf_new
_diff
[
i
]
≥
lsf_old
_diff
[
i
]
,
wherein w[i] is the first modification weight, wherein lsf_new_diff[i] is the LSF differences of the current frame, wherein lsf_old_diff[i] is the LSF differences of the previous frame, and wherein i is an integer.
3. The method of claim 2 , wherein the value of i ranges from 0 to 9.
4. The method of claim 1 , wherein modifying the linear predictive parameter of the current frame according to the determined first modification weight comprises modifying the linear predictive parameter of the current frame according to the formula:
L [ i ]=(1− w [ i ])* L _old[ i ]+ w [ i ]* L _new[ i ],
wherein L[i] is the modified linear predictive parameter of the current frame,
wherein w[i] is the first modification weight,
wherein L_new[i] is the linear predictive parameter of the current frame,
wherein L_old[i] is a linear predictive parameter of a previous frame of the current frame, and
wherein i is an integer.
5. The method of claim 4 , wherein the value of i ranges from 0 to 9.
6. The method of claim 1 , wherein the signal characteristic of the current frame meets the preset modification condition when the current frame is not a transition frame.
7. The method of claim 6 , wherein a frame is a transition frame when a tilt of a previous frame of the current frame is greater than a tilt threshold value and a coder type of the frame is transient.
8. The method of claim 6 , wherein a frame is a transition frame when a tilt of the previous frame of the current frame is greater than a first tilt threshold value and a tilt of the current frame is less than a second tilt threshold value.
9. The method of claim 6 , wherein a frame is a transition frame when a tilt of a previous frame of the current frame is less than a first tilt threshold value and a coder type of the previous frame is one of four types of VOICED, GENERIC, TRANSITION or AUDIO, and wherein a tilt of the current frame is greater than a second tilt threshold value.
10. The method of claim 1 , wherein the first modification weight is determined according to a ratio between one of the LSF differences of the current frame of the audio signal and one of the LSF differences of the previous frame of the current frame of the audio signal.
11. An audio coding apparatus comprising:
a memory storing instructions; and
a processor coupled to the memory and configured to execute the instructions to:
obtain an audio signal;
perform linear prediction analysis on the audio signal to obtain a linear predictive parameter of a current frame of the audio signal;
determine a first modification weight according to linear spectral frequency (LSF) differences of the current frame of the audio signal and the LSF differences of a previous frame of the current frame of the audio signal when a signal characteristic of the current frame meets a preset modification condition;
modify the linear predictive parameter of the current frame according to the determined first modification weight; and
code the current frame according to the modified linear predictive parameter of the current frame.
12. The apparatus of claim 11 , wherein determining the first modification weight according to the LSF differences of the current frame of the audio signal and the LSF differences of the previous frame of the current frame of the audio signal is determined according to the formula:
w
[
i
]
=
{
lsf_new
_diff
[
i
]
/
lsf_old
_diff
[
i
]
,
lsf_new
_diff
[
i
]
<
lsf_old
_diff
[
i
]
lsf_old
_diff
[
i
]
/
lsf_new
_diff
[
i
]
,
lsf_new
_diff
[
i
]
≥
lsf_old
_diff
[
i
]
,
wherein w[i] is the first modification weight, wherein lsf_new_diff[i] is the LSF differences of the current frame, wherein lsf_old_diff[i] is the LSF differences of the previous frame, and wherein i is an integer.
13. The apparatus of claim 12 , wherein the value of i ranges from 0 to 9.
14. The apparatus of claim 11 , wherein modifying the linear predictive parameter of the current frame according to the determined first modification weight comprises modifying the linear predictive parameter of the current frame according to the formula:
L [ i ]=(1− w [ i ])* L _old[ i ]+ w [ i ]* L _new[ i ]
wherein L[i] is the modified linear predictive parameter of the current frame,
wherein w[i] is the first modification weight,
wherein L_new[i] is the linear predictive parameter of the current frame,
wherein L_old[i] is a linear predictive parameter of a previous frame of the current frame, and
wherein i is an integer.
15. The apparatus of claim 14 , wherein a value of i ranges from 0 to 9.
16. The apparatus of claim 11 , wherein the signal characteristic of the current frame meets the preset modification condition when the current frame is not a transition frame.
17. The apparatus of claim 16 , wherein the current frame is a transition frame when a tilt of a previous frame of the current frame is greater than a tilt threshold value and a coder type of the current frame is transient.
18. The apparatus of claim 16 , wherein the current frame is a transition frame when a tilt of the previous frame of the current frame is greater than a first tilt threshold value and a tilt of the current frame is less than a second tilt threshold value.
19. The apparatus of claim 16 , wherein the current frame is a transition frame when a tilt of a previous frame of the current frame is less smaller than a first tilt threshold value and a coder type of the previous frame is one of four types of VOICED, GENERIC, TRANSITION or AUDIO, and wherein a tilt of the current frame is greater than a second tilt threshold value.
20. The apparatus of claim 11 , wherein the first modification weight is determined according to a ratio between one of the LSF differences of the current frame of the audio signal and one of the LSF differences of the previous frame of the current frame of the audio signal.