Preprocessing method, preprocessing apparatus and coding device

• US 8,566,085 B2
• Filed: 03/15/2010
• Issued: 10/22/2013
• Est. Priority Date: 03/13/2009
• 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: Miao, Lei, Qi, Fengyan, Xu, Jianfeng, Zhang, Dejun, Zhang, Qing
• Primary Examiner(s): Saint Cyr, Leonard
• Application Number:
  US12/724,066
• Publication Number:
  US 20100232540A1
• Time in Patent Office: 1,317 Days
• Field of Search: None
• US Class Current: 704/219
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• CPC Class Codes: G10L 19/09 Long term prediction, i.e. removing periodical redundancies, e.g. by using adaptive codebook or pitch predictor
• CPC Class Codes: G10L 19/18 Vocoders using multiple modes
• CPC Class Codes: G10L 21/06 Transformation of speech into a non-audible representation, e.g. speech visualisation or speech processing for tactile aids G10L15/26 takes precedence

Abstract

The present disclosure relates to coding and decoding technologies, and discloses a preprocessing method, a preprocessing apparatus, and a coding device. The preprocessing method includes: obtaining characteristic information of a current frame signal; identifying whether the current frame signal requires no coding operation of removing LTC according to the characteristic information of the current frame signal and preset information; and if identifying that the current frame signal requires no coding operation of removing LTC, performing the coding operation of removing STC for the current frame signal; and if identifying that the current frame signal requires the coding operation of removing LTC, performing the coding operations of removing both LTC and STC for the current frame signal. Through the technical solution provided herein, the coding operation of removing LTC is performed for only part of the input frame signals.

Claims

1. A preprocessing method, comprising:

obtaining characteristic information of a current frame signal;

identifying whether the current frame signal requires no coding operation of removing Long Term Correlation (LTC) according to the characteristic information of the current frame signal and preset information; and

if the current frame signal requires no coding operation of removing LTC, performing a coding operation of removing Short Term Correlation (STC) for the current frame signal;

if the current frame signal requires the coding operation of removing LTC, performing coding operations of removing both LTC and STC for the current frame signal;

wherein the characteristic information of the current frame signal is an energy value of the current frame signal;

the identifying of whether the current frame signal requires no coding operation of removing LTC according to the characteristic information of the current frame signal and the preset information comprises;

judging whether the energy value of the current frame signal is less than an absolute energy threshold, wherein the absolute energy threshold corresponds to a frame length of the current frame signal; and

identifying that the current frame signal requires no coding operation of removing LTC if the energy value is less than the absolute energy threshold.

2. The preprocessing method according to claim 1, wherein before identifying that the current frame signal requires no coding operation of removing LTC, the method further comprises:

judging whether several frame signals prior to the current frame signal comprise any Long Term Prediction (LTP) frame, wherein the number of the frame signals prior to the current frame signal corresponds to the frame length of the current frame signal; and

identifying that the current frame signal requires no coding operation of removing LTC if none of the several frame signals prior to the current frame signal comprises the LTP frame.

3. The preprocessing method of claim 1, wherein:

the characteristic information of the current frame signal is an energy value of the current frame signal;

if the current frame signal is not designed to initialize an average energy value of background noise, the identifying of whether the current frame signal requires no coding operation of removing LTC according to the characteristic information of the current frame signal and the preset information comprises;

judging whether a difference between the energy value of the current frame signal and the average energy value of the background noise is less than a difference threshold, wherein;

an initial value of the average energy value of the background noise is an average energy value of frame signals for initializing the average energy value of the background noise; and

the number of the frame signals for initializing the average energy value of the background noise corresponds to a frame length of the current frame signal; and

identifying that the current frame signal requires no coding operation of removing LTC if the difference is less than the difference threshold.

4. The preprocessing method according to claim 3, wherein before identifying that the current frame signal requires no coding operation of removing LTC, the method further comprises:

judging whether several frame signals prior to the current frame signal comprise any Long Term Prediction (LTP) frame, wherein the number of the frame signals prior to the current frame signal corresponds to the frame length of the current frame signal; and

identifying that the current frame signal requires no coding operation of removing LTC if none of the several frame signals prior to the current frame signal comprises the LTP frame.

5. The preprocessing method of claim 3, wherein if the difference is less than the difference threshold, the method further comprises:

buffering the energy value of the current frame signal into a buffer, and increasing a counter value of the buffer by 1.

6. The preprocessing method of claim 5, further comprising:

using an average value of energy values of the frame signals buffered in the buffer as the average energy value of the background noise if the counter value is a maximum value which corresponds to the frame length of the current frame signal; and

setting the counter value to 0, and emptying the buffer.

7. The preprocessing method of claim 1, wherein:

the characteristic information of the current frame signal is a periodicity factor parameter of the current frame signal;

the identifying of whether the current frame signal requires no coding operation of removing LTC according to the characteristic information of the current frame signal and the preset information comprises;

judging whether the periodicity factor parameter is greater than a periodicity factor threshold; and

identifying that the current frame signal requires no coding operation of removing LTC if the periodicity factor parameter is less than or equal to the periodicity factor threshold.

8. The preprocessing method according to claim 7, wherein before identifying that the current frame signal requires no coding operation of removing LTC, the method further comprises:

judging whether several frame signals prior to the current frame signal comprise any Long Term Prediction (LTP) frame, wherein the number of the frame signals prior to the current frame signal corresponds to the frame length of the current frame signal; and

identifying that the current frame signal requires no coding operation of removing LTC if none of the several frame signals prior to the current frame signal comprises the LTP frame.

9. A preprocessing apparatus comprising:

an obtaining unit, of a device, configured to obtain characteristic information of a current frame signal;

an identifying unit, configured to identifying whether the current frame signal requires no coding operation of removing Long Term Correlation (LTC) according to the characteristic information of the current frame signal obtained by the obtaining unit and preset information; and

an operating unit, configured to perform coding operations of removing both LTC and Short Term Correlation (STC) for the current frame signal if the identifying unit identifies that the current frame signal requires the coding operation of removing LTC;

or perform the coding operation of removing STC for the current frame signal if the identifying unit identifies that the current frame signal requires no coding operation of removing LTC;

wherein the obtaining unit comprises a calculating unit which is configured to calculate an energy value or a periodicity factor parameter of the current frame signal;

wherein the identifying unit comprises;

a judging unit, configured to judge whether the energy value calculated out by the calculating unit is less than an absolute energy threshold; and

a processing unit, configured to identify that the current frame signal requires the coding operation of removing LTC if the judging unit identifies that the energy value is greater than or equal to the absolute energy threshold, and identify that the current frame signal requires no coding operation of removing LTC if the judging unit identifies that the energy value is less than the absolute energy threshold.

10. The preprocessing apparatus according to claim 9, wherein:

the judging unit is further configured to judge whether several frame signals prior to the current frame signal comprise any Long Term Prediction (LTP) frame if the processing unit identifies that the current frame signal requires no coding operation of removing LTC; and

the processing unit is further configured to re-identify that the current frame signal requires the coding operation of removing LTC if the judging unit identifies that the several frame signals prior to the current frame signal comprise any LTP frame.

11. The preprocessing apparatus of claim 9, wherein the identifying unit comprises:

a judging unit, configured to judge whether a difference between the energy value calculated out by the calculating unit and an average energy value of background noise is less than a difference threshold; and

a processing unit, configured to identify that the current frame signal requires the coding operation of removing LTC if the judging unit identifies that the difference between the energy value and the average energy value of the background noise is greater than or equal to the difference threshold, and identify that the current frame signal requires no coding operation of removing LTC if the judging unit identifies that the difference between the energy value and the average energy value of the background noise is less than the difference threshold.

12. The preprocessing apparatus of claim 9, wherein the identifying unit comprises:

a judging unit, configured to judge whether the periodicity factor parameter calculated out by the calculating unit is greater than a periodicity factor threshold; and

a processing unit, configured to identify that the current frame signal requires no coding operation of removing LTC if the judging unit identifies that the periodicity factor parameter is less than or equal to the periodicity factor threshold, and identify that the current frame signal requires the coding operation of removing LTC if the judging unit identifies that the periodicity factor parameter is greater than the periodicity factor threshold.

13. A coding device,

comprising:

preprocessing apparatus, configured to obtain characteristic information of a current frame signal;

identify whether the current frame signal requires no coding operation of removing Long Term Correlation (LTC) according to the characteristic information of the current frame signal and preset information;

perform a coding operation of removing Short Term Correlation (STC) for the current frame signal if the current frame signal requires no coding operation of removing LTC, or perform coding operations of removing both LTC and STC for the current frame signal if the current frame signal requires the coding operation of removing LTC; and

an entropy coding apparatus, configured to perform entropy coding for the current frame signal by using a result of the coding operation;

wherein the preprocessing apparatus comprises;

an obtaining unit, configured to calculate an energy value of the current frame signal;

an identifying unit, configured to judge whether the energy value calculated out by the obtaining unit is less than an absolute energy threshold; and

an operating unit, configured to perform coding operations of removing both the LTC and STC for the current frame signal if the identifying unit identifies that the energy value is greater than or equal to the absolute energy threshold, or perform the coding operation of removing STC for the current frame signal if the identifying unit identifies that the energy value is less than the absolute energy threshold.

14. The coding device according to claim 13, wherein:

the identifying unit is further configured to judge whether several frame signals prior to the current frame signal comprise any Long Term Prediction (LTP) frame before the operating unit performs the coding operation of removing STC for the current frame signal; and

the operating unit is configured to perform the coding operation of removing STC for the current frame signal as long as the identifying unit identifies that none of the several frame signals prior to the current frame signal comprises the LTP frame, or perform coding operations of removing both the LTC and STC for the current frame signal if the identifying unit identifies that the several frame signals prior to the current frame signal comprise any LTP frame.

15. The coding device of claim 13, wherein the preprocessing apparatus comprises:

an obtaining unit, configured to calculate an energy value of the current frame signal;

an identifying unit, configured to judge whether a difference between the energy value calculated out by the obtaining unit and an average energy value of background noise is less than a difference threshold; and

an operating unit, configured to perform coding operations of removing both the LTC and STC for the current frame signal if the identifying unit identifies that the difference between the energy value and the average energy value of the background noise is greater than or equal to the difference threshold, or perform the coding operation of removing STC for the current frame signal if the identifying unit identifies that the difference between the energy value and the average energy value of the background noise is less than the difference threshold.

16. The coding device of claim 13, wherein the preprocessing apparatus comprises:

an obtaining unit, configured to calculate a periodicity factor parameter of the current frame signal;

an identifying unit, configured to judge whether the periodicity factor parameter calculated out by the obtaining unit is greater than a periodicity factor threshold; and

an operating unit, configured to perform coding operations of removing both the LTC and STC for the current frame signal if the identifying unit identifies that the periodicity factor parameter is greater than the periodicity factor threshold, or perform the coding operation of removing STC for the current frame signal if the identifying unit identifies that the periodicity factor parameter is less than or equal to the periodicity factor threshold.