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Encoding mode switching method and device, and decoding mode switching method and device

A coding mode and coding technology, applied in the field of voice and audio coding and decoding, can solve the problems of increasing transmission channel requirements, poor effect, and inability to achieve smooth switching effect

Active Publication Date: 2014-07-09
ZTE CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0009] An existing switching method between an ACELP-based coding mode and an MDCT-based coding mode uses precoding technology, and the computational complexity of this method is very high; Additional encoding or implementation based on a variable rate MDCT encoder, this method will increase the code rate during the switching process, or increase the delay of switching at a constant code rate, increasing the requirements for the transmission channel
Other switching methods, such as the method of using signal extrapolation to obtain the signal at the switching point, cannot achieve a good smooth switching effect
[0010] In summary, the published methods for switching between the ACELP-based coding mode and the MDCT-based coding mode are not effective, the computational complexity is high, or additional code rates or delays need to be added

Method used

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Embodiment 1

[0573] This embodiment describes a smooth switching method from the MDCT coding mode to the ACELP coding mode. In view of MLT (Modulated Lapped Transform, Modulated Lapped Transform) transformation is a variant of MDCT transformation, the audio encoder of G.722.1 (MLT transformation) is selected as the MDCT encoder, and the speech encoder of G.722.2 is selected as the ACELP encoder; It is assumed that after signal classification, the coding mode of the i-th frame and the previous signal is MDCT mode, which is coded by G.722.1; the coding mode of the i+1-th frame signal is ACELP mode, which is coded by G.722.2. The specific smooth handover method from G.722.1 to G.722.2 is as follows.

[0574] Such as figure 1 As shown, the encoding side includes the following steps:

[0575] Step E101: For the input signal of frames 0 to i-1, the encoding modes of the previous frame, the current frame and the next frame are all MDCT mode, using the original window type in G.722.1 encoding an...

Embodiment 2

[0740] This embodiment describes a smooth switching method from an ACELP-based coding mode to an MDCT-based coding mode. Also select the audio coder of G.722.1 as the MDCT coder, select the speech coder of G.722.2 as the ACELP coder; suppose after signal classification, the encoding mode of the k frame and the previous signal is the ACELP mode, use G.722.2 Coding; the coding mode of the k+1th frame is MDCT mode, which is coded with G.722.1. The specific smooth handover method from G.722.2 to G.722.1 is as follows.

[0741] Such as Figure 10 As shown, the encoding side includes the following steps:

[0742] Step E201: For the 0th to k-1th frame signals, the coding modes of the previous frame, the current frame and the next frame are all ACELP mode, from n=-N 2s =-175 position starts to read in the signal, and performs G.722.2 encoding, and outputs the encoded code stream of each frame and the encoding mode information of the next frame together;

[0743] The signal of n=-1...

Embodiment 3

[0851] This embodiment describes a codec device for smooth switching between audio coding modes that implements the smooth switching method of the above embodiment, including a coding mode switching device when the coding mode is switched from MDCT mode to ACELP mode, and a decoding mode from MDCT mode to ACELP mode. The decoding mode switching device when the mode is switched, the coding mode switching device when the coding mode is switched from the ACELP mode to the MDCT mode, and the decoding mode switching device when the decoding mode is switched from the ACELP mode to the MDCT mode.

[0852] The coding mode switching device when the coding mode is switched from MDCT mode to ACELP mode is used for encoding of the i+1th frame when the coding mode type of the i-th frame is a modified discrete cosine transform MDCT coding mode Encoding when the mode is Algebraic Code Excited Linear Prediction ACELP encoding mode, including a first encoding module E310, a first decoding modul...

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Abstract

The embodiment of the invention provides an encoding mode switching method which comprises the steps that when the i frame and the i+1 frame are in the MDCT encoding mode and the ACELP encoding mode, the MDCT encoding mode is carried out on the i frame through a pre-defined window pattern to obtain MDCT encoding information; encoding information of the i frame or the i frame and frames before the i frame are decoded to obtain decoding signals; according to the decoding signals, partial input signals of the i frame and partial input signals of the i+1 frame, history states of a filter in the ACELP encoding mode are set up and updated, and then subsequent input signals which are one frame long are subjected to the ACELP encoding process. The embodiment of the invention provides an encoding mode switching device from MDCT to ACELP, and a decoding mode switching method and device from MDCT to ACELP, and further provides an encoding mode switching method from ACELP to MDCT and a decoding mode switching method and device from ACELP to MDCT.

Description

technical field [0001] The present invention relates to the field of voice and audio codec, in particular to a coding mode switching method and device, and a decoding mode switching method and device. Background technique [0002] Coding techniques for audio signals can be divided into two categories: time-domain coding and frequency-domain coding. [0003] In the prior art, known frequency domain coding schemes include MP3 (Moving Picture Experts Group Audio Layer III, moving picture experts compression standard audio layer 3), AAC (Advanced Audio Coding, enhanced audio coding) and the like. These frequency-domain coding schemes are based on a time-domain / frequency-domain transform followed by quantization and coding of the frequency-domain coefficients. In the quantization stage, the psychoacoustic model is used to control the quantization error; in the encoding stage, the quantized spectral information and the corresponding side information are entropy coded using a code...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G10L19/20
Inventor 黄冬梅郭轶芹袁浩
Owner ZTE CORP
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