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Method and device for coding speech in analysis-by-synthesis speech coders

A coder, coding technology, used in the field of speech and audio signal coding, can solve unsatisfactory, low energy and other problems

Inactive Publication Date: 2009-05-20
NOKIA CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0020] The corresponding energy difference between the above-mentioned synthetic excitations is very pronounced when using a codebook with fewer pulse positions, so that the lower energy results in an unsatisfactory and barely audible sound

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  • Method and device for coding speech in analysis-by-synthesis speech coders
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  • Method and device for coding speech in analysis-by-synthesis speech coders

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Embodiment Construction

[0035] As mentioned in the previous section, it is often difficult for state-of-the-art AbS speech codecs to accurately model speech segments containing plosives or unvoiced sounds. High-quality speech can be achieved with a better understanding of speech signals and a wealth of knowledge about the properties of human perception. For example, it is known that certain types of coding distortion are not perceptible because they are masked by the signal. Taking advantage of this feature, combined with signal redundancy, improves speech quality at low bit rates.

[0036] Figure 4 shows a schematic diagram of an exemplary AbS encoding process. It should be noted that not all functional components are necessarily executed for each subframe. An example is given as follows: in the IS-641 speech codec, each frame is divided into, for example, four subframes, and the LPC filter parameters are determined once in each frame; the open-loop lag is determined twice in each frame; and the cl...

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Abstract

The present invention discloses a method for improving the quality of encoded speech in a low bit rate Analysis by Synthesis (AbS) speech codec. In the embodiment of the present invention, this object is achieved in the following way: by appropriately shifting the pulse position of the coded excitation signal, the constraints on the waveform matching of the non-stationary explosive speech segment of the speech signal are relaxed. This shift results in an encoded signal whose phase information does not exactly match the original signal at a perceptually unimportant position for the listener. In addition, an adaptive phase diffusion technique is introduced to the coded excitation signal to effectively preserve the signal characteristics such as the energy spread of the original signal.

Description

technical field [0001] The present invention relates generally to speech and audio signal coding, and more particularly to an improved excitation modeling process in an analysis-by-synthesis codec. Background technique [0002] Speech and audio coding algorithms are widely used in wireless communication, multimedia and voice storage systems. The need to save transmission and storage capacity while keeping the quality of the composite signal at a high level drives the development of encoding algorithms. These requirements often conflict with each other, so often a compromise must be made between capacity and quality. The use of speech coding in telecommunication systems is especially important because transmitting the entire speech spectrum in an environment with relatively limited spectral resources can require a large amount of bandwidth. It is therefore absolutely necessary for efficient speech transmission at low bit rates to use signal compression techniques by employi...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G10L19/10
CPCG10L19/10
Inventor A·P·海基宁
Owner NOKIA CORP