Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Reexamination Certificate
2000-08-25
2003-09-23
Chawan, Vijay (Department: 2654)
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
C704S200100, C704S212000, C704S214000, C704S230000, C704S219000, C704S503000, C704S225000, C381S002000, C381S022000, C375S240120, C375S253000, C375S240030
Reexamination Certificate
active
06625574
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of sub-band coding. In addition, this invention relates to a method of sub-band decoding. Furthermore, this invention relates to a sub-band coding apparatus and a sub-band decoding apparatus.
2. Description of the Related Art
Japanese published unexamined patent application 10-336038 discloses a method of encoding an audio signal which includes a step of separating the audio signal into signals in sub-bands. The resultant sub-band signals are encoded frame by frame. In general, scale factors are defined for the sub-band signals respectively. According to the method in Japanese application 10-336038, every frame is divided into a plurality of small frames, and scale factors are reduced in number by making some of them common to plural small frames. The encoding-resultant sub-band signals, and data representative of scale factors are combined into a bit stream. A 1-frame-corresponding portion of the bit stream is composed of a first area assigned to the data of scale factors, and second and later areas corresponding to the respective small frames and assigned to the encoding-resultant sub-band signals. Specifically, the second area is loaded with samples of the encoding-resultant sub-band signals which correspond to a first small frame. The later areas are loaded with samples of the encoding-resultant sub-band signals which correspond to second and later small frames.
According to the method in Japanese application 10-336038, even if scale factors remain unchanged over a plurality of successive frames, a given number of bits representing the scale factors are transmitted for every frame.
SUMMARY OF THE INVENTION
It is a first object of this invention to provide an improved method of sub-band coding.
It is a second object of this invention to provide an improved method of sub-band decoding.
It is a third object of this invention to provide an improved sub-band coding apparatus.
It is a fourth object of this invention to provide an improved sub-band decoding apparatus.
A first aspect of this invention provides a method of sub-band coding. The method comprises the steps of dividing an input digital audio signal into sub-band signals in respective sub-bands; determining scale factors of the respective sub-bands on the basis of the sub-band signals for every frame; calculating differences between the determined scale factors for a first frame and the determined scale factors for a second frame preceding the first frame; calculating absolute values of the calculated scale-factor differences and generating data representative of the calculated absolute values; encoding the data representative of the calculated absolute values into data of a Huffman code; generating sign bits representing signs of the calculated scale-factor differences; quantizing the sub-band signals in response to the determined scale factors for every frame to generate quantized samples of the sub-band signals; and combining the Huffman-code data, the generated sign bits, and the quantized samples of the sub-band signals into a bit stream.
A second aspect of this invention provides a method of sub-band coding. The method comprises the steps of dividing an input digital audio signal into sub-band signals in respective sub-bands; separating the sub-bands into groups on the basis of a perceptual model; determining scale factors of the respective sub-band groups on the basis of the sub-band signals for every frame; calculating differences between the determined scale factors for a first frame and the determined scale factors for a second frame preceding the first frame; calculating absolute values of the calculated scale-factor differences and generating data representative of the calculated absolute values; encoding the data representative of the calculated absolute values into data of a Huffman code; generating sign bits representing signs of the calculated scale-factor differences; quantizing the sub-band signals in response to the determined scale factors for every frame to generate quantized samples of the sub-band signals; and combining the Huffman-code data, the generated sign bits, and the quantized samples of the sub-band signals into a bit stream.
A third aspect of this invention provides a method of sub-band coding. The method comprises the steps of dividing an input digital audio signal into sub-band signals in respective sub-bands; determining scale factors of the respective sub-bands on the basis of the sub-band signals for every frame; calculating differences between the determined scale factors for a first frame and the determined scale factors for a second frame preceding the first frame; calculating absolute values of the calculated scale-factor differences and generating data representative of the calculated absolute values; encoding the data representative of the calculated absolute values into data of a Huffman code; generating sign bits representing signs of the calculated scale-factor differences; generating selection information representing a selected bit-stream format; quantizing the sub-band signals in response to the determined scale factors for every frame to generate quantized samples of the sub-band signals; combining the generated selection information, the Huffman-code data, the generated sign bits, and the quantized samples of the sub-band signals into a bit stream of a first format; generating information flags indicating whether or not the determined scale factors for the first frame are updated from the determined scale factors for the second frame, respectively; selecting one or more of the scale factors in the first frame which are updated from those in the second frame, and generating selected-scale-factor data representative of the selected scale factor or the selected scale factors; combining the generated selection information, the generated information flags, the selected-scale-factor data, and the quantized samples of the sub-band signals into a bit stream of a second format; and selecting one of the bit stream of the first format and the bit stream of the second format as an output bit stream to maximize a number of bits allocated to the samples of the sub-band signals.
A fourth aspect of this invention provides a method of sub-band coding. The method comprises the steps of dividing an input digital audio signal into sub-band signals in respective sub-bands; separating the sub-bands into groups on the basis of a perceptual model; determining scale factors of the respective sub-band groups on the basis of the sub-band signals for every frame; calculating differences between the determined scale factors for a first frame and the determined scale factors for a second frame preceding the first frame; calculating absolute values of the calculated scale-factor differences and generating data representative of the calculated absolute values; encoding the data representative of the calculated absolute values into data of a Huffman code; generating sign bits representing signs of the calculated scale-factor differences; generating selection information representing a selected bit-stream format; quantizing the sub-band signals in response to the determined scale factors for every frame to generate quantized samples of the sub-band signals; combining the generated selection information, the Huffman-code data, the generated sign bits, and the quantized samples of the sub-band signals into a bit stream of a first format; generating information flags indicating whether or not the determined scale factors for the first frame are updated from the determined scale factors for the second frame, respectively; selecting one or more of the scale factors in the first frame which are updated from those in the second frame, and generating selected-scale-factor data representative of the selected scale factor or the selected scale factors; combining the generated selection information, the generated information flags, the selected-scale-factor data, and the quantized samples of the sub-band signals into a bit s
Banba Yutaka
Taniguchi Shohei
Chawan Vijay
Matsushita Electric Industrial., Ltd.
Woo Louis
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