Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Reexamination Certificate
1998-01-12
2001-10-09
{haeck over (S)}mits, T{overscore (a)}livaldis Ivars (Department: 2641)
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
C704S229000, C704S500000
Reexamination Certificate
active
06301558
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an audio signal encoding apparatus and an encoding method and an audio signal decoding apparatus and a decoding method which are applied to transmit a digital audio signal by, for example, a digital satellite broadcasting.
2. Description of the Related Art
A powerful error correction code is used for transmission of information in a digital satellite broadcasting. Therefore, even if a C/N ratio of a transmission path deteriorates to a certain degree, information of substantially the same quality as that of a transmission signal can be received by error correction.
However, if the C/N ratio suddenly deteriorates as in case of a rainy day and if an error generated exceeds error correcting ability which the error correction code has, the quality of reproduced information suddenly deteriorates to such an extent that the contents cannot be understood. On the other hand, in case of an analog broadcasting, a quality of reproduced information gently changes with the decrease in C/N ratio.
FIG. 1A
conceptually shows the foregoing difference between the digital broadcasting and the analog broadcasting in the case where an axis of abscissa shows an error rate and an axis of ordinate indicates a quality of data that is reproduced. In case of the analog broadcasting, the quality gradually deteriorates as shown by a broken line. In case of the digital broadcasting, the quality suddenly deteriorates as shown by a solid line. Actually, even in case of the digital broadcasting, characteristics (graceful degradation) such that the quality of the reproduction data gradually deteriorates as in the analog broadcasting are preferable.
The transfer of audio data on a network will now be considered. Even if the signal processing abilities on the encoder side and the decoder side have abilities enough to execute real-time processes, when the network is busy and an enough data transfer amount cannot be assured, a reproduction signal cannot be obtained in a real-time manner. In such a case, since a decoding process cannot be performed until a predetermined amount of data is accumulated on the decoder side, a reproduction sound becomes an intermittent sound and a reproduction sound quality remarkably deteriorates. Further, even when data processing ability on the decoder side connected to the network is inadequate, the quality of the reproduction audio sound similarly deteriorates.
OBJECTS AND SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to provide an audio signal encoding apparatus and an encoding method and an audio signal decoding apparatus and a decoding method, in which when a C/N ratio of a transmission path deteriorates, the quality of the reproduced audio signal deteriorates gradually.
That is, according to the invention, as conceptually shown in
FIG. 1B
, a graceful degradation such that when a C/N ratio of a transmission path deteriorates, the quality of the reproduced audio signal deteriorates step by step is realized even in a digital transmission. In case of transmitting an audio signal, for example, the signal to be transmitted is separated to a middle low band and a high band and encoded, while data in the middle low band wherein quality deterioration is likely to be perceived is transmitted with higher error correcting ability. Thus, when the C/N ratio of the transmission path deteriorates, the signal first deteriorates in the high band component in which noise is more difficult to be perceived. Therefore, the graceful degradation can be realized.
Another object of the invention is to provide an audio signal encoding apparatus and an encoding method and an audio signal decoding apparatus and a decoding method, in which in a real-time reproduction system such that audio data is transmitted on a network, it is prevented that a reproduction sound becomes intermittent in dependence on a state of the network, processing ability on the reproduction side, or the like.
According to one aspect of the invention, there is provided an audio signal encoding apparatus comprising: a unit for separating an input audio signal into a plurality of hierarchical data on a frequency basis; a plurality of encoding units for respectively encoding the plurality of hierarchical data; and an error correction encoding unit for adding an error correction code to an output of each of the plurality of encoding units, wherein the error correction encoding unit raises error correcting ability which is caused by the error correction encoding for the hierarchical data on the low band side among the plurality of hierarchical data than that for the hierarchical data on the high band side.
According to another aspect of the invention, there is also provided an audio signal encoding apparatus comprising: a unit for dividing an input audio signal into a plurality of frequency components on a frequency basis; a quantizing unit for respectively quantizing the plurality of frequency components; and a formatting unit for dividing the plurality of quantized frequency components into blocks of a plurality of hierarchical data and for formatting to a plurality of bit streams every data divided into the blocks.
According to still another aspect of the invention, there is also provided an audio signal encoding apparatus comprising: a unit for separating an input audio signal to a plurality of hierarchical data on the basis of a frequency; a plurality of encoding units for respectively encoding the plurality of hierarchy data; and an error correction encoding unit for adding an error correction code to an output of each of the plurality of encoding units, wherein a busyness degree of a transmission path is detected and the hierarchy data to be used by a reception side which receives the encoded audio signal in accordance with the busyness degree through the transmission path is transmitted to the reception side.
According to another further aspect of the invention, there is provided an audio signal encoding apparatus comprising: a unit for separating an input audio signal to a plurality of hierarchy data on the basis of a frequency; a plurality of encoding units for respectively encoding the plurality of hierarchy data; and an error correction encoding unit for adding an error correction code to an output of each of the Plurality of encoding units, wherein the hierarchy data to be used by a reception side which receives the encoded audio signal through a transmission path is transmitted to the reception side in accordance with processing ability on the reception side.
According to further another aspect of the invention, there is provided a decoding apparatus for receiving and decoding bit streams formed by dividing an audio signal to a plurality of hierarchies in accordance with a frequency and encoding, comprising: a unit for decoding the received bit streams to a plurality of hierarchy data; and a unit for adaptively selecting a whole or a part of the plurality of hierarchy data.
The above and other objects and features of the present invention will become apparent from the following detailed description an e appended claims with reference to the accompanying drawings.
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Frommer William S.
Frommer Lawrence & Haug LLP.
Smid Dennis M.
Sony Corporation
{haeck over (S)}mits T{overscore (a)}livaldis Ivars
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