Audio Decoding Apparatus and Decoding Method and Program
First Claim
1. An audio decoding apparatus comprising:
- a bit stream separator for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream;
a low-frequency decoder for decoding said low-frequency bit stream to generate a low-frequency audio signal;
a subband divider for dividing said low-frequency audio signal into a plurality of complex-valued signals in respective frequency bands to generate low-frequency subband signals;
a corrective coefficient extractor for calculating an energy corrective coefficient based on said low-frequency subband signals;
an energy corrector for correcting a target energy described by said high-frequency bit stream with said energy corrective coefficient to calculate a corrected target energy;
a band expander for generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream, at said corrected target energy; and
a subband combiner for combining real parts of said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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Abstract
An energy corrector (105) for correcting a target energy for high-frequency components and a corrective coefficient calculator (106) for calculating an energy corrective coefficient from low-frequency subband signals are newly provided. These processors perform a process for correcting a target energy that is required when a band expanding process is performed on a real number only. Thus, a real subband combining filter and a real band expander which require a smaller amount of calculations can be used instead of a complex subband combining filter and a complex band expander, while maintaining a high sound-quality level, and the required amount of calculations and the apparatus scale can be reduced.
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Citations
39 Claims
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1. An audio decoding apparatus comprising:
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a bit stream separator for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoder for decoding said low-frequency bit stream to generate a low-frequency audio signal; a subband divider for dividing said low-frequency audio signal into a plurality of complex-valued signals in respective frequency bands to generate low-frequency subband signals; a corrective coefficient extractor for calculating an energy corrective coefficient based on said low-frequency subband signals; an energy corrector for correcting a target energy described by said high-frequency bit stream with said energy corrective coefficient to calculate a corrected target energy; a band expander for generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream, at said corrected target energy; and a subband combiner for combining real parts of said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal. - View Dependent Claims (2, 3, 4, 5)
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6. An audio decoding apparatus comprising:
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a bit stream separator for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoder for decoding said low-frequency bit stream to generate a low-frequency audio signal; a subband divider for dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals; a corrective coefficient generator for generating a predetermined energy corrective coefficient; an energy corrector for correcting a target energy described by said high-frequency bit stream with said energy corrective coefficient to calculate a corrected target energy; a band expander for generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream, at said corrected target energy; and
a subband combiner for combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal. - View Dependent Claims (7, 8)
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9. An audio decoding method comprising the steps of:
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separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; decoding said low-frequency bit stream to generate a low-frequency audio signal; dividing said low-frequency audio signal into a plurality of complex-valued signals in respective frequency bands to generate low-frequency subband signals; calculating an energy corrective coefficient based on said low-frequency subband signals; correcting a target energy described by said high-frequency bit stream with said energy corrective coefficient to calculate a corrected target energy; generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream, at said corrected target energy; and
combining real parts of said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal. - View Dependent Claims (10, 11, 12, 13)
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14. An audio decoding method comprising the steps of:
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separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; decoding said low-frequency bit stream to generate a low-frequency audio signal;
dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals;generating a predetermined energy corrective coefficient; correcting a target energy described by said high-frequency bit stream with said energy corrective coefficient to calculate a corrected target energy; generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream, at said corrected target energy; and combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal. - View Dependent Claims (15, 16)
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17. A program for enabling a computer to perform:
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a bit stream separating process for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoding process for decoding said low-frequency bit stream to generate a low-frequency audio signal;
a complex subband dividing process for dividing said low-frequency audio signal into a plurality of complex-valued signals in respective frequency bands to generate low-frequency subband signals;a corrective coefficient extracting process for calculating an energy corrective coefficient based on said low-frequency subband signals; an energy correcting process for correcting a target energy described by said high-frequency bit stream with said energy corrective coefficient to calculate a corrected target energy; a band expanding process for generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream, at said corrected target energy; and a subband combiner for combining real parts of said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal. - View Dependent Claims (18, 19, 20, 21)
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22. A program for enabling a computer to perform:
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a bit stream separating process for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoding process for decoding said low-frequency bit stream to generate a low-frequency audio signal; a complex subband dividing process for dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals; a corrective coefficient generating process for generating a predetermined energy corrective coefficient; an energy correcting process for correcting a target energy described by said high-frequency bit stream with said energy corrective coefficient to calculate a corrected target energy; a band expanding process for generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream, at said corrected target energy; and a subband combining process for combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal. - View Dependent Claims (23, 24)
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25. An audio decoding apparatus comprising:
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a bit stream separator for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoder for decoding said low-frequency bit stream to generate a low-frequency audio signal; a subband divider for dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals; an energy corrector for correcting a target energy described by said high-frequency bit stream with a predetermined energy corrective coefficient to calculate a corrected target energy; a band expander for generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream, at said corrected target energy; and a subband combiner for combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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26. (canceled)
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27. An audio decoding apparatus comprising:
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a bit stream separator for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoder for decoding said low-frequency bit stream to generate a low-frequency audio signal; a subband divider for dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals; an energy corrector for calculating a corrected target energy using an instruction of said high-frequency bit stream and a predetermined energy corrective coefficient; a band expander for generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream; and a subband combiner for combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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28. An audio decoding apparatus comprising:
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a bit stream separator for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoder for decoding said low-frequency bit stream to generate a low-frequency audio signal; a subband divider for dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals; a band expander for generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals using an instruction included in said high-frequency bit stream and a predetermined energy corrective coefficient; and a subband combiner for combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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29. An audio decoding apparatus comprising:
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a bit stream separator for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoder for decoding said low-frequency bit stream to generate a low-frequency audio signal; a subband divider for dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals; a band expander for generating a high-frequency subband signal by correcting the signal energy (Er) of a signal which is generated by copying and processing said low-frequency subband signals, rather than a target energy (R) described by said high-frequency bit stream, with the reciprocal (1/a) of a predetermined energy corrective coefficient (a) when a corrected target energy (aR) which is produced by correcting said target energy (R) with said predetermined energy corrective coefficient (a) and the signal energy (Er) are corrected in amplitude such that the corrected target energy (aR) and the signal energy (Er) are equal to each other; and a subband combiner for combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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30. An audio decoding method comprising the steps of:
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separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; decoding said low-frequency bit stream to generate a low-frequency audio signal;
dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals;correcting a target energy described by said high-frequency bit stream with a predetermined energy corrective coefficient to calculate a corrected target energy; generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream, at said corrected target energy; and combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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31. (canceled)
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32. An audio decoding method comprising the steps of:
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separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; decoding said low-frequency bit stream to generate a low-frequency audio signal;
dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals;generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals using an instruction included in said high-frequency bit stream and a predetermined energy corrective coefficient; and combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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33. An audio decoding method comprising the steps of:
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separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; decoding said low-frequency bit stream to generate a low-frequency audio signal;
dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals;generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals using an instruction included in said high-frequency bit stream and a predetermined energy corrective coefficient; and
a subband combiner for combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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34. An audio decoding method comprising the steps of:
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separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; decoding said low-frequency bit stream to generate a low-frequency audio signal;
dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals;generating a high-frequency subband signal by correcting the signal energy (Er) of a signal which is generated by copying and processing said low-frequency subband signals, rather than a target energy (R) described by said high-frequency bit stream, with the reciprocal (1/a) of a predetermined energy corrective coefficient (a) when a corrected target energy (aR) which is produced by correcting said target energy (R) with said predetermined energy corrective coefficient (a) and the signal energy (Er) are corrected in amplitude such that the corrected target energy (aR) and the signal energy (Er) are equal to each other; and combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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35. A program for enabling a computer to perform:
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a bit stream separating process for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoding process for decoding said low-frequency bit stream to generate a low-frequency audio signal; a subband dividing process for dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals; an energy correcting process for correcting a target energy described by said high-frequency bit stream with a predetermined energy corrective coefficient to calculate a corrected target energy; a band expanding process for generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream, at said corrected target energy; and a subband combiner for combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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36. A program for enabling a computer to perform:
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a bit stream separating process for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoding process for decoding said low-frequency bit stream to generate a low-frequency audio signal; a subband dividing process for dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals; an energy correcting process for outputting an energy corrective coefficient for a signal which is generated by copying and processing said low-frequency subband signals; a band expanding process for generating a high-frequency subband signal by correcting, in amplitude, the signal energy of the signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream, using said energy corrective coefficient; and a subband combining process for combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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37. A program for enabling a computer to perform:
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a bit stream separating process for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoding process for decoding said low-frequency bit stream to generate a low-frequency audio signal; a subband dividing process for dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals; an energy correcting process for calculating a corrected target energy using an instruction of said high-frequency bit stream and a predetermined energy corrective coefficient; a band expanding process for generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream; and a subband combining process for combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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38. A program for enabling a computer to perform:
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a bit stream separating process for separating a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoding process for decoding said low-frequency bit stream to generate a low-frequency audio signal; a subband dividing process for dividing said low-frequency audio signal into a plurality of real-valued signals in respective frequency bands to generate low-frequency subband signals; a band expanding process for generating a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals using an instruction included in said high-frequency bit stream and a predetermined energy corrective coefficient; and a subband combining process for combining said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal.
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39. (canceled)
Specification