Low bit rate transform coder, decoder, and encoder/decoder for high-quality audio
First Claim
1. An encoder for the encoding of digital information, said digital information comprising signal sample blocks representing analog audio signals, comprisingmeans for generating subband information blocks, each subband information block comprising a set of digital words generated in response to a signal sample block, said means comprising means for applying a discrete transform function to each of said signal sample blocks, andmeans for quantizing with a fixed number of bits one or more digital words corresponding to at least the lowest frequency spectral component of said analog audio signals, but not quantizing all digital words with a fixed number of bits.
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Abstract
A transform encoder, a transform decoder, and a transform encoder/decoder system employ adaptive bit allocation wherein each code word representing spectral information is allocated a fixed number of bits and an adaptive number of bits, except that at least some but not all code words are allocated a fixed number of bits.
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Citations
24 Claims
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1. An encoder for the encoding of digital information, said digital information comprising signal sample blocks representing analog audio signals, comprising
means for generating subband information blocks, each subband information block comprising a set of digital words generated in response to a signal sample block, said means comprising means for applying a discrete transform function to each of said signal sample blocks, and means for quantizing with a fixed number of bits one or more digital words corresponding to at least the lowest frequency spectral component of said analog audio signals, but not quantizing all digital words with a fixed number of bits.
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2. An encoder for the encoding of digital information, said digital information comprising signal sample blocks representing analog audio signals, comprising
means for defining subbands and for generating subband information blocks, each subband information block comprising a set of digital words generated in response to a signal sample block, and means for quantizing with a fixed number of bits one or more digital words corresponding to at least the lowest frequency spectral component of said analog audio signals, and for quantizing one or more digital words with a fixed number of bits and an adaptive number of bits.
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6. A decoder for the recovery of digital information from a coded signal, said digital information representing analog audio signals, comprising
means for reconstructing digital words from said coded signal, said means reconstructing with a fixed number of bits one or more digital words corresponding to at least the lowest frequency spectral component of said analog audio signals, but not reconstructing all digital words with a fixed number of bits, and means for generating signal sample blocks in response to said digital words, said means comprising means for applying an inverse discrete transform function to the reconstructed digital words.
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7. A decoder for the recovery of digital information from a coded signal, said digital information representing analog audio signals, comprising
means for reconstructing digital words from said coded signal, said means reconstructing with a fixed number of bits one or more digital words corresponding to at least the lowest frequency spectral component of said analog audio signals, and for reconstructing one or more digital words with a fixed number of bits and an adaptive number of bits, and means for generating signal sample blocks in response to said digital words.
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13. An encoding method for the encoding of digital information, said digital information comprising signal sample blocks representing analog audio signals, comprising
generating subband information blocks, each subband information block comprising a set of digital words generated in response to a signal sample block, by applying a discrete transform function to each of said signal sample blocks, and quantizing with a fixed number of bits one or more digital words corresponding to at least the lowest frequency spectral component of said analog audio signals, but not quantizing all digital words with a fixed number of bits.
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14. An encoding method for the encoding of digital information, said digital information comprising signal sample blocks representing analog audio signals, comprising
defining subbands and generating subband information blocks, each subband information block comprising a set of digital words generated in response to a signal sample block, and quantizing with a fixed number of bits one or more digital words corresponding to at least the lowest frequency spectral component of said analog audio signals, and quantizing one or more digital words with a fixed number of bits and an adaptive number of bits.
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18. A decoding method for the recovery of digital information from a coded signal, said digital information representing analog audio signals, comprising
reconstructing with a fixed number of bits one or more digital words corresponding to at least the lowest frequency spectral component of said analog audio signals, but not reconstructing all digital words with a fixed number of bits, and generating signal sample blocks in response to said digital words by applying an inverse discrete transform function to the reconstructed digital words.
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19. A decoding method for the recovery of digital information from a coded signal, said digital information representing analog audio signals, comprising
reconstructing with a fixed number of bits one or more digital words corresponding to at least the lowest frequency spectral component of said analog audio signals, and reconstructing one or more digital words with a fixed number of bits and an adaptive number of bits, and generating signal sample blocks in response to said digital words.
Specification