Low bit rate transform coder, decoder, and encoder/decoder for high-quality audio
AssigneeDolby Laboratories Licensing Corporation
InventorsLouis D. Fielder, Grant A. Davidson
Life of this patent
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Abstract
Quantizing noise is lessened in a speech signal system by using adaptive bit allocation for subband channels, wherein subband information of digital words is represented in block-floating-point form, and normalized mantiss as may allow dropping a sign bit.
Claims26
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 representing one or more of said digital words in block-floating-point form comprising a mantissa associated with an exponent, for normalizing at least some mantissas, and for dropping a sign bit for a single normalized mantissa uniquely associated with an exponent whenever the value of said sign bit can be established from the value of a most significant data bit in said normalized mantissa.
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 grouping a plurality of subband information blocks, and for representing a plurality of said digital words in block-floating-point form comprising a mantissa associated with an exponent, said exponent being shared by mantissas from a plurality of subbands in said plurality of subband information blocks.
An encoder for the encoding of digital information, said digital information comprising signal sample blocks representing analog audio signals, said analog audio signals representing a plurality of audio channels, 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 at least one of said digital words, for grouping a plurality of subband information blocks, each block in said plurality of subband information blocks corresponding to a respective one channel of said plurality of audio channels, and for representing a plurality of said digital words in block-floating-point form comprising a mantissa associated with an exponent, said exponent being shared by mantissas from a plurality of subbands in said plurality of subband information blocks.
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, and for reconstructing any missing sign bit for any of said digital words comprising a normalized mantissa uniquely associated with an exponent, and
- means for generating signal sample blocks in response to said digital words.
A decoder for the recovery of digital information from a coded signal comprising subband information blocks, each of said subband information blocks comprising mantissas associated with exponents, said digital information representing analog audio signals, comprising
- means for reconstructing a plurality of digital words from a plurality of mantissas sharing an exponent, each of said plurality of mantissas corresponding to a respective one of said subband information blocks, and
- means for generating signal sample blocks in response to said digital words.
A decoder for the recovery of digital information from a coded signal comprising mantissas associated with exponents, said digital information representing analog audio signals, said analog audio signals representing a plurality of audio channels, comprising
- means for reconstructing a plurality of digital words from a plurality of mantissas sharing an exponent, each mantissa corresponding to a respective one of said plurality of audio channels, and
- means for generating a plurality of signal sample blocks in response to said plurality of digital words, each one of said plurality of signal sample blocks corresponding to digital information representing a respective one of said plurality of audio channels.
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
- representing one or more of said digital words in block-floating-point form comprising a mantissa associated with an exponent, normalizing at least some mantissas, and dropping a sign bit for a single normalized mantissa uniquely associated with an exponent whenever the value of said sign bit can be established from the value of a most significant data bit in said normalized mantissa.
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
- grouping a plurality of subband information blocks, and representing a plurality of said digital words in block-floating-point form comprising a mantissa associated with an exponent, said exponent being shared by mantissas from a plurality of subbands in said plurality of subband information blocks.
An encoding method for the encoding of digital information, said digital information comprising signal sample blocks representing analog audio signals, said analog audio signals representing a plurality of audio channels, 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 at least one of said digital words, grouping a plurality of subband information blocks, each block in said plurality of subband information blocks corresponding to a respective one channel of said plurality of audio channels, and representing a plurality of said digital words in block-floating-point form comprising a mantissa associated with an exponent, said exponent being shared by mantissas from a plurality of subbands in said plurality of subband information blocks.
A decoding method for the recovery of digital information from a coded signal, said digital information representing analog audio signals, comprising
- reconstructing digital words from said coded signal, and reconstructing any missing sign bit for any of said digital words comprising a normalized mantissa uniquely associated with an exponent, and
- generating signal sample blocks to response to said digital words.
A decoding method for the recovery of digital information from a coded signal comprising subband information blocks, each of said subband information blocks comprising mantissas associated with exponents, said digital information representing analog audio signals, comprising
- reconstructing a plurality of digital words from a plurality of mantissas sharing an exponent, each of said plurality of mantissas corresponding to a respective one of said subband information blocks, and
- generating signal sample blocks in response to said digital words.
A decoding method for the recovery of digital information from a coded signal comprising mantissas associated with exponents, said digital information representing analog audio signals, said analog audio signals representing a plurality of audio channels, comprising
- reconstructing a plurality of digital words from a plurality of mantissas sharing an exponent, each mantissa corresponding to a respective one of said plurality of audio channels, and
- generating a plurality of signal sample blocks in response to said plurality of digital words, each one of said plurality of signal sample blocks corresponding to digital information representing a respective one of said plurality of audio channels.
Dependencies are inferred from the claim text.