Method of efficiently recording an audio signal in semiconductor memory
First Claim
1. A hierarchical encoder, comprising:
- frequency transformation means for transforming an input digital audio signal into transformation coefficients for a plurality of frequency bands; and
hierarchical quantizing means for extracting audible signal components from the transformation coefficients based on characteristics for a psycho-acoustic curve, and for generating, from the extracted audible signal components, first encoded data to n-th encoded data with priorities based on human auditory characteristics, n being an integer.
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Abstract
An audio signal is recorded in a semiconductor memory in a plurality of hierarchical levels, with the lowest level sufficing for reproduction with a certain reduced degree of fidelity. Successively higher hierarchical levels provide successively greater fidelity when reproduced. When the memory has been determined to have reached maximum capacity recording continues by overwriting the highest hierarchical level of data currently stored in the memory with lower hierarchical levels of new data. A code is recorded in the memory, indicating the number of hierarchical levels recorded therein, for subsequent reproduction. The audio signal can furthermore be recorded in variable-length frames and reproduced at high speed by reading every N-th frame, N being a positive integer, or by reading only frames having at least a certain minimum length.
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Citations
24 Claims
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1. A hierarchical encoder, comprising:
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frequency transformation means for transforming an input digital audio signal into transformation coefficients for a plurality of frequency bands; and hierarchical quantizing means for extracting audible signal components from the transformation coefficients based on characteristics for a psycho-acoustic curve, and for generating, from the extracted audible signal components, first encoded data to n-th encoded data with priorities based on human auditory characteristics, n being an integer. - View Dependent Claims (2)
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3. A hierarchical encoder, comprising:
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frequency transformation means for transforming an input digital audio signal into transformation coefficients for a plurality of frequency bands; and hierarchical dividing and quantizing means for extracting audible signal components from the transformation coefficients based on psycho-acoustic characteristics, for dividing the audible signal components into hierarchical levels, and for quantizing the audible signal components to produce encoded data divided into a plurality of hierarchical levels, a first hierarchical level of encoded data S1 being obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than a first predetermined frequency f1, with a quantization level from the most significant bit equal to or less than a first predetermined number of bits b1, a second hierarchical level of encoded data S2 being obtained as a residual signal obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than a second predetermined frequency f2 (f2 ≧
f1), with a quantization level from the most significant bit equal to or less than a second predetermined number of bits b2 (b2 ≧
b1), and subtracting out the transformation coefficients of the first hierarchical level, andan n-th hierarchical level of encoded data Sn being obtained as a residual signal obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than an nth predetermined frequency fn (fn ≧
fn-1), with a quantization level from the most significant bit equal to or less than an nth predetermined number of bits bn (bn ≧
bn-1), and subtracting out the transformation coefficients of each of the first hierarchical level to the (n-1)-th hierarchical level, wherein n is an integer. - View Dependent Claims (4, 5, 6)
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7. A hierarchical decoder, comprising:
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a decoding means, receiving input audio data hierarchically encoded with hierarchical priorities based on characteristics from a psycho-acoustic curve and receiving an identification code identifying a hierarchical priority level of the encoded audio data, for decoding said hierarchically encoded audio data responsive to a hierarchical level thereof, determined based on said received identification code, to produce transformation coefficients corresponding to frequency bands; and an inverse frequency transform means for performing an inverse frequency transformation on the produced transformation coefficients to thereby produce an original digital audio signal.
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8. A hierarchical decoder, comprising:
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a decoding means, receiving input audio data hierarchically encoded with hierarchial priorities based on human auditory characteristics and receiving an identification code identifying a hierarchical priority level of the encoded audio data, for decoding said hierarchically encoded audio data responsive to a hierarchical level thereof, determined based on said received identification code, to produce transformation coefficients corresponding to frequency bands; and an inverse frequency transform means for performing an inverse frequency transformation on the produced transformation coefficients to thereby produce an original digital audio signal, wherein said hierarchically encoded audio data is data which has been previously divided into hierarchical levels and quantized such that, a first hierarchical level of encoded data S1 is obtained by selecting, from among the transformation coefficients of audible signal components extracted according to human psycho-acoustic characteristics, transformation coefficients of frequency bands equal to or less than a first predetermined frequency f1, including a quantization level from the most significant bit equal to or less than a first predetermined number of bits b1, a second hierarchical level of encoded data S2 is obtained as a residual signal obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than a second predetermined frequency f2 (f2 ≧
f1) including a quantization level from the most significant bit equal to or less than a second predetermined number of bits b2 (b2 ≧
b1), and subtracting out the transformation coefficients of the first hierarchical level, andan n-th hierarchical level of encoded data Sn is obtained as a residual signal obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than an n-th predetermined frequency fn (fn ≧
fn-1), including a quantization level from the most significant bit equal to or less than an nth predetermined number of bits bn (bn ≧
bn-1), and subtracting out the transformation coefficients of each of the first hierarchical level to the (n-1)-th hierarchical level, wherein n is an integer. - View Dependent Claims (9, 10, 11, 12)
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13. A hierarchical encoder, comprising:
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frequency transformation means for transforming an input digital audio signal into transformation coefficients for a plurality of frequency bands; and hierarchical dividing and quantizing means for extracting audible signal components from the transformation coefficients based on psycho-acoustic characteristics, for dividing the audible signal components into hierarchical levels, and for quantizing the audible signal components to produce encoded data divided into a plurality of hierarchical levels, a first hierarchical level of encoded data S1 being obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than a first predetermined frequency f1, with a quantization level from the most significant bit equal to or less than a first predetermined number of bits b1, and an n-th hierarchical level of encoded data Sn being obtained as a residual signal obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than an nth predetermined frequency fn (fn ≧
fn-1), with a quantization level from the most significant bit equal to or less than an nth predetermined number of bits bn (bn ≧
bn-1), and subtracting out the transformation coefficients of each of the first hierarchical level to the (n-1)-th hierarchical level, wherein n is an integer. - View Dependent Claims (14, 15, 16)
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17. A hierarchical decoder, comprising:
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a decoding means, receiving input audio data hierarchically encoded with hierarchial priorities based on human auditory characteristics and receiving an identification code identifying a hierarchical priority level of the encoded audio data, for decoding said hierarchically encoded audio data responsive to a hierarchical level thereof, determined based on said received identification code, to produce transformation coefficients corresponding to frequency bands; and an inverse frequency transform means for performing an inverse frequency transformation on the produced transformation coefficients to thereby produce an original digital audio signal, wherein said hierarchically encoded audio data is data which has been previously divided into hierarchical levels and quantized such that, a first hierarchical level of encoded data S1 is obtained by selecting, from among the transformation coefficients of audible signal components extracted according to human psycho-acoustic characteristics, transformation coefficients of frequency bands equal to or less than a first predetermined frequency f1, including a quantization level from the most significant bit equal to or less than a first predetermined number of bits b1, and an n-th hierarchical level of encoded data Sn is obtained as a residual signal obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than an n-th predetermined frequency fn (fn ≧
fn-1), including a quantization level from the most significant bit equal to or less than an nth predetermined number of bits bn (bn ≧
bn-1) and subtracting out the transformation coefficients of each of the first hierarchical level to the (n-1)-th hierarchical level, wherein n is an integer. - View Dependent Claims (18, 19)
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20. A hierarchical encoder, comprising:
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frequency transformation means for transforming an input digital audio signal into transformation coefficients for a plurality of frequency bands; and hierarchical dividing means for extracting audible signal components from the transformation coefficients based on psycho-acoustic characteristics and for dividing the audible signal components into hierarchical levels, a first hierarchical level of encoded data S1 being obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than a first predetermined frequency f1, a second hierarchical level of encoded data S2 being obtained as a residual signal obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than a second predetermined frequency f2 (f2 ≧
f1), and subtracting out the transformation coefficients of the first hierarchical level, andan n-th hierarchical level of encoded data Sn being obtained as a residual signal obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than an nth predetermined frequency fn (fn ≧
fn-1), and subtracting out the transformation coefficients of each of the first hierarchical level to the (n-1)-th hierarchical level, wherein n is an integer. - View Dependent Claims (21, 22, 23)
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24. A hierarchical decoder, comprising:
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a decoding means, receiving input audio data hierarchically encoded with hierarchial priorities based on human auditory characteristics and receiving an identification code identifying a hierarchical priority level of the encoded audio data, for decoding said hierarchically encoded audio data responsive to a hierarchical level thereof, determined based on said received identification code, to produce transformation coefficients corresponding to frequency bands; and an inverse frequency transform means for performing an inverse frequency transformation on the produced transformation coefficients to thereby produce an original digital audio signal, wherein said hierarchically encoded audio data is data which has been previously divided into hierarchical levels such that, a first hierarchical level of encoded data S1 is obtained by selecting, from among the transformation coefficients of audible signal components extracted according to human psycho-acoustic characteristics, transformation coefficients of frequency bands equal to or less than a first predetermined frequency f1, a second hierarchical level of encoded data S2 is obtained as a residual signal obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than a second predetermined frequency f2 (f2 ≧
f1), and subtracting out the transformation coefficients of the first hierarchical level, andan n-th hierarchical level of encoded data Sn is obtained as a residual signal obtained by selecting, from among the transformation coefficients of said extracted audible signal components, transformation coefficients of frequency bands equal to or less than an n-th predetermined frequency fn (fn ≧
fn-1), and subtracting out the transformation coefficients of each of the first hierarchical level to the (n-1)-th hierarchical level, wherein n is an integer.
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Specification