Bit allocation method and device for digital audio signals using aural characteristics and signal intensities
First Claim
1. A bit allocation method for use in digital audio signal compression in which a digital audio signal is divided into frames at a predetermined time interval and each of the frames is divided into plural frequency bands to form a set of blocks so as to divide the digital audio signal in both time and frequency, and in which compression is performed using a bit allocation number determined for each of the blocks, the method comprising steps of:
- dividing a total number of bits into at least two portions for bit allocation among the blocks in the set, the portions including a first portion and a second portion, each of the portions including at least one of the total number of bits;
allocating the bits of the first portion among the blocks dependent upon an allowable noise spectrum based on aural characteristics;
calculating respective signal intensities for the blocks;
allocating the bits of the second portion among the blocks dependent upon the respective signal intensities calculated in the calculating step; and
combining the bits of the two portions together for each one of the blocks to determine the bit allocation number for the one of the blocks.
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Accused Products
Abstract
A method for compression encoding of digital speech signals in which the digital speech signals are divided at a predetermined time interval into plural frequency bands so as to be sub-divided along both the time scale and the frequency scale to form plural sub-blocks, and data encoding is performed using an allocation bit number determined for each of said sub-blocks. The total number of bits that may be used for bit allocation is divided into at least two portions, with the bits of one of these portions being allocated in dependence upon the allowable noise level based on aural characteristics and with the bits of the remaining portion being allocated in dependence upon the intensities of signals in each sub-block. The number of bits allocated to each of the small-sized sub-blocks are determined by the sum of the bits of the two portions. In addition to the total number of bits that may be used for bit allocation, a number of bits is also set for the subsidiary information at least including the floating information and the bit length information. The aural characteristics are combined from at least the masking threshold and the minimum audibility curve and corrected by the equal-loudness curve.
37 Citations
19 Claims
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1. A bit allocation method for use in digital audio signal compression in which a digital audio signal is divided into frames at a predetermined time interval and each of the frames is divided into plural frequency bands to form a set of blocks so as to divide the digital audio signal in both time and frequency, and in which compression is performed using a bit allocation number determined for each of the blocks, the method comprising steps of:
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dividing a total number of bits into at least two portions for bit allocation among the blocks in the set, the portions including a first portion and a second portion, each of the portions including at least one of the total number of bits; allocating the bits of the first portion among the blocks dependent upon an allowable noise spectrum based on aural characteristics; calculating respective signal intensities for the blocks; allocating the bits of the second portion among the blocks dependent upon the respective signal intensities calculated in the calculating step; and combining the bits of the two portions together for each one of the blocks to determine the bit allocation number for the one of the blocks. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of recording a digital audio signal as a compressed signal on a recording medium, the method comprising steps of:
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dividing the digital audio signal into frames at a predetermined time interval; dividing each of the frames into plural frequency bands to form a set of blocks; generating the compressed signal by re-quantizing the blocks using bit allocation number determined for each of the blocks, the bit allocation number being determined by steps of; providing a total number of bits that may be used for requantizing the set of blocks, dividing the total number of bits into at least two portions for allocation among the blocks, the portions including a first portion and a second portion, each of the portions including at least one of the total number of bits, allocating the bits of the first portion among the blocks dependent upon an allowable noise spectrum based on aural characteristics, calculating respective signal intensities for the blocks, allocating the bits of the second portion dependent upon the respective signal intensities calculated in the calculating step, and combining the bits of the two portions together for each one of the blocks to determine the bit allocation number for each one of the blocks; and recording the compressed signal on the recording medium. - View Dependent Claims (9, 10)
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11. A bit allocation encoder for use in digital audio signal compression in which the digital audio signal is divided into frames at a predetermined time interval, and each of the frames is divided into plural frequency bands to form a set of blocks so as to divide the digital audio signal in both time and frequency, and in which compression is performed using a bit allocation number determined for each of the blocks, the apparatus comprising:
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means for dividing a total number of bits into at least two portions for bit allocation among the blocks in the set, the portions including a first portion and a second portion, each of the portions including at least one of the total number of bits; means for allocating the bits of the first portion among the blocks dependent upon an allowable noise spectrum based on aural characteristics; means for calculating respective signal intensities for the blocks; means for allocating the bits of the second portion dependent upon the respective signal intensities calculated by the calculating means; and means for combining the bits of the two portions together for each one of the blocks to determine the bit allocation number for the one of the blocks. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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Specification