Digital audio signal coding method through allocation of quantization bits to sub-band samples split from the audio signal

Claim 2

A digital audio signal coding method for reducing the number of quantization bits allocated to each sample of each of a plurality of sub-band signals in order to code the samples, said method comprising the steps of: splitting a digital audio signal into said plurality of sub-band signals each being sampled and each having a specified frequency; calculating a level for each of said plurality of sub-band signals; calculating a logarithm value of the level of each sub-band signal; calculating an index by multiplying the logarithm value of the level by a weight which is dependent on the level and by weight which is dependent on the specified frequency allocated to each sub-band; and determining the number of quantization bits to be used for each sample according to the calculated index and a prescribed coding bit rate permitted to the entire band for coding the sub-band signals.

Claim 3

The method as claimed in claim 1, wherein a masking threshold level is applied from one sub-band signal to an adjacent sub-band signal, and when the level of the adjacent sub-band signal is lower than the masking threshold level applied from the one sub-band signal, the level of the adjacent sub-band signal is set to zero.

Claim 4

The method as claimed in claim 2, wherein, when the level of a sub-band signal is below a threshold of audibility of the sub-band, the level of the sub-band signal is set to zero.

Claim 5

The method as claimed in claim 2, wherein the level of each sub-band signal used for controlling the number of quantization bits allocated to each sub-band is determined according to a peak value in the sub-band in a prescribed time period.

Claim 6

The method as claimed in claim 1, wherein when the level of a sub-band signal is below a threshold of audibility of the sub-band, the level of the sub-band signal is set to zero.

Claim 7

The method as claimed in claim 5, wherein, even when the levels of all the sub-band signals are below the threshold of audibility, quantization bits are allocated to a plurality of continuous sub-bands including the sub-band having the highest level and the sub-bands adjacent to the sub-band with the highest level so to effectively use the prescribed coding bit rate.

Claim 8

The method as claimed in claim 6, wherein the level of each sub-band signal used for controlling the number of quantization bits allocated to each sub-band is determined according to a peak value in the sub-band in a prescribed time period.

Claim 9

The method as claimed in claim 5, wherein the level of each sub-band signal used for controlling the number of quantization bits allocated to each sub-band is determined according to a peak value in the sub-band in a prescribed time period.

Claim 10

A digital audio signal coding system comprising: splitting means for splitting a digital audio signal into a plurality of sub-band signals each being sampled and each having a specified frequency; and quantization bit number control means for controlling a number of quantization bits allocated to each sample of each of the sub-band signals in order to code the samples, wherein said quantization bit number control means further comprises: level calculating means for obtaining the level for each sub-band signal; logarithm calculating means for obtaining a logarithm of the level of each sub-band calculated by said level calculating means; and index calculating means for obtaining an index by multiplying the logarithm value of the level of each sub-band signal by a weight which is dependent on the level and by a weight which is dependent on the frequency specified to each sub-band, whereby the number of quantization bits allocated to each sample of the sub-band is determined using said index obtained by said index calculating means and using a prescribed coding bit rate permitted to the entire band for coding the sub-band signals.

Claim 11

A digital audio signal coding system comprising: splitting means for splitting a digital audio signal into a plurality of sub-band signals each being sampled and each having a specified frequency; and quantization bit number control means for controlling a number of quantization bits allocated to each sample of each of the sub-band signals in order to code the samples, wherein said quantization bit number control means further comprises: level calculating means for obtaining the level for each sub-band signal; logarithm calculating means for obtaining a logarithm of the level of each sub-band calculated by said level calculating means; and index calculating means for obtaining an index by multiplying the logarithm value of the level of each sub-band signal by a weight which is dependent on the level and by a weight which is dependent on the frequency specified to each sub-band, whereby the number of quantization bits allocated to each sample of the sub-band is determined using said index obtained by said index calculating means and using a prescribed coding bit rate permitted to the entire band for coding the sub-band signals.

Claim 12

A digital audio signal coding method for reducing the number of quantization bits allocated to each sample of each of a plurality of sub-band signals in order to code the samples, said method comprising the steps of: splitting a digital audio signal into said plurality of sub-band signals each being sampled and each having a specified frequency; calculating a level for each of said plurality of sub-band signals; calculating a logarithm value of the level of each sub-band signal; calculating an index by multiplying the logarithm value of the level by a weight which is dependent on the level and by a weight which is dependent on the specified frequency allocated to each sub-band; and determining the number of quantization bits to be used for each sample according to the calculated index and a prescribed coding bit rate permitted to the entire band for coding the sub-band signals, wherein the number of quantization bits allocated to each sub-band is controlled according to a ratio of an index of each sub-band to the sum of indexes of the plurality of sub-bands to which quantization bits are to be allocated.

Claim 13

A digital audio signal coding method for reducing the number of quantization bits allocated to each sample of each of a plurality of sub-band signals in order to code the samples, said method comprising the steps of: splitting a digital audio signal into said plurality of sub-band signals each being sampled and each having a specified frequency; calculating a level for each of said plurality of sub-band signals; calculating a logarithm value of the level of each sub-band signal; calculating an index by multiplying the logarithm value of the level by a weight which is dependent on the level and by a weight which is dependent on the specified frequency allocated to each sub-band; and determining the number of quantization bits to be used for each sample according to the calculated index and a prescribed coding bit rate permitted to the entire band for coding the sub-band signals, wherein the number of quantization bits allocated to each sub-band is controlled according to a ratio of an index of each sub-band to the sum of indexes of the plurality of sub-bands to which quantization bits are to be allocated.

Claim 14

The method as claimed in claim 10, wherein a masking threshold level is applied from one sub-band signal to an adjacent sub-band signal, and when the level of the adjacent sub-band signal is lower than the masking threshold level applied from the one sub-band signal, the level of the adjacent sub-band signal is set to zero.

Claim 15

The method as claimed in claim 10, wherein, when the level of a sub-band signal is below a threshold of audibility of the sub-band, the level of the sub-band signal is set to zero.

Claim 16

The method as claimed in claim 10, wherein the level of each sub-band signal used for controlling the number of quantization bits allocated to each sub-band is determined according to a peak value in the sub-band in a prescribed time period.

Claim 17

A digital audio signal coding method for reducing the number of quantization bits allocated to each sample of each of a plurality of sub-band signals in order to code the samples, said method comprising the steps of: splitting a digital audio signal into said plurality of sub-band signals each being sampled and each having a specified frequency; calculating a level according to a peak value for each of said plurality of sub-band signals; calculating a logarithm value of the level value of each sub-band signal; calculating an index by multiplying the logarithm value of the level by a weight which is dependent on the level and by a weight which is dependent on the specified frequency allocated to each sub-band; and determining the number of quantization bits to be used for each sample according to the calculated index and a prescribed coding bit rate permitted to the entire band for coding the sub-band signals.

Claim 18

A digital audio signal coding method for reducing the number of quantization bits allocated to each sample of each of a plurality of sub-band signals in order to code the samples, said method comprising the steps of: splitting a digital audio signal into said plurality of sub-band signals each being sampled and each having a specified frequency; calculating a level according to a peak value for each of said plurality of sub-band signals; calculating a logarithm value of the level value of each sub-band signal; calculating an index by multiplying the logarithm value of the level by a weight which is dependent on the level and by a weight which is dependent on the specified frequency allocated to each sub-band; and determining the number of quantization bits to be used for each sample according to the calculated index and a prescribed coding bit rate permitted to the entire band for coding the sub-band signals.