Method for encoding audio signals

Claim 1

A method of encoding an audio signal comprising the steps of: sampling a time-domain audio signal; converting said sampled audio signal into a frequency-domain signal divided into a plurality of critical bands; allocating to each critical band the number of quantization bits allowing the NMR (noise-to-mask ratio) for the corresponding critical band to be minimum; quantizing a frequency-domain-signal by the allocated number of quantization bits; wherein in said bit allocating step, quantization bits are allocated according to the weight of critical bands in the order from the critical band having the highest frequency to the one having the lowest frequency and the number of quantization bits allocated to an arbitrary critical band is determined by the weight of said critical band among the critical bands which are equal to or below said critical band.

Claim 2

A method of encoding an audio signal comprising the steps of: sampling a time-domain audio signal; converting said sampled audio signal into a frequency-domain signal divided into a plurality of critical bands; allocating to each critical band the number of quantization bits allowing the NMR (noise-to-mask ratio) for the corresponding critical band to be minimum; quantizing a frequency-domain-signal by the allocated number of quantization bits; wherein in said bit allocating step, quantization bits are allocated according to the weight of critical bands in the order from the critical band having the highest frequency to the one having the lowest frequency and the number of quantization bits allocated to an arbitrary critical band is determined by the weight of said critical band among the critical bands which are equal to or below said critical band.

Claim 4

A method of encoding an audio signal comprising the steps of: sampling a time-domain audio signal; converting said sampled audio signal into a frequency-domain signal divided into a plurality of critical bands; allocating to each critical band the number of quantization bits allowing the noise-to-mask ratio ("NMR") for the corresponding critical band to be minimum and according to the weight of critical bands in the order from the critical band having the highest frequency to the one having the lowest frequency, wherein the number of quantization bits allocated to an arbitrary critical band is determined by the following formula, in consideration of the magnitude of signal-to-masking threshold ratio (SMR) of said arbitrary critical band among the critical bands which are equal to or below said arbitrary critical band: ##EQU2## where BIT i is the number of quantization bits allocated to an arbitrary critical band, BIT total is the number of quantization bits which can be allocated to the critical bands which are equal to or below said arbitrary critical band, SMR i is the SMR of said arbitrary critical band, SMR min is the minimum SMR among SMRs of the critical bands which are equal to or below said arbitrary critical band, and SMR total is the total of SMRs of the critical bands which are equal to or below said arbitrary critical band, and N is the number of bands; and quantizing a frequency-domain-signal by the allocated number of quantization bits.

Claim 5

A method of encoding an audio signal comprising the steps of: sampling a time-domain audio signal; converting said sampled audio signal into a frequency-domain signal divided into a plurality of critical bands; allocating to each critical band the number of quantization bits allowing the noise-to-mask ratio ("NMR") for the corresponding critical band to be minimum and according to the weight of critical bands in the order from the critical band having the highest frequency to the one having the lowest frequency, wherein the number of quantization bits allocated to an arbitrary critical band is determined by the following formula, in consideration of the magnitude of signal-to-masking threshold ratio (SMR) of said arbitrary critical band among the critical bands which are equal to or below said arbitrary critical band: ##EQU2## where BIT i is the number of quantization bits allocated to an arbitrary critical band, BIT total is the number of quantization bits which can be allocated to the critical bands which are equal to or below said arbitrary critical band, SMR i is the SMR of said arbitrary critical band, SMR min is the minimum SMR among SMRs of the critical bands which are equal to or below said arbitrary critical band, and SMR total is the total of SMRs of the critical bands which are equal to or below said arbitrary critical band, and N is the number of bands; and quantizing a frequency-domain-signal by the allocated number of quantization bits.

Claim 6

A method of encoding an audio signal comprising the steps of: sampling a time-domain audio signal; converting said sampled audio signal into a frequency-domain signal divided into a plurality of critical bands; allocating to each critical band the number of quantization bits allowing the NMR for the corresponding critical band to be minimum; quantizing a frequency-domain-signal by the allocated number of quantization bits; wherein in said bit allocating step, quantization bits are allocated according to the weight of critical bands in the order from the critical band having the highest frequency to the one having the lowest frequency and the number of quantization bits allocated to an arbitrary critical band is compared with the new number of needed bits (NEEDBIT new ) determined by the below formula, the number of quantization bits is allocated to the corresponding critical band if said quantization bit number is greater than or equal to the new number of needed bits, and the number of quantization bits is not allocated to the corresponding critical band if said quantization bit number is smaller than the new number of needed bits: NEEDBIT.sub.new =W.sub.i ×NEEDBIT=W.sub.i (S+BIT.sub.min) where W i is a characteristic weight of each critical band, NEEDBIT is the used number of needed bits, S is the scalefactor, and BIT min is the minimum number of bits used for quantization.

Claim 7

A method of encoding an audio signal comprising the steps of: sampling a time-domain audio signal; converting said sampled audio signal into a frequency-domain signal divided into a plurality of critical bands; allocating to each critical band the number of quantization bits allowing the NMR for the corresponding critical band to be minimum; quantizing a frequency-domain-signal by the allocated number of quantization bits; wherein in said bit allocating step, quantization bits are allocated according to the weight of critical bands in the order from the critical band having the highest frequency to the one having the lowest frequency and the number of quantization bits allocated to an arbitrary critical band is compared with the new number of needed bits (NEEDBIT new ) determined by the below formula, the number of quantization bits is allocated to the corresponding critical band if said quantization bit number is greater than or equal to the new number of needed bits, and the number of quantization bits is not allocated to the corresponding critical band if said quantization bit number is smaller than the new number of needed bits: NEEDBIT.sub.new =W.sub.i ×NEEDBIT=W.sub.i (S+BIT.sub.min) where W i is a characteristic weight of each critical band, NEEDBIT is the used number of needed bits, S is the scalefactor, and BIT min is the minimum number of bits used for quantization.