Determining a masking level for a subband in a subband audio encoder
First Claim
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1. A method for determining a masking level for a particular subband in a subband audio encoder, wherein the subband audio encoder divides an audio frame into a plurality of subbands, the method comprising the steps of:
- A) receiving the audio frame and determining, by a signal level determiner, a signal level for each subband to produce a plurality of signal levels; and
B) calculating, by a masking level determiner, the masking level for the particular subband, based on the plurality of signal levels, an offset function, and a weighting function,wherein the offset function for each subband is a function of a threshold in quiet for the subband and a bark value for the subband,wherein the offset function is determined utilizing an equation of a form;
space="preserve" listing-type="equation">of(sb)=0.5*LTq(sb)-0.225*z(sb)+Cwhere C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb.
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Abstract
The first step for calculating a signal-to-mask ratio (806) for a subband in a subband in a subband audio encoder is calculating a signal level for each of the subbands based on an audio frame (604). Then, the masking level is calculated for the particular subband based on the signal levels, an offset function, and a weighting function (606).
56 Citations
18 Claims
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1. A method for determining a masking level for a particular subband in a subband audio encoder, wherein the subband audio encoder divides an audio frame into a plurality of subbands, the method comprising the steps of:
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A) receiving the audio frame and determining, by a signal level determiner, a signal level for each subband to produce a plurality of signal levels; and B) calculating, by a masking level determiner, the masking level for the particular subband, based on the plurality of signal levels, an offset function, and a weighting function, wherein the offset function for each subband is a function of a threshold in quiet for the subband and a bark value for the subband, wherein the offset function is determined utilizing an equation of a form;
space="preserve" listing-type="equation">of(sb)=0.5*LTq(sb)-0.225*z(sb)+Cwhere C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A device for determining a masking level for a particular subband in a subband audio encoder, wherein the subband audio encoder divides an audio frame into a plurality of subbands, the device comprising:
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A) a signal level determiner for determining a signal level for each of the plurality of subbands, based on the audio frame, to produce a plurality of signal levels; and B) a masking level determiner, operably coupled to the signal level determiner, for calculating the masking level for the particular subband, based on the plurality of signal levels, an offset function, and a weighting function, wherein the offset function for each subband is a function of a threshold in quiet for the subband and a bark value for the subband, and wherein the offset function is determined utilizing an equation of a form;
space="preserve" listing-type="equation">of(sb)=0.5*LTq(sb)-0.225*z(sb)+Cwhere C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A system having a device for determining a masking level for a subband in a subband audio encoder, wherein the subband audio encoder divides an audio frame into a plurality of subbands, the system comprises:
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A) a filter bank for receiving and transforming the audio frame to produce frequency transformed audio; B) a psychoacoustic unit for receiving the audio frame to produce a signal-to-mask ratio, wherein the psychoacoustic unit further comprises; B1) a signal level determiner for determining a signal level for each subband, based on the audio frame, to produce a plurality of signal levels; B2) a masking level determiner, operably coupled to the signal level determiner, for calculating the masking level for the subband, based on the plurality of signal levels, an offset function, and a weighting function; and B3) a signal-to-mask ratio calculator, for calculating a signal-to-mask ratio based on the masking level; C) a bit allocation element, operably coupled to the psychoacoustic unit, for using the signal-to-mask ratio to generate bit allocation information; D) a quantizer, operably coupled to the filter bank and the bit allocation element, for producing a compressed audio frame based on the frequency transformed audio and the bit allocation information; E) a bit stream formatter, operably coupled to the quantizer, for using the compressed audio frame to generate a bit stream output, wherein the offset function for each subband is a function of a threshold in quiet for the subband and a bark value for the subband, and wherein the offset function is determined utilizing an equation of a form;
space="preserve" listing-type="equation">of(sb)=0.5*LTq(sb)-0.225*z(sb)+Cwhere C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb.
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18. A system having a device for determining a masking level for a subband in a subband audio encoder, wherein the subband audio encoder divides an audio frame into a plurality of subbands, the system comprises:
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A) a filter bank for receiving and transforming the audio frame to produce frequency transformed audio; B) a simplified psychoacoustic unit, operably coupled to the filter bank, wherein the simplified psychoacoustic unit further comprises; B1) a subband sample signal level determiner, operably coupled to the filter bank, for determining a signal level for each subband, based on the frequency transformed audio, to produce a plurality of signal levels; B2) a masking level determiner, operably coupled to the signal level determiner, for calculating the masking level for the subband, based on the plurality of signal levels, an offset function, and a weighting function; and B3) a signal-to-mask ratio calculator, for calculating a signal-to-mask ratio based on the masking level; C) a bit allocation element, operably coupled to the psychoacoustic unit, for using the signal-to-mask ratio to generate bit allocation information; D) a quantizer, operably coupled to the filter bank and the bit allocation element, for producing a compressed audio frame based on the frequency transformed audio and the bit allocation information; E) a bit stream formatter, operably coupled to the quantizer, for using the compressed audio frame to generate a bit stream output, wherein the offset function for each subband is a function of a threshold in quiet for the subband and a bark value for the subband, and wherein the offset function is determined utilizing an equation of a form;
space="preserve" listing-type="equation">of(sb)=0.5*LTq(sb)-0.225*z(sb)+Cwhere C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb.
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Specification