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US5625743A
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Determining a masking level for a subband in a subband audio encoder
Assignee: Motorola Solutions Inc
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Filing: 1994-10-07
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Granted: 1997-04-29
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Expires: 2014-10-07
Abstract
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).
Inventors
- 👤 James L. Fiocca
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 09:03
CPC Classifications
G; G10; G10L; G10L19/00; G10L19/02; G10L19/0204; G10L19/0208; G10L25/00; G10L25/03; G10L25/18
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
151 words
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: of(sb)=0.5*LTq(sb)-0.225*z(sb)+C where C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb.
Claim 2
Independent Claim
151 words
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: of(sb)=0.5*LTq(sb)-0.225*z(sb)+C where C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb.
Claim 3
Dependent Claim
16 words
The method of claim 1, wherein the audio frame is a pulse code modulated audio signal.
Claim 4
Dependent Claim
54 words
The method of claim 1, wherein step A) further comprises the steps of: A) frequency transforming the audio frame using a filter bank to produce at least a first subband sample for each subband; and B) determining the signal level for each subband based on at least the first subband sample for each subband.
Claim 5
Dependent Claim
46 words
The method of claim 3, wherein step B) utilizes an equation of a form: ##EQU10## where sb is a subband number, s is a subband sample number, S(sb,s) is the subband sample s of subband sb, and nsamp is a number of subband samples per subband.
Claim 6
Dependent Claim
69 words
The method of claim 1, wherein step A) further comprises the steps of: A) frequency transforming the audio frame using a high resolution frequency transformer to produce at least a first frequency domain output for each subband; B) defining the signal level for each subband as one of: B1) the minimum; B2) the maximum; and B3) the average of at least the first frequency domain output for each subband.
Claim 7
Dependent Claim
17 words
The method of claim 5, wherein in the high resolution frequency transformer utilizes a Discrete Fourier Transform.
Claim 8
Dependent Claim
122 words
The method of claim 1, wherein step B) further comprises the steps of: A) determining, from a look-up table, the weighting function for each subband, which satisfies a predetermined distance requirement, relative to the particular subband; B) determining, from a look-up table, an antilog of the signal level for each subband; C) multiplying the weighting function by the antilog of the signal level for each subband to produce a plurality of products; D) accumulating the plurality of products to produce a final sum; E) determining a logarithm of the final sum; F) determining, from a look-up table, the offset function for the particular subband; and G) adding the logarithm of the final sum to the offset function to produce the masking level.
Claim 9
Dependent Claim
17 words
The method of claim 1, wherein the weighting function is a gain factor times a masking curve.
Claim 10
Dependent Claim
23 words
The method of claim 8, wherein the masking curve is non-linear with one of: A) a convex geometry; and B) a concave geometry.
Claim 11
Dependent Claim
31 words
The method of claim 9, wherein the masking curve is one of: A) an exponential function; B) a cube root function; C) a square root function; and D) a square function.
Claim 12
Independent Claim
160 words
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: 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: of(sb)=0.5*LTq(sb)-0.225*z(sb)+C where C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb.
Claim 13
Independent Claim
160 words
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: 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: of(sb)=0.5*LTq(sb)-0.225*z(sb)+C where C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb.
Claim 14
Dependent Claim
15 words
The device of claim 11, wherein the audio frame is a pulse code modulated signal.
Claim 15
Dependent Claim
70 words
The device of claim 11, wherein the signal level determiner further comprises: A) a filter bank for frequency transforming the audio frame to produce at least a first subband sample for each subband; and B) a subband sample signal level determiner, operably coupled to the filter bank, for determining the signal level for each of the plurality of subbands based on at least the first subband sample for each subband.
Claim 16
Dependent Claim
85 words
The device of claim 11, wherein the signal level determiner further comprises: A) a high resolution frequency transformer, for frequency transforming the audio frame to produce at least a first frequency domain output for each subband: B) a frequency domain signal level determiner, operably coupled to the frequency transformer, for defining the signal level for each subband as one of: B1) the minimum; B2) the maximum; and B3) the average of at least the first frequency domain output for each of the plurality of subbands.
Claim 17
Dependent Claim
17 words
The device of claim 14, wherein in the high resolution frequency transformer utilizes a Discrete Fourier Transform.
Claim 18
Dependent Claim
28 words
The device of claim 11, wherein the device further comprises a memory unit for storing the offset function and the weighting function for each of the plurality subbands.
Claim 19
Independent Claim
282 words
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: 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: of(sb)=0.5*LTq(sb)-0.225*z(sb)+C where C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb.
Claim 20
Independent Claim
282 words
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: 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: of(sb)=0.5*LTq(sb)-0.225*z(sb)+C where C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb.
Claim 21
Independent Claim
289 words
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: 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: of(sb)=0.5*LTq(sb)-0.225*z(sb)+C where C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb.
Claim 22
Independent Claim
289 words
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: 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: of(sb)=0.5*LTq(sb)-0.225*z(sb)+C where C is a constant, LTq(sb) is the threshold in quiet of subband sb, and z(sb) is the bark value of subband sb.
References Cited (Backward Citations)
US5179623A
Cited
US5109417A
Cited
US5222189A
Cited
US5357594A
Cited
US5185800A
Cited
US5394473A
Cited
US5285498A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-04-28 | 2000-10-28 | 2001-04-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-04-28 | 2004-10-28 | 2005-04-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-04-28 | 2008-10-28 | 2009-04-29 | $7700.00 | Window Closed / Lapsed |