Patent US5627938A successfully refreshed from Google Patents.
US5627938A
Expired / Lapsed
US
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Rate loop processor for perceptual encoder/decoder
Assignee: Nokia of America Corp
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Filing: 1994-09-22
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Granted: 1997-05-06
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Expires: 2014-09-22
Abstract
Abstract A method and apparatus for quantizing audio signals is disclosed which advantageously produces a quantized audio signal which can be encoded within an acceptable range. Advantageously, the quantizer uses a scale factor which is interpolated between a threshold based on the calculated threshold of hearing at a given frequency and the absolute threshold of hearing at the same frequency.
Inventors
- 👤 James D. Johnston
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 03:44
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/10; H; H04; H04B; H04B1/00; H04B1/66; H04B1/665
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
112 words
A method of coding an audio signal comprising: (a) converting a time domain representation of the audio signal into a frequency domain representation of the audio signal, the frequency domain representation comprising a set of frequency coefficients; (b) calculating a masking threshold based upon the set of frequency coefficients; (c) using a rate loop processor in an iterative fashion to determine a set of quantization step size coefficients for use in encoding the set of frequency coefficients, said set of quantization step size coefficients determined by using the masking threshold and an absolute hearing threshold; and (d) coding the set of frequency coefficients based upon the set of quantization step size coefficients.
Claim 2
Independent Claim
112 words
A method of coding an audio signal comprising: (a) converting a time domain representation of the audio signal into a frequency domain representation of the audio signal, the frequency domain representation comprising a set of frequency coefficients; (b) calculating a masking threshold based upon the set of frequency coefficients; (c) using a rate loop processor in an iterative fashion to determine a set of quantization step size coefficients for use in encoding the set of frequency coefficients, said set of quantization step size coefficients determined by using the masking threshold and an absolute hearing threshold; and (d) coding the set of frequency coefficients based upon the set of quantization step size coefficients.
Claim 3
Dependent Claim
14 words
The method of claim 1 wherein the set of frequency coefficients are MDCT coefficients.
Claim 4
Dependent Claim
40 words
The method of claim 1 wherein the using the rate loop processor in the iterative fashion is discontinued when a cost, measured by the number of bits necessary to code the set of frequency coefficients, is within a predetermined range.
Claim 5
Dependent Claim
146 words
A decoder for decoding a set of frequency coefficients representing an audio signal, the decoder comprising: (a) means for receiving the set of coefficients, the set of frequency coefficients having been encoded by: (1) converting a time domain representation of the audio signal into a frequency domain representation of the audio signal comprising the set of frequency coefficients; (2) calculating a masking threshold based upon the set of frequency coefficients; (3) using a rate loop processor in an iterative fashion to determine a set of quantization step size coefficients needed to encode the set of frequency coefficients, said set of quantization step size coefficients determined by using the masking threshold and an absolute hearing threshold; and (4) coding the set of frequency coefficients based upon the set of quantization step size coefficients; and (b) means for converting the set of coefficients to a time domain signal.
Claim 6
Dependent Claim
146 words
A decoder for decoding a set of frequency coefficients representing an audio signal, the decoder comprising: (a) means for receiving the set of coefficients, the set of frequency coefficients having been encoded by: (1) converting a time domain representation of the audio signal into a frequency domain representation of the audio signal comprising the set of frequency coefficients; (2) calculating a masking threshold based upon the set of frequency coefficients; (3) using a rate loop processor in an iterative fashion to determine a set of quantization step size coefficients needed to encode the set of frequency coefficients, said set of quantization step size coefficients determined by using the masking threshold and an absolute hearing threshold; and (4) coding the set of frequency coefficients based upon the set of quantization step size coefficients; and (b) means for converting the set of coefficients to a time domain signal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-05-05 | 2000-11-04 | 2001-05-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-05-05 | 2004-11-04 | 2005-05-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-05-05 | 2008-11-04 | 2009-05-06 | $7700.00 | Window Closed / Lapsed |