CA2525944A1 - Reciprocal index lookup for btsc compatible coefficients - Google Patents
Reciprocal index lookup for btsc compatible coefficients Download PDFInfo
- Publication number
- CA2525944A1 CA2525944A1 CA002525944A CA2525944A CA2525944A1 CA 2525944 A1 CA2525944 A1 CA 2525944A1 CA 002525944 A CA002525944 A CA 002525944A CA 2525944 A CA2525944 A CA 2525944A CA 2525944 A1 CA2525944 A1 CA 2525944A1
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- CA
- Canada
- Prior art keywords
- signal
- value
- digitally
- reciprocal
- filter coefficient
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000003595 spectral effect Effects 0.000 claims abstract 15
- 230000006835 compression Effects 0.000 claims abstract 2
- 238000007906 compression Methods 0.000 claims abstract 2
- 238000000034 method Methods 0.000 claims 42
- 230000009466 transformation Effects 0.000 claims 8
- 230000005236 sound signal Effects 0.000 claims 6
- 239000002131 composite material Substances 0.000 claims 4
- 230000003750 conditioning effect Effects 0.000 claims 4
- 238000000844 transformation Methods 0.000 claims 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
- H04N5/60—Receiver circuitry for the reception of television signals according to analogue transmission standards for the sound signals
- H04N5/602—Receiver circuitry for the reception of television signals according to analogue transmission standards for the sound signals for digital sound signals
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G7/00—Volume compression or expansion in amplifiers
- H03G7/007—Volume compression or expansion in amplifiers of digital or coded signals
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Compression, Expansion, Code Conversion, And Decoders (AREA)
- Transmission Systems Not Characterized By The Medium Used For Transmission (AREA)
Abstract
An algorithm calculates spectral expansion filter coefficients (712) using a value proportional to a reciprocal (720) of a feedback/feedforward signal (a) and stores the coefficients to a lookup table. The lookup table is indexed by a pre-selected set of coefficient bits to generate a filter coefficient function. A first portion of the lookup table stores a plurality of discrete values at index points of a line segment corresponding to a filter coefficient function approximation, so as to generate an initial discrete value corresponding to the filter coefficient function at a value of the high order bits and a second portion stores a plurality of slope values, which indicates a slope of the filter coefficient function. A linear circuit interpolates/decimates an approximation of the compression/expansion filter coefficient function based on the slope value, the initial discrete value and a preselected set of low order bits of the reciprocal value.
Claims (46)
1. A method for decoding an encoded BTSC composite audio signal comprising:
digitally separating a L-R signal and a L+R signal, both being encoded in the composite signal;
digitally applying deemphasis to the L+R signal;
digitally processing the L-R signal; and combining the de-emphasized L+R signal with the digitally processed L-R signal to produce separate L and R audio signals.
digitally separating a L-R signal and a L+R signal, both being encoded in the composite signal;
digitally applying deemphasis to the L+R signal;
digitally processing the L-R signal; and combining the de-emphasized L+R signal with the digitally processed L-R signal to produce separate L and R audio signals.
2. The method of claim 1 wherein the step of digitally processing includes decimation of the digitally processed L-R signal and the de-emphasized L+R
signal.
signal.
3. The method of claim 1 wherein the step of digitally processing includes computing spectral expansion coefficients and using said coefficients to spectrally expand the L-R signal into a spectrally expanded output signal.
4. The method of claim 3 wherein the coefficients for spectrally expanding the L-R signal are determined based on a band-limited feed-forward compressed L-R
signal.
signal.
5. The method of claim 4 wherein the reciprocal of the RMS value of the feed-forward signal is used to determine the spectral expansion coefficients.
6. The method of claim 5 wherein the coefficients are computed by interpolating between the reciprocal of the RMS value of the feedforward signal and values retrieved from a lookup table, the lookup table indexed by high order bits of the reciprocal of the RMS feedforward signal.
7. A method for decoding an encoded BTSC composite audio signal comprising:
digitally separating a L-R signal, a L+R signal and a SAP signal all being encoded in the composite signal;
digitally applying deemphasis to the L+R signal;
digitally processing the L-R signal;
digitally processing the SAP signal ;and combining the de-emphasized L+R signal with the digitally processed L-R signal to produce separate L and R audio signals.
digitally separating a L-R signal, a L+R signal and a SAP signal all being encoded in the composite signal;
digitally applying deemphasis to the L+R signal;
digitally processing the L-R signal;
digitally processing the SAP signal ;and combining the de-emphasized L+R signal with the digitally processed L-R signal to produce separate L and R audio signals.
8. The method of claim 7 wherein the step of digitally processing includes decimation of the digitally processed L-R signal, the de-emphasized L+R signal and the SAP signal.
9. The method of claim 7 wherein the step of digitally processing includes computing spectral expansion coefficients and using said coefficients to spectrally expand the SAP signal into a spectrally expanded output signal.
10. The method of claim 9 wherein the coefficients for spectrally expanding the SAP signal are determined based on a feedforward signal, which is based on a band-limited compressed L-R signal.
11. The method of claim 10 wherein the reciprocal of the RMS value of the feed-forward signal is used to determine the spectral expansion coefficients.
12. The method of claim 11 wherein the coefficients are computed by interpolating between the reciprocal of the RMS value of the feedforward signal and values retrieved from a lookup table, the lookup table indexed by high order bits of the reciprocal of the RMS feedforward signal.
13. A method for decoding a BTSC signal comprising digitally processing the signal using a digitally modeled ideal analog transfer function at a sample rate corresponding to a predetermined sample rate.
14. The method of claim 13 further comprising decimating the digitally processed signal based on the predetermined sample rate.
15. A method for decoding a digital BTSC-compatible stereo television audio signal to generate a left and right audio output signal comprising:
digitally processing a feedforward portion of the digital BTSC signal at a predetermined sample rate using digitally modeled transfer functions to generate spectral expansion coefficients, the digitally modeled transfer functions being compliant with BTSC standard continuous time transfer functions; and using the spectral expansion coefficients to expand the digital BTSC signal.
digitally processing a feedforward portion of the digital BTSC signal at a predetermined sample rate using digitally modeled transfer functions to generate spectral expansion coefficients, the digitally modeled transfer functions being compliant with BTSC standard continuous time transfer functions; and using the spectral expansion coefficients to expand the digital BTSC signal.
16. The method of claim 15 further comprising:
Adjusting the gain of the expanded digital BTSC signal with the reciprocal of the feedforward portion of the digital signal to form a gain adjusted signal; and decimating the gain adjusted signal at the predetermined sample rate.
Adjusting the gain of the expanded digital BTSC signal with the reciprocal of the feedforward portion of the digital signal to form a gain adjusted signal; and decimating the gain adjusted signal at the predetermined sample rate.
17. The method of claim 15 further comprising using digital modeling techniques to model amplitude and phase characteristics of ideal analog decoder transfer functions.
18. The method of claim 17 wherein the digitally modeled amplitude and phase characteristics do riot provide phase compensation for non-idealities.
19. The method of claim 17 wherein the step of digital processing includes digitally modeling a BTSC standard variable spectral expansion continuous time update transfer function.
20. The method of claim 17 wherein the step of digitally processing includes digitally modeling a BTSC standard gain control continuous time update algorithm.
21. The method of claim 17 wherein the step of digitally processing is accomplished using bilinear transformation of analog transfer functions.
22. The method of claim 17 wherein the step of digitally processing includes using an impulse invariance transformation of analog transfer functions.
23. The method of claim 17 wherein the step of digitally processing includes using a digital variable expansion filter controlled by a variable expansion feedforward loop modeled using bilinear transformations of analog transfer functions.
24. The method of claim 17 wherein the step of digitally processing includes using a digital variable expansion filter controlled by a variable expansion feedforward loop modeled using impulse invariance transformation of analog transfer functions.
25. The method of claim 17 wherein the step of digitally processing includes using a digital wideband feedforward gain control bandpass filter modeled using bilinear transformation of analog transfer functions.
26. The method of claim 17 wherein the step of digitally processing includes using a digital wideband feedforward gain control bandpass alter modeled using impulse invariance transformation of analog transfer functions.
27. The method of claim 17 wherein the step of digitally processing includes using a digital wideband feedforward RMS detector.
28. The method of claim 17 wherein the step of digitally processing includes using a digital wideband feedback 1/x function.
29. The method of claim 17 wherein the step of digitally processing includes processing the signal using a digital variable expansion feedforward bandpass filter modeled using the bilinear transformation of analog transfer functions.
30. The method of claim 17 wherein the step of digitally processing includes processing the signal using a digital variable expansion feedforward bandpass filter modeled using the impulse invariance transformation of analog transfer functions.
31. The method of claim 17 wherein the step of digitally processing includes processing the signal using a digital variable expansion feedforward rms detector.
32. The method of claim 17 wherein the method is performed using a digital signal processor.
33. The method of claim 17 wherein the method is performed using an application specific integrated circuit.
34. The method of claim 17 wherein the method is performed using a field programmable gate array.
35. A system for decoding a digital BTSC-compatible stereo television audio signal to generate a left and right audio output signal comprising:
a coefficient generator that receives the digital signal from a feedforward branch circuit;
a spectral expander that uses the generated coefficients to spectrally expand the digital signal;
an inverter for generating the reciprocal of the digital signal; and a combiner for digitally combining the output of the expander with the output of the inverter into a combined signal.
a coefficient generator that receives the digital signal from a feedforward branch circuit;
a spectral expander that uses the generated coefficients to spectrally expand the digital signal;
an inverter for generating the reciprocal of the digital signal; and a combiner for digitally combining the output of the expander with the output of the inverter into a combined signal.
36. The system of claim 35 further comprising a decimator for decimating the combined signal and digitally applying deemphasis.
37. A method of calculating a variable spectral expansion filter coefficient in a BTSC
compatible stereo encoder from a feed-forward variable, comprising the steps of a. calculating a reciprocal value that is proportional to the feed-forward variable;
b. indexing a lookup table using a pre-selected set of bits of the reciprocal value to generate at least one parameter of the filter coefficient function;
and c. linearly interpolating an approximation of the expansion filter coefficient based on the at least one parameter of the alter coefficient function.
compatible stereo encoder from a feed-forward variable, comprising the steps of a. calculating a reciprocal value that is proportional to the feed-forward variable;
b. indexing a lookup table using a pre-selected set of bits of the reciprocal value to generate at least one parameter of the filter coefficient function;
and c. linearly interpolating an approximation of the expansion filter coefficient based on the at least one parameter of the alter coefficient function.
38. A method of calculating a variable spectral expansion filter coefficient in a BTSC
compatible stereo encoder from a feed-forward variable, comprising the steps of a. calculating a reciprocal value that is proportional to the feed-forward variable;
b. indexing a lookup table using a pre-selected set of high order bits of the reciprocal value, wherein a first portion of the lookup table stores a plurality of discrete values at index points of a line segment corresponding to a filter coefficient function approximation, so as to generate an initial discrete value corresponding to the filter coefficient function at a value of the high order bits, and wherein a second portion of the lookup table stores a plurality of slope values, each slope value indicating a slope of a line segment of the filter coefficient function, so as to generate a slope value of a line segment corresponding to the filter coefficient function at the value of the high order bits; and c. linearly interpolating an approximation of the compression filter coefficient based on the slope value, the initial discrete value and a pre-selected set of low order bits of the reciprocal value.
compatible stereo encoder from a feed-forward variable, comprising the steps of a. calculating a reciprocal value that is proportional to the feed-forward variable;
b. indexing a lookup table using a pre-selected set of high order bits of the reciprocal value, wherein a first portion of the lookup table stores a plurality of discrete values at index points of a line segment corresponding to a filter coefficient function approximation, so as to generate an initial discrete value corresponding to the filter coefficient function at a value of the high order bits, and wherein a second portion of the lookup table stores a plurality of slope values, each slope value indicating a slope of a line segment of the filter coefficient function, so as to generate a slope value of a line segment corresponding to the filter coefficient function at the value of the high order bits; and c. linearly interpolating an approximation of the compression filter coefficient based on the slope value, the initial discrete value and a pre-selected set of low order bits of the reciprocal value.
39. The method claim 38, wherein the interpolating step comprises the steps of:
a. multiplying the slope value by a value of the pre-selected set of low order bits of the reciprocal value to generate a product value; and b. adding the initial discrete value to the product value thereby generating the approximation of the expansion filter coefficient.
a. multiplying the slope value by a value of the pre-selected set of low order bits of the reciprocal value to generate a product value; and b. adding the initial discrete value to the product value thereby generating the approximation of the expansion filter coefficient.
40. The method Claim 38, further comprising the step of generating the expansion filter coefficient by calculating a root-mean-squared value of a scaled and filtered output of an infinite impulse response spectral expansion filter.
41. An apparatus for calculating a variable spectral expansion filter coefficient in a BTSC compatible stereo encoder from a feed-forward variable, comprising:
a. a reciprocal value circuit that calculates a reciprocal value that is proportional to the feed-forward variable;
b. a lookup table that is indexed by a pre-selected set of high order bits of the reciprocal value, wherein a first portion of the lookup table stores a plurality of discrete values at index points of a line segment corresponding to a filter coefficient function approximation, so as to generate an initial discrete value corresponding to the filter coefficient function at a value of the high order bits, and wherein a second portion of the lookup table stores a plurality of slope values, each slope value indicating a slope of a line segment of the filter coefficient function, so as to generate a slope value of a line segment corresponding to the filter coefficient function at the value of the high order bits; and c. a linear interpolation circuit that interpolates an approximation of the expansion filter coefficient based on the slope value, the initial discrete value and a pre-selected set of low order bits of the reciprocal value.
a. a reciprocal value circuit that calculates a reciprocal value that is proportional to the feed-forward variable;
b. a lookup table that is indexed by a pre-selected set of high order bits of the reciprocal value, wherein a first portion of the lookup table stores a plurality of discrete values at index points of a line segment corresponding to a filter coefficient function approximation, so as to generate an initial discrete value corresponding to the filter coefficient function at a value of the high order bits, and wherein a second portion of the lookup table stores a plurality of slope values, each slope value indicating a slope of a line segment of the filter coefficient function, so as to generate a slope value of a line segment corresponding to the filter coefficient function at the value of the high order bits; and c. a linear interpolation circuit that interpolates an approximation of the expansion filter coefficient based on the slope value, the initial discrete value and a pre-selected set of low order bits of the reciprocal value.
42. The apparatus of Claim 41, wherein the interpolation circuit comprises:
a. a multiplier that multiplies the slope value by a value of a pre-selected set of low order bits of the reciprocal value to generate a product value; and b. an adder that adds the initial discrete value to the product value, thereby generating an approximation of the expansion filter coefficient.
a. a multiplier that multiplies the slope value by a value of a pre-selected set of low order bits of the reciprocal value to generate a product value; and b. an adder that adds the initial discrete value to the product value, thereby generating an approximation of the expansion filter coefficient.
43. The apparatus of Claim 41, further comprising a feed-forward signal conditioning circuit that generates a scaled, filtered and root-mean-squared signal corresponding to an output of an infinite impulse response spectral expansion filter.
44. The apparatus of Claim 43, wherein the feed-forward signal conditioning circuit comprises a multiplier that multiplies the output of an infinite impulse response spectral expansion filter by a scaling constant thereby generating a scaled signal.
45. The apparatus of Claim 44, wherein the feed-forward signal conditioning circuit further comprises a band pass filter weighted to high that generates a filtered signal from the scaled signal.
46. The apparatus of Claim 45, wherein the feed-forward signal conditioning circuit further comprises a root-mean-squared circuit that generates a root-mean-squared signal corresponding to a value of the scaled signal root-mean-squared.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/US2003/010834 WO2004100604A1 (en) | 2000-02-18 | 2003-04-09 | Reciprocal index lookup for btsc compatible coefficients |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2525944A1 true CA2525944A1 (en) | 2004-11-18 |
| CA2525944C CA2525944C (en) | 2012-06-05 |
Family
ID=34392765
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2525944A Expired - Fee Related CA2525944C (en) | 2003-04-09 | 2003-04-09 | Reciprocal index lookup for btsc compatible coefficients |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP1618760A4 (en) |
| CN (1) | CN1795697A (en) |
| AU (1) | AU2003224895A1 (en) |
| CA (1) | CA2525944C (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP6665610B2 (en) * | 2016-01-08 | 2020-03-13 | 株式会社ジェイテクト | Motor control device |
| US10122346B2 (en) * | 2017-03-03 | 2018-11-06 | Synaptics Incorporated | Coefficient generation for digital filters |
| JP7326285B2 (en) * | 2017-12-19 | 2023-08-15 | ドルビー・インターナショナル・アーベー | Method, Apparatus, and System for QMF-based Harmonic Transposer Improvements for Speech-to-Audio Integrated Decoding and Encoding |
| CN109063652B (en) * | 2018-08-06 | 2022-02-11 | 高维度（深圳）生物信息智能应用有限公司 | Signal processing method, system and computer storage medium |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5091957A (en) * | 1990-04-18 | 1992-02-25 | Thomson Consumer Electronics, Inc. | Wideband expander for stereo and SAP signals |
| US5627857A (en) * | 1995-09-15 | 1997-05-06 | Qualcomm Incorporated | Linearized digital automatic gain control |
| US5796842A (en) * | 1996-06-07 | 1998-08-18 | That Corporation | BTSC encoder |
| EP0936744B1 (en) * | 1998-02-12 | 2004-09-22 | Micronas GmbH | Carrier generating device for a digital demodulator of MPX signals |
| US6259482B1 (en) * | 1998-03-11 | 2001-07-10 | Matthew F. Easley | Digital BTSC compander system |
| US6192086B1 (en) * | 1999-01-14 | 2001-02-20 | Antec Corporation | Digital sub-systems and building blocks for a mostly digital low-cost BTSC compatible encoder |
-
2003
- 2003-04-09 CN CNA038266059A patent/CN1795697A/en active Pending
- 2003-04-09 CA CA2525944A patent/CA2525944C/en not_active Expired - Fee Related
- 2003-04-09 AU AU2003224895A patent/AU2003224895A1/en not_active Abandoned
- 2003-04-09 EP EP03721588A patent/EP1618760A4/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| CA2525944C (en) | 2012-06-05 |
| CN1795697A (en) | 2006-06-28 |
| EP1618760A1 (en) | 2006-01-25 |
| EP1618760A4 (en) | 2013-03-20 |
| AU2003224895A1 (en) | 2004-11-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |
Effective date: 20140409 |