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Method for Reduction of Aliasing Introduced By Spectral Envelope Adjustment in Real-valued Filterbanks
| Content Provider | The Lens |
|---|---|
| Abstract | The present invention proposes a new method for improving the performance of a real-valued filterbank based spectral envelope adjuster. By adaptively locking the gain values for adjacent channels dependent on the sign of the channels, as defined in the application, reduced aliasing is achieved. Furthermore, the grouping of the channels during gain-calculation, gives an improved energy estimate of the real valued subband signals in the filterbank. |
| Related Links | https://www.lens.org/lens/patent/011-528-861-906-037/frontpage |
| Language | English |
| Publisher Date | 2017-04-20 |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Patent |
| Jurisdiction | United States of America |
| Date Applied | 2016-12-28 |
| Applicant | Dolby Int Ab |
| Application No. | 201615392545 |
| Claim | Apparatus for performing gain adjustment on a plurality of audio sub band signals generated by filtering an audio signal using a filter bank, the filter bank having sub band filters, adjacent sub band filters of the filterbank having transition bands overlapping in an overlapping range, comprising: an analyzer for analysing the plurality of audio sub band signals generated by filtering the signal using the filter bank to determine, whether a subband signal of a sub band filter and a sub band signal of an adjacent sub band filter have aliasing generating signal components in the overlapping range between the sub band filter and the adjacent sub band filter to obtain grouped audio sub band signals; a calculator configured for calculating a first gain adjustment value and a second gain adjustment value for the grouped adjacent audio sub band signals comprising an audio sub band signal and an adjacent audio sub band signal, wherein the calculator is operative to determine a first energy measure indicating a signal energy of the audio sub band signal and a second energy measure indicating a signal energy of the adjacent audio sub band signal, to determine an indication of a reference energy for the grouped adjacent audio sub band signals as a linear combination of a first reference energy value for the audio sub band signal and a second reference energy value for the adjacent audio sub band signal, and to determine an energy estimate for an energy in the grouped adjacent audio sub band signals as a linear combination of the first energy measure for the audio sub band signal and the second energy measure for the adjacent audio sub band signal, and to calculate the first gain adjustment value and the second gain adjustment value for the grouped adjacent audio sub band signals based on the linear combination of the first reference energy value for the audio sub band signal and the second reference energy value for the adjacent audio sub band signal and based on the linear combination of the first energy measure for the audio sub band signal and the second energy measure for the adjacent audio sub band signal; and a gain adjuster configured for applying the first gain adjustment value to the audio sub band signal of the grouped adjacent audio sub band signals and for applying the second gain adjustment value to the adjacent audio sub band signal of the grouped adjacent audio sub band signals. Apparatus in accordance with claim 1 , in which the analyzer is operative to calculate signs of subband signals based on coefficients of prediction polynomials for the subband signal and the adjacent subband signal, and to indicate a positive result, when the signs have a predetermined relationship to each other. Apparatus in accordance with claim 1 or 2 , in which the analyser is operative to apply an auto-correlation method or a co-variance method. Apparatus in accordance with claim 2 , in which the prediction polynomial is a low order polynomial having a first order coefficient, wherein the order of the low order polynomial is smaller than 4 and in which the analyzer is operative to use the first order coefficient for calculating the signs of the subband signals. Apparatus in accordance with claim 2 , in which the analyzer is operative to calculate the sign for a subband signal based on the following equation: wherein k is the channel number, and α 1 is the first-order coefficient. Apparatus in accordance with claim 2 , in which the predetermined relationship is defined such that the subband signal having associated therewith a channel number k has a first sign and the adjacent subband signal having associated therewith a channel number k−1 has a second sign, which is opposite to the first sign. Apparatus in accordance with claim 6 , in which the first sign is negative, and the second sign is positive. Apparatus in accordance with claim 1 , in which the analyzer is operative to perform a tonal analysis for the subband signal and the adjacent subband signal for determining a tonal component having a tonality measure above a tonality threshold. Apparatus in accordance with claim 8 , in which the analyzer is operative to determine, whether the tonal component is in the overlapping range of channel k and channel k−1. Apparatus in accordance with claim 1 , in which the calculator is further operative to calculate the first gain adjustment value and the second gain adjustment using a quotient comprising a numerator and a denominator, wherein the numerator comprises the linear combination of the first reference energy value and the second reference energy value and the denominator comprises the linear combination of the first energy measure and the second energy measure. Apparatus in accordance with claim 1 , in which the calculator is operative to calculate the first and the second gain adjustment values such that the first and the second gain adjustment values are equal to each other. Apparatus in accordance with claim 1 , in which the calculator is operative to calculate the first gain adjustment value and the second gain adjustment value based on an average energy of the subband signal and the adjacent subband signa Apparatus in accordance with claim 1 , in which the calculator is operative to calculate the first and second gain adjustment values according to the following equation: wherein g k-1 (m) is the first gain adjustment value for the audio sub band signal of the grouped adjacent audio sub band signals, wherein g k (m) is the second gain adjustment value for the adjacent audio sub band signal of the grouped adjacent audio sub band signals, wherein E k-1 ref (m) is the first reference energy value for the audio sub band signal, wherein E k ref (m) is the second reference energy value for the second audio sub band signal, wherein E k-1 (m) is the first energy measure of the audio sub band signal, wherein E k (m) is the second energy measure of the adjacent audio sub band signal, and wherein m indicates a point in time. Apparatus in accordance with claim 1 , in which the first or the second energy measures for a audio sub band signal is calculated by summing of squared subband samples of the audio sub band signa Apparatus in accordance with claim 1 , further comprising a synthesis filter bank for synthesis filtering gain adjusted audio sub band signals to obtain a synthesized output signa Apparatus in accordance with claim 1 , in which the analysis filterbank is a real valued filterbank, and in which a synthesis filter bank for synthesis filtering gain adjusted audio sub band signals is a real valued filterbank. Method of performing gain adjustment on a plurality of audio sub band signals generated by filtering an audio signal using a filter bank, the filter bank having audio sub band filters, adjacent audio sub band filters of the filter bank having transition bands overlapping in an overlapping range, comprising: an analyzer for analysing the plurality of audio sub band signals generated by filtering the signal using the filter bank to determine, whether a subband signal of a sub band filter and a sub band signal of an adjacent sub band filter have aliasing generating signal components in the overlapping range between the sub band filter and the adjacent sub band filter to obtain grouped audio sub band signals; calculating a first gain adjustment value and a second gain adjustment value for the grouped adjacent audio sub band signals comprising a audio sub band signal and an adjacent audio sub band signal, wherein the calculating comprises: determining a first energy measure indicating a signal energy of the audio sub band signal and a second energy measure indicating a signal energy of the adjacent audio sub band signal, determining an indication of a reference energy for the grouped adjacent audio sub band signals as a linear combination of a first reference energy value for the audio sub band signal and a second reference energy value for the adjacent audio sub band signal, determining an energy estimate for an energy in the grouped adjacent audio sub band signals as a linear combination of the first energy measure for the audio sub band signal and the second energy measure for the adjacent audio sub band signal, and calculating the first gain adjustment value and the second gain adjustment value for the grouped adjacent audio sub band signals based on the linear combination of the first reference energy value for the audio sub band signal and the second reference energy value for the adjacent audio sub band signal and based on the linear combination of the first energy measure for the audio sub band signal and the second energy measure for the adjacent audio sub band signal; and applying the first gain adjustment value to the audio sub band signal of the grouped adjacent audio sub band signals and applying the second gain adjustment value to the adjacent audio sub band signal of the grouped adjacent audio sub band signals. A non-transitory storage medium having stored thereon a computer program having a program code for performing, when the computer program runs on a computer, a method eof performing gain adjustment on a plurality of audio sub band signals generated by filtering an audio signal using a filter bank, the filter bank having audio sub band filters, adjacent audio sub band filters of the filter bank having transition bands overlapping in an overlapping range, the method comprising: an analyzer for analysing the plurality of audio sub band signals generated by filtering the signal using the filter bank to determine, whether a subband signal of a sub band filter and a sub band signal of an adjacent sub band filter have aliasing generating signal components in the overlapping range between the sub band filter and the adjacent sub band filter to obtain grouped audio sub band signals; calculating a first gain adjustment value and a second gain adjustment value for grouped adjacent audio sub band signals comprising a audio sub band signal and an adjacent audio sub band signal, wherein the calculating comprises: determining a first energy measure indicating a signal energy of the audio sub band signal and a second energy measure indicating a signal energy of the adjacent audio sub band signal, determining an indication of a reference energy for the grouped adjacent audio sub band signals as a linear combination of a first reference energy value for the audio sub band signal and a second reference energy value for the adjacent audio sub band signal, determining an energy estimate for an energy in the grouped adjacent audio sub band signals as a linear combination of the first energy measure for the audio sub band signal and the second energy measure for the adjacent audio sub band signal, and calculating the first gain adjustment value and the second gain adjustment value for the grouped adjacent audio sub band signals based on the linear combination of the first reference energy value for the audio sub band signal and the second reference energy value for the adjacent audio sub band signal and based on the linear combination of the first energy measure for the audio sub band signal and the second energy measure for the adjacent audio sub band signal; and applying the first gain adjustment value to the audio sub band signal of the grouped adjacent audio sub band signals and applying the second gain adjustment value to the adjacent audio sub band signal of the grouped adjacent audio sub band signals. |
| CPC Classification | SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS;SPEECH RECOGNITION;SPEECH OR VOICE PROCESSING TECHNIQUES;SPEECH OR AUDIO CODING OR DECODING IMPEDANCE NETWORKS; e.g. RESONANT CIRCUITS;RESONATORS |
| Extended Family | 072-338-365-981-834 064-072-987-802-268 191-247-520-477-445 020-562-308-956-755 055-955-244-177-53X 155-179-580-425-156 153-651-820-642-293 096-330-373-364-347 095-892-863-827-787 072-988-045-749-352 095-178-553-571-079 102-512-467-787-888 193-310-234-293-161 102-031-830-892-82X 100-359-831-279-636 178-232-146-391-066 040-318-290-588-085 182-617-691-107-720 040-305-171-292-30X 195-093-284-873-118 166-257-511-660-865 010-056-162-576-906 104-120-131-883-884 011-528-861-906-037 053-125-531-468-289 068-271-981-601-550 094-876-661-476-548 191-506-697-658-392 081-924-477-319-480 101-218-891-659-750 100-535-146-385-211 159-201-039-153-205 112-778-990-396-516 166-845-942-991-413 181-807-730-636-635 012-933-157-726-468 004-645-487-533-11X 004-557-890-244-334 097-502-336-842-770 044-206-388-242-671 077-593-983-821-651 049-579-339-102-596 065-246-226-993-745 183-304-373-030-018 072-784-685-696-987 024-159-125-546-759 092-582-783-991-568 164-969-456-681-120 117-133-818-247-926 156-717-899-336-325 175-432-288-697-906 106-936-464-066-537 085-206-525-583-024 020-872-117-427-491 174-744-898-163-772 174-497-885-644-010 016-739-705-589-465 018-300-527-719-301 050-369-466-653-681 064-003-070-161-084 167-965-942-571-614 101-342-719-207-689 149-998-658-630-785 057-597-090-772-904 113-282-903-295-686 048-326-720-787-166 017-259-634-974-473 191-573-044-142-84X 052-062-730-934-586 006-162-378-529-513 069-264-980-374-537 083-192-246-792-731 036-927-324-133-02X 150-239-213-919-20X 139-059-647-329-796 125-805-613-184-895 007-953-324-467-932 036-090-825-408-552 160-194-506-572-795 112-952-559-060-063 131-416-814-573-510 036-898-008-989-74X 086-678-665-008-20X 065-484-439-169-120 014-997-090-216-791 176-211-685-676-153 095-103-108-376-084 171-533-486-094-636 068-479-036-642-06X 046-434-658-227-568 176-801-773-104-083 010-478-571-619-786 137-780-590-079-802 158-043-405-483-275 155-351-390-134-165 012-059-987-840-296 005-423-598-762-751 043-474-585-705-414 151-318-395-834-945 039-153-324-782-92X 115-554-476-896-688 019-009-907-604-058 077-799-476-004-298 115-358-678-345-050 012-112-439-692-704 188-913-402-419-221 160-368-513-865-18X 056-129-240-097-999 046-102-953-144-393 039-808-021-802-078 162-454-553-713-854 103-945-849-133-388 064-219-293-075-100 126-511-107-706-702 175-196-539-276-021 144-746-462-270-447 097-672-129-194-151 157-300-604-489-213 048-720-835-185-531 123-567-667-529-058 018-090-099-029-95X 010-068-793-848-451 105-321-781-855-874 062-017-917-018-430 109-774-214-435-926 002-805-891-813-276 038-380-158-959-729 131-356-169-098-531 169-100-871-609-821 131-738-040-181-653 044-459-022-603-079 122-221-687-105-936 080-895-027-870-535 194-482-729-824-312 009-579-768-404-532 092-580-586-522-43X |
| Patent ID | 20170110136 |
| Inventor/Author | Kjoerling Kristofer Villemoes Lars |
| IPC | G10L19/083 G10L19/02 G10L19/025 G10L19/26 G10L25/12 G10L25/18 G10L25/48 H03H17/02 |
| Status | Expired |
| Owner | Dolby International Ab |
| Simple Family | 072-338-365-981-834 064-072-987-802-268 191-247-520-477-445 020-562-308-956-755 055-955-244-177-53X 155-179-580-425-156 153-651-820-642-293 096-330-373-364-347 095-892-863-827-787 072-988-045-749-352 095-178-553-571-079 102-512-467-787-888 193-310-234-293-161 102-031-830-892-82X 100-359-831-279-636 178-232-146-391-066 040-318-290-588-085 182-617-691-107-720 040-305-171-292-30X 195-093-284-873-118 166-257-511-660-865 010-056-162-576-906 104-120-131-883-884 011-528-861-906-037 053-125-531-468-289 068-271-981-601-550 094-876-661-476-548 191-506-697-658-392 081-924-477-319-480 101-218-891-659-750 100-535-146-385-211 159-201-039-153-205 112-778-990-396-516 166-845-942-991-413 181-807-730-636-635 012-933-157-726-468 004-645-487-533-11X 004-557-890-244-334 097-502-336-842-770 044-206-388-242-671 077-593-983-821-651 049-579-339-102-596 065-246-226-993-745 183-304-373-030-018 072-784-685-696-987 024-159-125-546-759 092-582-783-991-568 164-969-456-681-120 117-133-818-247-926 156-717-899-336-325 175-432-288-697-906 106-936-464-066-537 085-206-525-583-024 020-872-117-427-491 174-744-898-163-772 174-497-885-644-010 016-739-705-589-465 018-300-527-719-301 050-369-466-653-681 064-003-070-161-084 167-965-942-571-614 101-342-719-207-689 149-998-658-630-785 057-597-090-772-904 113-282-903-295-686 048-326-720-787-166 017-259-634-974-473 191-573-044-142-84X 052-062-730-934-586 006-162-378-529-513 069-264-980-374-537 083-192-246-792-731 036-927-324-133-02X 150-239-213-919-20X 139-059-647-329-796 125-805-613-184-895 007-953-324-467-932 036-090-825-408-552 160-194-506-572-795 112-952-559-060-063 131-416-814-573-510 036-898-008-989-74X 086-678-665-008-20X 065-484-439-169-120 014-997-090-216-791 176-211-685-676-153 095-103-108-376-084 171-533-486-094-636 068-479-036-642-06X 046-434-658-227-568 176-801-773-104-083 010-478-571-619-786 137-780-590-079-802 158-043-405-483-275 155-351-390-134-165 012-059-987-840-296 005-423-598-762-751 043-474-585-705-414 151-318-395-834-945 039-153-324-782-92X 115-554-476-896-688 019-009-907-604-058 077-799-476-004-298 115-358-678-345-050 012-112-439-692-704 188-913-402-419-221 160-368-513-865-18X 056-129-240-097-999 046-102-953-144-393 039-808-021-802-078 162-454-553-713-854 103-945-849-133-388 064-219-293-075-100 126-511-107-706-702 175-196-539-276-021 144-746-462-270-447 097-672-129-194-151 157-300-604-489-213 048-720-835-185-531 123-567-667-529-058 018-090-099-029-95X 010-068-793-848-451 105-321-781-855-874 062-017-917-018-430 109-774-214-435-926 002-805-891-813-276 038-380-158-959-729 131-356-169-098-531 169-100-871-609-821 131-738-040-181-653 044-459-022-603-079 122-221-687-105-936 080-895-027-870-535 194-482-729-824-312 009-579-768-404-532 092-580-586-522-43X |
| CPC (with Group) | G10L19/0204 G10L25/18 G10L25/48 H03H17/0266 H03H17/02 G10L19/20 G10L19/00 G10L19/025 G10L19/083 G10L19/12 G10L19/26 G10L25/12 G10L25/21 |
| Issuing Authority | United States Patent and Trademark Office (USPTO) |
| Kind | Patent Application Publication |
