Effective deployment of temporal noise shaping (TNS) filters
First Claim
1. A method comprising:
- calculating a filter for each of a plurality of frequency bands;
determining a distance between coefficients in adjacent frequency bands;
clustering the filters into at least two groups based on energies in each of the frequency bands covered by the filters;
merging the clustered filters with a shortest distance between coefficients; and
processing audio signals using the merged filters.
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Abstract
The MPEG2 Advanced Audio Coder (AAC) standard limits the number of filters used to either one filter for a “short” block or three filters for a “long” block. In cases where the need for additional filters is present but the limit of permissible filters has been reached, the remaining frequency spectra are simply not covered by TNS. Two solutions are proposed to deploy TNS filters in order to get the entire spectrum of the signal into TNS. The first method involves a filter bridging technique and complies with the current AAC standard. The second method involves a filter clustering technique. Although the second method is both more efficient and accurate in capturing the temporal structure of the time signal, it is not AAC standard compliant. Thus, a new syntax for packing filter information derived using the second method for transmission to a receiver is also outlined.
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Citations
18 Claims
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1. A method comprising:
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calculating a filter for each of a plurality of frequency bands; determining a distance between coefficients in adjacent frequency bands; clustering the filters into at least two groups based on energies in each of the frequency bands covered by the filters; merging the clustered filters with a shortest distance between coefficients; and processing audio signals using the merged filters. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A system comprising:
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a processor; and a computer-readable storage medium having instructions stored which, when executed by the processor, cause the processor to perform a method comprising; calculating a filter for each of a plurality of frequency bands; determining a distance between coefficients in adjacent frequency bands; clustering the filters into at least two groups based on energies in each of the frequency bands covered by the filters; merging the clustered filters with a shortest distance between coefficients; and processing audio signals using the merged filters. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A non-transitory computer-readable storage medium having instructions stored which, when executed by a computing device, cause the computing device to perform a method comprising:
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calculating a filter for each of a plurality of frequency bands; determining a distance between coefficients in adjacent frequency bands; clustering the filters into at least two groups based on energies in each of the frequency bands covered by the filters; merging the clustered filters with a shortest distance between coefficients; and processing audio signals using the merged filters. - View Dependent Claims (14, 15, 16, 17, 18)
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Specification