Packet loss concealment for overlapped transform codecs
First Claim
1. A method for concealing missing coefficients of a transform of a signal by reconstructing blocks of samples of sample of the signal corresponding to the missing coefficients, comprising steps for:
- extracting a set of coefficients from frames of the transform of the signal;
determining which coefficients are missing;
locating an under-determined block of samples of the signal corresponding to at least one missing coefficient;
constructing from a subset of the extracted coefficients a set of linear equations representing partial constraints on the under-determined block of samples;
modeling samples of the signal neighboring the under-determined block of samples to construct a basis for the under-determined block of samples;
optimizing the coefficients of the under-determined block of samples with respect to the constructed basis and the partial constraints; and
reconstructing a block of samples corresponding to the missing coefficients from the optimized coefficients with respect to the basis.
2 Assignments
0 Petitions
Accused Products
Abstract
Real-time packet-based audio communications over packet-based networks frequently results in the loss of one or more packets during any given communication session. The real-time nature of such communications precludes retransmission of lost packets due to the unacceptable delays that would result. Consequently, packet loss concealment methods are employed to “hide” lost packets from the listener. Unfortunately, conventional loss concealment methods, such as packet repetition or stretch/overlap methods, do not fully exploit information available from partially received samples. Therefore, when a single frame of N coefficients is lost, 2N samples are only partially reconstructed, thereby degrading the reconstructed signal. To address this problem, an optimized packet loss concealment solution is identified for particular lost packets by solving an underdetermined system of linear equations representing partially received samples while minimizing a computed error based on a model of the signal obtained from neighboring blocks or frames received by the decoder.
13 Citations
20 Claims
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1. A method for concealing missing coefficients of a transform of a signal by reconstructing blocks of samples of sample of the signal corresponding to the missing coefficients, comprising steps for:
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extracting a set of coefficients from frames of the transform of the signal; determining which coefficients are missing; locating an under-determined block of samples of the signal corresponding to at least one missing coefficient; constructing from a subset of the extracted coefficients a set of linear equations representing partial constraints on the under-determined block of samples; modeling samples of the signal neighboring the under-determined block of samples to construct a basis for the under-determined block of samples; optimizing the coefficients of the under-determined block of samples with respect to the constructed basis and the partial constraints; and reconstructing a block of samples corresponding to the missing coefficients from the optimized coefficients with respect to the basis. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A computer-readable medium having computer executable instructions for, concealing missing frames of coefficients of an overlapped transform of a signal by reconstructing blocks of samples of the signal corresponding to the missing frames of coefficients, said computer executable instructions comprising:
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determining which frames are missing from a set of received frames of the overlapped transform of the signal; locating an under-determined block of samples of the signal corresponding to a missing frame; extracting coefficients from at least one received frame; constructing from the extracted coefficients a set of linear equations representing partial constraints on the under-determined block of samples; modeling samples of the signal neighboring the under-determined block of samples; constructing from the modeled samples a basis for the under-determined block of samples; optimizing the coefficients of the under-determined block of samples with respect to the constructed basis and the partial constraints; and reconstructing a block of samples corresponding to the missing frame from the optimized coefficients with respect to the basis. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A method for reconstructing one or more missing data frames of an overlapped transform coded signal by reconstructing one or more of the missing data frames, comprising:
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storing received data frames of the coded signal to a signal buffer; determining whether any data frames are of the data frames are missing; constructing a set of under-determined linear equations from partial information extracted from at least one of a preceding neighboring frame and a succeeding neighboring frame, relative to a missing frame; modeling the at least one neighboring frame and using the at least one modeled neighboring frame for generating a basis for the missing frame; identifying an optimal solution to the set of under-determined linear equations as a function of the generated basis; reconstructing the missing frame from the identified optimal solution; and inserting the reconstructed missing frame into its proper position between corresponding neighboring frames in the signal buffer. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification