Method and apparatus for performing packet loss or frame erasure concealment
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Accused Products
Abstract
The invention concerns a method and apparatus for performing packet loss or Frame Erasure Concealment (FEC) for a speech coder that does not have a built-in or standard FEC process. A receiver with a decoder receives encoded frames of compressed speech information transmitted from an encoder. A lost frame detector at the receiver determines if an encoded frame has been lost or corrupted in transmission, or erased. If the encoded frame is not erased, the encoded frame is decoded by a decoder and a temporary memory is updated with the decoder'"'"'s output. A predetermined delay period is applied and the audio frame is then output. If the lost frame detector determines that the encoded frame is erased, a FEC module applies a frame concealment process to the signal. The FEC processing produces natural sounding synthetic speech for the erased frames.
23 Citations
28 Claims
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1. (canceled)
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2. A receiver adapted to receive signal packets comporting with the G.71 1 IEEE standard, where received valid packets are converted to corresponding audio signal samples in a decoder circuit, coupled to an audio port, the improvement comprising:
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a FIFO buffer interposed between said decoder and said audio port to enable executing an overlap and add operation, a history buffer;
a pitch buffer into which at least some of the audio samples of said history buffer are copied when said receiver detects that a number of consecutive ones of said packets are unusable because they are either not received or received but otherwise invalid; and
a pitch-estimation processor for estimating pitch of a preselected portion of the most recent of speech in said history buffer. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A receiver adapted to receive signal packets comporting with the G.711 IEEE standard, where received valid packets are converted to corresponding audio signal samples in a decoder circuit, coupled to an audio port, the improvement comprising:
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a first buffer interposed between said decoder and said audio port to enable executing an overlap and add operation, a second buffer for storing audio signal samples developed by the decoder circuit; and
a processor for developing an estimate of pitch of a preselected portion of the most recent speech in said second buffer and, based on the developed pitch estimate, identifying a set of audio signal samples in the second buffer and combining the identified set of audio signal samples with samples exiting said first buffer, where the identified set of audio signal samples is in lieu of audio signal samples that were not developed by said decoder in response to an expected packet, because the expected packet is not received or is received but otherwise is invalid, and where the identified set, for a given estimate of the pitch corresponds, at times, to a different multiple of the period of the estimate of the pitch.
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Specification