Low-Complexity Packet Loss Concealment for Transcoded Audio Signals
First Claim
1. A method for concealing packet loss in a received audio stream, the method comprising:
- receiving, by an audio communication system comprising one or more servers, packets of an audio stream, the received audio stream being in a non-lapped transform domain format, the packets having a sequential order, where a block of packets is missing in the sequence, the block of packets including at least one packet, each packet of the audio stream having a received window size;
decoding, by the audio communication system, the received packets to a sequence of blocks of a raw audio signal;
replacing, by the audio communication system, each missing packet in the sequence with a reduced-energy signal block, whereby the sequence of blocks of the raw audio signal comprises at least one reduced-energy signal block, wherein the reduced-energy signal block has a lower energy in comparison to remaining blocks of the raw audio signal, such that the reduced-energy signal block is distinguishable from remaining blocks of the received raw audio signal;
modifying, by the audio communication system, each reduced-energy signal block of the raw audio signal at one of a beginning boundary and an ending boundary;
shifting, by the audio communication system, the raw audio signal by a predetermined delay such that a start and end of each reduced energy block of the raw audio signal does not coincide with a peak of a transform window of a lapped transform domain format;
encoding, by the server, the raw audio signal into transform windows having the lapped transform domain format, wherein packet loss concealment is performed for a selected transform window of the encoded audio signal, the selected transform window having a modified reduced energy signal block located at a center portion; and
transmitting, by the audio communication system, the encoded audio signal to an endpoint.
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Abstract
Systems and methods are described for concealing packet loss in a received audio stream. Packets of the audio stream may be received in a non-lapped transform domain format, where at least one packet is missing in the stream. The received packets are decoded, and each missing packet in the decoded stream is replaced by a reduced-energy signal block. Each reduced-energy signal block may also be modified at a beginning or ending boundary, and shifted such that a start or end of each missing packet does not coincide with a peak of a transform window of a lapped transform domain format. The raw audio signal may then be encoded into transform windows having the lapped transform domain format. Packet loss concealment may then be performed for selected transform windows that include modified reduced-energy blocks, either prior to transmission or after transmission by the receiving endpoint.
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Citations
19 Claims
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1. A method for concealing packet loss in a received audio stream, the method comprising:
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receiving, by an audio communication system comprising one or more servers, packets of an audio stream, the received audio stream being in a non-lapped transform domain format, the packets having a sequential order, where a block of packets is missing in the sequence, the block of packets including at least one packet, each packet of the audio stream having a received window size; decoding, by the audio communication system, the received packets to a sequence of blocks of a raw audio signal; replacing, by the audio communication system, each missing packet in the sequence with a reduced-energy signal block, whereby the sequence of blocks of the raw audio signal comprises at least one reduced-energy signal block, wherein the reduced-energy signal block has a lower energy in comparison to remaining blocks of the raw audio signal, such that the reduced-energy signal block is distinguishable from remaining blocks of the received raw audio signal; modifying, by the audio communication system, each reduced-energy signal block of the raw audio signal at one of a beginning boundary and an ending boundary; shifting, by the audio communication system, the raw audio signal by a predetermined delay such that a start and end of each reduced energy block of the raw audio signal does not coincide with a peak of a transform window of a lapped transform domain format; encoding, by the server, the raw audio signal into transform windows having the lapped transform domain format, wherein packet loss concealment is performed for a selected transform window of the encoded audio signal, the selected transform window having a modified reduced energy signal block located at a center portion; and transmitting, by the audio communication system, the encoded audio signal to an endpoint. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A computer program product comprising computer-readable program code to be executed by one or more processors when retrieved from a non-transitory computer-readable medium, the program code including instructions to:
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receive packets of an audio stream, the received audio stream being in a non-lapped transform domain format, the packets having a sequential order, where at least one packet is missing in the sequence, each packet having a received window size; decode the received packets to a sequence of blocks of a raw audio signal; replace each missing packet in the sequence with a reduced-energy signal block, whereby the sequence of blocks of the raw audio signal comprises at least one reduced-energy signal block, wherein the reduced-energy signal block has a lower energy in comparison to remaining blocks of the raw audio signal, such that the reduced-energy signal block is distinguishable from remaining blocks of the received raw audio signal; modify each reduced-energy signal block of the raw audio signal at one of a beginning boundary and an ending boundary of the inserted blocks; shift the raw audio signal by a predetermined delay such that a start and end of each reduced energy block of the raw audio signal does not coincide with a peak of a transform window of a lapped transform domain format; encode the raw audio signal into transform windows having the lapped transform domain format, packet loss concealment being performed for a selected transform window, of the encoded audio signal, having a modified reduced energy signal block located at a center portion of the selected transform window; and transmit the encoded audio signal.
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15. A system for concealing packet loss in a received audio stream, the system comprising:
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a communications transceiver that receives packets of an audio stream, the received audio stream being in a non-lapped transform domain format, the packets having a sequential order, where at least one packet is missing in the sequence, each packet having a received window size; a decoder that decodes the received packets from the non-lapped format to a sequence of blocks of a raw audio signal and replaces each missing packet in the sequence with a reduced-energy signal block, whereby the sequence of blocks of the raw audio signal comprises at least one reduced-energy signal block, wherein the reduced-energy signal block has a lower energy in comparison to remaining blocks of the raw audio signal, such that the reduced-energy signal block is distinguishable from remaining blocks of the received raw audio signal; a preprocessor that modifies each reduced-energy signal block of the raw audio signal at one of a beginning boundary and an ending boundary of the blocks of silence and shifts the raw audio signal by a predetermined delay such that a start and end of each reduced energy block of the raw audio signal does not coincide with a peak of a transform window of a lapped transform domain format; and an encoder that encodes the raw audio signal into transform windows having the lapped transform domain format, the communications transceiver transmitting the encoded audio signal to one or more endpoints, packet loss concealment being performed for a selected transform window, of the encoded audio signal, having a modified reduced energy signal block located at a center portion of the selected transform window. - View Dependent Claims (16, 17, 18, 19)
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Specification