Low-complexity packet loss concealment for transcoded audio signals

A computer program product comprising a non-transitory computer-readable medium storing computer-readable program code that, when executed by one or more processors, causes the one or more processors to perform operations comprising:

• receiving 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;
• decoding the received packets to a sequence of blocks of a raw audio signal;
• replacing 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 each reduced-energy signal block of the raw audio signal at one of a beginning boundary and an ending boundary of inserted blocks;
• shifting 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 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
• transmitting the encoded audio signal.

A system for concealing packet loss in a received audio stream, the system comprising:

• 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.