Method and apparatus for performing packet loss or frame erasure concealment

• US 8,731,908 B2
• Filed: 12/21/2010
• Issued: 05/20/2014
• Est. Priority Date: 04/19/1999
• Status: Expired due to Fees

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Intellectual Property II LP (AT&T, Inc.)
• Inventors: Kapilow, David A.
• Primary Examiner(s): Armstrong, Angela A
• Application Number:
  US12/974,120
• Publication Number:
  US 20110087489A1
• Time in Patent Office: 1,246 Days
• Field of Search: 704/201, 704/207, 704/208, 704/228, 704/500, 714/747
• US Class Current: 704/201
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 25/90 Pitch determination of speech signals

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.

Claims

1. A method executed in a receiver in response to packets representing encoded speech of a speech signal, comprising:

determining whether a first packet of the packets is an expected packet or an unexpected packet, wherein an expected packet includes a packet that is not lost, corrupted, erased or delayed, and wherein an unexpected packet includes a packet that is lost, corrupted, erased or delayed;

when the determining concludes that the first packet is an expected packet,

decoding the first packet to create a plurality of speech samples;

delaying the plurality of speech samples by a delay; and

sending the plurality of speech samples that has been delayed to an output port;

when the determining concludes that a second packet is an unexpected packet,

computing a pitch period estimate, using a number of speech samples that correspond to a most recent 20 msec span of speech samples of the speech signal;

obtaining a segment of the plurality of speech samples in accordance with the pitch period estimate;

performing an Overlap-Add process on the segment with an Overlap-Add segment, wherein the performing generates a first synthesized speech segment;

delaying the first synthesized speech segment by the delay; and

sending the first synthesized speech segment that has been delayed to the output port.

2. A receiver for creating output speech samples from packets representing encoded speech of a speech signal, comprising:

a lost frame detector that determines whether a first packet of the packets is an expected packet or an unexpected packet, wherein an expected packet includes a packet that is not lost, corrupted, erased or delayed, and wherein an unexpected packet includes a packet that is lost, corrupted, erased or delayed;

a decoder that, when the lost frame detector concludes that the first packet is an expected packet, decodes the first packet to create a plurality of speech samples;

a buffer, that, stores and delays the plurality of speech samples by a delay and sends the plurality of speech samples that has been delayed to an output port;

a frame erasure concealment module, that, when the lost frame detector concludes that a second packet is an unexpected packet;

computes a pitch period estimate, using a number of speech samples that correspond to a most recent 20 msec span of speech samples of the speech signal;

obtains a segment of the plurality of speech samples in accordance with the pitch period estimate;

performs an Overlap-Add process on the segment with an Overlap-Add segment, wherein the performing generates a first synthesized speech segment;

delays the first synthesized speech segment by the delay; and

sends the first synthesized speech segment that has been delayed to the output port.

3. A receiver for creating output speech samples from packets representing encoded speech of a speech signal, comprising:

a memory; and

a processor coupled to the memory for performing operations, the operations comprising of;

determining whether a first packet of the packets is an expected packet or an unexpected packet, wherein an expected packet includes a packet that is not lost, corrupted, erased or delayed, and wherein an unexpected packet includes a packet that is lost, corrupted, erased or delayed;

when the determining concludes that the first packet is an expected packet,

decoding the first packet to create a plurality of speech samples;

delaying the plurality of speech samples by a delay; and

sending the plurality of speech samples that has been delayed to an output port;

when the determining concludes that a second packet is an unexpected packet;

computing a pitch period estimate, using a number of speech samples that correspond to a most recent 20 msec span of speech samples of the speech signal;

obtaining a segment of the plurality of speech samples in accordance with the pitch period estimate;

performing an Overlap-Add process on the segment with an Overlap-Add segment, wherein the performing generates a first synthesized speech segment;

delaying the first synthesized speech segment by the delay; and

sending the first synthesized speech segment that has been delayed to the output port.