Method and apparatus for performing packet loss or frame erasure concealment

• US 8,612,241 B2
• Filed: 04/15/2013
• Issued: 12/17/2013
• Est. Priority Date: 04/19/1999
• Status: Expired due to Fees

• Current Assignee: AT&T Intellectual Property II LP (AT&T, Inc.)
• Original Assignee: AT&T Intellectual Property II LP (AT&T, Inc.)
• Inventors: Kapilow, David A.
• Primary Examiner(s): Abebe, Daniel D
• Application Number:
  US13/863,182
• Publication Number:
  US 20130226571A1
• Time in Patent Office: 246 Days
• Field of Search: 704/219, 704/500, 370/240.11
• US Class Current: 704/500
• CPC Class Codes: G10L 19/0017 Lossless audio signal coding; Perfect reconstruction of coded audio signal by transmission of coding error G10L19/24 takes precedence
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 19/028 Noise substitution, i.e. substituting non-tonal spectral components by noisy source comfort noise for discontinuous speech transmission G10L19/012
• CPC Class Codes: G10L 21/003 Changing voice quality, e.g. pitch or formants

Abstract

A method for performing packet loss or Frame Erasure Concealment (FEC) for a speech coder receives encoded frames of compressed speech information transmitted from an encoder. The method determines whether an encoded frame has been lost, corrupted in transmission, or erased, synthesizes properly received frames, and decides on an overlap-add window to use in combining a portion of the synthesized speech signal with a subsequent speech signal resulting from a received and decoded packet, where the size of the overlap-add window is based on the unavailability of packets. If it is determined that an encoded frame has been lost, corrupted in transmission, or erased, the method performed an overlap-add operation on the portion of the synthesized speech signal and the subsequent speech signal, using the decided-on overlap-add window.

Claims

1. A method for processing packets representing encoded speech of a speech signal, comprising:

determining, by a receiver, whether a first packet of the packets is an expected packet or an unexpected packet, wherein an expected packet comprises a packet that is not lost, corrupted, erased or delayed, and wherein an unexpected packet comprises 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 in a buffer;

delaying the plurality of speech samples by a delay corresponding to one quarter of a longest expected pitch period of the speech signal, and

sending the delayed plurality of speech samples to an output port.

2. The method of claim 1, where the one quarter of the longest expected pitch period comprises 3.75 msec.

3. The method of claim 1, where the one quarter of the longest expected pitch period comprises 30 speech samples.

4. A receiver for processing packets representing encoded speech of a speech signal, comprising:

a lost frame detector module for determining whether a packet of the packets is an expected packet or an unexpected packet, wherein an expected packet comprises a packet that is not lost, corrupted, erased or delayed, and wherein an unexpected packet comprises a packet that is lost, corrupted, erased or delayed;

a decoder module for decoding the packet to create a plurality of speech samples, when the lost frame detector module determines that the packet is an expected packet; and

a delay module for delaying the plurality of speech samples by a delay corresponding to one quarter of a longest expected pitch period of the speech signal, and for sending the plurality of speech samples that is delayed to an output port.

5. The receiver of claim 4, where the one quarter of the longest expected pitch period comprises 3.75 msec.

6. The receiver of claim 4, where the one quarter of the longest expected pitch period comprises 30 speech samples.