Method and apparatus for performing packet loss or frame erasure concealment

• US 7,797,161 B2
• Filed: 09/12/2006
• Issued: 09/14/2010
• 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 Corporation (AT&T, Inc.)
• Inventors: Kapilow, David A.
• Primary Examiner(s): ABEBE, DANIEL DEMELASH
• Application Number:
  US11/519,700
• Publication Number:
  US 20080140409A1
• Time in Patent Office: 1,463 Days
• Field of Search: 704/224, 704/500, 375/240.27
• 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. In a process for concealing the effect of missing speech information, said speech information having been compressed and transmitted in packets to a receiver to which some of the transmitted packets are unavailable or unsuitable for decoding, which packets are collectively referred to herein as unavailable packets, a method for concealing unavailable packets in decoded speech, comprising:

synthesizing a speech signal corresponding to at least one unavailable packet;

performing an overlap-add operation on a portion of the synthesized speech signal with a portion of a subsequent speech signal that was decoded by the receiver, wherein the size of the overlap-add window is based on number of consecutive unavailable packets.

2. A method for creating an output signal in response to received packets, said method including the steps of (a) decoding an available packet to form an audio signal segment, and (b) synthesizing an audio signal segment when a packet is unavailable, where an available packet is a packet that is received when expected and is decodable, and a packet is unavailable when it is not received when expected or is not decodable, the improvement comprising:

performing an overlap-add operation to modify a portion of a decoded audio signal segment, R_j, that follows a number of consecutive synthesized audio signal segments R_j-1, R_j-2, . . . R_j-k, where k is 1 or more, by employing a portion of a previously-decoded audio signal segment, where duration of said repeating portion is ¼

wavelength of pitch estimate of R_j-1 plus m(k-1), where m is a preselected time interval.