Method and Apparatus for Performing Packet Loss or Frame Erasure Concealment

• US 20100274565A1
• Filed: 07/02/2010
• Published: 10/28/2010
• Est. Priority Date: 04/19/1999
• Status: Active Grant

• Current Assignee: AT&T Intellectual Property I LP (AT&T, Inc.)
• Original Assignee: AT&T Intellectual Property I LP (AT&T, Inc.)
• Inventors: Kapilow, David A.
• Granted Patent: US 8,185,386 B2
• Time in Patent Office: Days
• 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 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 on audio signal segment, that is decoded by said step of decoding and which follows a number of consecutive audio signal segments R_j-1, R_j-2, . . . R_j-k, that were synthesized by said step of synthesizing, where k is 1 or more, to modify a portion of said segment R_j-1 with a portion of said segment R_j to form a modified segment, R′

_j where duration of said portion is a function of k; and

outputting segment R′

_j.

3. The method of claim 1 where, when duration of said consecutive segments R_j-1, R_j-2, . . . R_j-k, that were synthesized by said step of synthesizing exceeds 10 msec, said segment R_j-1 is attenuated before performing said overlap-add operation.

2. The method of claim 2 where said duration is ¼

pitch period plus