Forward error correction in speech coding

Abstract

An improved forward error correction (FEC) technique for coding speech data provides an encoder module which primary-encodes an input speech signal using a primary synthesis model to produce primary-encoded data, and redundant-encodes the input speech signal using a redundant synthesis model to produce redundant-encoded data. A packetizer combines the primary-encoded data and the redundant-encoded data into a series of packets and transmits the packets over a packet-based network, such as an Internet Protocol (IP) network. A decoding module primary-decodes the packets using the primary synthesis model, and redundant-decodes the packets using the redundant synthesis model. The technique provides interaction between the primary synthesis model and the redundant synthesis model during and after decoding to improve the quality of a synthesized output speech signal. Such ''interaction'', for instance, may take the form of updating states in one model using the other model.

Description

Background of the invention [0001] The present invention relates to systems and methods for performing forward error correction in the transmission of audio information, and more particularly, the present invention relates to systems and methods for performing forward error correction in the transmission of packet-based speech coded information method. [0002] 1. Speech coding [0003] The shortcomings of state-of-the-art forward error correction (FEC) techniques are best understood through a guided discussion of some conventional speech coding concepts. [0004] 1.1 Code Excited Linear Prediction (CELP) Coding [0005] FIG. 1 shows a conventional code-excited linear prediction (CELP) analysis-by-synthesis encoder 100 . Encoder 100 includes functional units referred to as framing module 104 , linear predictive coding (LPC) analysis module 106 , difference calculation module 118 , error weighting module 114 , error minimization module 116 , and decoder module 102 . The dec...

AI Technical Summary

Problems solved by technology

This can cause "delay" issues in speech synthesis quality

For example, an insufficiently updated adaptive codebook may result in distorted waveforms for more than ten frames

Conventional FEC techniques do not address these types of delays

[0058] In addition, FEC-based speech coding techniques may suffer from many other problems that FEC techniques have not addressed so far

Phase discontinuities can be very audible, for example, in an analysis-by-synthesis technique using a linear predictor

In techniques using adaptive codebooks, the phase error located in the feedback loop may persist for many frames

Also, in speech coders that use LP coefficients predicted at encoding time, the loss of LPC parameters reduces the accuracy of the predictor

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