Method and system for generating colored comfort noise in the absence of silence insertion description packets

Abstract

A method and system for utilizing information content in speech and a transition hangover between speech and noise to generate comfort noise on the decoder side. This adaptation to noise may be accomplished using various algorithms of estimating the spectrum of color noise. According to an embodiment of the present invention, an adaptation algorithm may be implemented that adapts, with time, rather than a block based algorithm to prevent the repeated generation of artifacts present in the block that are being adapting to. The method and system of the present invention generates comfort noise in the absence of silent insertion descriptions containing spectrum information thereby saving bandwidth and generating colored comfort noise that reflects the spectrum of the actual noise.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority from provisional applications Ser. No. 60 / 297,265, filed Jun. 12, 2001 and Ser. No. 60 / 305,157, filed Jul. 16, 2001, which are incorporated by reference.FIELD OF THE INVENTION [0002] The present invention relates generally to enhancing bandwidth efficiency and to voice transmission and silence compression and, more particularly, for generating colored comfort noise in absence of silence insertion description packets containing spectrum information. BACKGROUND OF THE INVENTION [0003] Digital Subscriber Line (DSL, Digital Subscriber Loop, xDSL) involves a technology that enables high-speed transmission of digital data over traditional copper telephone lines. This technology involves digital telecommunications protocols designed to allow high-speed data communication over existing copper telephone lines between end-users and telephone companies. [0004] When two conventional modems are connected through the ...

AI Technical Summary

Benefits of technology

[0018] Aspects of the present invention overcome the problems noted above, and realize additional advantages. One such inventive aspect provides methods and systems for implementing a low complexity spectrum estimation technique for comfort noise generation. One aspect of this invention is the manner of estimating the signal spectrum and generating comfort noise (CN) with reduced complexity as compared to existing methods. Another aspect of this invention involves segregating filter parameter encoding from the adaptation process for transmission in the form of silence insertion descriptors. In systems where MIPS and memory are expensive, the invention employs a method, which utilizes the fact that the signal spectrum essentially stays constant over an extended period of time and the method adapts to the spectrum over time. This has an advantage in that the comfort noise generated is a more realistic representation of the input noise and the comfort noise generated is uniform. The segregation of filter parameter encoding for transmission offers enhanced flexibility as such a separation leads to greater interoperability between various systems. Another benefit is that the MIPS and memory are more efficiently used.

[0019] Further, existing ITU recommendation G. series G729AB uses a different approach for comfort noise generation (CNG), which approach requires a high level of MIPS and memory. Various other implementations for CNG exist. This inventive aspect of the present invention has, for example, one or more of the following advantages over such approaches: a more pleasing colored comfort noise (as opposed to white) is generated; a less complex algorithm is utilized having a reduced demand for MIPS and memory, which are critical elements in real time systems; and filter parameter encoding (into reflection coefficients) is done independent of the adaptation process, which affords greater flexibility of using the MIPS only when necessary, which allows the filter parameters to be encoded into some other form of encoding, while the fundamental algorithm remains the same (the only change would be to the encoding algorithm)

Problems solved by technology

When the period of the pseudo-random generator is limited, as is often the case, this form of noise generation leads to periodic artifacts, especially when synthesizing a stable spectrum signal.

This causes unpleasant sounding differences in the background noise when someone is speaking versus when they are not speaking.

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