Browse Prior Art Database

Three-State Voice Framing

IP.com Disclosure Number: IPCOM000043719D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Daugan, G: AUTHOR [+5]

Abstract

A number of techniques have been developed which take advantage of the fact that a conversation is a sequence of silences and talk-spurts to increase the efficiency of digital voice transmission systems. More particularly in a packet switching transmission system, packets representing silence are deleted from the data flow; i.e., they are not transmitted over the communication link. This technique obviously requires means for discriminating voice packets from silence packets. This operation is generally performed by using a Voice Activity Detector (VAD) which exhibits a binary decision setting a VAD flag to zero for silence and to one for a voice signal.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 91% of the total text.

Page 1 of 2

Three-State Voice Framing

A number of techniques have been developed which take advantage of the fact that a conversation is a sequence of silences and talk-spurts to increase the efficiency of digital voice transmission systems. More particularly in a packet switching transmission system, packets representing silence are deleted from the data flow; i.e., they are not transmitted over the communication link. This technique obviously requires means for discriminating voice packets from silence packets. This operation is generally performed by using a Voice Activity Detector (VAD) which exhibits a binary decision setting a VAD flag to zero for silence and to one for a voice signal. During transitions from silence to talk-spurt, and vice- versa, the VAD flag operates close to its detection threshold, and its decision remains uncertain during a short frame sequence. To limit these drawbacks, an additional flag is provided, i.e., an Incertitude flag. During the transient periods, both the VAD flag and the Incertitude flag are set to 1. This information is transmitted with the data bits and used at the receiving end of the transmission network to warn of a possible break in the arriving packet sequence. The two-flag system offers the following combinations of flags, with each combination defining a type of data frame:

(Image Omitted)

The above system also enables the detection of transmission errors by noting that two consecutive frame sequences of the SV or VS type wo...