Browse Prior Art Database

Grey-Scale Enforcement Aid

IP.com Disclosure Number: IPCOM000045923D
Original Publication Date: 1983-May-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Baxter-Moore, CN: AUTHOR [+3]

Abstract

A grey-scale enforcement aid consisting of a strip of material carrying various shades of grey including white and black is superimposed on a predetermined region of a picture to be transmitted by a Teleconferencing system, to force the system to adopt a lower compression mode of operation than would otherwise have been automatically selected by the system based on the sampling of the actual grey-scale content of the predetermined region of the picture.

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Grey-Scale Enforcement Aid

A grey-scale enforcement aid consisting of a strip of material carrying various shades of grey including white and black is superimposed on a predetermined region of a picture to be transmitted by a Teleconferencing system, to force the system to adopt a lower compression mode of operation than would otherwise have been automatically selected by the system based on the sampling of the actual grey-scale content of the predetermined region of the picture.

Teleconferencing systems speed up transmission of low contrast pictures, such as text, by sampling the grey-scale content of a predetermined region of the picture, for example, the top 25%, and selecting an appropriate degree of compression for the whole picture based on the grey-scale content of the sample. It is clear that some images with a high grey-scale content over selected regions lose legibility during transmission because the grey-scale content of the sampled region happened to be low, thus causing a too high degree of compression to be selected for the picture as a whole. Under these circumstances, provided the grey-scale enforcement aid has a sufficient range of shades of grey, its superimposition over the sample region will ensure that a low level of compression is selected for transmission and the legibility of the transmitted picture is preserved.

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