Browse Prior Art Database

Four Phase Raster Scan Pattern for Compressed Image Transmission

IP.com Disclosure Number: IPCOM000076490D
Original Publication Date: 1972-Mar-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Grossman, DD: AUTHOR

Abstract

This is an improved raster-scan pattern for image transmission.

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Four Phase Raster Scan Pattern for Compressed Image Transmission

This is an improved raster-scan pattern for image transmission.

Suppose that a one-dimensional data compression method is applied to video data, as shown in Fig. 1. If the method is perfect, then the output data will be identical to the input data. For a wide class of compression methods, however, the output is only approximately equal to the input, e.g., delta- modulation, PCM, etc. It is to this class of compression methods that this raster- scan pattern applies.

In standard TV, the raster-scan pattern consists of horizontal scan lines running from left to right. Thus, if such approximate compression is applied using a standard raster-scan pattern, two distortions will arise:
1) Astigmatism. There will be horizontal blurring

due to slope overloading, but there will be no

corresponding vertical blurring.
2) Asymmetry. Overshoots will occur only on the

right hand side of edges.

The instant four-phase raster-scan pattern reduces the effects of both of these distortions by modifying the standard TV raster-scan pattern as follows:
1) To reduce astigmatism, interleave frames of

horizontal scan lines with frames of vertical

scan lines.
2) To reduce asymmetry, interleave scan lines of

opposing direction.
3) To further reduce asymmetry, interleave frames

in which the first scan line goes in one

direction with frames in which the first scan

line goes in the opposite direction.

Any one of the above three met...