Browse Prior Art Database

Reducing Motion Artifacts in Video Standard Conversion

IP.com Disclosure Number: IPCOM000121103D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 87K

Publishing Venue

IBM

Related People

Rickard, TW: AUTHOR [+2]

Abstract

This article describles a technique that eliminates screen discontinuities and reduces temporal distortion when an interlaced video image is displayed at a different rate on a non-interlaced monitor. Problem

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Reducing Motion Artifacts in Video Standard Conversion

      This article describles a technique that eliminates
screen discontinuities and reduces temporal distortion when an
interlaced video image is displayed at a different rate on a
non-interlaced monitor.
Problem

      Consider the system in Fig. 1 which leads to various motion
artifacts, particularly jagged vertical edges.  These can be reduced
by a technique known as "line doubling" whereby the monitor displays
each even line in the buffer twice for an entire screen followed by
each odd line twice. But other artifacts remain.  Note the two
address counters in the system, one keeping track of the next pixel
to be updated, and the other looking at the next pixel to be
displayed.  As both counters are asynchronous and of differing
frequencies, the gap between them will change with time as the
display counter catches up with the update counter and finally
overtakes it.  If the update counter is less than about 15% through a
field as the display counter starts to read it (Fig. 2a), then there
will be a marked visual discontinuity as the monitor displays a pixel
that has just been updated followed by a pixel which is 2 x field
times old.  This is not the case in Fig. 2b where the update counter
is too far ahead to be caught before the end of the frame.
Solution

      The solution is to stop displaying a frame of even lines
followed by a frame of odd lines and instead make a decision as to
which frame (even or odd) to display next, alternating wherever
possible.  This will eliminate the discontinuities.  For example, if
the display counter is at the last pixel of an odd field then:
*    If update counter is...