Browse Prior Art Database

A Method for Adaptively Changing Display Refresh Rate

IP.com Disclosure Number: IPCOM000123481D
Original Publication Date: 1998-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Hino, A: AUTHOR

Abstract

Disclosed is a method for adaptively changing display refresh rate. By the method, useless power dissipation can be reduced without sacrificing visual quality on display screen. This enables gradual power reduction instead of shutting off, quicker return from the low power state and power saving in much shorter period of time.

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A Method for Adaptively Changing Display Refresh Rate

   Disclosed is a method for adaptively changing display
refresh rate.  By the method, useless power dissipation can be
reduced without sacrificing visual quality on display screen.  This
enables gradual power reduction instead of shutting off, quicker
return from the low power state and power saving in much shorter
period of time.

   In many cases, changes of pixel data between successive
frames are not so frequent as the refresh rate.  And some kinds of
display devices do not or may not need such high refresh rate for
just sustaining visual screens.  Thus, plenty of refresh cycles may
dissipate electric power uselessly.  The disclosed method tracks
temporal activity of images shown on the display device.  According
to the activity measure, refresh rate is heightened for high activity
measure and lowered for low activity measure so that side effects on
visual quality is minimized.

   The activity measure, A, can be defined as average
absolute difference between corresponding pixels in successive
frames.
    A = 1/M *  Sum( |Xi - Yi| )
  where,
    Sum(z)  Summation of value z in Set S
    S    Set of indices for selected pixels
    i    Index of a pixel
    M    Number of elements in S
    X    Pixel data in current frame
    Y    Pixel data in previous frame

   Note that S does not necessarily cover the whole display
screen.  It can be a subset, e.g., every N-th scan line.  As will be
obvious to one skilled in the art, there are alternati...