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Video Frame-Rate Acceleration Technique

IP.com Disclosure Number: IPCOM000112815D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 6 page(s) / 229K

Publishing Venue

IBM

Related People

Moller, CHL: AUTHOR

Abstract

Given an ordered set of digitized video frames representing an animated image, the technique described herein will create a second ordered set of such frames that, if displayed sequentially, will either correct for a sampling rate faster than the display rate, or create the appearance of accelerated motion.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 25% of the total text.

Video Frame-Rate Acceleration Technique

      Given an ordered set of digitized video frames representing an
animated image, the technique described herein will create a second
ordered set of such frames that, if displayed sequentially, will
either correct for a sampling rate faster than the display rate, or
create the appearance of accelerated motion.

      The appearance of motion on a video display is done by showing
sequences of static images in rapid succession.  Typically, the
sequence of static images is obtained either by sampling and
digitizing a scene using a video camera of some sort, or by rendering
a succession of synthetic images using appropriate computer-graphic
techniques.  In the former case, the sequence has been captured at a
specific sampling rate; in the latter case, a specific real-time
interval has been assumed between the computation of successive
frames.

      The sequence, having been sampled or created at a specific
rate, can only be replayed accurately if the successive images are
displayed at that same rate.  It is possible, however, for the sample
rate to be different than the display rate.  For example, in
animation sampled at, for example, 44 frames per second (fps), might
be displayed on a television monitor at a different rate such as 30
fps.  Under these circumstances, one second of a source sequence,
comprising 44 frames, would be displayed in 44/30 seconds, resulting
in an apparent slowing of the motion represented.

      Under other circumstances, it may be desirable to play an
animation at a speed faster than that which it was captured.  Given
equivalent capture and display rates, this is essentially the same
problem as above:  reducing the number of frames to be displayed
while retaining the best possible approximation of the content of the
original animation.

      From the previous example, the original 44 source frames must
somehow be used to create 30 resultant frames, each sequence of
frames representing one second of real time in its own domain.
Alternatively, given an animation sampled at a given rate and a
desire to display that animation accelerated by some arbitrary factor
on equipment using the same refresh rate, it is necessary to reduce,
by that same factor, the number of frames available.

      A simple solution to the rate-adjustment problem is through the
use of a frame buffer, allowing the sequence source to update pixels
in the frame buffer at one rate, while allowing the display system to
sample the same frame buffer at another rate.  This mechanism,
however, can result in omitting some source frames entirely, or in
displayed frames that consist of parts of two sequential source
frames.  This in turn results in potential animation jerkiness or in
various kinds of image distortion such as elongation or
foreshortening of objects as they move.

      Since accelerated motion and rate-adjustment may be achieved by
reducing the number of frames a...