Method and apparatus for providing motion estimation signals for communicating image sequences
First Claim
1. In an image sequence transmission method for transmitting a sequence of images over a bandwidth limited channel, a motion estimation method for estimating for successive image frames, a measure of motion displacement between successive images comprising the steps ofdividing each said image into non-overlapping blocks, each block having a plurality of picture elements,selecting an initial value of a motion vector displacement for each successive block,iteratively determining, using a steepest descent method, succession values of said motion vector displacement for successive blocks of an image, andterminating said iteration step for a block when an iteration error measure, associated with said steepest descent method, is less than a predetermined threshold value.
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Abstract
An image sequence transmission method and apparatus transmit a sequence of successive images over a bandwidth limited channel. The transmitter has a motion estimator for estimating the motion displacement between successive image frames of the sequence. The motion estimator divides each image into nonoverlapping blocks, each block including a plurality of picture elements. The apparatus then successively selects, in accordance with a steepest descent estimation technique, an initial value of a motion vector displacement for each successive block. Thereafter, an iterative process determines using the steepest descent approach, successive values of the motion displacement vector for a block and the iteration process is terminated when an iteration error measure, which is associated with the steepest descent method, is less than a predetermined threshold value. In particular embodiments of the invention, an adaptive approach is used wherein the step size parameter is incremented in accordance with a gradient error used in the steepest descent technique. In addition, methods and apparatus for determining an initial motion vector field value based upon of the motion displacements in adjacent blocks advantageously determine the initial displacement vector for a block.
153 Citations
22 Claims
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1. In an image sequence transmission method for transmitting a sequence of images over a bandwidth limited channel, a motion estimation method for estimating for successive image frames, a measure of motion displacement between successive images comprising the steps of
dividing each said image into non-overlapping blocks, each block having a plurality of picture elements, selecting an initial value of a motion vector displacement for each successive block, iteratively determining, using a steepest descent method, succession values of said motion vector displacement for successive blocks of an image, and terminating said iteration step for a block when an iteration error measure, associated with said steepest descent method, is less than a predetermined threshold value.
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11. In an image sequence transmission method for transmitting a sequence of images over a bandwidth limited channel, a motion estimation method for estimating for successive image frames, a measure of motion displacement between successive images comprising the steps of
dividing each said image into non-overlapping blocks, each block having a plurality of picture elements, generating an initial value of the motion vector displacement for a block from a weighted average of previously determined motion vector displacements for adjacent blocks, iteratively determining, using a steepest descent method, succession values of said motion vector displacement for successive blocks of an image, modifying, for each iteration, a previous motion vector displacement in accordance with a multiplicative product of an incremental step value and an error gradient, adaptively modifying an initial step value in accordance with said error gradient value, and terminating said iteration step for a block when a multiplicative product of said initial step value and said error gradient is less than a predetermined threshold value.
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12. In an image sequence transmission system for transmitting a sequence of images over a bandwidth limited channel, a motion estimation apparatus for estimating, for successive image frames, a measure of motion displacement between successive images comprising
means for dividing each said image into non-overlapping blocks, each block having a plurality of picture elements, means for selecting an initial value of a motion vector displacement for each successive block, means for iteratively determining, using a steepest descent approach, successive values of said motion vector displacement for successive blocks for an image, and means for terminating said iteration for a block when an iteration error measure associated with said steepest descent, is less than a predetermined threshold value.
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22. In an image sequence transmission system for transmitting a sequence of images over a bandwidth limited channel, a motion estimation apparatus for estimating, for successive image frames, a measure of motion displacement between successive images comprising
means for dividing each said image into non-overlapping blocks, each block having a plurality of picture elements, means for generating an initial value of the motion vector displacement for a block from a weighted average of previously determined motion vector displacements for adjacent blocks, means for iteratively determining, using a steepest descent approach, successive values of said motion vector displacement for successive blocks for an image, means for modifying, for each iteration, a previous motion vector displacement in accordance with a multiplicative product of an incremental step value and an error gradient, means for adaptively modifying an initial step value in accordance with said error gradient value, and means for terminating said iteration for a block when a multiplicative product of the initial step value and said error gradient is less than a predetermined threshold value.
Specification