Editing Motion estimation (section)

==Related terms==
More often than not, the term motion estimation and the term ''[[optical flow]]'' are used interchangeably.{{citation needed|date=August 2019}} It is also related in concept to ''[[image registration]]'' and ''[[stereo correspondence]]''.<ref name="Liu2006">{{cite book|author=John X. Liu|title=Computer Vision and Robotics|url=https://books.google.com/books?id=pmXzAbPUvnYC&q=%22motion+estimation%22+correspondence|year=2006|publisher=Nova Publishers|isbn=978-1-59454-357-9}}</ref> In fact all of these terms refer to the process of [[correspondence problem|finding corresponding points]] between two images or video frames. The points that correspond to each other in two views (images or frames) of a real scene or object are "usually" the same point in that scene or on that object. Before we do motion estimation, we must define our measurement of correspondence, i.e., the matching metric, which is a measurement of how similar two image points are. There is no right or wrong here; the choice of matching metric is usually related to what the final estimated motion is used for as well as the optimisation strategy in the estimation process.

Each ''motion vector'' is used to represent a ''[[macroblock]]'' in a picture based on the position of this macroblock (or a similar one) in another picture, called the reference picture.

The [[H.264/MPEG-4 AVC]] standard defines ''motion vector'' as:

<blockquote>
motion vector: a two-dimensional vector used for inter prediction that provides an offset from the coordinates in the decoded picture to the coordinates in a reference picture.<ref>[http://www.stewe.org/itu-recs/h264.pdf Latest working draft of H.264/MPEG-4 AVC] {{webarchive|url=https://web.archive.org/web/20040723160536/http://www.stewe.org/itu-recs/h264.pdf |date=2004-07-23 }}. Retrieved on 2008-02-29.</ref><ref>{{Cite web|url=http://www.hhi.fraunhofer.de/fileadmin/hhi/downloads/IP/ip_ic_H.264-MPEG4-AVC-Version8-FinalDraft.pdf|title=Latest working draft of H.264/MPEG-4 AVC on hhi.fraunhofer.de.}}{{Dead link|date=October 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
</blockquote>