## What is hierarchical motion estimation?

Hierarchical estimation of the motion vector field (also known as or pyramid search) is a widely applied approach to motion estimation. It offers low computational complexity and high efficiency, plus a large degree of flexibility in the trade-off between the two.

### What is the block based motion estimation?

The algorithm, named as block based motion estimation with true region motion field, is actually based on the successive motion estimation from the highest confidence motion vectors to lowest one. It is utilizing fact that the image pixels corresponding to the same object projection all account similar movement.

How do you do motion estimation?

There are two mainstream techniques of motion estimation: pel-recursive algorithm (PRA) and block-matching algorithm (BMA). PRAs are iterative refining of motion estimation for individual pels by gradient methods. BMAs assume that all the pels within a block has the same motion activity.

How does block matching work?

The Block Matching is a temporal compression technique used in the video encoding. The main purpose of this method is to determine the displacements of each block of pixels between two successive frames. This technique, performed in the step of motion estimation, occupies the majority of the total time of video coding.

## What is motion estimation how it is useful for video compression?

The motion estimation block in a video codec computes the displacement between the current frame and a stored past frame that is used as the reference. Usually the immediate past frame is considered to be the reference.

### How do you find the motion vector?

A “motion vector” is calculated by finding a correspondence between rectangles at time t, and rectangles at time t − 1, where t is the frame index in a video signal. Motion vectors were originally invented for video coding.

What is meant by exhaustive search?

any search process in which every item of a set is checked before a decision is made about the presence or absence of a target item.

What are the type of block matching algorithms?

Diamond Search (DS) algorithm uses a diamond search point pattern and the algorithm runs exactly the same as 4SS. However, there is no limit on the number of steps that the algorithm can take. Two different types of fixed patterns are used for search, Large Diamond Search Pattern (LDSP)

## What is motion estimation in video coding?

Motion estimation is the process of determining motion vectors that describe the transformation from one 2D image to another; usually from adjacent frames in a video sequence. It is an ill-posed problem as the motion is in three dimensions but the images are a projection of the 3D scene onto a 2D plane.

### What are the three types of frame used in motion estimation of MPEG compression algorithm for video?

Three types of pictures (or frames) are used in video compression: I, P, and B frames. An I‑frame (Intra-coded picture) is a complete image, like a JPG or BMP image file. A P‑frame (Predicted picture) holds only the changes in the image from the previous frame. P and B frames are also called Inter frames.

What do you mean by motion vector?

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.

What is a scalar motion?

Unlike ordinary vectorial motion, which is defined by both direction and magnitude, called a vector, scalar motion has no direction, but only magnitude.

## Which is the best search algorithm for motion estimation?

2.1 Three Step Search (TSS) [1,2] This algorithm was introduced by Koga et al in 1981. It became very popular because of its simplicity and also robust and near optimal performance. It searches for the best motion vectors in a coarse to fine search pattern. The algorithm may be described as: Step 1: An initial step size is picked.

### How is block matching used in motion estimation?

One of the first algorithms to be used for block based motion compensation is what is called the Full Search or the Exhaustive Search. In this, each block within a given search window is compared to the current block and the best match is obtained (based on one of the comparison criterion).

When to use approximate model for motion estimation?

Approximate Model: Orthographic Projection compared to the distance of the object. Can be used as long as the depth variation within the object is small , When the object is very far ( ) x X y Y Z © Yao Wang, 2016 EL-GY 6123: Image and Video Processing Rigid Object Motion ‘ [ ]( ) ; [ ]:x ,y ,z ; :T x ,T y ,T z

What is hierarchical motion estimation? Hierarchical estimation of the motion vector field (also known as or pyramid search) is a widely applied approach to motion estimation. It offers low computational complexity and high efficiency, plus a large degree of flexibility in the trade-off between the two. What is the block based motion estimation? The algorithm,…