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

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 does a motion vector work?

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 motion estimation in data compression?

Motion estimation examines the movement of objects in an image sequence to try to obtain vectors representing the estimated motion. Motion compensation uses the knowledge of object motion so obtained to achieve data compression. In real video scenes, motion can be a complex combination of translation and rotation.

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 is a vector in film?

In video compression, a motion vector is the key element in the motion estimation process. It 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.

What is meant 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.

Is motion a vector or scalar?

The resulting motion of the aircraft in terms of displacement, velocity, and acceleration are also vector quantities. These quantities can be determined by application of Newton’s laws for vectors.

What is meant by optical flow in image processing?

Optical flow or optic flow is the pattern of apparent motion of objects, surfaces, and edges in a visual scene caused by the relative motion between an observer and a scene. Optical flow can also be defined as the distribution of apparent velocities of movement of brightness pattern in an image.

What is compensation and how it helps in motion estimation in video?

Motion compensation is an algorithmic technique used to predict a frame in a video, given the previous and/or future frames by accounting for motion of the camera and/or objects in the video. It is employed in the encoding of video data for video compression, for example in the generation of MPEG-2 files.

What is the difference between I frame and P frame?

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. For example, in a scene where a car moves across a stationary background, only the car’s movements need to be encoded.

What is P stand for in MPEG?

Short for predictive frame, or predicted frame, a video compression method used by the MPEG standard. In a motion sequence, individual frames of pictures are grouped together (called a group of pictures, or GOP) and played back so that the viewer registers the video s spatial motion.