What is meant by motion compensation?

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. Motion compensation describes a picture in terms of the transformation of a reference picture to the current picture.

What is motion estimation and motion compensation?

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. Such motion is difficult to estimate and may require large amounts of processing.

What are the main steps of video compression based on motion compensation MC?

The three main steps of these algorithms are:

• Motion estimation (motion vector search)
• Motion compensation – based prediction.
• Derivation of the prediction error – the difference.

What is motion estimation in 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. It is called a vector since it has both horizontal and vertical components of displacement.

When do you use global motion compensation ( GMC )?

Global motion compensation (GMC) is a technique used in video compression to reduce the bitrate required to encode video. It is most commonly used in MPEG-4 ASP, such as with the DivX and Xvid codecs .

How does global motion compensation work in Photoshop?

Global motion compensation describes the motion in a scene based on a single affine transform instruction. The reference frame is panned, rotated and zoomed in accordance to GMC warp points to create a prediction of how the following frame will look.

How is motion compensation used in video coding?

When images can be accurately synthesized from previously transmitted/stored images, the compression efficiency can be improved. Motion compensation is one of the two key video compression techniques used in video coding standards, along with the discrete cosine transform (DCT).

How does motion compensation work in figure 3.14?

Areas in the preceding frame of Figure 3.14 are found that best match the areas in the current frame. These are transmitted along with instructions for their new position and the differences needed to update them. This minimizes the amount of information that must be conveyed to the receiver.