Deinterlacing - Deinterlacing Methods

Deinterlacing Methods

Deinterlacing requires the display to buffer one or more fields and recombine them into full frames. In theory this would be as simple as capturing one field and combining it with the next field to be received, producing a single frame. However, the originally recorded signal was produced as a series of fields, and any motion of the subjects during the short period between the fields is encoded into the display. When combined into a single frame, the slight differences between the two fields due to this motion results in a "combing" effect where alternate lines are slightly displaced from each other.

There are various methods to deinterlace video, each producing different problems or artifacts of its own. Some methods are much cleaner in artifacts than other methods.

Most deinterlacing techniques can be broken up into three different groups all using their own exact techniques. The first group are called field combination deinterlacers, because they take the even and odd fields and combine them into one frame which is then displayed. The second group are called field extension deinterlacers, because each field (with only half the lines) is extended to the entire screen to make a frame. The third type uses a combination of both and falls under the banner of motion compensation and a number of other names.

Modern deinterlacing systems therefore buffer several fields and use techniques like edge detection in an attempt to find the motion between the fields. This is then used to interpolate the missing lines from the original field, reducing the combing effect.