Interlaced video is a technique of doubling the perceived frame rate introduced with the signal used with analog television without consuming extra bandwidth. Since the interlaced signal contains the two fields of a video frame captured at two different times, it enhances motion perception to the viewer and reduces flicker by taking advantage of the persistence of vision effect. This results in an effective doubling of time resolution (also called temporal resolution) as compared with non-interlaced footage (for frame rates equal to field rates). Interlaced signals require a display that is natively capable of showing the individual fields in a sequential order. Only CRT displays and ALiS plasma displays are capable of displaying interlaced signals, due to the electronic scanning and lack of apparent fixed-resolution.
Interlaced scan refers to one of two common methods for "painting" a video image on an electronic display screen (the other being progressive scan) by scanning or displaying each line or row of pixels. This technique uses two fields to create a frame. One field contains all the odd lines in the image, the other contains all the even lines of the image. A PAL-based television set display, for example, scans 50 fields every second (25 odd and 25 even). The two sets of 25 fields work together to create a full frame every 1/25 of a second (or 25 frames per second), but with interlacing create a new half frame every 1/50 of a second (or 50 frames per second).
To display interlaced video on progressive scan displays, deinterlacing is applied to the video signal (which adds input lag).
The European Broadcasting Union has argued against the use of interlaced video in production and broadcasting, recommending 720p 50 fps (frames per second) as current production format and working with the industry to introduce 1080p50 as a future-proof production standard which offers higher vertical resolution, better quality at lower bitrates, and easier conversion to other formats such as 720p50 and 1080i50. The main argument is that no matter how complex the deinterlacing algorithm may be, the artifacts in the interlaced signal cannot be completely eliminated because some information is lost between frames.
Despite arguments against it, interlacing continues to be supported by the television standards organizations. It is still included in digital video transmission formats such as DV, DVB, and ATSC. Some video compression standards in development, like High Efficiency Video Coding, target high-definition progressive video and do not support interlaced coding tools.
Read more about Interlaced Video: Description, Benefits of Interlacing, Problems Caused By Interlacing, Deinterlacing, History
Famous quotes containing the words interlaced and/or video:
“See where my Love sits in the beds of spices,
Beset all round with camphor, myrrh, and roses,
And interlaced with curious devices
Which her apart from all the world incloses!
There doth she tune her lute for her delight,
And with sweet music makes the ground to move,
Whilst I, poor I, do sit in heavy plight,
Wailing alone my unrespected love;”
—Bartholomew Griffin (d. 1602)
“We attempt to remember our collective American childhood, the way it was, but what we often remember is a combination of real past, pieces reshaped by bitterness and love, and, of course, the video past—the portrayals of family life on such television programs as “Leave it to Beaver” and “Father Knows Best” and all the rest.”
—Richard Louv (20th century)