Interlaced video refers to the technique for doubling the frame
rate of a video display without the making use of extra bandwidth. Generally
speaking, the interlaced signal consists of two fields of a video frame
captured at two different times. Interlaced video are powerful in function as
it can enhance motion perception to the viewer and reduce flicker by making use
of the phi phenomenon effect.
As a result, compared to non-interlaced footage (for frame rates
equal to field rates), interlaced video doubles the time resolution (also known
as temporal resolution). At the same time, interlaced video has a lot of
requirements which need to be satisfied in order to make it function well. A
display capable of showing the individual fields in a sequential order is
necessary for interlaced signals. As a result, considering the electronic
scanning and apparent fixed-resolution, there are only two kinds of displays
are able to display interlaced signals: CRT displays and ALiS
Interlaced scan, along with progressive scan, is one of the two
common methods for “painting” a video image on the electronic display screen
which is realized by scanning or displaying each line or row of pixels. Under
such condition, two fields are utilized to create a frame by this technique.
One field contains all odd lines in the image, while the other contains all
even lines.
For example, a PAL-based television set display scans 50 fields
every second (25 odd and 25 even). A full frame, every 1/25 of a second (or 25
frames per second), is created by the two sets of 25 fields working together.
At the same time, a new half frame every 1/50 of a second (or 50 fields per
second) is created with interlacing. On the other hand, deinterlacing is
applied to the video signal in order to display interlaced video on progressive
scan displays in the process of playback.
