System and method for converting a non-interlaced video signal into an interlaced video signal

DETAILED DESCRIPTION The present invention is directed to a system and method for converting successive frames of a non-interlaced video signal into successive fields of an interlaced video signal.
As used herein, the terms "frame" and "field" are understood to have the meanings generally ascribed to them in the field of video imagery; i.
e.
, a frame comprises a plurality of raster lines defining a complete video image, whereas a field comprises a subset of the raster lines (usually all the odd lines or all the even lines) defining a given frame.
A non-interlaced video image comprises successive frames of image information displayed one on top the other, while an interlaced image comprises successive fields displayed with their raster lines interlaced alternatingly with those of the immediate preceding field.
The system of the present invention comprises means for receiving an input signal defining successive frames of a non-interlaced video image and means for producing concurrently an output signal defining an interlaced version of the same image; the field rate of the output signal being equal to the frame rate of the input signal.
Provision is also made for operating the system in timed synchrony with either an internal or an external timing source, and for conforming the output signal to either U.
S.
or European television standards.
A unique feature of the present invention is that transformation of the non-interlaced input signal into its interlaced equivalent is accomplished without requiring the intermediate storage of a full frame, or even a full line, of input information.
This is made possible primarily through the use of a first-in/first-out (FIFO) oriented line buffer to process alternate lines of the input signal in a line-by-line manner.
In operation, every other line (e.
g.
, even) of a first frame of input information is written into the line buffer at a first non-interlaced rate at the same time that it is read from the buffer at a second slower, interlaced rate.
The process is then repeated for the alternate lines (e