A set of alternating scan lines that make up half of a complete image on an interlaced display. In traditional analog television formats like NTSC, one field contains all the odd-numbered lines and the next field contains all the even-numbered lines. Drawing the image in two sequential fields reduces perceived flicker without doubling the required transmission bandwidth.
The video capture card is dropping the odd field, which is why the recorded footage looks jagged during fast motion.
Related terms
Scan line
A single horizontal row of pixels or phosphors drawn across a display screen.
Cathode ray tube
A vacuum tube containing one or more electron guns and a phosphorescent screen used to display images.
CVBS
Composite video, blanking, and sync is an analog video format carrying standard-definition signals on a single channel.