User Guide

320 Glossary
In MPEG-2 video, the I-, B-, and P-pictures can contain either frames or fields. In MPEG-1
video, they contain only frames.
The I-picture (also known as a key frame) contains all the image information for a single
frame or field, and is thus only moderately compressed. B-pictures and P-pictures contain
only information that is different from the previous or next frame/field, and reference the
nearest I-picture for the remaining information. This means they are much more highly
compressed than I-pictures.
See also B-picture, chapter point, I-picture, P-picture, sequence header.
GOP size Number of frames in a group of pictures (GOP). For example, a GOP size of 10
looks like this if the I-, B-, and P-pictures contain whole frames:
I B B P B B P B B P
and like this if the I-, B-, and P-pictures contain fields:
I P B B B B P P B B B B P P B B B B P P
See also field, frame.
GOP structure The number of B-pictures before each P-picture in a group of pictures.
Typical GOP structures are I B P (one B-picture) and I B B P (two B-pictures).
Hz (Hertz) Cycles per second. Unit of measurement for frequencies.
I-picture (Intra-Picture) MPEG video picture that contains all the information necessary to
create a single frame or field. Every GOP in an MPEG video stream starts with an I-picture,
which provides a reference point for the B- and P-pictures in the GOP. See also B-picture,
GOP, P-picture.
i.link Sony Corporation’s term for the IEEE-1394 standard.
I420 The FOURCC code for a compressed YUV color format developed by Intel Corporation.
Identical to IYUV.
IEEE-1394 Standard for transmitting digital signals between various devices including DV
cameras and computers. Also known as FireWire or i.LINK.