User Guide

MPEG Overview 309
Block Each macroblock is comprised of four blocks:
MPEG Compression Schemes
The MPEG algorithm uses two main compression strategies: interframe and intraframe.
Interframe Compression
Much of the information in a picture within a video sequence is similar to information in a
previous or subsequent picture. The MPEG standard takes advantage of this temporal
redundancy to represent some pictures in terms of their differences from a reference
picture. This section describes the picture types and explains the techniques used in
interframe compression.
Picture Types The MPEG specification defines three types of pictures:
• I-pictures (Intra-pictures), coded using only information present in the picture itself. I-
pictures provide random access points into the compressed video data. I-pictures
typically use about 2 bits per coded pixel.
DIVIDE PICTURE
INTO 16X16 BLOCKS
(MACROBLOCKS)
EACH MACROBLOCK IS
16 PIXELS BY 16 LINES
(4 BLOCKS)
EACH BLOCK IS
8 PIXELS BY 8 LINES