Glossary - A Practical Guide to Video and Audio Compression - page 733

Topic Description

Modem The modem equipment at each end of a telephone line is used to

create a data connection between two systems. The word is
contracted from modulator-demodulator.
Modulator-demodulators are used to transfer digital signals
over analog telephone lines.

Motion compensation The use of motion vectors to improve the compression of

macroblocks by recycling previously decoded blocks and
applying a move to them before adding residual data.

Motion estimation The process of generating motion-compensating vectors during

the encoding process. Technically, this is the most difficult part
of the algorithm to understand.

Motion JPEG A means of creating moving-image files by storing a series of

still images that are individually coded with the JPEG standard
protocol. This is a key frame-only format but now that the JPEG
standard has been revised to the wavelet-based JPEG 2000
version, this is a somewhat dated codec. Motion JPEG is still
widely used since it is embedded in a lot of studio-quality video
servers but it is a legacy format when choosing codecs for new
projects.

Motion vector This is used to compensate for motion when constructing one

macroblock from another. These vectors can be forward- or
backward-referencing and are specified in two dimensions.

MP3 MPEG-1 Audio Layer 3.

MPEG Motion Picture Experts Group. A working group within the

ISO/IEC standards body. This group is concerned with the
standardization of moving-picture representations in the digital
environment.

MPEG-1 The original MPEG video standard designed for CD-ROM

applications and other similar levels of compression. This is a
legacy format. Still useful for some solutions but new projects
should use a later codec.

MPEG-2 Widely used for digital TV and DVD products. A much-

improved codec that supersedes MPEG-1 in many respects. It
has been popularized by DVD content encoding and DVB
transmission.

MPEG-3 This was cancelled because the proposed work was included in

MPEG-2 with a small enhancement.

MPEG-4 A huge leap forward in the description of multimedia content.

MPEG-4 is the essence container.

Continued