Glossary - A Practical Guide to Video and Audio Compression - page 736

Topic Description

wavelet-based compressor. The codec name is contracted from
Pixar wavelet. It has a pretty good compression ratio and the
specifications quote an example of reducing a 6-GB file down to
250 MB. It is only available on the Macintosh platform and
requires a G5 processor. The animation codec is a viable
alternative unless you need high performance. Then you would
probably justify deploying G5 machines wherever you need them.
One of the important features is that it is a key frame-only codec.

Pixmap An area of pixels.

Port One of many thousands of connections that can be made to an

IP-addressed system. Ports are blocked by firewalls and must be
accessible in order to join a session between any two systems.

Porting The process of re-engineering a product so it works on another

platform. We do a lot of this with content, too.

Program stream Program streams are created by multiplexing the elementary

streams containing the media. These program streams are then
multiplexed in groups to create a transport stream. The
transport stream has other supporting data added and is then
fed to the broadcasting medium. That is sometimes called a
multiplex or a transponder.

Progressive scanning Scanning from the top of the screen to the bottom in one pass.

Computer displays typically use progressive scanning and TV
receivers typically use interlaced scanning.

Pro-MPEG Pro-MPEG consortium. Start here when looking for MXF

information.

PVR Personal video recorders were first successfully launched by

TiVo but early work on the concept was done by MIT many
years before. The MIT work used multiple analog video
recorders with computer-controlled serial interfaces—certainly
primitive but functionally recognizable. The future of these
devices will be dependent on standards such as TV-Anytime.

QCIF Quarter Common Intermediate Format. Commonly defined as

176 × 144 or 176 × 120 depending on whether a 625- or 525-line

source is used.

Quantization The process of reducing the variability of data so that it uses one

of a set of predefined values. Snapping to a grid is another way
of understanding quantization. The quantization process is
applied to the DCT output to reduce the data in that block.