NAIM AV2 Owner's Manual - page 16
14
14 Video Formats Explained
In the early days of domestic video and home theatre
the issue of different video formats and interfaces did
not really arise. There was only one way of connecting
a VCR to a TV - via the aerial cable. However the
growth in domestic high quality video, along with the
introduction of widescreen and non-CRT displays has
meant that video interface issues, once of concern
only to professionals, have become significant in
domestic systems.
The following few paragraphs provide an explanation
of some of the issues and technologies that impinge
on the DVD5, its installation and operation.
14.1 Video Display - Interlaced and Progressive Scan
Video is nothing more than a series of still pictures displayed
sequentially at such a rate that the brain perceives continuous
motion. A video signal comprises elements that describe the
colour and brightness of each individual display pixel and an
element that describes the necessary timing information required
to create an image. Each picture is “drawn”, pixel by pixel and
line by line, across and down the screen - again at a rate such
that the brain does not distinguish the segmented nature of the
information.
In conventional “interlaced” video, each still picture is drawn
half a screen at a time in two sections (or scans) constructed
from sets of alternate lines. This technique is used to reduce the
amount of information required for each frame. In “progressive
scan” video, rather than being constructed from two sections,
pictures are constructed in a single top to bottom scan. The result
is a significantly sharper, more detailed and more stable image.
14.2 Video Interface Formats
Table 6.4 (page 4) of this manual lists the video interface
formats supported by the DVD5 in order of preference defined
by the display quality potential of each. There are fundamental
technical reasons why alternative formats can provide different
levels of display quality and an explanation of these provides a
useful introduction to the techniques and technologies of video.
The formats are described, in reverse quality order, over the
following paragraphs.
14.2.1 Interlaced Composite Video (SCART, analogue)
The SCART (Syndicat des Constructeurs d’Appareils
Radiorécepteurs et Téléviseurs) connector first became familiar
on the introduction of high quality domestic video recorders.
These recorders were able to generate both “composite” and
“component” video signals and both, along with stereo analogue
audio, are carried by the SCART. Component video generally
describes those formats that carry the various elements of the
signal on separate cables - sometimes known as channels.
Composite video is a signal that encodes the three elements of a
moving image - colour, brightness and timing - in a single signal
carried by a single cable. Two different encoding formats are
common - NTSC generally in America and the Far East, and PAL
in Europe. Encoding the signal brings the advantages of single-
wire simplicity and convenience, but the necessary downstream
decoding produces unavoidable and visible artifacts. Composite
video thus offers the lowest display quality of the options
available and should be used if there is really no other option.
Very few contemporary displays or TVs will offer a composite
video input only .
14.2.2 S-Video (4 Pin mini-DIN, analogue)
The S-Video format offers the next higher quality video
connection. S-Video is a two channel based connection with the
colour and brightness information separated, and the timing
signal combined with the brightness signal. The separation
of colour and brightness reduces the need for downstream
processing to decode the signals and results in potentially a
sharper image.
14.2.3 YPbPr and RGB (SCART, analogue)
In addition to carrying a composite video signal the SCART
interface also carries a set of “RGB” or “YPbPr” video signals
selectable via the video setup menu. RGB denotes the
fundamental Red, Green and Blue components that define
a colour image. A timing signal is combined with the Green
signal. YPbPr is mathematically derived from RGB and denotes
brightness (Y) and two colour difference signals (Pb & Pr). The
video timing signal for the YPbPr format is combined with the
brightness signal. YPbPr carries the same information as RGB but
does so with reduced bandwidth demands. Both RGB and YPbPr
offer a further potential quality increase over S-Video by again
reducing the demands on downstream decoding. It is marginally
preferable to use RGB over YPbPr.
14.2.4 High Definition Progressive Scan YPbPr (3 x
BNC, analogue)
The first connection interface from which a Progressive Scan
signal is available. YPbPr Progressive Scan can be selected for
the BNC interface via the video setup menu.
14.2.5 High Definition Progressive Scan YPbPrHV (5x
BNC, analogue)
A second YPbPr/BNC interface provides the highest potential
video quality YPbPr signal. YPbPr HV is a five channel interface
with separate horizontal and vertical timing signals again
selectable via the video setup menu. Connecting to a display with
each signal element carried separately reduces the necessity for
downstream signal processing and potentially provides another
step up in video quality.
14.2.6 High Definition Progressive Scan RGB (3x BNC,
analogue)
A Progressive Scan RGB signal is also selectable via the video
setup OSD menu and available from the same three BNC
connectors described in paragraph 14.2.4. RGB is the native
video format of most displays and potentially provides better
quality than YPbPr thanks to reduced demands for downstream
signal processing. As with the SCART RGB interface, the video
timing signal is combined with Green signal.
Note:
RGB progressive scan output is disabled when replaying
Macrovision encoded material.