Ulead 1.0 - Manual (Page 177)

SpruceUp User’s Guide 13—5
Video Basics
There are three predominant video standards in the world; NTSC, PAL, and SECAM. NTSC
(National Television Standards Committee) is based on 525 lines per frame of video, with
29.97 video frames per second (see Why NTSC’s 29.97 Frame Rate at the end of this topic).
PAL (Phase Alternating Line) is based on 625 lines per frame, with 25 video frames per
second. SECAM (SÉquential Couleur Ávec Memoire) uses PAL frame and line values, but a
different color encoding scheme. There are also a number of variants of all three systems.
In all cases, standard broadcasts use an interlace technique to divide each frame into two
fields, in effect providing twice as many pictures per second (59.94 fields per second NTSC
and 50 fields per second PAL). For historical reasons, countries that use 60Hz AC power
typically use video based on 60 fields per second; 50Hz AC power leads to 50 fields per
second video.
NTSC, PAL, and SECAM all are actually terms used to describe a composite television signal
(one where the luminance and chrominance combine into one signal). While this makes
broadcasting simpler, it compromises the overall picture quality. An improvement is S-Video
(Y/C Video). In this case, the chrominance is kept separate from the luminance, but is still
encoded with a high frequency subcarrier.
The best picture quality comes from component video, where three signals (RGB, YUV, or Y,
R-Y, B-Y) contain the luminance and chrominance information. While component signals are
often referred to as NTSC and PAL, they really are not, and it is better to refer to them as
525 and 625. There is no difference between PAL and SECAM signals when converted into
component video. PAL-M is a standard (used by Brazil) that uses PAL chroma encoding and
NTSC line and frame rates. When converted to component, it is the same as NTSC/525, not
PAL/625 as would seem logical.
MPEG Video
MPEG DVD encoded video is always component (4:2:0) based. This means that composite
and S-Video sources must be converted to component before encoding. Particularly in the
case of composite, this process is difficult and tends to degrade the picture and introduce
artifacts.
Horizontal Pixels
Both PAL and NTSC have 720 active pixels per horizontal line for their full D-1 settings. DVD
compliant MPEG-2 is allowed two other settings: 704 and 352. 704 pixels approximates the
length of the active area of an analog line. 352 is half of the 704 setting, and is used for the
1/2 D-1 setting (along with all the vertical lines) and the SIF (Standard Interface Format)
used for MPEG-1 and MPEG-2 with half of the vertical lines.
Vertical Lines
NTSC's 525 line and PAL's 625 line values include lines not actually displayed. DVD
compliant MPEG lists the number of active lines for each standard.
NTSC MPEG-2 has 480 active lines for both the D-1 and 1/2 D-1 standards. This is halved to
240 lines for the SIF used with MPEG-1 and MPEG-2.
PAL MPEG-2 has 576 active lines for both the D-1 and 1/2 D-1 standards. This is halved to
288 lines for the SIF used with MPEG-1 and MPEG-2.
MPEG-1
• SIF: 352x240 NTSC, 352x288 PAL
MPEG-2
• Full D-1: 720x480 NTSC, 720x576 PAL