iSignager-LCD-S Series Digital Signage Display
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BMP, reduces file size by reducing the number of colors. PNG can also be 24-bit
true-color and maintain all the original image information, but file sizes are large.
A.4 Standard Definition (SD) Introduction
A.4.1
SDTV
Standard-definition television or SDTV refers to television systems that have a lower
resolution than HDTV systems. The term is usually used in reference to digital television,
in particular when broadcasting at the same (or similar) resolution as analog systems.
In ATSC, SDTV can be broadcast in 704 pixels × 480 lines with 16:9 aspect ratio (40:33
rectangular pixel), 704 pixels × 480 lines with 4:3 aspect ratio (10:11 rectangular pixel) or
640 pixels × 480 lines with 4:3 ratio (and square pixels). The refresh rate can be any of
24, 30 or 60 pictures per second.
Digital SDTV in 4:3 aspect ratio has the same appearance as the regular analogue TV
(NTSC, PAL, PAL2, SÉCAM) minus the ghosting, snowy images and static noises.
However, if the reception is poor, the user may encounter various other artifacts such as
blockiness and stuttering.
Standards that can broadcast digital SDTV include DVB, ATSC and ISDB. The latter two
were originally developed for HDTV, but they have proved to be more often used for their
ability to deliver multiple SD video and audio streams via multiplexing, than to use the
entire bitstream for one HD channel.
A.5
High Definition (HD) Introduction
High-definition video or HDTV generally refers to any video system of higher resolution
than standard-definition (SD), i.e. NTSC, SÉCAM and PAL. HDTV is broadcast digitally,
and therefore its introduction sometimes coincides with the introduction of digital television
(DTV). High-definition signals require a high-definition television or computer monitor in
order to be viewed. High-definition video generally has an aspect ratio of 16:9 (1.78:1).
The aspect ratio of regular widescreen film shot today is typically 1.85:1 or 2.40:1.
Standard-definition television (SDTV) has a 4:3 (1.33:1) aspect ratio.
High-definition television (HDTV) resolution is 1080 or 720 lines. In contrast, regular digital
television is 480 lines (NTSC-like) or 576 lines (PAL/SECAM-like).
