|
What is HDTV?
HDTV stands for high-definition television, with the emphasis on high definition. Currently your television is receiving an analog signal. In analog TV, a 6 MHz signal produces 500 horizontal pixels (dots). These pixels comprise the picture you see on your screen. HDTV can have a resolution of up to 1920 by 1080 pixels, or more than two million pixels. That's more than six times the detail of regular television.
> Back to Top
What is aspect ratio?
Aspect ratio is the width of a picture relative
to its height. 4:3 and 16:9 are common aspect ratios.
The majority of current NTSC transmissions are
4:3 aspect ratio. Virtually all HDTV transmissions
are in 16:9 aspect ratio.
> Back to Top
What is the ATSC?
ATSC stands for the Advanced Television Systems
Committee. It was responsible for defining the 18
different formats of HDTV. It was formed to develop
technical standards for advanced television systems,
including high-definition television. The ATSC specifies
MPEG2 for video compression and AC-3 (more commonly
known as Dolby Digital) for audio compression. The
18 formats of HDTV are as follows:
| Scan Lines
|
Pixelization
|
Frame
Rate |
Aspect
Ratio |
Formats
|
|
SDTV |
525 Total
480 Active |
480 x 640 |
24p, 30p, 60p, or 60i fps |
4:3 |
4 |
525 Total
480 Active |
480 x 704 |
24p, 30p, 60p, or 60i fps |
4:3 or 16:9 |
8 (4x2) |
|
HDTV |
750 Total
720 Active |
720 x 1080 |
24p, 30p, 60p |
16:9 |
3 |
1125 Total
1080 Active |
1080 x 1920 |
24p, 30p, 60i |
16:9 |
3 |
> Back to Top
What is MPEG?
MPEG stands for Motion Picture Experts Group,
the standard settings body that developed the video
and audio compression standards used in today’s
digital television transmissions. MPEG has several
different standards for video compression. MPEG1
was the original compression standard meant for
use in computers.
MPEG2 was developed for broadcast television applications.
MPEG2 has several profiles and levels.
> Back to Top
What is MP@ML?
This stands for main profile at main level.
This is the format used for most standard-definition
digital channels. It supports resolutions up to
720 x 480i and data rates up to 15 Mbps.
> Back to Top
What is MP@HL?
This stands for main profile at high-level. This
is the format used for high-definition digital channels.
It supports resolutions up to 1920 x 1080i and data
rates up to 19.25 Mbps.
> Back to Top
What is interlaced scanning?
Interlaced scanning is a broadcast process used
in TV sets in which half the lines are transmitted
as one field and the other half is transmitted as
the second field. These two fields are displayed
sequentially to form an image.
Standard-definition television is broadcast at
a total of 525 interlaced lines, of which 480 of
those lines are visible (hence the term 480i).
High-definition television has several scan rates.
The most common of these is broadcast at a total
of 1125 interlaced lines, of which 1080 of those
lines are visible (hence the term 1080i).
> Back to Top
What is Progressive Scanning?
Progressive scanning is typically used by computer
monitors. This scanning process paints all the horizontal
scan lines on the screen at one time.
The other common scanning scheme used in HDTV is
broadcast at 750 progressive lines, of which 720
of those lines are visible (hence the term 720P).
Some television broadcasters have chosen to broadcast
525 progressive lines, of which 480 of those lines
are visible (hence the term 480P). Many DVD players
output the picture in 480P format.
> Back to Top
What is scan rate?
Scan rate has two components. There is a vertical
scan rate and a horizontal scan rate. The vertical
scan rate is the number of frames/fields per second
transmitted. The horizontal scan rate is the number
of horizontal lines of video transmitted per second.
The vertical frame rates supported in the ATSC
specification are 24P, 30P, 60P, and 60i.
> Back to Top
What is frame rate?
A frame of video is a complete image in a sequence
of images. The frame rate is the number of frames
transmitted every second.
> Back to Top
What is data rate? How does it
impact video quality?
The data rate is the number of bits per second
used to transmit a video and audio stream. The ATSC
specification calls for 19.25 Mbps data rate for a
high-definition terrestrial transmission. However,
some cable/satellite broadcasters use a lower data
rate because most of these transmissions are movies
without a lot of high-speed motion. Generally, a higher
data rate will translate to better video quality,
especially with high-speed motion scenes. For content
such as movies, you most likely would not be able
to tell the difference between a data rate of 12 Mbps
and one of 19 Mbps. For content such as sports, you
probably would see a difference between those data
rates.
> Back to Top
What does component video mean?
It means that video is represented as three
different components which may be combined in an
HDTV to provide video. There are different component
video formats such as YPbPr and RGB.
> Back to Top
What does YPbPr mean?
YPbPr is the component video format in which
the luminance (Y) is represented separately from
the color components (Pb and Pr). The majority of
HDTV’s today support this format. These HDTV’s
accept the YPbPr formatted video per EIA specification
770.3. The Y output on HDTV’s and HDTV receivers
is provided as a Green jack, the Pb is provided
as a Blue jack, and the Pr is provided as a Red
jack. The colors themselves are not to be confused
as an RGB output.
The Explorer 3100HD has a YPbPr output only.
> Back to Top
What does RGB mean?
RGB is the component format in which the primary
TV monitor colors (red, green and blue) are transmitted as
three independent components. Some older HDTV monitors
have only RGB inputs. Monitors with RGB inputs also
require separate horizontal and vertical sync inputs.
The Explorer 3100HD does not have a RGB output.
It has only a YPbPr output. Scientific-Atlanta provides
an external RGB adapter that converts the YPbPr
output from the Explorer 3100HD to RGB with horizontal
and vertical sync for those HDTV monitors requiring
that type of input.
> Back to Top
What are the differences between
an HDTV and an SDTV?
Some of the differences between and HDTV and a regular
TV are summarized in the chart below:
| |
NTSC |
HDTV
(ATSC) |
| Total Lines |
525 |
1125 |
Active Lines
|
480 |
1080 |
Sound
|
2 Channels (Stereo) |
5.1 Channels (Surround) |
Aspect Ratio
|
4:3 |
16:9 |
Max. Resolution
|
720 x 480 |
1920 x 1080 |
Pixels
|
Rectangular |
Square |
> Back to Top
What does DVI mean? What is
HDCP? What is HDMI?
DVI stands for Digital Visual Interface. DVI is
an all digital link between a video/audio source
such as an HDTV settop and a display device such
as an HDTV. The DVI link provides an uncompressed
digital stream at rates up to 5 Gbps between the
two devices. The DVI link does not contain audio,
so audio is still needed to be connected from
the settop to the HDTV or home theatre system. One
advantage of DVI is that the link allows graphics
to be sent along the link as well. This allows the
user interface from the settop to be displayed on
the HDTV. The DVI 1.0 connector on the settop and
HDTV looks as follows:
HDCP stands for High-Bandwidth Digital Content Protection.
HDCP is the copy protection standard that is tied
to DVI.
HDMI is the next generation of DVI. HDMI stands for
High-Definition Multimedia Inteface. The main difference
between HDMI and DVI 1.0 is that HDMI adds audio to
the DVI link and is a smaller connector. The HDMI
interface will be backwards compatible to the DVI
1.0 interface, meaning that you can connect up a settop
to an HDTV, where one has DVI 1.0 and the other has
HDMI. HDMI is not expected in HDTV's until 2004. It
will be available on future generations of Scientific-Atlanta
HDTV settops. The HDMI connector on the settop will
look as follows:
> Back to Top
|
