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| Native: |
This is the normal uncompressed
signal that is output through VGA, DVI or DisplayPort
interfaces and delivered via VGA, HDMI, or DisplayPort
formats. These formats can be amplified and transmitted
using traditional wideband methods, but typically require
a dedicated point-to-point link to accommodate the very
high bandwidth demand. |
| Compressed: |
The PC video can be compressed using
codecs such as JPEG2000 and H.264/MPEG-4 AVC. These
formats can reduce bandwidth substantially (10 –
20 times) at the expense of additional delay (1 to 3
frames typical). |
| Video Over IP: |
This is a broad category that encompasses
many different implementations. The most well known
variants are IPTV and Internet TV. All implementations
require some form of video compression and the availability
of an IP stack at the target. |
| Remote Desktop: |
In this version, another PC at the target
recreates the desktop at the source. Again, there are
many possible variants, including VNC (open) RDP (Windows)
and ICA (Citrix). |
| Video Over USB: |
This is a proprietary technology developed
by DisplayLink. Software running in the PC captures
the current desktop view and transmits the information
over USB to an IC which recreates a VGA or DVI signal
that can be delivered to a standard monitor. Potentially
a very cost-effective solution. |
Table 1. Video Signal
Options for TV 2.0
There are tradeoffs when deciding what video to use in TV
2.0 including bandwidth required and latency added when using
compressed versus uncompressed video. Cost and consumer installation
issues are also important as the compressed solutions require
either host PC processing power, requiring a software load
and use of PC resources, or extra hardware in the PC and TV
boxes. Native and compressed video are the logical choices
for TV 2.0 as Video over IP requires an IP stack at the TV
and the remote desktop options require a PC at the TV (defeating
the entire purpose of PC to TV). The DisplayLink option will
work for TV 2.0 however additional investigation on user installation,
bandwidth and cost are required.
2 - Signal Transmission Media
This section outlines the options available for transmitting
the audio, video and control information (typically USB) from
the PC to the TV. The origin of the signals is the PC which
sends video (VGA, DVI, or DisplayPort) plus audio (USB) plus
USB to the PC Box. The transmission media delivers the signals
from the PC Box to the TV Box where the audio/video signals
are fed to the TV and the USB signals are sent to the peripheral
control devices. The options for video and audio signal transmission
include:
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