and control data in one cable. It is arguably the most
popular AV interface right now. With abilities to carry
8K video, multichannel audio, and control data, Display-
Port aspires to compete with HDMI. However, it remains
mostly a computer display interface, which is its original
application. USB-C is gaining acceptance as a pro AV
interface. It has a reversible double-sided connector,
supports up to 8K video, multichannel audio,“superspeed”
data, and up to 100 watts of power delivery. USB-C’s
Alternate Mode enables connection via adapters to HDMI,
DisplayPort, Thunderbolt, and other video connectors.
Video Resolution
Resolution is the number of distinct pixels in each
dimension (width x height) that can be displayed. Pixels
are the smallest component of a screen image, composed
of red, green and blue primary colors. The higher the
resolution, the sharper and more detailed the image.
Viewers demand the highest resolution to obtain the
most life-like experience possible, and the makers of
video cameras and video displays continue to deliver.
4K/ultra high definition (UHD) is rapidly eclipsing full
HD for market dominance as prices fall. On the horizon
is 8K, aiming to hit the limit of human visual acuity.
Figure 1 shows the evolution of video resolution.
Cinema 2K and 4K are targeted toward professional
digital cinema. Unlike consumer video, where resolution
FIGURE 1: Digital video resolutions and how they have increased over time.
8 I ICT TODAY
Cinema 4K
4096x2160
4K/UHD
2K 3840x2160
Full HD 2048x1080
HD 1920x1080
SD 12080x720
720x480
is stated as number of vertical lines (480p, 720p, 1080p),
cinema resolutions are stated as width. This is because
film has many different aspect ratios, making width the
only constant value. 4K/UHD, which is 3840 x 2160 and
can be considered 2160p, is the consumer equivalent
of Cinema 4K. Cinema 4K is 6% wider than 4K/UHD.
Extended Display Identification Data (EDID)
EDID is a standardized data format that contains video
display parameter information. Its purpose is to allow
video displays to communicate their identity and capabilities
to video source devices so that the source can
deliver content in the formats compatible with the dis-
play. This provides plug-and-play compatibility between
devices. EDID data is transmitted over the display data
channel (DDC). DDC is the communications protocol
and the physical link for EDID transmission. The DDC
link is a bidirectional serial data line, a clock line, and
a +5 volt line. The data and clock lines support EDID
data transmission. The +5 volt line powers the EDID
circuitry in the display, allowing the source to read the
EDID data even if the display is powered off.
All mainstream AV interfaces, including HDMI, DVI,
video graphics array (VGA) and DisplayPort, support EDID
and DDC. EDID message mishandling by devices along
the signal path can create EDID issues resulting in incor-
rect display resolutions. These issues can be mitigated by
EDID management devices that can supply
the sources with a resolution selected by
the user or the native resolution captured
from the display. EDID management de-
vices also improve reliability by keeping
the EDID handshake closer to the sources,
reducing attenuation or interference pos-
sible with long cable runs.
The original DDC protocol defined 128
bytes of EDID data. As display capabilities
increased, 128 bytes were not enough. The
latest specification is called E-EDID/E-DDC.
It retains the first 128 bytes as a mandatory
base EDID to which up to 255 extension
blocks can be appended.