HDMI_Demystified_April_20_2011-EN.pdf

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HDMI Demystified
April 2011
What is HDMI?
High-Definition Multimedia Interface, or HDMI, is a digital audio, video
and control signal format defined by seven of the largest consumer
electronics manufacturers. HDMI specifications and compliance are
enforced by an organization called HDMI LLC, which is controlled by
representatives from the seven founding companies. Released on
12/9/2002, it is supported by more than 300 companies. HDMI has
several advantages over previous connection solutions:
• 1080p and higher resolution capability
• Multichannel high-resolution audio
• One cable for video, audio and control
• Two-way communication for easy system control
• Automatic display and source matching for resolution, format
and aspect ratio
• Computer compatibility
• Ethernet/Internet Connectivity
The Evolution of HDMI
Since HDMI’s inception, the capabilities have changed as updates
have been made to the specification. Version numbers, such as 1.2,
1.3, and most recently 1.4 and 1.4a, have marked these updates.
The majority of the changes involve an increased number of options
for manufacturers to choose from. All new versions are compatible
with electronics designed to meet previous standards, but will not
add features that the existing products in your system do not have.
For example, a Blu-ray player with 1080p, built to version 1.3 spec
will work with a 1080i television built to version 1.2 spec, but will not
give you 1080p.
The current version of HDMI, version 1.4a, includes many new
feature options, including audio return channel, 4k x 2k resolution,
support for 3D video and 3D broadcast video formats, as well as
support for Ethernet.
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Features and Data
Electronics manufacturers must carefully choose from these
features. This is because the current HDMI specification limits the
amount of data any piece of electronics can send and receive to 10.2
Gbps (Gigabits per second) or less. This limit is not arbitrary, but is
based on current technological realities. A good way to think of this
is as if HDMI LLC has created a buffet of options and has given you a
10.2 Gbps plate. It is all you can eat, but it must fit on this 10.2 Gbps
plate. Some features take up more room on this plate than others, so
the electronics manufacturers must determine what features will be
most desirable for their customers.
Video Options
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Resolution:
Refers to the number of pixels in both the horizontal
and vertical direction per frame. Although measured in both
dimensions, it is usually referred to by only one of the dimensions.
For example, 1080p is 1920x1080 pixels per frame, which is in
wide use on Blu-ray Disc and a variety of other consumer high-
definition sources. The current highest resolution video format
supported by HDMI 1.4 and 1.4a is 4k, which can be defined
as either 3840x2160 or 4096x2160 pixels per frame. While 4k
is often mentioned prominently in discussions of HDMI 1.4’s
capabilities, no current or planned consumer video formats employ
4k resolution. Such an increase in resolution would dramatically
affect the amount of data transmitted.
•
Interlaced/Progressive Scan:
Progressive scan displays the
video as a series of complete images or frames, while interlaced
divides these frames into two fields, one made of the even hori-
zontal rows of pixels and the other of the odd rows. The most common
interlaced format is 1080i, which uses half as much data as 1080p/60.
Color Depth:
This is the amount of color information per channel/
per pixel (red, green, and blue), usually described as the
number of bits per color channel, such as 8-bits, for a total of 24-bits
per pixel. While color depths up to 16-bits per color channel are
currently supported by HDMI 1.3 and HDMI 1.4, when engaged,
Deep Color transmission is typically 10-bits or 12-bits per color
channel, increasing the color bit depth to 30-bits or 36-bits total
•
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per pixel. Increases in color bit depth, such as those typical when
the Deep Color feature in HDMI 1.3 and HDMI 1.4 components
is engaged, dramatically increases the amount of data sent over
HDMI cables.
•
Color Space:
Different types of source material use different
ranges of colors. Color spaces act as a map to translate these
different color ranges between sources. For example, standard
definition video from DVD, cable and satellite sources all conform
to a different color space than HDTV and HD video sources like
Blu-ray. Having multiple color spaces available allows color to
be more accurately reproduced from source to source. Additional
color space options do not affect the amount of data transmitted.
3D:
A 3-dimensional effect is created by rapidly displaying
separate images for each eye, and keeping the images intended
for each eye as entirely separate as possible. This new feature
offers resolutions up to 1080p in a variety of configurations for a
3D effect. The data rate for 3D varies depending on the system
being used. The frame compatible 3D systems used for cable
and satellite broadcast signals are most commonly 1080i using
so-called “top/bottom” or “side by side” formats that reduce
either horizontal or vertical resolution to conform to the data rates
required for typical 1080i HD broadcast signals. Broadcast 3D
doesn’t require a higher data rate than a typical 2D 1080p signal.
The frame sequential, or frame packing system currently used
for Blu-ray 3D offers full 1080p resolution for each eye, which
doubles the data rate of the signals transmitted via HDMI.
Refresh rate:
Refresh rate refers to the number of times the
image on the television is updated per second. It is described in Hz
(hertz), and should not be confused with fps (frames per second).
One of the most common refresh rates used in HDTVs in the
United States is 60 Hz. Currently1080p at 60Hz is the maximum
signal resolution and refresh rate that will be transmitted between
HDMI-connected components. The 120 Hz and 240 Hz refresh
rates that are increasingly common in today’s HDTVs are created
in the display and not encoded in the source or created by the
source component, so they have no impact on the data rates of
HDMI-connected devices.
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